SDR overload - Page 1
Forum section: electronics / rf-microwave

author: djacobow
author_rank: Super Contributor
timestamp: January 16, 2016, 09:00:18 pm
content: Not nearby signal overload, options overload.I'm interested in getting a quality SDR receiver that will not break the bank or frustrate me with narrow sampling b/w, birdies, low snr, etc. I have a handful of RTL-SDRs, which have been kinda fun, but a disappointment when really digging in. I also have a Fun Cube Dongle Pro+, which works nicely, but is limited to 192kHz b/w. Under $500 (including potential upverter) would be my range.My main interest is casual HF / SWL listening using ready made software (HDSDR,SDR#,gqrx,etc), as well as some simple decoding projects using gnuradio or raw handling of the buffers -- so a clean SDK+API is desirable, too.I cam across this list of devices:https://en.wikipedia.org/wiki/List_of_software-defined_radios#cite_note-65and it made my head spin.I notice also that many won't tune to HF, so that means using an upverter, so I'd guess I'd be looking for a cheap, good one of those, too. :-)What do you guys like?

author: cdev
author_rank: Super Contributor
timestamp: January 16, 2016, 10:06:46 pm
content: I would get a SoftRock RX III, and a cheap $11 RTLSDR for VHF.I agree- the combination of RTLSDR and upconverter is just not adequate for serious HF listening and you can spend endless amounts of time trying to fix it, but you're far better off starting with a better HF sdr, but not spending a lot of money.The ultimate determinant of your ability to receive weak signals with a softrock style radio will then become your sound card.Especially if your computer has decent internal sound, you'll have better results with something like a softrock, once you get it all set up right. Its literally like day and night.I could show you how hugely different it is visually, if you want.What kind of signals do you want to listen to?

author: retrolefty
author_rank: Super Contributor
timestamp: January 16, 2016, 10:12:01 pm
content: I'll be following your progress. I just pulled the trigger on a SDRplay RSP, a $150 job with seemingly impressive specs.http://www.sdrplay.com/index.html

author: cdev
author_rank: Super Contributor
timestamp: January 16, 2016, 10:15:15 pm
content: Retrolefty,I'm sure we would all be interested in hearing your impression of it once you get it.

author: djacobow
author_rank: Super Contributor
timestamp: January 17, 2016, 01:29:43 am
content: Quote from: cdev on January 16, 2016, 10:06:46 pmAlready have the RTLSDR, as well as 2m/7cm transceiver that also receives over a range much broader than its bands, so VHF/UHF are covered.Quote from: cdev on January 16, 2016, 10:06:46 pmI'm fairly new to the hobby, so I don't know. For now, just SSB voice over 80/40/20/10, but also going to try to learn CW. I didn't understand the popularity of CW until I started listening and realized that you can make out a CW signal much farther away and weaker than an equivalent power SSB. Hearing is believing. I'm also interesting in writing and testing decoders for various digital modes.

author: donmr
author_rank: Regular Contributor
timestamp: January 17, 2016, 05:38:33 am
content: One major limitation of many of the SDRs with very broad coverage is that they don't have the bandpass filters that conventional transceivers do. This means that they can be overloaded by strong broadcast signals or even noise that is far outside the band you are trying to listen to. Notice that part of the HPSDR set is a board of bandpass filters.

author: Kalvin
author_rank: Super Contributor
timestamp: January 17, 2016, 01:17:47 pm
content: Adding a box with external bandpass filters should not be too difficult, though. Controlling the bandpass filter selection can be made manually (easy with rotary switch) or if one can hack existing SDR-software, controlling the bandpass filters with relays is also feasible.

author: nowlan
author_rank: Frequent Contributor
timestamp: January 17, 2016, 01:46:27 pm
content: What happened to hackrf or bladerf?http://shop.hackrfblue.com/?product=discount-basket-hackrf$150us or 230$http://www.nooelec.com/store/hackrf.html$315.I recall these sold out a year ago. No progress?

author: mehdi
author_rank: Regular Contributor
timestamp: January 17, 2016, 05:26:36 pm
content: I own HackRF, SDRPlay, SoftRock, Avala, RTL-SDR and FunCube .When I'm in the office and want to tune to ham bands, I either use my Icom R72 or Softrock.But on nearly all other occasions, I prefer SDRPlay. Unlike Softrock, it does not need a computer with sound cards.I even use it with my Windows tablet as a portable SDR solution.HackRF is not good for SWLing (It's more of a wide-band radio research and experimentation device, than a high quality receiver)There are more capable and high quality SDRs for HF (like Elad's products), but they're all expensive.SDRPlay is really good for the price (especially with HF coverage)Two notes from my experience:* There are FM images in VHF/UHF range, so you need external band-stop filters (like this:http://lna4all.blogspot.com/2015/10/diy-fm-trap-or-88-108-mhz-band-stop.html)* It's better to use a shielded USB cable (the one with ferrites)As one of the members said, these SDRs can not beat commercial receivers with lots of bandpass filters.

author: cdev
author_rank: Super Contributor
timestamp: January 17, 2016, 06:50:35 pm
content: One cool thing about what appears to be a growing DIY SDR community is the emergence of aftermarket or standardized SDR hosting platforms such as the "Mobo" project. The Mobo appears to have evolved around the 6.x series Softrock rx/tx which was modifiable to make an all band transceiver. Basically, people have now created fairly standardized upgrade paths with this mobo being a good example, its a sort of backplane that can host filters, antenna, BPF Rx filters, LPF Tx filters, PAs, antenna T/R switching and so on. They are controllable via (mostly) AVR based hardware that speaks via i2c and USB/serial IO.BTW, Softrock Rx does contain four switchable BPFs, so image problems are minimal compared to RTLSDR. OTOH, you're limited to what appears to me to be a bit less than 192 kHz.But on HF, when you are receiving a great deal more signal which previously would have been down in the noise, seeing 192 kHz all at once seems huge. In practical terms, you almost never "need" to see that much unless you are doing a rapid band survey for EMI, (and in that case its really useful, even more bandwidth is useful)

author: modelman
author_rank: Newbie
timestamp: January 20, 2016, 01:22:59 am
content: FWIW -I have been using an AFEDRI Net SDR for casual listening. It uses a 30MHz antialiasing filter. Although it doesn't use any BP filters it is a 12bit A/D DDC and is quite tolerant of moderately high signal environments. One must only avoid using excessive RF gain.ModelmanQuote from: djacobow on January 16, 2016, 09:00:18 pm

author: piranha32
author_rank: Unknown
timestamp: March 01, 2016, 06:28:45 am
content: I have several RTL dongles, both versions of Funcube Dongle, RedPitaya, but the radio I really like is BladeRF. It's not the cheapest, but you did not define how big is your budget; However, out of all the budget-priced radios I think this one offers the best price-to-features ratio. The original board goes down only to 300MHz, but with transverter board the usable continuous coverage spans from less than 1MHz up to 3.8G. Using direct sampling ADC input it should be possible to go down to single kHz (I haven't tested it). In addition to the receiver, the board can also generate RF signals (identical frequency span). Using USB3 connector and computer sufficiently powerful CPU you can transmit and receive up to 28MHz wide chunks of spectrum.Another option for a receiver may be FDM-S2, however the maximum bandwidth is narrower than for bladeRF. If you have bigger budget, take a look at USRPs from Ettus Research.Stay away from HackRF. The price may look attractive, but with only 8 bit ADC and wider converted RF spectrum it can be even worse than RTL dongle. I talked with several users of this board and they all complained about low dynamic range.It's just too expensive to be cheap, and to cheap to be good. Better spend money for one of the receivers with higher resolution ADCs.

author: djacobow
author_rank: Super Contributor
timestamp: March 03, 2016, 08:09:46 pm
content: My latest receiver is an SDRplay RSP-1. I got it form HRO for $149.So far I like it a lot. It's better than the others I've owned, for sure. It can sample 8MHz wide -- much more than I need for most purposes, and has an array of front-end pre-filters that switch in automatically. When I'm on the HF ham bands, they do a good job keeping out nearby high power FM. Unfortunately, the bottom filter is 0-12MHz, so I still get plenty of energy from nearby commercial AM when I'm on the lower amateur bands. :-( A tuned antenna system helps. I'm using a G5RVjr, so I can't use 80m or 160m, but I suspect if I did, I would be dealing with lots of commercial AM interference.That said, I'm reasonably happy for the time being.

author: babysitter
author_rank: Frequent Contributor
timestamp: March 03, 2016, 09:38:58 pm
content: I've got a EZCAP RTL-SDR stick that is now in use at our local makerspace Schaffenburg, and a FifiSDR Rev.1 for shortwave - as I was attending the Fifi. This has a preselector control included, and one year after the Fifi where they published the Fifi they offered a preselector circuit.

author: justinDavidow
author_rank: Newbie
timestamp: March 04, 2016, 03:33:45 am
content: Quote from: djacobow on March 03, 2016, 08:09:46 pmThanks for bringing this little guy up; I've been looking for something exactly like this and somehow had not come across it!I've heard mixed things about it having a gap from 380-430, which would suck if true as I've got a pile of sensors listening in 406-420MHz. I don't see anything about it on the site; and all documentation I've seen has clearly listed "all frequencies from 100KHz up to 2 GHz." Do you (or anyone else) know if that was a pre-release issue? (they appear to have changed from an F connector -> SMA as well at some point)

author: djacobow
author_rank: Super Contributor
timestamp: March 04, 2016, 03:52:38 am
content: Quote from: justinDavidow on March 04, 2016, 03:33:45 amI tuned in that range much, but I don't think there's a gap. It might have been a legal thing that they somehow got around. I have a 430 MHz thermometer that I can listen for to be sure.

author: Astralix
author_rank: Regular Contributor
timestamp: March 09, 2016, 08:48:54 am
content: Hi!Did you see this one?http://www.m0nka.co.uk/I am not sure if you want to buy a box and use it, or if you're able to assemble one on your own, if that drops the price. But I built that one and it works pretty fine. While the original software is a bit stuck, a team of really good developers forked the software and it is learning new features every week.After finishing my license tests in a few weeks, this will be the station I start off with, until I repaired the IC-720A + 2KL I got as a present.