Urgent need for an open source HF SDR thats affordable ... - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: August 12, 2020, 01:27:52 pm
content: As somebody who would very much like to be a ham I am tremendously depressed by the failure of the ham community to come up with a good, community based (transceiver) solution to the lack of affordable SSB capable HF gear for beginners, thats affordable to people who want to get on the air today..(With a few exceptions, which are notable.)Why cant we do better?Given that most people already have access to a computer or can afford to buy a cheap one (like the Raspberry Pi 3 or 4, which both have enough power to manage an SDR transceiver and do the DSP required) I think we should concentrate on the making the hardware available and affordable.Why isnt there a project to do this faster?We should create one! One that doesnt try to reinvent the wheel in any way, instead leveraging every single possible bit of existing toechnology and mass production to try to create a two way transceiver that can be clean and a good radio citizen, although maybe not the most feature rich, or cutting edge.Instead aiming for the trailing edge, extendability, modularity and extensibility, low BOM cost, low manufacturing cost, and ease of making ones-self from a kit.It should target a cost of $100 for the entire board, sans case, (we can target some already existing affordable cases, since its just an SDR it just needs a box to put it in to keep it safe, it doesnt need any desplays or switches. Maybe it can contain a connection for an encoder so it can have a big knob. (and also support external encoder collections like DJ consoles and Midi devices for use as controllers if desired)It could use an external 12v power supply. Cost should be kept down by use the computer for all its DSP and its audio, so does not need a microphone+speaker.The reason that I think low prices are important are several. One is that the actual proce to make a small SDR most certainly has fallen a great deal, look at how chips made to sell profitably in DTV dongles for $10 have made their way into SDR receivers that sel for $100. Also, services liberalization is raming up and with it will coe tremendous job losses, especially in developed countries. So the price pressures will increase, not decrease.. Nobody is epecting a big burst in prosperity, lets put it that way.Ham radio could also be a lifeline for many disabled people or people in rural areas. The recent situation with online education makes it clear that any families dont have Internet access.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 12, 2020, 01:51:56 pm
content: For the receive side, direct sampling RTL-SDR will work nicely. Probably would be good to add adjustable gain and selectable filters to boost the performance.For the transmit side, just use fl2k with the addition of output filtering. If half duplex operation only is OK, it could be possible to reuse the filter bank for the receive side as a cost savings.

author: A.Z.
author_rank: Super Contributor
timestamp: August 12, 2020, 02:46:40 pm
content: uBitx 20 - 150$https://www.hfsignals.com/

author: janoc
author_rank: Super Contributor
timestamp: August 12, 2020, 03:03:29 pm
content: Cdev, you really should do more research before you post. There is really no "urgent need".BITX is popular and can be had/built for much less than the $150 mentioned - depending on how much elbow grease you want to put into it ($150 is the pre-assembled kit).SSB gear doesn't mean SDR, but RTL-SDR has been mentioned already, there is ILER-40:https://www.qrphamradiokits.com/transceivers/iler-40-20-v3-ssb/There is HackRF One:https://www.aliexpress.com/item/4000635360544.htmland many others. For some you may need an upconverter/downconverter and power amp to work on HF bands, but hey, what do you want for the price!However, if you want ready-to-go "box" that you just plug in and can use, you aren't going to find one for $100. That's simply not realistic, the components alone for an SSB radio (e.g. filters and mixers if you go the analog route or RPi + SDR + power amp) cost more than that + labor, etc. If you want to sell if for $100, you would need have the BOM costs < $50 to cover your overhead and labor costs. RPi alone costs about $35.You won't find even Chinese CB radios with SSB for that price. Ten-tec 507 Patriot is about the closest to what you want (open source, Arduino-based, SDR) - and costs $300. People don't work for free (HAM radio is extremely niche market, so no economies of scale) and the components do cost something - especially if you want a multiband rig (filters, transformers, relays ... All that you need even for an SDR radio).And once you go down that rabbit hole, you can find a used transciever on eBay for $400-$500 easily. Even a new Yaesu FT-450D can be had for some $700 or so - all band, 100W radio, with a built-in antenna tuner and DSP processing.I just don't see which niche is your $100 radio going to fit in.But feel free to try to design a viable radio that could be sold for $100. Even single band would be enough already (in many countries people with novice license have large restrictions on HF bands - usually only 160 and 80 meters, CW/digi only ...)

author: DH1AKF_Wolfgang
author_rank: Contributor
timestamp: August 12, 2020, 04:35:03 pm
content: Another approach: the UCX, also known as µSDX.look here:https://groups.io/g/ucx/topic/started_on_the_ucx_build/74417554?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,74417554or here:https://groups.io/g/ucx/topicsBy now this is a full open source project in development. You can see, that also beginners have a chance to build the modules themselves.

author: mark03
author_rank: Frequent Contributor
timestamp: August 12, 2020, 05:07:48 pm
content: There are a huge number of options already out there. Besides those already mentioned, there is Hermes Lite and KiwiSDR. Agree with the previous posters that $100 is not yet realistic. $100 would only cover the BOM.Edit: Unless your concern is for folks in the developing world, I am baffled by the fixation on cheap gear. If you live in the West, $100 is pocket change. I get that $100 is a lot of money for some people, and lots of folks are struggling especially now with COVID, but groceries and rent cost way more than that, so anyone who can't manage to save a couple hundred $$ for a radio is probably facing much bigger problems and doesn't have the time for a new hobby in the first place.I'm pretty sure radio gear is cheaper today than at any time in history, if you adjust for inflation. We're spoiled.

author: cdev
author_rank: Super Contributor
timestamp: August 12, 2020, 07:46:21 pm
content: Thats an interesting option but as far as I know, its not an SDR, right? Still, its good thats its out there. Thats a big improvement over much of what is for sale in terms of value.Quote from: A.Z. on August 12, 2020, 02:46:40 pm

author: cdev
author_rank: Super Contributor
timestamp: August 12, 2020, 07:58:31 pm
content: People in the developing world have - for many things much lower prices, plus they have jobs, many jobs are being shifted to developing countries.Americans have multiple disadvantages if jobs are shufted elsewhere because we still have by far the highest prices in the world for many things, particularly healthcare and Rx drugs. Housing although perhaps not the highest in the world, in many places it can be pretty high, for example, $4000 a month for a small two bedroom apartment in the San Francisco Bay Area is not unusual.Also the low energy prices we've had here for 40 years or more are ending due to natural gas export. And so we'll also lose a whole generation of postwar housing. It will be redeveloped.. Which will totally change our cities character.So this is going to squeeze people a lot. Many may have to move to other parts of the country or world. Luxuries like cars or electronics will be out of the question for many people. and many will be struggling to simply stay alive.Technology may become less of a hobby than something people do to preserve their sanity and keep a constructive side to their lives. Something thats important for young peoples self esteem in a world where jobs are drying up.Quote from: mark03 on August 12, 2020, 05:07:48 pmHermes Lite looks very promising. That looks like a real winner!The BITX does too.. (even though its not an SDR) I like their design philosophyhttps://www.hfsignals.com/index.php/ubitx-v6/---------Does KiwiSDR transmit?Quote from: mark03 on August 12, 2020, 05:07:48 pmExcept that every time I go looking for used radios on ebay, most of what I find with few real exceptions are 'deals' like this. Well, maybe this is not the best example, but hopefully people get the idea.Frankly, although I am enthusiastic about the hobby I am also afraid of putting even a modest amount of money into something that might easily be wiped out - at least on the higher frequencies because the companies that sell broadband services make the point thats the ham bands are abandoned and not being used.On the other hand they offer all sorts of money earning services. Its like Linux, it may add tremendous value to society but what were its sales figures last year.. Ya know...Thats the world we live in today, profit is king. Anything that is pleasurable and is not generating lots of money is being phased out. Because its stealing market share from something that would. Thats just the way things work now. Everything must be monetized. If it aint profitable, its history. the same applies to people, unfortunately.Frankly, most of the bands seem empty when tuning around, especially in the day time. Finer points like how the ionosphere worlks will be lost on legislators.Use it or lose it. the only way to prevent band loss is to make radios a lot cheaper and make ham radio a lot more popular.A good selling point is the fact that its real, it would he very hard to manipulate ham radio the way the Internet is being. .

author: fourfathom
author_rank: Super Contributor
timestamp: August 12, 2020, 08:17:24 pm
content: Look at QRP Labs for virtually open-source ham radio kits (https://www.qrp-labs.com/). Many of these kits can be used for digital comms such as WSPR, FT8, and my favorite JS8Call. These modes seem to be where the newer and tech-savvy hams gravitate, and these typically use fairly low-power transmitters. QRP Labs hosts a very nice discussion forum with lots of technical content. They don't have a classic SDR design in their stable, but their designs can still be quite interesting.

author: janoc
author_rank: Super Contributor
timestamp: August 12, 2020, 08:30:25 pm
content: Quote from: cdev on August 12, 2020, 07:58:31 pmAin't happening any time soon, especially not on the HF bands - those aren't all that useful for broadband, there the pressure is more various broadcasters and services needing long range comms. And the infamous BPL schemes (broadband over power lines) that cause a metric ton of interference on HF are pretty much a commercial flop. It just isn't that good and mobile (3G-4G/LTE and now 5G) are simply blowing it out of water.Also, keep in mind that the HAM band allocations are done worldwide, amateur radio is defined as one of the "services" by ITU. So a government somewhere can't just unilaterally declare that hey, nobody seems to be using this, let's sell this spectrum to someone else!And finally - it is only up to us HAMs whether or not the bands remain allocated to amateur radio or not. Voting, lobbying and mainly using the bands is up to us.Anyhow, that said - you really don't need to invest several thousands into an expensive radio to get started with the hobby! Especially if you know some basics and know which end of a soldering iron to grab. Building a reasonable HF receiver is not difficult, transmitter is even easier, even for SSB, especially if you stay in the QRP power limits. Even more so today, when you don't need to mess with "wandering" VFOs, something like Si5351 will give you a rock stable VFO across the entire HF spectrum, it easy to have digital control of everything, we have computers - and it costs peanuts.Even SDR is possible to build yourself - just look at Pete's N6QW's projects:http://www.n6qwradiogenius.us/Personally, I have found it much more interesting and satisfying to build a homebrew piece of kit, with all the naked copper and messy wires look than to operate a commercial radio or even an SDR receiver. You learn so much more building something yourself.

author: janoc
author_rank: Super Contributor
timestamp: August 12, 2020, 08:40:30 pm
content: Quote from: cdev on August 12, 2020, 07:46:21 pmNo, BITX is not an SDR, it is a classic analog transciever. However, it is an excellent value - both because you get all the "difficult" parts (filters, coils, etc.) made for you and because everything is documented and simple, down to bare basics. I am not even sure whether uBITX has AGC. It is meant to be modified, tweaked and adapted to your own needs.Oh and if you buy the kit, you support also some poor ladies in India who are manually winding the coils and preparing the kits.

author: DH1AKF_Wolfgang
author_rank: Contributor
timestamp: August 13, 2020, 03:58:03 am
content: An open source project, a really SDR transceiver for a low budget:https://github.com/threeme3/QCX-SSBhttps://hackaday.com/2020/05/27/atmega328-ssb-sdr-for-ham-radio/Don't know, why you ignored my post from yesterday (USX, µSDX).73, Wolfgang (DH1AKF)

author: vk6zgo
author_rank: Super Contributor
timestamp: August 13, 2020, 05:04:52 am
content: The low price area is primarily occupied by secondhand equipment.eBay prices are quite high, especially for anything like that Heathkit, which might masquerade as a "collectors item".All except two of my radios are older units, the exceptions being a Quansheng which is itself, a few years old now, & a Baofeng which doesn't work properly, so might as well not exist.I normally buy all my stuff at Hamfests-----prices are reasonable to "dirt cheap" on older radios.My main 2m FM radio cost me $A40, & it's a proper mobile rig, not a lousy handheld.The other stuff hovers around $A200.SDRs are trendy, but superheterodynes are "a pretty hard act to follow", especially if you aren't hung up on "waterfall" displays.The biggest problem is that with the present situation, Hamfests aren't happening.

author: A.Z.
author_rank: Super Contributor
timestamp: August 13, 2020, 06:41:19 am
content: Quote from: cdev on August 12, 2020, 07:58:31 pmWell, if you absolutely, positively want a "true SDR", then you may check the "HackRF one"https://greatscottgadgets.com/hackrf/it's an SDR which also offers transmit capabilities, and the design (hw/sw) is totally open source, so you may build it, or, if you prefer, you may buy it, here's an Amazon pagehttps://www.amazon.com/HackRF-Software-Defined-ANT500-Antenna/dp/B01H3T2U7Gbut it can probably be found at lower price on other places; the TX power is around 0.5W on the HF bands (if I'm not wrong), so willing to use it as a serious transmitter you may add (again, build or buy) an RF linear amplifier module to its output (a 5...20W amplifier won't cost you an arm and a leg) and you'll be in the QRP range; just ensure you have a license and the amplifier is properly built (linear, lowpass filters...)Here's an idea for the amplifierhttps://www.qrp-labs.com/linear.htmlthis one will give around 10W output and could fit well, just add a TX/RX relay to bypass it when receiving (power it using the bias-tee voltage, in TX it won't be present), connect a decent antenna for the HF bands and you'll be up and running

author: A.Z.
author_rank: Super Contributor
timestamp: August 13, 2020, 09:15:20 am
content: Quote from: janoc on August 12, 2020, 03:03:29 pmFor that price range, one may go for aXIEGU G90; not open source, but is a complete HF rig which can also be used as an SDR by connecting it to a computer using the USB port, but then I falls outside the "open source" part of the request

author: aristarchus
author_rank: Regular Contributor
timestamp: August 13, 2020, 09:28:53 am
content: Quote from: cdev on August 12, 2020, 01:27:52 pmThese types of threads are always started from people that are not radio amateurs and never had any proper experience with radio amateur equipment nor radio amateur legal framework or operating in the allocated spectrum.My advice to them, before they express an opinion to have first hand experience, get your license, operate and then speak again if you want.Quote from: A.Z. on August 13, 2020, 06:41:19 amSpreading ideas for PA's without LPF's is not a clever move.Puts you immediately in the illegal category.IMHO this thread has a real problem.It makes readers to fall in the trap of low cost as the ony parameter.Instead you guys should focus on how can a properly funtioning transceiver be also low cost.Whatever though the low cost of a transceiver could be, the real and always present problem is the human factor, its behaviour, you can have this as food for thought.73

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: August 13, 2020, 09:55:25 am
content: Quote from: aristarchus on August 13, 2020, 09:28:53 amWhy would a good linear PA need a LPF? If you have a highly-nonlinear PA, sure, you might have a lot of harmonic current (which may or may not be an issue). With dense modulated signal you'll also get expansion on your sidebands which could require suppression. But there is no reason a PA *needs* any filter on the output.

author: aristarchus
author_rank: Regular Contributor
timestamp: August 13, 2020, 10:38:34 am
content: Quote from: TheUnnamedNewbie on August 13, 2020, 09:55:25 am..no comments../Edit: Actually there is a comment, try to identify on which category you belong on my previous post, Hint, look at the first paragraph..

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: August 13, 2020, 11:37:25 am
content: Quote from: aristarchus on August 13, 2020, 10:38:34 amYes, cause clearly trying to be cryptic is the best approach. Instead of waving your fist going 'you fools', try to educate. All I see right now is a grumpy person who thinks they are experts, and assumes everyone else must also be an idiot, but refuses to help others.

author: aristarchus
author_rank: Regular Contributor
timestamp: August 13, 2020, 12:34:39 pm
content: @Newbie,All I said is that first you have to read and take your exams to be a radio amateur operator, then to speak.Even so, if someone has not done this, as an electronics amateur, whould first read and get educated about electronics stuff before everything else.I will not try to educate you, you have to do that yourself.As a final note, I did not called names anyone, you did, that makes you seem as the perfect candidate for the persons mentioned in the last paragraph of my fist post in this topic.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: August 13, 2020, 12:44:11 pm
content: Quote from: aristarchus on August 13, 2020, 12:34:39 pmI would just like to point out that you assumed I didn't know what I was talking about. You can' t know that. I could be a hobby electronics guy just being curious, but I could also be a expert in PA design. It's precisely because I have a good bit of experience with the topic that I'm curious as to why you make such a black-white statement as saying that A PA without LPF cannot possibly be legal.And with regards to calling names: No, you did not literally call people fools. But your intonation and attitude of refusing to help educate (not even give a pointer where to start...) really does send that message. Perhaps it is a cultural thing.

author: janoc
author_rank: Super Contributor
timestamp: August 13, 2020, 12:52:17 pm
content: Aristarchus, while what you are saying is undoubtedly true, there is no need to be an acerbic "hollier than thou" jerk, when someone is genuinely curious about something.@TheUnnamedNewbieThe reason why a low pass filter is mandatory even on a linear PA is twofold:a) No linear PA is 100% linear, some distortion will always happen (or you could be overdriving the amp!) -> harmonics causing interference, both in and out of band.b) You absolutely must not radiate anything* outside the band. It is the law. The output of your transmitter may not be 100% clean (even though you are supposed to have a filter there too!) and what was only an annoying QRM on nearby frequencies at low power is now splatter both in an out of band thanks to your PA (even the weaker harmonics are now strong enough) - possibly interfering with air bands, weather stations, broadcast radios, even governmental services (military ...). Not good if you want to keep your license and wallet intact (the fines if caught are steep - some truckers with their 1kW amps on CB could tell stories ... ).* Anything in quotes - the rules specify how many dBs has the signal to be attenuated for the radio to be legal. Real filters are not "brick wall", so nobody expects a "zero" there. The US rules (because those I can find the quickest and are in English - but the rest of the world is similar) are here:http://www.arrl.org/part-97-text,, part "§97.307 Emission standards.":QuoteAll this is well described in literature, both in the materials when preparing for your license exam and also in publications like the ARRL Handbook, for example.

author: cdev
author_rank: Super Contributor
timestamp: August 13, 2020, 01:44:09 pm
content: Quote from: vk6zgo on August 13, 2020, 05:04:52 amThat is a big problem. When I was a kid I used to go to hamfests and had several ham friends. Its kind of a chicken and egg problem, so I think I am going to need to either build my first rig or go without because buying a new rig is just not finacially wise right now. But, I already have a lot of stuff that can go into one, nomatter what I decide to build. I even have a receiver that would work perfectly well. It might be possible to adapt the designs of some of these open source rigs to my existing receiver because they use the same principles. I'd like my transmitter to integrate well enough tomy receiverto transmit on the same frequency as I'm reciving. And work with already existing software, ideally some that work well with Linux. (quisk, or Linrad both look promising in that respect. )And of course I am happy to build low pass filtration in. I could not see using a transmitter without an LPF, especially not an SDR. (actually, SDR receivers require a BPF to perform optimally, so it makes sense to use the same filter for both and switch them in and out with relays.)For people who doubt me about ebay prices, I suggest they scan the ads for good basic starter rigs. You'll find that many of the sellers are literally trying to get almost full retail for them. And for older rigs, the chance of getting a rig thats 100% working to me seems pretty small. And the rigs too heavy to make sending one back anything less than an ordeal.So its just too risky.A transmitter is not the same as a piece of test equipment, especially if tubes are involved. So building something, especially a solid state rig, thats extensible, if there is a community that can lend support, is very appealing, very appealing.It also has a better chance of being tolerated by a spouse. Because of the cost of new gear.

author: aristarchus
author_rank: Regular Contributor
timestamp: August 13, 2020, 03:39:06 pm
content: Quote from: janoc on August 13, 2020, 12:52:17 pmThanks @janoc for pointing out to me that I should have considered @newbie's post as actually asking. To be honest based on how I interpret it, he was puting a rhetorical question and I thought that he wants to just make a point rather than to ask.Nevertheless, apologies if I was in error.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: August 13, 2020, 04:30:23 pm
content: Quote from: aristarchus on August 13, 2020, 03:39:06 pmI think we both may have misunderstood eachother. I'm working in RFIC research for a while now, and I have a lot of experience with HAM radio operators telling me 'I don't know what I'm talking about'. And while I will agree that making 10W PAs at a few (hundred) MHz is a completly different beast with different challenges and tradeoffs than my day-job, it always frustrates me.I was curious in this case because when I look at designs in WiFi/4G (which is not what I work on) it seems to be uncommon to include a true filter for the PA. Instead they ensure with signal processing and design that the linearity of the amplifier is sufficient. I was not aware that within HAM radio it was legally required, I would have assumed that if your output spectral mask met the requirements you were good.

author: janoc
author_rank: Super Contributor
timestamp: August 13, 2020, 04:58:26 pm
content: Quote from: TheUnnamedNewbie on August 13, 2020, 04:30:23 pmWell, strictly speaking it isn't legally required to have a filter if you can achieve the spurious emissions limits by other means - the rules don't explicitly demand a filter, only that you don't radiate where you shouldn't.However, there is a big difference with e.g. wifi or 4G radio, where everything is tightly controlled from the start to the end, there is only ever one type of modulation going to be used, power is strictly controlled, only well defined frequencies are used, etc. And everything is locked down and normal peeps are not allowed to touch it.Compare that with HAM radio, where people are actually allowed to build their own gear (the only ITU service where this is true) and it is very common that a typical HAM "rig" consists of a haphazard mix or components - transciever, separate PA, antenna tuner, antenna itself, some bought, some homebrewed, some second-hand in who knows what state. Worse, those radios operate with all sorts of different modulations (AM, FM, SSB, phase shifting, CW, FSK ...), so you do get a rich source of harmonics at the output, even in situations where the gear is well adjusted (and a lot of it isn't!)So the simplest way how to meet those legal limits is to slap a beefy LPF at the output of both your transciever and PA, to make sure anything undesirable stays down even if you screw something up and e.g. overdrive your PA or your DIY transmitter is producing more a square wave than a sine at its output.

author: aristarchus
author_rank: Regular Contributor
timestamp: August 13, 2020, 05:31:49 pm
content: Ok, so just to add a bit of numbers and ITU recommendations on what is legaly allowed in the HF radio amateur bands.According to R-REC-SM.328, R-REC-SM.329, R-REC-SM.1539, R-REC-SM.1540 and R-REC-SM.1540 where they describe the out of band and spurious domains and respective levels, the out of band limit in our case (Radio amateur) extends -/+ 10KHz (250% of 4KHz BL) from the center frequency in use, after that frequency limit comes the spurious domain.The amplitude limits for signals emitted in the Spurious domain (> -/+ 10KHz) it is required to have 43+10*log(Pout) dB of attenuation with maximum the 50dB (for the radio amateur service specifically).So, for a PA that gives a signal of 10W and above, the required attenuation to signals in the spurious domain is 43+10*log(10) = 53dB, since it is above the maximum limit then the 50dB is taking effect for radio amateurs.(Rec. ITU-R SM.329-12 pg 9 & Annex 5, Rec. ITU-R SM.1539-1 pg 4, Rec. ITU-R SM.1541-6 pg 57 Annex 9)

author: vk6zgo
author_rank: Super Contributor
timestamp: August 14, 2020, 12:33:12 am
content: Quote from: cdev on August 13, 2020, 01:44:09 pmMost ham radios since the mid 1960s aretransceivers, so they are a "stand alone" piece of equipment.Integrating an existing receiver's operation with a transmitter can be done, & was, in the past, but is sometimes a bit messy.There are many old, cheap, solid state radios around, most are not as heavy as a good quality analog 'scope or early model DSO.If you can fix test equipment, you can fix radios.If you look back, I agreed with you about eBay prices.I can only go by my experience, but I have have almost universally had good results with hamfest purchases, both radios & test equipment.Some ham based websites have their own "virtual hamfests" sections.Have a look at QRZ.com, as probably the best ham forum.Without hamfests regularly popping up, you are stuck with the "virtual" ones, buying new, or building either a kit, or from scratch.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: August 14, 2020, 05:41:36 am
content: Quote from: janoc on August 13, 2020, 04:58:26 pmQuote from: aristarchus on August 13, 2020, 05:31:49 pmThat makes sense, thanks for clarifying guys!

author: cdev
author_rank: Super Contributor
timestamp: August 14, 2020, 06:11:47 pm
content: Since the cost of LPF components and instruments to adjust them is now so modest is there any legitimate reason not to use one? No, not really. So why wouldn't one?I have heard people running very dirty transmitters on the shortwave bands. (the bible thumper station here in the US comes to mind) and also probably illegal 27 Mhz activity. (isnt very common now in the subspot minima) but I honestly either have never heard hams broadcasting ssb noise or Ive forgotten it. Usually ham signals seem well behaved to me. Maybe its more common in other parts of the world?What is a real problem is ever rising levels of RFI from e-junk, badly made electronics hardware, IMHO.With the caveat that maybe again its the sunspot minima the noise seems higher now than ever before (or maybe its the interesting signals on HF are lower than they have been for a long time)Good excuse to improve the filters.

author: fourfathom
author_rank: Super Contributor
timestamp: August 14, 2020, 09:04:05 pm
content: Quote from: cdev on August 14, 2020, 06:11:47 pmThis is true for a single-band rig, but switched filter banks for multiband operation can add significant size, cost and complexity. True, they may still be necessary, but if you have a low-distortion amplifier and driver design where the output meets the legal requirements then I can see not adding them (especially for a QRP transmitter).

author: aristarchus
author_rank: Regular Contributor
timestamp: August 14, 2020, 10:00:33 pm
content: Quote from: fourfathom on August 14, 2020, 09:04:05 pmDo you have or seen, old or modern, a HF 160m to 10m, PA design that by delivering 37dBm (QRP=5Wmax) in its fundamental frequency can have in its spurious/harmonics -50dBc attenuation (43+10*log(5) = 49.9897) without a LPF?This is not a rhetoric question, I am sincerely asking. If such a design actually exists it would be really great.

author: fourfathom
author_rank: Super Contributor
timestamp: August 14, 2020, 10:21:00 pm
content: Quote from: aristarchus on August 14, 2020, 10:00:33 pmAnd no, I don't know of one, but I've not seriously researched this. The few linear amps I glanced at all had switchable filters. But I'm fairly sure that it's possible -- it may not be practical given the desire for power efficiency, but it should be possible to optimize for low distortion.

author: aristarchus
author_rank: Regular Contributor
timestamp: August 14, 2020, 10:52:59 pm
content: Quote from: fourfathom on August 14, 2020, 10:21:00 pmWell, for many decades now there is no company that has achieved this in the PA area, transceiver companies eg Yaesu, Kenwood, Icom, Elecraft, Flexradio, TenTec, you name it.That definitively means something.

author: janoc
author_rank: Super Contributor
timestamp: August 14, 2020, 11:14:09 pm
content: It is a red herring. Even if you have achieved such PA design somehow, you would also need to guarantee that the driving signal (i.e. your transciever) is clean and not distorted. Otherwise you would be only perfectly linearly amplifying all the trash that your radio is producing.How are you going to achieve that when the radio the operator is connecting to the PA can be literally anything? From something like a Michigan Mighty Mite up to a $1000 factory made transciever.

author: fourfathom
author_rank: Super Contributor
timestamp: August 15, 2020, 03:43:01 am
content: Quote from: janoc on August 14, 2020, 11:14:09 pmIt's not a red herring, it's a hypothetical situation. I did stipulate that the combination of driver and amplifier had to be clean enough to comply with regulations. I will gladly agree that commercial power amplifiers include filters for the reasons you point out.But there plenty of ways you can generate an illegal signal even with filters in the power amp -- those only attenuate harmonics but there are many other sorts of distortion. And I still say that it may be impractical to build a no-filter system, but it's not impossible.

author: janoc
author_rank: Super Contributor
timestamp: August 15, 2020, 08:10:51 am
content: Well, OK, we can argue about semantics however in practice such a system would be possible only for completely dedicated transmitters, such as some sort of a beacon or telemetry transmitter - with only one or very few fixed frequencies, one modulation and everything closely integrated. And even there the builder will probably add an LPF for a good measure, just to be on the safe side should anything go wrong.Not when talking about a general purpose power amplifier, as is commonly understood in HAM radio.QuoteSure. But nobody claims that a filter is a fix-all-cure-all solution.QuoteAs said above - that's a theoretical debate with little to no bearing on practical amateur radio construction. You or your employer may have the tools and a lab full of $$$ test equipment to both design such systemand to verifythat it really performs as it should. An average HAM does not - they have to rely on the manufacturer's specs and what they hear on their receivers. And pray that when the complaint from a neighbor comes and the regulator with a van full of gear turns up, they will measure low enough so that the eventual fine is tolerable.So for all practical purposes the gear will be "overdesigned" to stay on the safe side. It really isn't because people love to throw money out of the window for useless filters, especially when we are talking PAs in the 100-1000W range (which is what most people imagine when talking about a "linear" or "power amplifier", not a puny 5W single transistor circuit).

author: fourfathom
author_rank: Super Contributor
timestamp: August 15, 2020, 07:23:01 pm
content: Quote from: janoc on August 15, 2020, 08:10:51 amIf we can agree on the goals I think we can agree on most everything else. If the goal is a practical general-purpose high-power amplifier (say >= 10W) then the switched band filter approach is probably the best overall design.However, I was responding to the OP's initial idea of a custom SDR design. In that case, a low-power amplifier matched to a specific driver might be designed without switchable output filters. For that matter, if the antenna will be some extremely narrow-band design such as a small loop, then pre-filtering may be unnecessary. But this requires difficult design and good test equipment, perhaps out of reach of the typical ham builder -- but not impossible for an expert, which is all I was claiming.So broadly speaking, you are correct.

author: paul002
author_rank: Regular Contributor
timestamp: August 16, 2020, 01:00:13 pm
content: It's fun to read all the reactions in this thread. I think there are a lot of initiatives for lowcost SDR's. But the main issue is the software and the fast changing components. Some designs really use expensive components like AD converters, FPGA's etc. Which also need some steep learning cycle. I like a lot the approach op I2PHD he uses a single board stm32 as SDR.https://www.i2phd.org/armradio/index.htmlBased on this I am designing a arduino shield board for a stm32f746 disco board ($50)with an si5351 pll, mixer LPF and a VGA AD8396. Component cost around 20$ Maybe it can be made cheaper the VGA is most expensive. But the biggest challenge will be the software, it should be nice to have an opensource project (software only) for which you can build your own hardware. I already have most modules (I also saw on this site that a lot of other people also have designed bpf's, lpf's if units etc.). So building the hardware for SDR will not be the problem.

author: janoc
author_rank: Super Contributor
timestamp: August 16, 2020, 01:16:46 pm
content: Quote from: paul002 on August 16, 2020, 01:00:13 pmGNURadio is not good enough? Or Quisk? Or CubicSDR? What more open source, free and available software do you need?You can even get a ready-to-go SD card with these for an RaspberryPi, so no need to mess with compiling and configuring them yourself:https://pisdr.luigi.ltd/I don't see much of an advantage in doing this on an STM32 micro** when you will still need user interface somewhere, requiring a big, expensive micro like STM32F7 series.Something like RPi costs 20-30 bucks can both talk to the low level hw like ADCs and run "grown-up" software like GNURadio or Quisk. The price will end up being similar, as will the form factor if you use a small cheap TFT touch screen with it - and the usability much better and the amount of required effort to set it up much less.Folks, do some research before you post that "something is needed".** I mean if you are interested in actually operating the radio. If you are building it to learn SDR or DSP processing or just for fun, by all means, knock yourself out.

author: DH1AKF_Wolfgang
author_rank: Contributor
timestamp: August 16, 2020, 02:53:27 pm
content: If you only need an SDR receiver, I can recommend the suggestion of DD4WH. It uses a Teensy 3.6 as processor and also the SI5351 as clock. However, an I/Q- mixer is at work here, which allows a real digital processing (after the AD- converter). I have successfully built a receiver based on this proposal:Software is written with the Arduino IDE, in the Teensyduino version.This Receiver is able to decode AM,SSB, and also wide FM in the VHF band.Links to the project:https://github.com/DD4WH/Teensy-ConvolutionSDRand my own version:http://www.wkiefer.de/x28/DD4WH_RX.htm

author: aristarchus
author_rank: Regular Contributor
timestamp: August 16, 2020, 05:34:31 pm
content: Here are two SDR implementations from a fellow ham from belarus, cheap parts from aliexpress, could be read with google translatehttp://www.cqham.ru/forum/showthread.php?35923-DDC-DUC-%F2%F0%E0%ED%F1%E8%E2%E5%F0-%F1-%E8%ED%F2%E5%F0%F4%E5%E9%F1%EE%EC-Ethernet-%E8%E7-%EC%EE%E4%F3%EB%E5%E9-%F1-%C0%EB%E8http://www.cqham.ru/forum/showthread.php?37592-%C1%FE%E4%E6%E5%F2%ED%FB%E9-%E4%E2%F3%F5%EA%E0%ED%E0%EB%FC%ED%FB%E9-%EC%EE%E4%F3%EB%FC%ED%FB%E9-DDC-DUC-%CA%C2-%D3%CA%C2-%CF%D7And here again is an idea from the author of hermeslite to have a SDR from inexpensive parts from aliexpress like the implementations abovehttps://groups.google.com/g/hermes-lite/c/_xhZanzt9KE/m/SqQuimxHCAAJ

author: janoc
author_rank: Super Contributor
timestamp: August 16, 2020, 11:52:40 pm
content: Quote from: DH1AKF_Wolfgang on August 16, 2020, 02:53:27 pmIs that a Tayloe mixer? That reminds me a lot of the good old SoftRock kit (http://www.wb5rvz.org/softrock40r/index?projectId=20), it even uses the same chips. However, that one used PC soundcard as ADC and Si570 for clock (Si5351 got "discovered" only later).BTW, if you are using Si5351 as clock, you can ditch the 74LVC74 clock divider and create the 90 degrees phase shifted clock directly using two outputs of the Si5351. It will save you a few components, space and having to run at 4x frequency.

author: DH1AKF_Wolfgang
author_rank: Contributor
timestamp: August 17, 2020, 04:26:15 am
content: Thank you, Janoc,for the hint with 90 degree phase clocks from one SI5351! So one can elimininate the clock divider.I found the example code from Jason Milldrum immediately.https://github.com/NT7S/Si5351andhttp://wp.andreas.bieri.name/myblog/2016/05/24/si5351-democode-phase-einstellen/Now it is not very hard to match the software, but my PCB is now timed out... But reception of the 2m- band is now easy to implement.Yes, the FST3253 is a Tayloe mixer.

author: janoc
author_rank: Super Contributor
timestamp: August 17, 2020, 10:37:13 am
content: Quote from: DH1AKF_Wolfgang on August 17, 2020, 04:26:15 amI am not quite sure how fast FST3253 can go, though. I have seen it used only for HF reception before, not VHF. It is just a puny 4:1 multiplexer, not a dedicated mixer. Given the 6ns propagation delays and the input capacitance, 2m is likely going to be pushing its capabilities. You will be likely better off using two ADE-1s and two clocks from the Si5351.

author: DH1AKF_Wolfgang
author_rank: Contributor
timestamp: August 17, 2020, 01:32:21 pm
content: You are right, Janoc:better would be a dedicated mixer. Just I have ordered 2 pcs. ADE-1H+.In my shack I found some IAM81008, but they are specified only above 50 Mc.If someone is interested: I have constructed and built a stand- alone SSB transceiver, based onRedPitayaand anSTM32F7 Discoveryboard. But the price for the components exceed 100 € widely (in summa about 570 €)!Second builder was Jacinto (CU2ED), and DL7ASK has also built my "DiscRedTRX:Here is a short article about building and ingeneering (in German):http://www.wkiefer.de/x28/Red%20Pitaya.htm

author: cdev
author_rank: Super Contributor
timestamp: August 17, 2020, 05:03:30 pm
content: That looks interesting! The additional cost if for the power amplifier, filters and some kind of interface to the Red Pitaya, its not the total cost, right?Quote from: DH1AKF_Wolfgang on August 17, 2020, 01:32:21 pm

author: DH1AKF_Wolfgang
author_rank: Contributor
timestamp: August 17, 2020, 06:28:14 pm
content: My own cost table was (2016/17):Here is a PowerPoint presentation about the DiscoRedTRX (excuse, in German):https://slideplayer.org/slide/12229306/

author: cdev
author_rank: Super Contributor
timestamp: August 17, 2020, 07:22:54 pm
content: I have always thought that its likely there was an inverse relationship between the number of bits supported by an SDR transmitter and the need for output filtration, in other words, the less bits the more likely the output is to have nasty spurious products, but is that really true? I am really thinking about the need for either band pass filtration/more poles in the filter, and simple LPF, more bits the more likely to be able to just use an LPF.So this seems like an ideal time to be attempting any kind of project because there are so many building blocks available for almost nothing.I've been reading old copies of QEX (not that old) and the sophistication of the various components available in a single chip or board is really improving very rapidly.

author: aristarchus
author_rank: Regular Contributor
timestamp: August 17, 2020, 07:41:53 pm
content: Hi @DH1AKF,If you intent to work on all of the HF bands, it requires a filter bank with 5 or 6 or even more filters, considering that is to withstand 10W the expense (relays, toroids, circuitry parts, pcb, etc) is considerable and the parts list looks to me (excuse me but I do not speak german) that do not include it.Are you operating this rig in your country as it is?

author: DH1AKF_Wolfgang
author_rank: Contributor
timestamp: August 17, 2020, 07:48:16 pm
content: Hello, "cdev",you're always riding on the low pass or band pass filter, but what about interfering intermodulation products within the filtered band? You can't get rid of them that way.A new feature that is also successfully used in the RedPitaya is adaptive pre-distortion. This allows non-linear power amplifiers to be brought to raison.Your objections are correct, but they miss the topic of this thread.

author: DH1AKF_Wolfgang
author_rank: Contributor
timestamp: August 17, 2020, 08:04:53 pm
content: Hi aristarchus,indeed I use my 10W TRX from time to time on air.But in the moment I'm constructing an automatic tuner for my 300W PA. And here I will use a switchable split filter from Russia (ebay).

author: aristarchus
author_rank: Regular Contributor
timestamp: August 17, 2020, 08:09:21 pm
content: Thats nice, from what I know in your country the relevant federal agency is not joking about regulations, (BNetzA or something).

author: janoc
author_rank: Super Contributor
timestamp: August 18, 2020, 08:40:25 pm
content: Quote from: cdev on August 17, 2020, 07:22:54 pmNope, it doesn't work like that.The problems with out of band interference/harmonics are not only because of quantization errors due to the limited amount of bits. SDR isn't really any different than a conventional radio in this regard - e.g. if you generate square wave signal modulation using your SDR (e.g. for CW) and don't use a "key click" filter (whether physical or in software) to round off the edges, you will be spilling harmonics well into VHF, regardless of how many bits your ADCs and DACs use.The type/depth of modulation you use matters, as does the linearity (or lack of it) of any mixers and amplification stages.That's whyaristarchusTheUnnamedNewbie was wondering why 4G or wifi doesn't need a filter - if you design a radio that works only on a single set of frequencies (channels), with a single modulation type, tightly constrained (so no overdriving/overmodulation), you can get away with not having a filter. However, for a general purpose HAM radio (i.e. not some kind of beacon/telemetry transmitter) this wouldn't really work.

author: aristarchus
author_rank: Regular Contributor
timestamp: August 18, 2020, 10:41:09 pm
content: Quote from: janoc on August 18, 2020, 08:40:25 pmme ?? are you sure ??..??

author: A.Z.
author_rank: Super Contributor
timestamp: August 19, 2020, 04:48:36 am
content: here is a full open source sdrhttp://www.steila.com/blog/index.php?controller=post&action=view&id_post=18

author: janoc
author_rank: Super Contributor
timestamp: August 19, 2020, 08:48:34 am
content: Quote from: aristarchus on August 18, 2020, 10:41:09 pmAh sorry, mixed you two up when writing that comment from memory. That was TheUnnamedNewbie, not you. I have fixed my comment.

author: aristarchus
author_rank: Regular Contributor
timestamp: August 19, 2020, 09:19:10 am
content: Quote from: A.Z. on August 19, 2020, 04:48:36 amThats a receiver-only though. it is not a transceiver.From what I understand the OP is asking about TRx.

author: vk4ffab
author_rank: Frequent Contributor
timestamp: August 19, 2020, 09:43:27 am
content: Quote from: TheUnnamedNewbie on August 13, 2020, 09:55:25 amThere is nothing in the law that says you MUST use a low pass filter, if you can design a PA that meets or exceeds the spectral purity laws in your jurisdiction without using a LPF then rock on my friend. However, even the most inefficient class A amplifier is going to struggle to make the cut. Here is the law from here:God i hate how this forum is a PITA to insert images

author: A.Z.
author_rank: Super Contributor
timestamp: August 19, 2020, 09:45:53 am
content: Quote from: aristarchus on August 19, 2020, 09:19:10 amYou're right, but then nobody forbids the OP from adding a TX section (hopefully only covering the Ham bands!!) to that SDR design

author: A.Z.
author_rank: Super Contributor
timestamp: August 19, 2020, 09:50:25 am
content: Quote from: vk4ffab on August 19, 2020, 09:43:27 amI believe that adding an LPF would be a good idea, all in all, even if the SDR unit will give wide frequency coverage, I hope that the TX section will only be used on Ham bands, so adding a switchable LPF would be easier, and by the way, the same people which sells that amplifier kit I posted, also sells a relay switched LPF unithttps://www.qrp-labs.com/ultimatelpfand the LPF modules kithttps://www.qrp-labs.com/lpfkit.htmlthe latter can withstand 10W (or possibly more), so it will fit that 10W amplifier

author: vk4ffab
author_rank: Frequent Contributor
timestamp: August 19, 2020, 09:54:34 am
content: Quote from: A.Z. on August 13, 2020, 06:41:19 amThe problem with the Hackrf is that its not a transceiver, it is a receiver or it is a transmitter, it is not both at the same time and requires another receiver when using it as a transmitter. Also, its signal is not very nice. Take a look close in with a spec-an its quite ugly, intermod, jitter etc, its ok for experiments but its not really good enough to be a transmitter for voice comms. I have one and have used it as a TX a few times, amplifying it 50W.

author: A.Z.
author_rank: Super Contributor
timestamp: August 19, 2020, 10:00:54 am
content: Quote from: vk4ffab on August 19, 2020, 09:54:34 amI believe it's a problem with most SDR unit embedding a TX section; they aren't designed for "Ham use" but to be wideband, so the same approach goes to the TX, a solution to this could be starting from an existing, open design likehttp://www.steila.com/blog/index.php?controller=post&action=view&id_post=18and modifying it to limit its range to the Ham bands or either limit the TX section to the Ham bands only, that way it could be possible to add LPF/BPF to the TX section and obtain a usable SDR RTX

author: vk4ffab
author_rank: Frequent Contributor
timestamp: August 19, 2020, 10:06:15 am
content: Quote from: A.Z. on August 19, 2020, 09:50:25 amGood idea? Sure, but it depends on what you are doing. If your designing a farting novelty gadget and you can meet spectral purity laws without one and pass certification etc, why bother, its BOM costs for no real need. The reality is, I dont think anyone can design a ham amp that does not require filtering. Class AB push pull PA's like the qrplabs one you linked are always going to be non linear enough to require harmonic suppression. Thats just the nature of things. I mostly build CW transmitters and use class C amps, and they obviously require them.

author: cdev
author_rank: Super Contributor
timestamp: August 19, 2020, 06:19:23 pm
content: And I am also asking about what people think on the relative merits of the different designs, in terms of general usability and flexibility. Which ones represent as close to a good long term general ham TRX.With an upgrade path. (if you put it in a box and of course have appropriate filters of needed. (also whats a affordable source of capacitors suitable for use in filters)There are a lot of great projects discussed here.Quote from: aristarchus on August 19, 2020, 09:19:10 am

author: cdev
author_rank: Super Contributor
timestamp: August 19, 2020, 06:30:54 pm
content: I already have a (Softrock) general coverage receiver that covers from 1.8-30 Mhz and seems quite adequate to the tasc of being a ham station's main receiver. If I could build a transmitter on to it, designing itto use the same frequencies and ideally also an external frequency standard, that would definitely meet my requirements. I need some way to verify however that the spurious emissions are as reduced as is humaly possible. The emissions requirements might vary from country to country but the figure 60 db down from fundamental seems to stick in my mind and as I like building filters I dont see any problem getting that.Building my rig that way, even using a quite conventional design (its the receive SDR that matters more to me than transmit) I might even save enough money to build a modest amp. I dont feel as if I need to necessarily follow anybody else's path. I might learn more by turning a bunch of parts into a transmitter, but if I do that, you better believe I am going to need the help of some local hams, preferably some well experienced in the art and science of home building, including testing the output.because there are things you can see in the flesh that dont translate well to the internet and here is where it matters since they would be the folk who would have to deal the most with my dirty signals if I messed up. they and the FCC!Maybe some local radio clubs would help?Most importantly I dont own a spectrum analyzer - which is indispensable for checking spurious emissions, its the one thing that you cant fudge using cheap sdrs, as far as I can tell.If you read the story of the German ham who was using the HackRF as his transceiver he mentions something about his vision being damaged when some government agency raided his shack! ??That made me wonder.Quote from: A.Z. on August 19, 2020, 09:45:53 am

author: vk4ffab
author_rank: Frequent Contributor
timestamp: August 19, 2020, 10:48:54 pm
content: Quote from: cdev on August 19, 2020, 06:30:54 pmLook on n6qw.blogspot.com and Charlie Morris on youtube(has a blog also) and there are others who have designed SDR transmitters/transceivers and have published the details of their builds. You should be able to find what you are looking for there, or at least the inspiration to point you in the right direction.

author: cdev
author_rank: Super Contributor
timestamp: August 20, 2020, 12:43:45 am
content: I would love to see a subgroup for discussion of stable frequency multiplication and division schemes, and generation of needed frequencies from other stable references in various ways.Thats seems to be a quite basic and important thing.There are discussions of that on time-nuts from time to time and I have noticed, those are the posts that I most often end up saving a copy of (or links included in) to disk from there. That must mean something, like that I think knowing this will be useful someday.

author: radiolistener
author_rank: Super Contributor
timestamp: August 20, 2020, 04:33:22 am
content: Quote from: cdev on August 20, 2020, 12:43:45 amThere are two basic option available for ham-radio purposes:1) si53512) si570si5351 is more cheap, but it has more phase noise. Usually si5351 is used for SDR with dynamic range about 100 dB. si570 has much better phase noise, but it's more expensive and don't cover frequencies below 10 MHz.Phase noise affects dynamic range of the receiver. Higher phase noise leads to worse dynamic range. This is why SDR receiver with high dynamic range ADC needs expensive ultra low phase noise oscillator.You can readthis articlefor more details.For si5351 you can find a lot of modules on aliexpress, it is very popular.For example si5351 has multiplier and divider, they can be configured as a + b / c. So, the output frequency is:Fout = Fin * (a1+b1/c1) / (a2+b2/c2)You're needs to setup a1,b1,c1,a2,b2,c2 constants into si5351 registers and get Fout frequency

author: fordem
author_rank: Regular Contributor
timestamp: August 20, 2020, 08:37:25 pm
content: Quote from: cdev on August 12, 2020, 07:58:31 pmI'd just like to remind you that President Trump is building a wall along your southern border to keep the refugee migrants from the developing world out - if things were as rosy as you make them out to be, the migrants wouldn't be risking their lives to reach the US.FWIW - I live in a developing country.

author: cdev
author_rank: Super Contributor
timestamp: August 21, 2020, 12:47:38 am
content: Thank you, I have one (the Adafruit 5131 breakout board) and also have a receiver that uses a 570 so I have a (very as you will see) small amount of experience with both of them. In the case of the 5131 enough to realize that I need to put more energy into breadboarding circuits that use it. The signals coming out of the 5131 - are square waves, of course and so they have to be used in a square wave using design, for some they are ideal.. Its definitely not a sine wave.. LOL.. looking at the waveform on my scope when I was doing this was before I realized quite a bit that I now know so its time to revisit it with an eye to understanding the proper approach, impedance, signal integrity.I really know quite a bit more than I did then,most of it thanks to the very fine people of this community.

author: cdev
author_rank: Super Contributor
timestamp: August 21, 2020, 01:40:00 am
content: Quote from: fordem on August 20, 2020, 08:37:25 pmI think you misunderstood what I said. I dont want to argue with you about a misunderstanding. Our lives are too short for that.

author: radiolistener
author_rank: Super Contributor
timestamp: August 21, 2020, 08:19:19 am
content: Quote from: cdev on August 21, 2020, 12:47:38 amSquare wave consists of many sine waves. It's not a problem with proper filtering. Just put square wave through proper low pass filter and you will get sine waveThe main pearl of si5351 and si570 is that they provide output with very low jitter. si570 even better for such purpose. So, after proper filtering you will get very clean and stable sine

author: janoc
author_rank: Super Contributor
timestamp: August 21, 2020, 08:21:31 am
content: Quote from: radiolistener on August 20, 2020, 04:33:22 amFor HAM radio use, especially on HF, the phase noise of Si5351 is more than sufficient, especially when the output is buffered (see e.g. here:https://www.qrp-labs.com/qcx/phasenoise, here:https://nt7s.com/2014/11/si5351a-investigations-part-7/and here:https://groups.io/g/BITX20/topic/si5351a_facts_and_myths/5430607).Also worth keeping in mind is that Si570 has only a single output, Si5351 has multiple (most commonly 3 but there are versions with up to 8 outputs) - this matters if you are generating I/Q signals or building a classic (non-SDR) transciever because a single chip can generate both the VFO and BFO frequencies.There is also the AD9850/9851 DDS IC which has the advantage that it generates a sine wave output (unlike the Si570/5351 which are clock generators and generate square wave signals).

author: vk4ffab
author_rank: Frequent Contributor
timestamp: August 21, 2020, 08:41:19 am
content: Quote from: cdev on August 21, 2020, 12:47:38 amSquare waves are perfectly fine. Mixers are non linear devices, so square waves are perfect with diode mixers as they ensure the diodes are fully switched on and off. Even my CW transmitters use square waves, amplify them up and use them to slam a mosfet on and off in class c for high power with good efficiency, then recover the sine wave with low pass filtering before it goes up the antenna. There is really no advantage to using a sine wave in all but the most rare circumstances.

author: noreply
author_rank: Frequent Contributor
timestamp: August 21, 2020, 12:57:19 pm
content: I just had aquickread through all the posts - and could not see any mention of the mcHF QRP transceiver (my apologies if I missed an existing reference to it already).This is a great HF SDR - I have just ordered a 'kit' myself.Considering what you get and the performance of this little gem - its not expensive - GBP297 or US$390 at today's exchange rate.Here is the link ...http://www.m0nka.co.uk/The creator of this project is Chris - M0NKA and he is based in the UK.Its an open source project - so if you feel you can contribute and enhance the design / software - I'm sure you will be welcome.Unfortunately despite the project being open source - software - Chris never gave permission for his HW design to be manufactured as a 'commercial fully assembled project' - despite this there are two major Chinese 'clones' - the first company 'cloned' an older design ver .4 - and within a short time another Chinese company 'cloned' the clone - again the older ver .4Needless to say Chris cannot do anything about this.But is you believe in 'due credit' and to encourage Chris to keep enhancing this great bit of 'kit' (currently at ver .64) - then you should not buy any clones and get the original design directly from the creator.I will report my experience - when I assemble the kit next week.This device definitely fits the OP title of this thread ...Urgent need for an open source HF SDR thats affordable ...You must appreciate (see the YouTube reviews) that this device is 'affordable' if you consider what you get for your $Just saying ...

author: janoc
author_rank: Super Contributor
timestamp: August 21, 2020, 01:25:34 pm
content: Quote from: vk4ffab on August 21, 2020, 08:41:19 amWell, that depends on the mixer as well. Not everything is a Tayloe or diode mixer where you often want the sharp on/off transition.Also, the consequence of using square wave local oscillator signal is much higher harmonic content of the resulting signal - you get not only the wanted F+LO/F-LO signals but also quite strong products of all the odd LO harmonics with the original signal. So the filtering becomes a lot more critical.

author: radiolistener
author_rank: Super Contributor
timestamp: August 21, 2020, 05:50:34 pm
content: Quote from: janoc on August 21, 2020, 01:25:34 pmBut it is more easy to achieve very clean synthesizer output for square wave. Harmonics are located on large distance from the main carrier, it allows to simplify filtering and use simple filters with wide bandwidth. On the contrary, sine wave synthesizer have a lot of jitter/phase noise which is almost impossible to filter and requires much expensive and complicated filters with very narrow bandwidth.

author: janoc
author_rank: Super Contributor
timestamp: August 21, 2020, 06:52:24 pm
content: Quote from: radiolistener on August 21, 2020, 05:50:34 pmThat's not true for PLL synthesis (Si5351 or Si570) and tuning all over the place (i.e. you can't pick a frequency where the division works out nicely) as is common in HAM radio transcievers. The sine wave generating DDS ICs like the AD9850 or AD9912 have actuallymuch lowerphase noise - and I mean like 20dB lower vs Si570, Si5351 would be even worse.See e.g. here:http://www.hanssummers.com/ddssi570.htmlAgain, for an average HAM application it is very unlikely to matter either way but I think it is important to set the record straight.

author: radiolistener
author_rank: Super Contributor
timestamp: August 22, 2020, 08:56:10 am
content: Quote from: janoc on August 21, 2020, 06:52:24 pmThis is not true, si5351 works much better than AD9850 even for worst case fractional divider. The secret here is that si5351 PLL works at almost 1 GHz frequency and has very cool multisynth technology which allows to setup fractional multipliers/dividers with high precision.Quote from: janoc on August 21, 2020, 06:52:24 pmThis is also not true. I have AD9851 it has very dirty, noisy and very spurious output. si5351 has much more clean output. I tested their spectrum.Also there is experience with replacement of AD9850 with si5351 in a hand made amateur transceiver. si5351 provide less spurs, less dead frequencies, less whistles and better dynamic range for superheterodyne receiver.si570 is even better, it has worst case RMS jitter about 1-2 ps, or worst case peak-to-peak jitter 14 ps.si5351 worst case peak-to-peak jitter is smaller than 70 ps.For comparison, AD9850 has about 80 ps RMS jitter or even worse.This is why AD9850 and other DDS synthesizers were quickly replaced with si5351 and si570 in ham radio transceivers.AD9912 is a cool thing, at a glance it's jitter performance should be compared with si570, but AD9912 is very expensive.

author: janoc
author_rank: Super Contributor
timestamp: August 22, 2020, 10:15:37 am
content: Quote from: radiolistener on August 22, 2020, 08:56:10 amWell, I am looking at the datasheets and the measurements people did on these chips, soQuote from: radiolistener on August 22, 2020, 08:56:10 amThat's very likely due to extremely crappy Chinese modules with AD9850 (many have extremely bad filters and oscillators) and/or pushing the chip to the upper limit of its frequency range where the signal gets heavily distorted and spurs appear.Si5351 has spurs as well, see e.g. this thread:https://www.eevblog.com/forum/rf-microwave/what-spur-level-to-expect-from-si5351-and-ad9851/Quote from: radiolistener on August 22, 2020, 08:56:10 amWasn't that more because Si5351 is much cheaper, easier to implement and provides 3 outputs vs one on AD9850/9851?Few people who build these transcievers have means to measure these things (or even care so much). And you won't find these ICs in commercially made transcievers, that's for sure.

author: radiolistener
author_rank: Super Contributor
timestamp: August 22, 2020, 10:25:21 am
content: Quote from: janoc on August 22, 2020, 10:15:37 amSo, why you don't see that according to the datasheet, AD9850 output comparator has typical peak-to-peak jitter = 80 ps?While si5351 worst case output jitter is less than 70 ps.Do you want to say that datasheet claim false specification?

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: August 22, 2020, 10:37:47 am
content: Quote from: radiolistener on August 22, 2020, 10:25:21 amI'm an RF guy and not a baseband guy, so I don't really know about jitter and what is 'good', and what is 'bad'. However, the comparator output of the AD9850 is optional, and you don't have to use it. Neither of the two devices really provides a nice phase-noise metric. The AD9850 does provide at least one 'attempt' of a phase-noise plot in the datasheet, and the silicon labs does not (which for the RF guy in me is an immediate red flag).In addition, the worst case output jitter I see in the SI5351 datasheet is not 70 ps, but 150 ps.All in all, this is an apples-to-oranges comparison, and without a good reference-layout of both to measure with a proper phase-noise analyzer, you can't draw any usefull conclusions. In my experience, the phase noise of these kinds of devices are mostly dominated by the skill/experience of the designer implementing the board, rather than the chip itself.

author: radiolistener
author_rank: Super Contributor
timestamp: August 22, 2020, 10:52:48 am
content: The big issue of DDS synthesizers is that unlike a PLL-based system, the higher order harmonics of the fundamental output frequency in a DDS system will fold back into the baseband because of aliasing. These harmonics cannot be removed by the antialiasing filter.This problem is very bad because you cannot fix it with filters.When you clock it with noisy oscillator the problem will be even worse. SNR will be degraded, the same as it happens with any DAC/ADC, clocked from noisy oscillator.PLL-based synthesizer, like si5151 don't have such issue

author: radiolistener
author_rank: Super Contributor
timestamp: August 22, 2020, 10:56:22 am
content: Quote from: TheUnnamedNewbie on August 22, 2020, 10:37:47 amlook at typical column. Max value probably shown for the worst case condition, for extreme hot temperatures, low voltage, etc. Real si5351 performance much better than described in the datasheet. And typical peak-to-peak jitter is much less than specified 70 ps for worst case fractional divider (which is almost not used in the real life). Also it allows to use integer mode to improve jitter performance.

author: radiolistener
author_rank: Super Contributor
timestamp: August 22, 2020, 11:12:54 am
content: Quote from: janoc on August 22, 2020, 10:15:37 amno, the main problem of AD9850 are spurious components that float across the spectrum as you change the output frequency.I think this is just because AD9850 is a DAC based synthesizer, so it has typical DAC problem with harmonics folded into the first Nyquist zone from a half sample rate frequency border. The big problem is that you cannot remove it with filters.si5351 and si570 don't have such issue, because they don't have DAC.They have jitter for fractional divider/multipliers which depends on the frequency, but it is very low, because PLL works at almost 1 GHz.In simple words, si5351 and si570 don't have half sample rate border, it allows to get clean output with no spurs from high-order harmonics folded into the first Nyquist zone due to the DAC sample rate limitation.Quote from: janoc on August 22, 2020, 10:15:37 amyes, si5351 is much more cheaper and produce more clean output than AD9850/AD9851. So what is the reason to pay more and get worse result?There is no needs for sine wave and you can eliminate effect from high-order harmonics existing in a square wave with proper filters.May be AD9912 with 1 GHz sample rate DAC is better than si5351, I didn't tested it. But AD9912 is much more expensive.Quote from: janoc on August 22, 2020, 10:15:37 amActually there is an issue with channel cross-talk, which prevents to use several channels of si5351 if you're needs high dynamic range.So, it's better to use two si5351 with single channel output, than single si5351 with two channel output.

author: fourfathom
author_rank: Super Contributor
timestamp: August 22, 2020, 05:52:54 pm
content: Si5351 - Spurious OutputsI really like the Si5351, but you do have to be careful with the spurious outputs. The fractional dividers are extremely flexible, and they include some sort of phase-adjustment-smoothing that significantly reduces the high-frequency jitter components to a level well below what you would see with a traditional clock-dropping fractional divider. Without this smoothing, the output square-wave would not be significantly different than the output of the most-significant bit of an DDS/NCO, where the pulse is regularly stretched by one clock-cycle.But jitter still shows up, and it can be quite bad when looking at it in the frequency domain. A few years ago I did some spectrum-snooping, using an Adafruit Si5351 breakout board and my SignalHound spectrum analyzer. I was playing with the output divider for these scans, looking at the effect of using the fractional vs integer modes. You will probably get cleaner outputs using fractional division with the PLL feedback divider (keeping the output divider in integer mode), but this does limit the frequency tuning range.Here's the output of the 5351, PLL at 500 MHz and the divider set to 50, giving a 10 MHz output:You can see strong odd harmonics, weak even harmonics, and non-harmonic artifacts. There is some close-in crud on the 10 MHz signal.Here is a close-in look at the 10 MHz signal (1 KHz span)Now, I change the output divider to 49+1000000/1000001. This should result in (on average) stretching the output pulse by 2ns at a 10Hz rate.Lots of low-level spurs, but down 80dB or better. Still not too good if you are trying for a high dynamic-range receiver.A closer look (50 Hz span):We see 20Hz and also many strong close-in 1Hz spurs. I honestly don't know where these are coming from, as I was expecting to see a strong 10Hz modulation.I will eventually set this up again for more study (especially trying the fractional PLL feedback dividers), but for now I present this as a cautionary tale -- it may be more complicated than is initially obvious.

author: radiolistener
author_rank: Super Contributor
timestamp: August 22, 2020, 06:36:29 pm
content: Quote from: fourfathom on August 22, 2020, 05:52:54 pmI think it's better to use high PLL frequency. Higher PLL frequency leads to a smaller jitter for fractional divider. For example for 10 MHz it's better to use PLL = 900 MHz.PLL=900 MHz can be obtained with multiplier (36+0/1) for 25 MHz crystal.For your case, in order to get 10000000.2 Hz, you can use 900 MHz / (89 + 555555/555556).Can you try the following dividers with PLL = 900 MHz on your spectrum analyzer?- 9999999 Hz = 900 MHz / (90 + 1/111111)- 10000000 Hz = 900 MHz / (90 + 0/1)- 10000001 Hz = 900 MHz / (89+888881/888889)

author: fourfathom
author_rank: Super Contributor
timestamp: August 22, 2020, 07:22:06 pm
content: Quote from: radiolistener on August 22, 2020, 06:36:29 pmYes, I will make some measurements with a 900 MHz PLL, but it might take me a few days. I've been running the PLL around 900 MHz lately, I don't recall why I was using 500 MHz for those tests -- it was a long time ago. To make experimenting with that chip easier I put a breakout board and a tiny arduino-style controller in a box. Next, I want to lay out a board with the bare components, a small OLED display, a better oscillator, regulator and some controlled-Z buffering and switchable AC-coupling.

author: vk4ffab
author_rank: Frequent Contributor
timestamp: August 23, 2020, 09:07:49 am
content: Quote from: janoc on August 21, 2020, 01:25:34 pmHow does the saying go, Good enough for Elecraft, Good enough for me. Terminate the IF port of the mixer with a diplexer and win.

author: vk4ffab
author_rank: Frequent Contributor
timestamp: August 23, 2020, 09:27:57 am
content: Quote from: fourfathom on August 22, 2020, 05:52:54 pmThe issue with phase noise was solved a long time ago by Hans Summers et al. The number is greater than -130dbc/hz. Do not load the outputs heavily, use dc blocking caps on the output and the library and code being use heavily influenced the results and use a 27mhz xtal. Why this keeps coming up again and again, i do not know.Elecraft used the SI5351a in their radios, some of the highest scoring radios on Sherwoods list.

author: fourfathom
author_rank: Super Contributor
timestamp: August 23, 2020, 03:59:25 pm
content: Quote from: vk4ffab on August 23, 2020, 09:27:57 amYes, I am aware of that -- I had wanted to explore the effects of the fractional output divider when I was making those measurements. I assume the participants in this thread already know of Hans' work, but for completeness here are links to two very useful papers from Hans:http://qrp-labs.com/qcx/phasenoise.htmlhttps://qrp-labs.com/images/news/dayton2018/fdim2018.pdfIf I'm not mistaken, the significance of 27 MHz vs a 25 MHz xtal is that the 27 MHz one makes hitting the WSPR modulation frequencies easier. But the nice thing about fractional dividers is that you do have excellent resolution by shifting the numerator and denominator together. For example, changing the output divider from 90+1000001/1000000 to 90+1000002/1000001 gives a very small step indeed; with a 900 MHz PLL, this step is about 0.11 uHz (did I calculate that right?). So I'm not sure how critical this 27 MHz is. Perhaps the glitches are worse when the fractional denominator is changed? Or perhaps the 27 MHz xtal lets Hans use divider values that generate a higher "dither" frequency, letting the PLL filter do a better job of cleaning up the output? I'm just guessing here.

author: fourfathom
author_rank: Super Contributor
timestamp: August 25, 2020, 06:32:57 am
content: Quote from: radiolistener on August 22, 2020, 06:36:29 pmHere are some plots, with a 25 MHz xtal and the PLL running at 900 MHz. The +1Hz spectrum looks virtually identical to the -1Hz one, so I'm only attaching the the 10.000... MHz and the -1Hz ones:10.000... MHz, PLL div 36, output div 90.The xtal driving my '5351 is a bit off-frequency, so when I set up for a 10 MHz output the actual frequency generated is a perhaps 150 Hz low.9.999999 MHz, PLL div 36, output div 90 + 1/111111What has me surprised is how these same spurs show up any time I generate a 9.999999 MHz clock, regardless of the dividers. I've tried fractional PLL dividers, fractional output dividers, even both fractional at the same time with prime numbers , and with the VCO frequency set at numerous frequencies between 600 and 900 MHz. These strong close-in spurs seem to occur whenever I set the '5351 to within a few hundred Hz of a value on a 1 MHz multiple (actually, I've only tried a few discrete frequencies, so it's probably more complicated than this.)At this point I have about a hundred spectrum plots, and a few phase noise plots. I've done tests with a 10 MHz bandpass filter, in-line attenuators, and with a known-clean 10 MHz TCXO to verify that my spectrum analyzer isn't generating these spurs. I will probably put all these on my blog (too much stuff to post here), and I do hope that someone else can try to duplicate or refute my results. I did try to compare the spur generation of the PLL dividers vs the output dividers, but in my tests I didn't see much difference, at least with the close-in stuff. I suppose the good news is that most ham-radio-related frequencies are probably going to be far enough away from these trouble-spot frequencies that the spurs are far away and small.I wish I knew the cut-off frequency of the PLL loop filter, but I suppose you might be able to figure that out by looking at the way the spurs roll off. The phase modulation generated by a fractional divider will be an asymmetrical sawtooth, and this should have a characteristic set of sidebands. But the 5351 does have some sort of output divider phase-smoothing function, so that's going to complicate any attempt at analysis.But some frequencies seem to be quite problematic. Here's an example -- with a 25 MHz xtal, generating a 25.000010 MHz output gives you this:PLL divider 25+1/100000, output divider 25. Setting the PLL divider to 25 and the output divider to 24+999986/1000000 gives virtually the same picture. So does running the VCO at a much different frequency.Any thoughts?And by the way, Hans said that the only reason he uses a 27 MHz xtal is because it lets him hit the WSPR frequencies precisely.

author: Lord of nothing
author_rank: Super Contributor
timestamp: September 26, 2020, 08:09:04 pm
content: Does anyone here own a Xiegu Radio?Where does the come from? Sound Chinese to me.The X5105 look interesting to me. I would need a Radio that support: NFM on CB Band (yes in Europe NFM is use mostly...), SSB with >10khz Bandwith for Digital Radio (I dont think the can decode it inside so I will use my Tablet for with "Dream")Thanks

author: cdev
author_rank: Super Contributor
timestamp: September 29, 2020, 01:47:57 am
content: Do you have an amateur radio license?Any HF radio requires a ham license. Get one, and then, yes, i do think its Chinese and its probably a pretty good deal. Xiegu radios seem to be well rated by their users.I wouldnotexpect a ham radio to be legal for CB in europe but I don't know. Ask.Quote from: Lord of nothing on September 26, 2020, 08:09:04 pm

author: cdev
author_rank: Super Contributor
timestamp: September 29, 2020, 01:57:30 am
content: Hi, please keep us in the loop here, that sounds just perfect for me because I have lots of time now and like to put kits together, my success rate with kits has been quite good so far. Saving money is important to my being able to do it. Also i will understand it much more if I help build it.It looks like a beautiful radio. I have been following it ever since it was first announced.Quote from: noreply on August 21, 2020, 12:57:19 pmThanks for telling us the price, its a bit more than I wanted to send but its better integrated/standalone radio is worth more.Acan it be operated connected to a computer (for a bigger screen) too?

author: Lord of nothing
author_rank: Super Contributor
timestamp: September 29, 2020, 08:44:32 am
content: Quote:palm:Who say its one?I would use them as Commercial one.