hybridfree/eevblog-posts huggingface dataset:
Crystal oscillators, cap values and real world testing - Page 1
Forum section: electronics / rf-microwave

author: Chris Wilson
author_rank: Super Contributor
timestamp: February 01, 2018, 07:00:02 pm
content: I have modified a Colpitts style oscillator to run on a different crystal frequency than that for which a series of schematics were available. I used cap values in the capacitive divider given to me by another ham. It doesn't always start reliably. A finger near it or on the PCB will usually get it going. I have no idea how the other ham derived the cap values. What I am needing to know is, is their a bench test procedure where I could play with the cap values and measure something with perhaps a scope to see if I can improve things? My crystals are new old stock and I have no info on them save the oscillate at the right frequency and they are fundamental, not over tone. Crystals "down there" are hard to find in the UK, what would happen if I used a ceramic resonator? Are they less accurate / stable?The values for the divider caps I am using and the feed cap to the buffer amp are typed ON TOP of the schematic. Thanks

author: tautech
author_rank: Super Contributor
timestamp: February 01, 2018, 07:09:49 pm
content: ChrisBy chance I noticed bd139 put something up just the other day you might find useful:https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg1414372/#msg1414372

author: Chris Wilson
author_rank: Super Contributor
timestamp: February 01, 2018, 07:54:55 pm
content: Thanks for that. I had, at the very back of mind, a thought that I had some device with a never used menu option about crystals. Then it came to me, the AIM4170 antenna analyser!!!Lo and behold, it may give enough enough to actually calculate something, we'll see....
Advice for Power divider/combiner - Page 1
Forum section: electronics / rf-microwave

author: pursey
author_rank: Newbie
timestamp: January 31, 2018, 09:39:16 pm
content: Me and my senior student friends trying to design an 800w power divider and combiner at 3Ghz. We use microstripline, silver as conductor and Rogers 6010 as substrate.Which type of divider/combiner types is suitable for our application? So far we worked on Wilkinson and Gysel dividers.This is an old design which is not suitable for our project. But we are curious about which type of divider used can you identify it?Also, do you know any good calculator in order to calculate minimum width for the conductor?Any kind of help/tip appreciated.

author: chrisl
author_rank: Regular Contributor
timestamp: February 01, 2018, 02:56:42 am
content: Looks like Branchline Couplers...https://www.microwaves101.com/encyclopedias/branchline-couplers
#156 Swan Cygnet 270B repair - Page 1
Forum section: electronics / rf-microwave

author: Radio Tech
author_rank: Frequent Contributor
timestamp: January 29, 2018, 02:23:18 am
content: In this video I take a look at a classic old Swan Cygnet 270B that was brought in for repair.Problems:Low transmit powerCloudy meter faceSelf oscillationCarrier balance control inoperable.

author: AF6LJ
author_rank: Unknown
timestamp: January 30, 2018, 08:15:06 pm
content: Good video;Nice recovery on the meter, those are as I remember...0-1Ma and (I think) the coil resistance was 100 ohms.I know this has not escaped you.....Take out the 80-15 meter coils, rewire the band switch a little...And steal the front panel off a Swan 500C with the dial drive and you have a Swan-1011.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: February 01, 2018, 12:24:48 am
content: Quote from: AF6LJ on January 30, 2018, 08:15:06 pmYou are correct on the meter. In fact after further testing it is the same that is used in the Siltronix 1011C/D. Probably all the same in this series.Yes, this reminded me of the Swan 1011 while I was working on it. I was going to mention that in the video but I cut about an hour out of it. Was getting so long and so many other rigs to work on. I had fun with it though. Made over 1 dozen winter field day contacts with it.Thanks Sue.
Using a tracking gen as sweep generator. - Page 1
Forum section: electronics / rf-microwave

author: Jesset1996.5
author_rank: Regular Contributor
timestamp: January 26, 2018, 05:23:18 pm
content: I need to calibrate a Kenwood TS-120s and i need a sweep gen to calibrate the rf board. I have heard before that a tracking gen can be used for this purpose. Is there any truth to this?I need to sweep at 8.83mhz +/- 5 khz deviation and a sweep rate of 5 sec/cm.To set this up i suppose i would need to set the start freq to 8.825mhz and the stop at 8.835mhz

author: danadak
author_rank: Super Contributor
timestamp: January 26, 2018, 09:20:57 pm
content: Tracking generators very handy. But you can use a cheap DDS module,drive it with Arduino, and have Arduino trigger start of sweep. Then usingan RF detector fed to Vertical on scope do a bode plot.Dave Jones did a clever Bode plot with a scope -Lastly you can build a simple log OpAmp converter so that scope scale is in DB. Oruse scope math to create a secondary waveform log plot.Regards, Dana.

author: Damianos
author_rank: Frequent Contributor
timestamp: January 27, 2018, 09:42:36 am
content: If the tracking generator, that you refer to, is part of a spectrum analyzer, then you have what you need.Otherwise, use any generator that have sweep function and supports the frequencies of interest (signal and sweep rate).What is to be used as a detector?

author: donmr
author_rank: Regular Contributor
timestamp: January 27, 2018, 06:46:17 pm
content: The tracking generator on my Rigol DSA does not output a simple clean sweep. It jumps around and often outputs junk. I think the analyzer knows when its at a stable point and only listens then.

author: Jesset1996.5
author_rank: Regular Contributor
timestamp: January 31, 2018, 06:04:06 am
content: I will be using the detector that is mentioned in the service manual. It uses a 2 1n60 diodes with 1 cap between the output and gnd at 100pf and a second cap at 5pf between the input and the first diode.It seems this particular detector is popular with kenwood as they use this same schematic with many of there radios. The schematic is attached.
Using a Vector Network Analyzer as a Signal Generator with Amplitude Modulation - Page 1
Forum section: electronics / rf-microwave

author: Plkmo
author_rank: Newbie
timestamp: January 27, 2018, 03:33:43 pm
content: HiI am trying to configure my VNA to act as a signal generator with amplitude modulation. Basically, I have set the VNA to use a CW power sweep from high to lower power (2 points), with an external trigger (supplied by a low frequency (LF) source) Because the LF signal triggers the power sweep of the VNA, and each sweep generates (or is supposed to) a high power followed by a low power CW (one cycle), I would expect the VNA output to be a cycled CW with the cycle frequency being the same as the LF frequency, which essentially has the same waveform as an amplitude modulated CW. However, I find (by measuring the waveform with an oscilloscope), that the amplitude modulation period seems not to follow the LF signal. Any ideas or has anyone done it before? Thanks.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: January 29, 2018, 05:48:10 pm
content: It could be beneficial to mention the VNA you are using.
High voltage, high frequency amplifier? - Page 1
Forum section: electronics / rf-microwave

author: icon
author_rank: Regular Contributor
timestamp: January 28, 2018, 08:23:36 pm
content: Having a conversation with someone about an application that requires what seems to me to be an unlikely combination of requirements. If it's possible at all I suspect it would be rare and expensive - it requires a signal with a fundamental frequency around 200MHz, but with at least a squarish wave so a low GHz bandwidth - and a peak voltage of, wait for it - 200V. I'm no expert by any means, but this seems implausible. Or is there a commercially available module that would meet these requirements?Ta.

author: PA0PBZ
author_rank: Super Contributor
timestamp: January 28, 2018, 08:42:55 pm
content: Depends on what it is driving, 50 Ohm or 50K would make a big difference...

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 28, 2018, 08:46:09 pm
content: Yeh... into what impedance?High voltages are common in high speed optics and particle accelerators. Such applications are usually more concerned about working at all, than cost or efficiency, so the solutions are usually brute-force, like ramming a high voltage pulse down a 50 ohm coax (200V into 50 ohms is 4A peak), or whatever impedance is necessary for the desired physical effect (usually the load is a small capacitance, so the rise time from a 50 ohm source is acceptable).If brute force and off-the-shelf is acceptable, then any wideband 1kW amp will do. I've probably seen Amplifier Research racks that can do that.Tim

author: dmills
author_rank: Super Contributor
timestamp: January 28, 2018, 08:50:20 pm
content: First thought is "Amplifier Research" may well have something off the shelf, 200V into 50R is less then a kW, so expensive, but somewhat doable.Regards, Dan.Edit, great minds and all that!

author: David Hess
author_rank: Super Contributor
timestamp: January 29, 2018, 02:53:13 am
content: Even oscilloscope vertical CRT amplifiers never reached that voltage level. There was always a quest to improve CRT deflection sensitivity so that a lower voltage amplifier but higher frequency parts could be used.Does the amplifier have to be linear? The restricted operating requirements sound like a job for an untuned class-E design.
SA Demo Ideas - Page 1
Forum section: electronics / rf-microwave

author: mbtronix
author_rank: Newbie
timestamp: January 28, 2018, 01:56:28 pm
content: Hi guys,For my undergrad capstone my group and I designed a swept spectrum analyzer. We are in the process of characterizing the complete signal chain right now, and are considering ideas on how to demo it for the college tech expo.Does anyone have any ideas that might be more interesting than looking at the FM band or hooking up a sig-gen to it? BTW, its bandwidth is from DC to 2G

author: w2aew
author_rank: Super Contributor
timestamp: January 28, 2018, 02:16:53 pm
content: Quote from: mbtronix on January 28, 2018, 01:56:28 pmMaybe take a look at the harmonic content of various signal types (square wave, triangle wave, etc.) and show that the dBc measurements of the harmonic magnitudes match up with the theory for each waveform type.Measure pulsed RF waveforms, and discuss the affects of RBW vs. pulse width and the results you get in the spectrum measurements.

author: Richard Head
author_rank: Frequent Contributor
timestamp: January 28, 2018, 09:00:22 pm
content: Extract the sawtooth freq ramp output and feed it to an external sweep generator. You now have a tracking generator that can be used to characterise filters, attenuators etc.

author: mbtronix
author_rank: Newbie
timestamp: January 28, 2018, 10:23:29 pm
content: Thanks for the idea Richard! That would be pretty interesting to do.I am using a PLL/VCO synthesizer from ADI, so I do not have an analog tuning voltage that I believe you are talking about.Marshall
ADF4350 - VCO range question, 2170MHz possible? - Page 1
Forum section: electronics / rf-microwave

author: Yansi
author_rank: Super Contributor
timestamp: January 28, 2018, 08:14:39 pm
content: Hiplaying with some interesting ideas to use the ADF4350 for, I run into an issue regarding the VCO range. I need to generate two frequencies: 2170MHz and 1085MHz, which is exactly a half of the first one. ADF4350 (4351) did look exact fit for the job, until I realized the bottom end of the VCO range is 2200MHz.I need 2170, which is a 1.36% lower, than the specified minimum. Do you think it is possible or wise to use the ADF4350 slightly out of the range? I currently do not have any of these so I can't test it myself.Do you know any other suitable single chip solution, that could output simultaneously these two frequencies? (2170MHz, 1085MHz) I did search a bit on the Analog Devices website, but could not find any suitable ones.Thanks,Y

author: RadioNerd
author_rank: Regular Contributor
timestamp: January 28, 2018, 08:33:02 pm
content: as far as I know the ADF4350/1 has an output divider... you can thetefore set the VCO to twice the desired frequency and divide it by 2. Or by 4 for 1084 MHz

author: Yansi
author_rank: Super Contributor
timestamp: January 28, 2018, 08:36:00 pm
content: There is only one divider present on RFoutA, RFoutB is directly VCO output. There is no other divider available.I need output of 2170 and 1085 MHzsimultaneouslyfrom a single IC.I do not want two ICs, if it can be done with only one.

author: Yansi
author_rank: Super Contributor
timestamp: January 28, 2018, 08:50:12 pm
content: According to fig 20 from the datasheet, it may be possible to operate at 2170MHz (red line marker), but guessing at reduced temperature range. After reading through the datasheet a bit, cold temperatures <0°C may become an obstacle.

author: RadioNerd
author_rank: Regular Contributor
timestamp: January 28, 2018, 08:51:25 pm
content: sorry I didnt read your post carefully...pushing the spec by 1-2% is probaby no problem as long as you stay around room temperature.The actual VCO range is wider than the spec anyway to guarantee correct operation within the full temperature range (-40 to at least 85deg C).

author: Yansi
author_rank: Super Contributor
timestamp: January 28, 2018, 09:06:59 pm
content: Okay, I will try it, once I'll have a bit of time spared for it. It is one (of many) ideas for some future RF projects. If it'll work from at least 0°C and up, it will be good enough.It is a kind of idea how to make a convertor for a 3400MHz HAM band - I am still trying to attack that one.More orless successfully.3400MHz input, 1230MHz IF1, 145MHz IF2/output. (Hence LO1=2170, LO2=1085)There are suitable SAW filters available for 1230MHz, input filter could be realized using microstrip.
HP 8566B Tracking Gen? - Page 1
Forum section: electronics / rf-microwave

author: Mrt12
author_rank: Regular Contributor
timestamp: January 29, 2018, 06:53:20 pm
content: Hi,yet another TG thread... I recently got that spectrum analyzer. A really nice machine, even though it is known as the 'boat anchor' :-)My network analyzers only cover the range up to 6GHz. It would be handy sometimes to go higher, so I wonder whether that's possible. I have already seen various TGs for the 8566B, but they all cover only the baseband up to 2.5GHz. I know there was a HP 85644 or so, but this is unobtanium and too expensive.So I wonder whether there is a design of a TG at least to 10GHz or so? 20GHz is probably difficult to build, but 10GHz should be possible.On the other hand, I have an 8341A sweeper which goes up to 20GHz, I wonder whether it could be theoretically possible to sync the spectrum analyzer to the sweeper...It would be really handy to be able to make network measurements above 6GHz, but a 8510 NWA or so is probably unobtanium as well :-(Tobias
Video: Using a Smith Chart to design a L matching network - Page 1
Forum section: electronics / rf-microwave

author: w2aew
author_rank: Super Contributor
timestamp: January 27, 2018, 02:51:11 pm
content: Building upon the lessons in videos #274 and #275, this video describes how to design a 2-element L-Network to create an impedance match to the desired system impedance using series and shunt (parallel) inductors and capacitors. The design process is described, and then actual matching results are measured using a Smith Chart on a VNA. PDF of the show notes:http://www.dorkage.com/youtube/Smith_Chart_L-Network.pdf

author: 1design
author_rank: Regular Contributor
timestamp: January 27, 2018, 03:20:27 pm
content: Great video, brought back a lot of memories from UNII really like your no drama approach. Can you work with the team at TEK on adding a frequency offset capability to the TTR500? This would bring it in line with Copper Mountain products.I just saw the TTR500 LE option, that looks like a great deal, can you give us some more detail about all the differences from a standard TTR506A? At first glance it looks like a try on selling lower performance units that didn't pass the cut for the full spec version.

author: German_EE
author_rank: Super Contributor
timestamp: January 28, 2018, 11:38:20 am
content: Ever had one of those 'Ah!' moments when you suddenly realized how something actually worked? That happened twice with this video, once when I found out which combination of LC I should use in a particular situation and once when Alan showed how to calculate the value of a capacitor or inductor from the length of the curve.Once this series is done I suspect that quite a few people will owe Alan a beer (or two). Alan, do you ever get to Friedrichshafen?

author: w2aew
author_rank: Super Contributor
timestamp: January 28, 2018, 02:13:44 pm
content: Quote from: German_EE on January 28, 2018, 11:38:20 amNever been to Europe - so I'll just have to say "thanks" for the virtual beer!
Looking for highly integrated 300-450 MHz receiver with IF/RSSI/AM out - Page 1
Forum section: electronics / rf-microwave

author: jm0112
author_rank: Newbie
timestamp: January 27, 2018, 02:01:10 am
content: I'm working on a project which uses very cheap transmitters to send data from sensors in the field, using an audio modulated carrier (1KHz modulation). This has not only allowed us to keep the transmitters very cheap, but also has allowed reception at a great distance because of the filtering that is possible at the Rx end.For development purposes we've been using off-the-shelf scanners to tune and demodulate (AM) and then passed the audio out to our digital filters. We're now looking for a more practical solution (specifically we're looking to lower the power use of the receiver). There are abundant highly integrated ICs for receiving in the 300-450 MHz ballpark, but almost all contain integrated FSK demodulation, and don't provide access to either the IF, or analog RSSI.What I'm looking for is ideally something like the TI CC1101:http://www.ti.com/lit/ds/symlink/cc1101.pdfor the Semtech SX1213:https://www.semtech.com/uploads/documents/sx1213.pdfi.e. something highly integrated (synth, amps, mixers) but these all seem to have integrated OOK/ASK/FSK demodulators, and no access to the signal before the demodulator. I'd be happy to take the IF out and though an AM demodulator, but I haven't found a chip which provides the IF out.Specifically we want to cover 300-340 MHz - but up to 450 would be advantageous.Current draw in Rx <40 mA.Does anyone have any suggestions?

author: MasterT
author_rank: Frequent Contributor
timestamp: January 27, 2018, 04:33:28 am
content: SiLabs Si4432 the only chip I know allows direct access to IF. Not sure, need to check DS if both I and Q could be routed to pin, I played with Chinese module, and there is one pin is assign to RF switch, so I did me test with one mixer output. Range 240-960 MHz.
Quarterwave power splitter / combiner - Page 1
Forum section: electronics / rf-microwave

author: Senf123
author_rank: Newbie
timestamp: January 24, 2018, 03:20:17 pm
content: Hi everyone!Can aquarterwave power splitteralso work as a combiner for 2 different antenna signals?What is the difference between the type of combiner linked above and Wilkinson power splitter/combiner? Can both work in either way with 2 different antenna signals?Help much appreciated!

author: rfeecs
author_rank: Frequent Contributor
timestamp: January 24, 2018, 07:25:24 pm
content: The difference is, your quarterwave power splitter has no isolation between port X1 and port X2. They are directly connected together.A Wilkinson would have good isolation between those two ports at the center frequency. It could also be used as a combiner, but each signal would have 3dB of loss (assuming the two signals are uncorrelated).

author: Senf123
author_rank: Newbie
timestamp: January 24, 2018, 08:36:31 pm
content: Right so would that mean no signal gets to the X3 port? Only out again to X2 port?No loss in Wilkinson would only be acheived with same signal on both antennas in phase and of same amplitude?

author: rfeecs
author_rank: Frequent Contributor
timestamp: January 24, 2018, 08:46:49 pm
content: Quote from: Senf123 on January 24, 2018, 08:36:31 pmNo, some signal would get to X3. The quarter wave section transforms 50 ohms to 25 ohms, so the signal would be divided between X2 and X3 and some would be reflected back out of X1. A bit of a mess.QuoteYes, in an ideal case there would be no loss.
Setting up WSJTX on linux from scratch with an FT817 - Page 1
Forum section: electronics / rf-microwave

author: jcrubin
author_rank: Frequent Contributor
timestamp: January 15, 2018, 01:17:02 pm
content: Ive put together a two part series on setting up a QRP station using a Yaesu FT817 and Ubuntu Linux, all required hardware, and steps needed to turn up WSJTX from scratch.Part 1 of 2

author: jcrubin
author_rank: Frequent Contributor
timestamp: January 22, 2018, 01:01:23 pm
content: Part 2 of 2

author: bd139
author_rank: Super Contributor
timestamp: January 22, 2018, 01:56:36 pm
content: Thanks for this. That exact set up is on my list of “things to play with”
Video: Using Smith Chart to determine VSWR, RL, and Transmission line effects - Page 1
Forum section: electronics / rf-microwave

author: w2aew
author_rank: Super Contributor
timestamp: January 18, 2018, 03:54:46 am
content: This video shows how to determine complex reflection coefficient (gamma), VSWR, Return Loss given a complex load impedance, and easily determine how this impedance is transformed when a transmission line is added between the source and the load:

author: VK5RC
author_rank: Unknown
timestamp: January 19, 2018, 06:39:04 am
content: Thanks for these videos, I found them extremely helpful.I wish I had one of those nice Tek VNAs! If I use my brain (the hard part) I can do pretty well without though.Regards Rob Culverde VK5RC

author: rx8pilot
author_rank: Super Contributor
timestamp: January 19, 2018, 05:51:44 pm
content: I want that Tek VNA pretty bad now too.My bench has plenty of 80's and 90's machines that are the size of Volkswagen Beatles. Amazing how much fits in a tiny box these days.Alan, your talents are so amazing. Well done!The online smith chart simulator you linked is a cool tool to reinforce the lessons.https://niyeradori.github.io/QuickSmith-Web/index.html

author: slurry
author_rank: Regular Contributor
timestamp: January 19, 2018, 10:38:49 pm
content: Thanks again Alan,you truly have found an area of RF engineering that no one had presented in a more educational way than you did in this video, thanks!
Can someone explain how does a wireless mouse work? - Page 1
Forum section: electronics / rf-microwave

author: sevenofnine33
author_rank: Contributor
timestamp: January 18, 2018, 05:42:04 pm
content: What is the technology behind signals not interfering? How does the signal from a certain mouse "know" which receiver is his?

author: w2aew
author_rank: Super Contributor
timestamp: January 18, 2018, 06:09:10 pm
content: They generally use Bluetooth which includes a number of interference fighting technologies (frequency hopping, pairing of specific devices, etc.).

author: sevenofnine33
author_rank: Contributor
timestamp: January 18, 2018, 06:49:54 pm
content: Yes, I get all that. But why don't two mouses of the same manufacturer, same frequency, and all don't interfere with each other?

author: IanB
author_rank: Super Contributor
timestamp: January 18, 2018, 06:53:12 pm
content: Quote from: sevenofnine33 on January 18, 2018, 06:49:54 pmThey have a specific code that is paired between the sender and receiver.

author: james_s
author_rank: Super Contributor
timestamp: January 18, 2018, 06:56:03 pm
content: The same way you can have dozens of mobile phones in the same area without stepping on each other. It's not a simple RF link, it's closer in operation to a computer network.

author: Richard Crowley
author_rank: Super Contributor
timestamp: January 18, 2018, 07:01:40 pm
content: The majority of wireless keyboards and mice that I see use a proprietary RF link. Bluetooth appears to be the minority implementation. If you look closely, you will see that most wireless mic (and keyboards) come with a miniscule receiver which fits into a USB port. For example, Logitech has some sort of proprietary standard where a single receiver can be used with mouse and keyboard (and perhaps multiple mice/keyboards for whatever reason).But, as @w2aew says, they execute a "pairing" routine where link a particular transmitter with the receiver, whether proprietary or generic Bluetooth.On a side-note, I use several Bluetooth mice (and some keyboards) and I must say that they are at least an order of magnitude less reliable than the proprietary kind. Some must be re-paired every few days. Perhaps BT is more relaible for fixed applications (desktop) vs. mobile/portable use where the receiver is powered up and down all the time.
Does anybody know the Yaesu FT-65R cable pinout? - Page 1
Forum section: electronics / rf-microwave

author: ikrase
author_rank: Regular Contributor
timestamp: January 16, 2018, 05:45:34 am
content: While most ham radio PC programming link cables are cheap usbserial-to-audio-plug adapters sold at markup, the SCU-35 cable used with Yaesu's new FT-65R handheld dual band radio is a bit of a mystery. Does anybody know its pinout and voltage, or whether there is another cable that will work?

author: jgalak
author_rank: Regular Contributor
timestamp: January 17, 2018, 06:37:29 am
content: This might work:https://www.rtsystemsinc.com/USB-55-Programming-and-Data-Cable-p/usb-55.htmI've used their cable with my FT-60R successfully, but that was a different model cable.
Minivna Tiny Reflection Measurement Issue - Page 1
Forum section: electronics / rf-microwave

author: vaughn22
author_rank: Newbie
timestamp: November 25, 2017, 01:26:18 pm
content: I was wondering if someone could help me with this. I recently purchased an MRS Minivna Tiny and I'm observing something weird. The port terminations are supposed to be 50 Ohm, but when in reflection mode, I sometimes get different results depending on whether the 2-port device I'm measuring is terminated with a standalone 50 Ohm load and when it's terminated on the DET port. Obviously, neither termination is EXACTLY 50 Ohm, but the difference is too substantial for it to be normal variation. I observed this around 140 MHz by the way.Is the DET not really 50 Ohm? Is there uncalibrated crosstalk between the DET and DUT ports when in reflection mode if both are connected? what's going on???

author: jjvicente
author_rank: Newbie
timestamp: January 17, 2018, 09:00:36 am
content: Hi,I am deciding whether to buy one MiniVNA tiny and I´ve done some of researching about it.It seems that measurements are not consistent until it reaches its working temperature ~50ºC. Maybe this can be the root cause of your issue...

author: hagster
author_rank: Frequent Contributor
timestamp: January 17, 2018, 06:12:19 pm
content: I tried one a few years ago and though it was very painful use. Today I had a go with an ELAD SNA. Again I thought that was totally useless too.The KC901 looks like about the best cheap VNA that I have seen. There is a review on The Signal Path.
ASK module extended range idea? - Page 1
Forum section: electronics / rf-microwave

author: Danesh_SA
author_rank: Contributor
timestamp: January 12, 2018, 09:03:03 pm
content: Dear friends,Im working on new project that use 4 ASK receiver and one ASK transmitter , just for ON/OFF relay,and im using PT2262 in transmitter ,PT2272 in receiversbut the operation range is too short.i think about how to extend the range of them , and one of my idea is to use repeater between transmitter and receivers,like this:Transmitter ----->Repeater---->Receiver(1)---->Receiver(2)---->Receiver(3)---->Receiver(4)1-Does it works?2-if i want to implement it, just need to connect DATA pin reciever to DATA pin transmitter and it works as repeater?or i should use a couple of PT decoder/encder?

author: danadak
author_rank: Super Contributor
timestamp: January 14, 2018, 03:06:39 pm
content: What range are you seeking ? What is the data rate ?Are you using an external antenna ?There are protocol modes that using very low power can span 1000's of kilometers -http://wb8nut.com/digital/Regards, Dana.

author: Danesh_SA
author_rank: Contributor
timestamp: January 16, 2018, 07:20:46 pm
content: Hello Dana ,Thanks for your replyi use PT2262/PT2272 Remote controller encoder/decoder. yes i use the best antenna that i found in market for 433Mhz ,but i want to build repeater for ASK module .i want to know how to make it, i dont have any idea of the operation of repeater.Best Regards .Danesh
FET triode region mixers/Potentiometric mixers - any experiences - Page 1
Forum section: electronics / rf-microwave

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: January 15, 2018, 05:39:39 pm
content: Hi guys. I'm planning to do a video tutorial about CMOS Triode region mixers (also sometimes called Potentiometric mixers). I am not that familiar with what HAMs like to use, but I don't think I've come across this topology in any HAM stuff before. I have however seen it more than once in integrated circuits.The circuit can be seen in the figure here. The concept is simple - the FETs are biased in their triode region. As such, they appear as resistors. The LO modulates their resistance, and as the gain of the amplifier with feedback depends on the ratio between the feedback resistor and the input resistors, the gain of the circuit depends on the LO. Since Vout = A*Vin, you are multiplying the LO with the RF input, and hence mixing.The great thing about this circuit is that it can operate a good bit above the ft of the process it is built in, at least when we are building a downcoverter. In order to do so, we replace the X component in the circuit with a capacitor, which will "short" the two inputs at RF, and hence the amplifier doesn't need to provide the virtual ground for RF frequencies anymore. The amplifier onlyneeds the bandwidth required for the IF. (this has for example been done to build mixers with a 200+ GHz RF/LO in a 170 GHz ft CMOS process).For upconversion, the amplifier needs to be able to have sufficient bandwidth to drive the feedback network. However, we can "help" it by tuning the capacitance at the input out with inductors (ie, replace X with the right value inductor)For the tutorial video I'm building a downconverter based on this architecture (though just a single ended one, using a BS270 as triode). It works to about 35-40 MHz (I don't have enough RF sources to test it to any higher frequency).Most of the times I see people discussing mixers in HAM use it tends to either be diode mixers or Gilbert cells. Has anyone else used this topology before in radio work? Anything interesting to add about this that is (or isn't) potentially worth mentioning? Any reason why you don't use it?

author: phenol
author_rank: Regular Contributor
timestamp: January 15, 2018, 07:00:36 pm
content: Passive H-mode mixers based on various analog switches are modern these days in HF and low VHF receivers. In pursuit of high dynamic range and IP3 diode ring mixers and other low level active topologies are generally avoided. Proper wide-band termination of all mixer ports is also very important.sometimes people resort to extremes with things like this:http://dl2kq.de/trx/2-1.htmThe power uhf mosfet quad needs 15v or so p-p to fully saturate and maintain sensible conversion loss.
AD831 with BFO as product detector? - Page 1
Forum section: electronics / rf-microwave

author: ChristofferB
author_rank: Frequent Contributor
timestamp: January 08, 2018, 12:57:07 am
content: Hi! I've become a massive fan of those little cheap ebay SMA boards from China, especially the AD831 and LNA ones. I try to use these boards as blocks for building RF gear as much as possible, and i've wondered if one of these would do as product detector for an SSB receiver? the output would be AF, of course, so i'd have to short the RF decoupling cap on the IF side, but would it function as such?I've always had a hard time understanding if a product detector really just is a mixer or what.

author: danadak
author_rank: Super Contributor
timestamp: January 14, 2018, 02:58:44 pm
content: Looks like the 2'ond mixer in this design is used as a productdetector.http://lea.hamradio.si/~s57nan/ham_radio/ssb_80m/ssb_80m.htmlRegards, Dana.

author: cncjerry
author_rank: Unknown
timestamp: January 14, 2018, 10:45:30 pm
content: Did you find the AD831 to be low noise? Decent performance vs a passive like TUF-3 etc? I've had one sitting around since inception, never built out the circuit.Thanks.Jerry

author: ChristofferB
author_rank: Frequent Contributor
timestamp: January 15, 2018, 05:16:23 pm
content: true, that's looks as if it's been done before! i'm gonna try it!-I've had great experiences with the AD831 in previous projects! I can't really compare it to a passive mixer, but considering the convenience in that it also has some gain, it's given me the greatest sensitivity of any SSB RX i've built. Note that this could be the result of more factors than just the mixer, though.
Discrete DC-few GHz FET device? - Page 1
Forum section: electronics / rf-microwave

author: toli
author_rank: Frequent Contributor
timestamp: January 14, 2018, 10:11:11 am
content: Hi All,I have a need for a device that has to withstand about 15V of VDS, and pass a couple 100's of mA's. The catch is it must be fast enough to operate up to a few GHz for the intended circuit.I would prefer some sort of FET device for this application due to requirement from the circuit.I normally design IC's, therefore, I have a very limited familiarity with discrete devices that go up to these frequencies. Short google search resulted in mostly bipolar devices, and all with very limited current handing capability (<10% of my needs).Are there devices that would fit my needs?Any general tips for choosing/using the device to meet the requirements?Thanks.

author: toli
author_rank: Frequent Contributor
timestamp: January 14, 2018, 10:38:43 am
content: Thank you for the infoI will check this device and similar devices.I'm actually trying to stretch it to above 6GHz. The circuit it works with works there, and I would like this additional device to have limited affect on the overall BW.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 14, 2018, 10:44:14 am
content: Is this for switching a 50 ohms termination?

author: toli
author_rank: Frequent Contributor
timestamp: January 14, 2018, 10:44:48 am
content: It will be used as a linear device, not for switching.
Looking for someone in netherlands/belgium area with working SpecAn/Powermeter - Page 1
Forum section: electronics / rf-microwave

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: January 13, 2018, 08:13:07 am
content: Hi guys,I recenetly got myself a HP 8657A that had a "Calibration Reject" sticker on it. After some testing, it seems to work, though I can't be certain because I have nothing to test it with fully.I suspect that if something is wrong with it, it will either be power levels not being within spec, or poor frequency accuracy.I was therefore hoping to find someone in the north-east Belguim/South-east Netherlands area with a decently calibrated spectrum analyzer (and perhaps a powermeter to really verify power levels) that is willing to let me come over for a few hours just to see what is up. I'm open to small fees though I'm just a student so I can't give that much.Just let me know if there is anyone that is willing to do this for me. If so, It'll have to take place after the 30th of Jan. since I have my university exams untill then.The HP 8657A goes from 10 kHz (though specs are only guaranteed to 100 kHz) up to 1040 MHz.
Lumped component RF combiner "tuning" question - Page 1
Forum section: electronics / rf-microwave

author: Chris Wilson
author_rank: Super Contributor
timestamp: January 10, 2018, 11:34:19 pm
content: I built this lumped component combiner to run two lowish power, cheap to build Class D amps combined on 137khz. (2200 meters) Whilst it worked the drain waveforms were like those into a very poorly matched antenna load, so I went with a Wilkinson using ferrite beads to make two lengths of Teflon co-ax act as 1/4 waves and a ferrite cored auto transformer. This works well but I want, for the knowledge, to see if I can make the lumped component one work properly. I believe this to be a narrow band, high Q device. Given I have a decent sig gen and scope and access to a very decent SA, can anyone explain in simple terms how I might "tune" it with regard to coil turns or cap values, on the bench, at low power as from the sig gen, to better resonate it please? Thanks. I link to the lumped device and attach the schematic of the Wilkinson with ferrite, albeit I now use an auto transformer unlike the schematic.Lumped component I want to tweak to my desired frequency is at:https://www.amateurradio.com/630m-wilkinson-power-combiner/Combiner that works fine attached.
Crystal radio Observations with an oscilloscope and signal tracer - Page 1
Forum section: electronics / rf-microwave

author: jcrubin
author_rank: Frequent Contributor
timestamp: January 29, 2018, 01:36:43 pm
content: In this video I break out the Tektronix 2235 oscilloscope and the Heathkit IT 12 to take a close look at a crystal radio I picked up many years ago in Switzerland. The Heathkit will be used so that the radio can be heard in the video itself.This includes an internal inspection as well as an observation of the waveforms at each stage.
Input impedance of RTL Dongle - Page 1
Forum section: electronics / rf-microwave

author: jgalak
author_rank: Regular Contributor
timestamp: January 05, 2018, 07:24:15 pm
content: I have the NooElec Mini2 SDR dongle (this one:https://www.amazon.com/NooElec-NESDR-Mini-RTL2832-Antenna/dp/B00P2UOU72) and am trying to figure out its input impedance.I believe the original, TV-oriented dongles were 75 Ohm, but this one seems aimed more at experimenters and such, so maybe the changed it to 50? Does anyone know? Is there an easy way to check?

author: yl3akb
author_rank: Regular Contributor
timestamp: January 05, 2018, 07:39:39 pm
content: Hi!By looking at board pictures of that dongle it has bare R820T tuner at frontend, with no external wideband matching components. Zin of R820 is 75 ohms. Although not explicitly shown, datasheet (https://www.rtl-sdr.com/wp-content/uploads/2013/04/R820T_datasheet-Non_R-20111130_unlocked1.pdf) has few clues that it is 75 ohm device

author: Yansi
author_rank: Super Contributor
timestamp: January 05, 2018, 09:01:25 pm
content: Although not clearly specified, it is a 75ohm device.
Good Coax Cable Stripper? - Page 1
Forum section: electronics / rf-microwave

author: RCHRDM
author_rank: Regular Contributor
timestamp: January 04, 2018, 04:56:48 pm
content: I looked on Amazon and eBay for a stripping tool that would fit a range of cable sizes from RG-8X to RG-8 and LMR-213. Many of them only seem set up for smaller versus larger cable and have mixed reviews.Can anyone recommend one?Richard
DIYing an LF signal generator with phase modulation - Page 1
Forum section: electronics / rf-microwave

author: philpem
author_rank: Frequent Contributor
timestamp: January 04, 2018, 01:14:37 pm
content: Hi guys,I'm doing some experimenting with LF radio navigation (specifically, Datatrak). I'm at a point where I'd like to generate a test signal...What I'd like to do is generate a pair of LF signals (around 130-140kHz) with phase modulation. I need to modulate the phase at ~1kHz (1ms per step) or faster, ideally with ~1 millicycle (0.36 degree) phase resolution.Both signals would go down the same cable to the RF In of the nav receiver.I was thinking of using a pair of Analog Devices AD9837 DDS chips and a mixer stage (probably with a dual digital pot so I can vary the amplitude of the signal). Question is, is the phase noise of a DDS likely to cause me problems?I need good frequency accuracy too -- the receiver uses a TCXO, an I'm planning to do the same.Are there any other ways to generate a PSK signal with this kind of resolution?The modulation is analog - part of the signalling involves phase-modulating the carrier with a 50Hz or 33Hz modulating signal to transfer data.Thanks.
SimSmith - Real Time Plotting of Smith charts and SWR Plots - Page 1
Forum section: electronics / rf-microwave

author: kerrsmith
author_rank: Regular Contributor
timestamp: December 30, 2017, 02:33:16 pm
content: I have just found a really great program for doing RF analysis and have not seen it mentioned on the forum so though I would put up a few details.The program is called SimSmith and it does real time plotting of Smith charts and SWR plots:http://www.ae6ty.com/Smith_Charts.htmlI first discovered this program when Youtube suggested videos by Larry Benko to me, he has a huge range of videos about this piece software and goes into great detail on many different RF subjects and how to utilise SimSmith to analyse them.https://www.youtube.com/channel/UCKSyLSu4fm_1RHoO3Jvk4YQI thought others may be interested in this software as it so useful to see real time plots of your RF designs.I have been learning the basics of how to use it for the last few days and in the process have been designing a crystal ladder filter and its accompanying matching network. It is so handy to be able to be able to change a capacitance or inductance just by scrolling your mouse wheel over its value and instantly see the changes this makes to your filter's output.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 30, 2017, 08:16:08 pm
content: Hmm, I've got a web app of similar aim,https://www.seventransistorlabs.com/Calc/Filter1~.htmlI could add Smith charts to it. Have received very little interest on it though.Tim

author: kerrsmith
author_rank: Regular Contributor
timestamp: December 31, 2017, 03:07:32 pm
content: You have a very handy looking site, I really like the tools on your calculator page:https://www.seventransistorlabs.com/Calc/index.htmlThe LC Resonance ones will be very helpful as I am always doing these calculations and having all the different ones on the same page is very useful.

author: slurry
author_rank: Regular Contributor
timestamp: January 02, 2018, 06:52:49 pm
content: Quote from: T3sl4co1l on December 30, 2017, 08:16:08 pmWow, thats some handy calculators therethank you!
Setting the bias on an Rf amp - Page 1
Forum section: electronics / rf-microwave

author: Jesset1996.5
author_rank: Regular Contributor
timestamp: January 02, 2018, 05:06:51 am
content: I have a Kenwood TS 690s and a few other radios that need the bias re calibrated either due to age or have had there caps replaced. The manuals are not very descriptive of how i measure the current or have the wrong info all together....Couldn't i just measure the idle current through the 12v power leads?I have herd that some pa decks have a jumper specifically for this purpose but this isn't the case with the radio's i will be working on.Thanks, Jesse J Trimble (AC8WP)

author: LA7SJA
author_rank: Regular Contributor
timestamp: January 02, 2018, 08:17:27 am
content: Hi JesseAccording to the Transmitter Section Adjustment page 124 item 6 (HF final bias) in the service manual (http://www.radiomanual.info/schemi/TS450S_690S_serv.pdf) you should turn down the bias setting to min on VR1 and VR2, record the total current and adjust the bias to the recorded current + 250mA with VR1 then adjust VR2 so that the total current is equal to the recorded current + 500mA.The adjustment procedure of "a few other radios" is in their respective service manuals. Some radios have a link/bridge/connector that can be removed so that you can measure the current in line with the PA output transistors and others use this metode and some have a small resistor in serie (so that you can measure the voltage over the resistor and calculate the bias current) with the PA transistors.73Johan-Fredrik
RF Power Meter IC Comparison - Page 1
Forum section: electronics / rf-microwave

author: ocw
author_rank: Regular Contributor
timestamp: January 01, 2018, 08:03:16 pm
content: I just completed construction of a RF Power Meter which uses an ADL5513 IC. I thought that its specifications best met those that I was looking for--significantly higher frequency response than the common AD8307 IC with as much dynamic range as possible. I previously tried an AD8313 IC but was only partially satisfied with the results due to its limited dynamic range. The ADL5513 seems like a better compromise. Its biggest limitation for battery operation is that it requires four times the current which the AD8307 needs.The first attachment shows the measured frequency response comparison of the ADL5513, AD8313 and two AD8307 power meters that I built. The ADL5513 is rated for use up to 4 GHz, but I could only verify that up to 3.2 GHz due to my test equipment limitations. The AF version didn't loose a tenth of a dB at 6 Hz until the reading became too unstable at 5 Hz. Its response starts to roll off at 100 kHz with it being down 0.3 dB there. The bottom of the graph shows a comparison of their spec sheet +/-1 dB dynamic range. That's followed by pictures of each unit that I built. The smaller AD8307 unit (note its size compared to the BNC connector) was originally made for RF use. After I built the second AD8307 unit with 0.01 dB resolution I modified the smaller one for lower frequency response without worrying about its performance at RF.The AD8313 unit was based on an eBay circuit board special which I couldn't pass up. See:https://www.ebay.com/itm/RF-Power-Meter-Range-0-1-2-4GHz-Radio-Frequency-Power-Meter-1nW-1W-65-0-dBm/221545339277?hash=item339521998d:g:8nEAAOSwJ7RYT-OOThe ADL5513 unit uses a RF board available at:https://www.ebay.com/itm/ADL5513-RF-Power-Detector-Module-1-4000-MHZ/122615908508?hash=item1c8c7a489c:g:cVMAAOSwY~VZdoKGThe AD8307's were completely self built. With batteries, there's not much extra room in any of them.
Any way to make this Si5351A synthesiser drive this FET driver chip direct? - Page 1
Forum section: electronics / rf-microwave

author: Chris Wilson
author_rank: Super Contributor
timestamp: January 01, 2018, 09:29:37 am
content: I use a U3S QRP Labs exciter to drive a PA on 137kHz, and it works fine. The designers, Hans Summer made changes allowing a 180 out of phase pair of signals to come from the Si5351A synthesizer chip with the intention of this being able to drive a push pull Class D FET driver chip directly without a X2 signal being divided and split by a preceding IC, please see circuit below. I tried this but the circa 2.2V outputs of the Si5351A chip is not sufficient to drive the inputs of the IR2110 FET driver.Any ideas please?
FCC etc. for nRF52840 - Page 1
Forum section: electronics / rf-microwave

author: FrankBuss
author_rank: Unknown
timestamp: December 29, 2017, 05:02:47 pm
content: So I found this nice Bluetooth chip, nRF52840:https://www.nordicsemi.com/eng/Products/nRF52840But looks like it needs a PCB antenna. There are application notes how the layout should look like, shouldn't be too difficult, but do I need to do all the certification for FCC etc. when I want to sell it? There are other modules with integrated antenna, e.g. from Silabs. Is certification easier and cheaper with these modules?

author: chrisl
author_rank: Regular Contributor
timestamp: December 29, 2017, 08:29:46 pm
content: If you are planning to sell your device in the U.S. market then you will need to comply the FCC.You may also have to deal with the BQB as well....

author: FrankBuss
author_rank: Unknown
timestamp: December 29, 2017, 08:39:25 pm
content: Quote from: blueskull on December 29, 2017, 08:34:08 pmOk, but needs the module to have the antenna included? I plan to do a quite small device, can't use a module with an included antenna. Is the nRF52840 alone the RF module, or is the nRF52840 with the antenna the RF module?

author: FrankBuss
author_rank: Unknown
timestamp: December 29, 2017, 10:11:45 pm
content: On the devboard it looks like a PCB antenna, with an additional SMA connector:Thereference layoutdoesn't show an antenna, but maybe they mean this with this open RF trace?So I guess this is getting expensive, certifying as intended radiator.