hybridfree/eevblog-posts huggingface dataset:
A cheap VGA adapter as SDR TX - Page 1
Forum section: electronics / rf-microwave

author: A.Z.
author_rank: Super Contributor
timestamp: February 07, 2021, 09:05:37 am
content: just found this interesting blogpost by Oscar Steilahttps://sdr-prototypes.blogspot.com/2021/01/fl2knoise-generator.html?m=1which shows how it is possible to modify a cheap USB VGA adapter to use it as a transmitter or a signal/noise generator and thought that other people here may be interestedfor futher infos also see (linked in the above page too)https://osmocom.org/projects/osmo-fl2k/wiki
GSM PCB antenna - Page 1
Forum section: electronics / rf-microwave

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: January 24, 2021, 01:11:07 pm
content: Hi,I want to know how to design a PCB antenna for SIM800 GSM Module, do we have an open source design file like Altium or gerbers? any app notes, or hints.Thanks

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: February 04, 2021, 11:34:37 am
content: Any one?

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: February 05, 2021, 10:37:21 am
content: These generally don't exist because the antenna depends on the surroundings. An antenna is not limited to it's PCB footprint - your case, surrounding components, in cases like cell phones even the head of the user needs to be taken into account when designing an antenna. Hence, you don't have ready-made solutions that really work well.

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: February 06, 2021, 08:04:38 am
content: I get your points, But they already sell a lot of these antennas!? do we have an app note or design files?

author: ThomasDK
author_rank: Regular Contributor
timestamp: February 06, 2021, 12:26:44 pm
content: Quote from: ali_asadzadeh on February 06, 2021, 08:04:38 amIt's not that simple - in the examples you show the coax is part of the antenna. Changing the length, rolling it up (or removing it) will severely change the performance... Or completely stop it working.If you have no experience in designing F antennas, I suggest you go for a chip antenna. Follow the datasheet recommandations on ground plane size, and you will probably do alright - you will still need to tune it with a VNA.
rydberg reciever development and specifications - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: February 06, 2021, 08:59:00 am
content: https://tech.slashdot.org/story/21/02/05/239207/new-quantum-receiver-the-first-to-detect-entire-radio-frequency-spectrumSO it looks like the instantaneous bandwidth right now is 4MHz and the noise floor is -140dbm (with preamplifier), comparable to normal high end spectrum analyzers but it has a somewhat smaller dynamic rangehttps://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.15.014053But it still makes me think of Akira because it used the word army like 10 times and if you look up a rydberg atom orbital on wikipedia it looks like the brain scanner from Akira. I wonder if they have deep philosophical discussions on what the military is on the development teamwhen is it for sale so I can put something smaller in the basement rack mount
45MHz crystal filter with 3rd overtone 27MHz crystals! Possibile?  - Page 1
Forum section: electronics / rf-microwave

author: Dom13c
author_rank: Regular Contributor
timestamp: December 12, 2020, 04:23:24 pm
content: After constructing BiTx20, version 3( classic , all analog one) ( took me two years of components and test equipment gathering), I had a thought of scratch building uBiTx. I can gather most of the parts except for the 45MHz crystal filter.I'm from India, so buying off digikey is a joke! ( I'd end up paying 4X the price of the components for shipping only!)Upon searching , I found an interesting circuit that uses 27MHz( 9 MHz fundamental) crystals, driven at 5th overtone by adding up an LC filter-ish cricuit at the input for the filtering action.https://www.elektormagazine.com/magazine/elektor-198299/45099What's the opinion of you gentlemen about the performance of this circuit.....Since I don't have an oscilloscope or a spectrum analyser , IF possible could anyone post the overall performance ,characteristics of this kind of filter here!That'd be of great help.....73,Dom13c

author: Gerhard_dk4xp
author_rank: Frequent Contributor
timestamp: February 06, 2021, 01:00:29 am
content: Not impossible, but unpredictable at least without KNOWN crystals and equipment.Maybe it would be wise to get hold of one of these cheap DDS boards from ebayas a reproducible signal source and a power meter board with one of these Analog Deviceslog detector chips.Some 10 dB attenuators would be helpful to check the behaviour of thelog detector chip. At 50 MHz, they can be home-built and verified with DC.It is better to cascade some 10 or 20 dB attenuators than to try 50 dB in one hop.Then you could at least measure the parameters of the crystals you haveand use one of these filter design programs. You would also need some LC high passto suppress the unwanted pass bands at 9 and 27 MHz.A 2-pole filter will not get you a lot of selection. Even the common 9 MHz filters used to have 8 crystals,the cheaper ones still 6. The BW is primarily a function of the frequency difference of the xtals,but it is the far-out attenuation that sucks.vy 73, Gerhard DK4XP
Australia's ACMA proposes fee free 'class licence' for VK amateurs - Page 1
Forum section: electronics / rf-microwave

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: February 03, 2021, 07:23:18 pm
content: Some potentially important changes to amateur radio licensing arrangements are being proposed by ACMA.Instead of paying a fee for an apparatus licence, ACMA are consulting on whether to make it a fee free class licence.A potential risk is less protection from interference and reduced service if we are no longer fee paying customers.The videos below explain the proposals in more detail:Also you can read them on the ACMA website and lodge a submission.https://www.acma.gov.au/consultations/2021-01/review-non-assigned-amateur-and-outpost-regulatory-arrangements-consultation-012021This has already provoked a lot of discussion in the amateur community.

author: Kerlin
author_rank: Regular Contributor
timestamp: February 07, 2021, 02:53:49 am
content: If it is decided to keep the licensing fees it would be because some protection is offered from interference.Only if stated minimum service were to be clearly defined I would then go for that option.Far, far too many Nany's rules in Australia were if I do some thing wrong I get slammed down and if people, who disrespect rules, only get a slap on the wrist.In the case of amateur radio this is apparent were I would be shut down if interfering with others entertainment equipment, even if I complied 100% with the rules.Yet if their entertainment equipment interferes with mine (use of the spectrum) then its viewed by the useless government authorities as bad luck.Not to mention solar systems, large screen displays pool pumps and all the other very clearly non compliant systems that are never ever investigated, free living for some departments to sit back take it easy and do nothing for an easy life, then get retirement benefits.There that's a rambling rambunctious opinion!
Signal Integrity of RF on a VGA/D-sub Cable - Page 1
Forum section: electronics / rf-microwave

author: ROFLCat
author_rank: Contributor
timestamp: February 03, 2021, 12:30:01 pm
content: Hi everyone!I recently got this pretty interesting OCXO second-hand and it has 2 connectors on the can; a female SMA connector for the 10MHz output and a D-sub connector for RS-232 communication, power, and the same 10MHz RF output.I was wondering if I wanna set the OCXO like 2 meters away and have an SMA-terminated cable to get the RF to another board, would there be a problem if I connect an off-the-shelf monitor VGA cable to give it power and also get the RF out of the VGA?I'm guessing the RF output expects 50 ohm impedance. As I read somewhere, these VGA cables have an impedance of 75 ohms. Would the VGA cable cause a lot of reflections and potentially damage the RF buffers in the can?The output RF power is about 11.5dBm.Oh and it needs around 24V @ 1A to power the oven and stuff.Thank you in advance
Cleaning contacts attenuator Marconi 2031  - Page 1
Forum section: electronics / rf-microwave

author: LR
author_rank: Newbie
timestamp: February 02, 2021, 01:46:08 pm
content: Hello,Does anyone have experience with cleaning bad contacts in the attenuator of the Marconi generator 2031.Are there pictures of how you can open this part for cleaning the contacts.Thanks in advance,LR

author: eevjohn
author_rank: Newbie
timestamp: February 02, 2021, 10:48:48 pm
content: Join the Marconi Group on Groups.io.Read the content there and ask if required.Good luck.
NanoVNA saver impedance vs recalculated S1P files - Page 1
Forum section: electronics / rf-microwave

author: BelgianEngineer
author_rank: Contributor
timestamp: January 30, 2021, 11:54:20 pm
content: Hey all,Is someone else observing different impedance between what is displayed in NanoVNA saver and what can be recalculated in excel (from exported S1P touchstone files) through the formula Z = Z0*(1+s)/(1-s). I am observing a couple of Ohms of difference and I am wondering if it could be related to calibration info which may not be exported on the touchstone files.See in the files attached. The spikes on the excel file are me manually entering a couple of values as displayed in nanoVNA saver
3  ghz   rf  probe - Page 1
Forum section: electronics / rf-microwave

author: maxcy
author_rank: Newbie
timestamp: February 03, 2021, 02:24:47 am
content: I have an Auburn Technology 3 GHz RF Probe and have a few questions about using it. It comes with three adapters: a straight through pin, a very short grounding adapter (1/4"), and a longer grounding adapter, about an 1 1/2" flexible ground adapter. From what the manual says I think the straight through adapter is meant to be used with the barrel attached to RF ground for best response. The second best response is the very short (1/4") adapter. I don't see many PCB layouts where a RF ground is that nearby. The third, 1 1/2" flexible ground adapter, seems to be the most useful, although this has the worst response. I've been using it mostly with the lower response adapter with my signal generator and SA, but I am looking for some feedback from someone who really knows how to use this RF probe. I really cannot see how to use the straight through and smaller grounding adapters.73 wt1v

author: coppercone2
author_rank: Super Contributor
timestamp: February 03, 2021, 03:57:01 am
content: well the idea alot of the time is with HF probes of various kinds is that you design your circuit to be friendly with them, often not using barrel thing provided, but instead being able to do something like solder a small coil-clamp to the PCB and then put the probe into that.I.e. you wind a brass? spring around a drill blank slightly smaller then your probe jacket, aim it, solder it to the PCB, and insert the probe into that. It is generally tricky to use them.and you want to buy all those accessories like table-top probe holding arms right?My 3GHz probe never got much use, lol.But that probe looks decent, its a passive probe. Mine is a active probe that is very thick and unwieldy.

author: coppercone2
author_rank: Super Contributor
timestamp: February 03, 2021, 04:16:11 am
content: To obtain consistent and accurate RF amplitude measurements PROPERRF grounding is REQUIRED.Measurements from 100 kHz to 12 GHz can be accurately measured by directly grounding the P-20B’s grounding barrel or by using the Short Ground clip.The Long Ground clip is very versatile and adapts to a wide range of circuits bur SHOULD NOT be used if RF frequencies are above 1 GHz.See TYPICAL P-20B PR0BE RESPONSE for more details located in next section.Ground clips can be changed by grasping the ring portion of the clip and twisting it, while pulling to remove or pushing to assemble. Moderate force may be required.If a good RF ground is out of reach, a 6 inch metal ruler or similar item can often beused to extend the ground to the probe. To minimize inductance, it’s better to makedirect contact with the grounding barrel of the probe.***Their website is pretty specific with what the various probes are good enough for. Make a test PCB that accepts all the probes nicely in the best possible way to specific error.Keep in mind just looking at it, it looks like they gave you some piece of braid or something covered in insulation, not your regular wimpy oscilloscope probe wire with an alligator clip, have a bit more faith in that.
How easy is it to "kill" RF LNA input on SI4735 FM chip - Page 1
Forum section: electronics / rf-microwave

author: Axk
author_rank: Regular Contributor
timestamp: January 28, 2021, 10:53:53 am
content: I'm trying to debug a circuit including the SI4735 chip having no reception (just regular radio-sounding noise) with a thin piece of wire connected through a 1nF capacitor to the FM input pin of the chip.I think the control interface is working correctly, but there's absolutely no reception.I can receive just fine with other receivers in the same spot.I wonder if I killed the input.How easy is it to kill an RF LNA input like this?Is it possible to kill it just measuring resistance to ground or with continuity testing with a DMM?https://electronics.stackexchange.com/questions/545117/si4735-d60-chip-no-fm-signal-reception

author: CJay
author_rank: Super Contributor
timestamp: January 28, 2021, 12:06:45 pm
content: So, blue sky thinking as I've not got experience of that chip and haven't looked at the datasheet (yet), is there a way to control something like a GPIO or indicator pin on the chip, can you read back the registers of the chip, is there for instance an RSSI register you can read out?That way you could work out if the chip is responding to your control words correctly.Does the hiss change if you remove the antenna?

author: Axk
author_rank: Regular Contributor
timestamp: January 28, 2021, 12:55:31 pm
content: The control interface is working fine, I'm using a library from github and it has a good UART terminal based sample that I'm using.It shows that it's tuning, the frequencies it's going through and SNR of around 0 dB (it's around 10-20 dB with RTLSDR) and I can hear it tuning in the headphone.I'm now thinking maybe the exposed trace + capacitor lead between the capacitor and the chip is picking up low frequency noise overwhelming the LNA (I'm testing near a PC)Gonna try in a different room and see if I can get any reception.

author: CJay
author_rank: Super Contributor
timestamp: January 28, 2021, 02:23:45 pm
content: Possible, it does say in the sketch comments to not use it connected to a mains powered PC.It's possible you may have damaged the chip I suppose but it wouldn't be my first thought, my experience is that it's almost always something less 'final' but it wouldn't hurt to have another one.I assume the volume up/down from software works?Is it bad on AM too?

author: chrisl
author_rank: Regular Contributor
timestamp: January 30, 2021, 08:51:06 am
content: Quote from: Axk on January 28, 2021, 10:53:53 amYes, it is possible as the max allowed voltage at the RF input pins is 0.4Vpk while a DMM can have the higher voltage at the leads. The continuity test mode will for sure use even a higher voltage than just the resistance mode.
Can the LTC2208 (Rx-888) SDR be used under Linux ?  - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: March 05, 2021, 06:07:23 pm
content: Could anybody here who owns one answer some questions about it?What's needed to use it under Linux using USB.How is its VHF and UHF performance?(its wideband performance is not important to me.sensitivity/selectivity/signal quality is. )
best op-amp for active biased dipole (electrometer instrumentation amplifier)? - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: January 28, 2021, 04:09:02 am
content: So this is the associate or perhaps counterpart of a active mag loop, the active dipolehttp://www.vlf.it/cr/differential_ant.htmSo I read this article first, and I figured out how to make a high quality version of the 30cmx1M dipole sides, by welding stainless steel sheet to make 'rings' that are stacked on top of each other to make large cylinders. The author found this to be the best way to get the parameters he wants. But then I thought that there might be a better device, so I came across thishttps://datasheet.octopart.com/INA116UA-Texas-Instruments-datasheet-8441915.pdfI thought to use this part with a mechanical chopper to occasionally short out the input to ground to keep DC level down. The bias current is really small, at 3fA, so the rate of voltage rise in an antenna is going to be slow. I think you can also AC-couple it using a array of wet tantalum capacitors.Anyway, the author was under the impression that getting resistance > 100Megaohm is difficult, but that part seems to have.. knocked it out of the park (seems appropriate with what is happening on wall street with the stock 'suggestions' today).So other then the problem of bias current build up, it seems to me that the equation the author is using for bandwidth suddenly has the size requirement decreased by quite a bit going from 100Meg to 1 Peta.I am probobly missing stuff, but it seems simple enough to be worth a try. The noise is also smaller on the part I found.What is your take on this?
What is this connector? - Page 1
Forum section: electronics / rf-microwave

author: mddpub
author_rank: Newbie
timestamp: January 27, 2021, 12:33:39 am
content: What type of connector is CN2? I have not seen this type of test point before. It is very small, perhaps 3.5mm wide. I need an adapter or cable to BNC male so I can attach to a spectrum analyzer to tune a band pass filter on this board.

author: bob91343
author_rank: Super Contributor
timestamp: January 27, 2021, 07:27:18 am
content: That looks like a common connector on many transceivers. I think they are called something like SMx where the x is a letter other than A or B. My Kenwood rigs use those.

author: K7SJB
author_rank: Newbie
timestamp: January 27, 2021, 08:27:30 am
content: Humm,I'm not sure, but it just might be a probe attachment test-point. Im sure Tektronix and quite likely HP made versions of these. I will include a pictures to show you what I'm talking about. Plus, I found this Tektronix data sheet.Don't you just love that homemade test-point? I have to wonder how many readers will start using that trick!- Stan

author: CJay
author_rank: Super Contributor
timestamp: January 27, 2021, 11:48:37 am
content: Looks kinda Taiko Denki to me.

author: mddpub
author_rank: Newbie
timestamp: January 27, 2021, 11:08:23 pm
content: Bingo, it's a Taiko Denki aka a TMP connector. Thanks very much!I google'd it and found this company, sent them the photo and they confirmed it.https://rfconnection.com/tmp-tmp-cables-taiko-denki-connectors/
Subtone VHF ADI AR 147 - Page 1
Forum section: electronics / rf-microwave

author: CACHIVACHE
author_rank: Newbie
timestamp: January 27, 2021, 01:58:05 pm
content: Dear Friends:I have an ADI AR 147 VHF without the sub-tone board and I wonder how I can replace it. I'm looking for simple circuit and how to connect it.Thank you very muchAlberto
Alternative to HP5082-1001 / 1N4456? Diode-coupled pulse sharpener. - Page 1
Forum section: electronics / rf-microwave

author: Qbort
author_rank: Newbie
timestamp: January 27, 2021, 12:39:27 pm
content: Hi all,I hope someone could help me out. I am trying to build a Diode coupled pulse sharpener as detailed inHP AN918Figure 12 (see attached image).The text suggest using HP's 5082-1001 (see attached datasheet). An equivalent to that one seems to be the1N4456 from Jersey semiconductorbut it is not particularly easy to get hold of either.I'm quite a newbie and just trying to get started with this, so have a few question: What parameters of the diode should I care about when looking for an alternative in this application?Any help is greatly appreciated!Thanks in advance.Qbort
Extend spectrum analyzer range from 3 to 6 GHz - The easy way? - Page 1
Forum section: electronics / rf-microwave

author: rfspezi
author_rank: Regular Contributor
timestamp: April 11, 2018, 08:40:16 am
content: I'd like to extend the frequency range of my spectrum analyzer (SAA3032) from 3.2 GHz up to about 6 Ghz.I guess the easiest way is to get a mixer and a signal generator to downconvert the range from 3.2 - 6 GHz?My primary goal is not to have a super spuriouse/harmonic free spectrum but beeing able to measure specific frequencies.A mixer modul equiped with an ADL5801 and the 6 GHz baluns would be interresting.However i then need a (at least) 3.2 to 5.4 GHz LO source range and can not use a cheap e.g. ADF4351 modul but need to use a e.g. ADF5355 modul.

author: hagster
author_rank: Frequent Contributor
timestamp: April 11, 2018, 01:15:02 pm
content: Something like this might do the trick.https://www.crowdsupply.com/outernet/morfeus#products-topThey also list a number of alternative products.

author: rhb
author_rank: Super Contributor
timestamp: April 11, 2018, 01:19:05 pm
content: Why not use the 3rd harmonic from an ADF4351 operating over 1-2 GHz?

author: hendorog
author_rank: Super Contributor
timestamp: April 11, 2018, 07:45:28 pm
content: This could be a good option:https://www.crowdsupply.com/outernet/morfeusOtherwise it's not hard to put something together cheaply with ADL5801 and ADF4351 boards from ebay.At the higher end there are a couple of downconverters out there for 499 USD I think from DS Instruments and Windfreak.

author: eb4fbz
author_rank: Regular Contributor
timestamp: April 12, 2018, 02:42:30 pm
content: Don't forget band pass filtering. Both RF (3-6GHz) and LO must be filtered to avoid images and mixing spurs.

author: medical-nerd
author_rank: Regular Contributor
timestamp: April 12, 2018, 04:39:23 pm
content: HiyaIs this any good?https://www.ebay.co.uk/itm/Used-Wiltron-Frequency-Converter-4-6-5-6GHz-in-0-1GHz-Out-Spectrum-Analyser-Use/273000867953?hash=item3f901ea871:g:lGoAAOSwiBJaJ9ZDCheers

author: zmetzing
author_rank: Contributor
timestamp: January 27, 2021, 01:35:42 am
content: This might be useful.http://www.sm6why.n.nu/spectrum-analyzer-extender(Yes, I necropost. If I found this thread with a search engine, odds are others will find it too. Better to answer the question here than create a new, non-indexed, thread somewhere else.)
cool way to explore global radio - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: January 26, 2021, 10:09:31 pm
content: Not really related to electronics but I think it is a very interesting concepthttp://radio.gardenI wonder if other data with receivers can be added to the map, to show field propagation or something. WIth a fork of that map program.

author: fsenseman
author_rank: Newbie
timestamp: January 27, 2021, 05:15:58 am
content: Also worthy of checking out:http://kiwisdr.comClick on the link to the map and pick a receiver to connect to. Then, listen to whatever the receiver is able to pick up in that area. Software Defined Radio (SDR) is something I'm just getting into. Pretty cool stuff.

author: cdev
author_rank: Super Contributor
timestamp: January 27, 2021, 07:24:52 pm
content: Some people have been able to decode digital modes using a web sdr..Which is surprising to me..It would be very cool to visualize whatever common signals were audible in pairs of simultaneously captured signals, and if so, how they might relate to one another, especially phenomena like echoes, etc. which I have heard.

author: coppercone2
author_rank: Super Contributor
timestamp: January 30, 2021, 05:27:59 am
content: I see people use VLF to make some kind of impedance analyzer of the atmosphere.I thought perhaps the original song being played online + some kind of SDR hookup to make some kind of plot of signal quality to do something similar with web resources.I assume the file they are using is the same as the one playing online for free, and I wonder how much error their front end adds, and how much of this is generally accountable/repeatable. The problem of course will be shady web SDRs. But it might be fun ? The problem with such propagation stuff is that you cannot legally transmit your own preferred signal, but you can use existing music.
Litz wire for an HF unun transformer - EFHW 8010 antenna - Page 1
Forum section: electronics / rf-microwave

author: iMo
author_rank: Super Contributor
timestamp: January 26, 2021, 09:03:00 pm
content: So.. I've been using a standard 1:49 imp. transformer wound with an 1mm dia enameled Cu wire on an FT240-43 core for my EFHW 80-10m antenna (3.5-29MHz).Within my experimentation effort I've made a DIY "litz wire" - made of 60x 0.1mm enameled+cotton coated wires and used for a version 2 of my unun.I've done some reading on that matter and they mention a "special weaving or twisting pattern of the wires in the bundle" is required in order to avoid various parasitic effects at higher frequencies (>2MHz). Is there any experience with the litz wire in such an application? Did somebody create a DIY litz wire suitable for such an application? Thanks!
RFI interference at 16.5MHz - Page 1
Forum section: electronics / rf-microwave

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: January 18, 2021, 05:33:54 pm
content: Hi,I've been tracking down some noise issues on an analog signal processing board and have found that some of it is RFI. The attached photos were taken with a x1 probe hooked up to the scope with a 20cm or so piece of wire connecting the probe tip and ground (to act as an antenna). Nothing else. The photos show the same signal at difference timebases (200us, 1us and 50ns).There is a regular short burst at 16.5MHz. I've tried turning off as many things in the house as possible but it persists.Any ideas?Until last year, I lived in a very rural area and didn't have this kind of problem. Now I live in a townhouse...Thanks.

author: fcb
author_rank: Super Contributor
timestamp: January 18, 2021, 06:58:08 pm
content: Any harmonics at 33MHz etc..? Could it be 16.384MHz, which can be used in audio gear?

author: Bud
author_rank: Super Contributor
timestamp: January 18, 2021, 07:35:39 pm
content: Are you sure it is not the rigol scope itself. The spikes period seems to be 700-800kHz which may be a switching regulator. When i had a ds2070a it suffered from a very similar issue at low V/div

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: January 18, 2021, 07:48:47 pm
content: Quote from: Bud on January 18, 2021, 07:35:39 pmHmmm - interesting thought. I'll see if I can pick it up on my old Tek 475 and, if so, turn the Rigol on and off.

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: January 18, 2021, 11:14:25 pm
content: I found the culprit. I have an LED flex tape stuck to the underside of the shelves above my workbench. The controller emits the pulse even when the LEDs are off. In fact, I can hear the controller "whining" at about 3kHz which is the frequency of the RF bursts.It's good to know. I installed the LEDs to improve lighting for soldering etc but don't need them otherwise. I'm building some electronics for a scientific instrument that measures laser light scattered by nanoparticles and I'd have the lights off anyway for that. Now I know I have to unplug the controller, not just turn it off.

author: cdev
author_rank: Super Contributor
timestamp: January 19, 2021, 01:47:51 am
content: Ferrites would probably clean it up. The kind that are designed to work with ribbon cable.
E-field probe from high-z RF probe? - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: January 18, 2021, 08:32:40 pm
content: I have a active RF probe (HP 85024A) and I noticed when you move it around near things it works as a sensitive antenna, i.e. hold it near monitor, computer port, etc and it shows a nice spectrum of stuff.If I were to make a sleeved ball that fits over the tip (it is like an oscilloscope probe), would that be a useful detector?Just had a idea because I finally got a BNC to N connector that lets me hook this up nice to a oscilloscope that has the power supply built into it.
1 tube regenerative *and* reflexed? - Page 1
Forum section: electronics / rf-microwave

author: Circlotron
author_rank: Super Contributor
timestamp: January 07, 2021, 11:45:30 pm
content: Everybody that has been around radio for a while has probably built a regenerative set at one stage. And back in the valve/tube days some radios had a reflexed IF stage where the demodulated audio was fed back into the IF stage to get some “free” audio amplification as well.What I’d like to know is, has anyone seen any details of a single tube radio that uses both regen *and* reflexing? The idea being to get the absolute most out of a single tube.Edit -> found some references on google but can’t delete this thread.

author: bob91343
author_rank: Super Contributor
timestamp: January 08, 2021, 12:20:18 am
content: That could work only if you stay well below the threshold of oscillation. Else the audio would be terribly distorted, with whistles and clipping. If you apply just a few dB of positive feedback it might work.

author: oPossum
author_rank: Super Contributor
timestamp: January 08, 2021, 12:31:56 am
content: Double reflex radio repair with circuit explanation

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 08, 2021, 12:38:23 am
content: Regen or superregen?I don't know that regen is all that useful, feedback needs to be tuned perfectly and it's awful at reception and distortion and etc...Superregen is out, it's specifically nonlinear.Perhaps if one could devise a way to use external limiting (diodes, saturable reactor?) to reproduce the nonlinear dynamics of superregen, so the amplifier can remain linear, it could work. Hmm, that'd be a challenge.Tim

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: January 18, 2021, 08:50:41 am
content: Maybe this is cheating, but consider using a dual tube like a 12AX7 (triode + triode) or 6BL8 (triode + pentode).The first section could be an RF preamp (useful for isolating antenna from regen detector).Second section oscillating detector.Audio from that could be fed back into the first section which does double duty as an audio amp.Haven't built it so can't confirm it works.
Extraterrestrial signal picked up by Australians in 2019 on 982.02 MHz.  - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: January 02, 2021, 07:57:50 pm
content: The signal was picked up by the Parkes Observatory and appears to have been an unmodulated carrier that shifted in frequency very slightly.Origin appears to be in approximately the direction of Proxima Centauri.https://www.nytimes.com/2020/12/31/science/radio-signal-extraterrestrial.htmlhttps://www.theguardian.com/science/2020/dec/18/scientists-looking-for-aliens-investigate-radio-beam-from-nearby-starThis signal, unlike many others seems to check out so far, but as they say there are lots of caveats..Still, its quite interesting that this signal has been received and after a year still seems definitely to come from another star or somewhere in that direction, and hasn't been eliminated by some means as being of human origin.Once before, a similarly artificial seeming signal observation was made. It was also a one time only occurrence.http://www.bigear.org/wow20th.htm#vast

author: SilverSolder
author_rank: Super Contributor
timestamp: January 02, 2021, 08:51:24 pm
content: Uh oh, they're coming!

author: HB9EVI
author_rank: Frequent Contributor
timestamp: January 02, 2021, 08:54:43 pm
content: like always it will turn out to have a rather unspectacular source of origin.We also didn't hear anything anymore about the supposed lifeforms on Venus which are responsible for the monophosphane traces in the spectrum of the atmosphere.

author: Twoflower
author_rank: Frequent Contributor
timestamp: January 02, 2021, 09:34:26 pm
content: Quote from: HB9EVI on January 02, 2021, 08:54:43 pmActually:A stringent upper limit of the PH3 abundance at the cloud top of Venus. There is an article about that topic in the NZZ (Leben auf der Venus? Vermutlich eher nicht, in German).

author: coppercone2
author_rank: Super Contributor
timestamp: January 03, 2021, 07:52:11 pm
content: keep in mind the data processing for this year (2020) is gonna suck ballsI would say a CW source is something thats been some how filtered broader band source

author: M0HZH
author_rank: Regular Contributor
timestamp: January 04, 2021, 02:56:11 am
content: Worth mentioning that the same observatory has been detecting (since 1998) very unusual radio bursts that appeared to be coming from outside of our galaxy. They even named the signals "perytons" after a mythical creature. In 2015 they realized the signals were coming from an old microwave oven in their kitchen.Seriously though, Proxima Centauri is a red dwarf and life is quite improbable in its system, so this is quite intriguing.

author: Lord of nothing
author_rank: Super Contributor
timestamp: January 17, 2021, 05:08:58 pm
content: Well it seem that its in the Rage where normally Cellphone Signals are.So maybe its related to that? Or even some fly a Drone who Broadcast something or someone on an Airplane dont turn of there Phone during flight and the broadcast something.

author: bson
author_rank: Unknown
timestamp: January 17, 2021, 07:58:44 pm
content: Is it grant review time again?
fluidic antennas review article - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: January 15, 2021, 08:29:41 pm
content: https://pdfs.semanticscholar.org/ad61/35738acad5069b43a172a25986a72fd9a4f4.pdf?_ga=2.197296875.572962716.1610742542-523010835.1610265735Very interesting stuff.Has anyone tried to make one ?
NRF51 & ESP32 Same Antenna - Page 1
Forum section: electronics / rf-microwave

author: 24602
author_rank: Contributor
timestamp: February 06, 2021, 12:32:49 am
content: Hey AllI think I already know the answer to this question, Im using a ESP32 and NRF51 on the same board (NRF is a OEM product don't have access to firmware) they can both transmit and receive in this project, Can a RF mixer or something be used for them both to use just the one antenna?Thanks!
Does someone want help me understand how the Hytera DMR work? - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: January 27, 2021, 12:27:43 am
content: In the CPS I can set for example:QuoteAnd:QuoteWell why choose one of that option?Its a legal PMR446 Radio and I try to understand all option. Well I know 80% of that and now I got it work after I got them used. In my case the work fine but I wish I would know everything.
SonarBlue 1Ghz USB frequency counter PC software - Page 1
Forum section: electronics / rf-microwave

author: RiZsho
author_rank: Contributor
timestamp: January 14, 2021, 04:35:00 pm
content: Hi Guys!A while back, I bought a SonarBlue 1GHz frequency counter that looked kinda OK for the job and it did. Couple of years later I want to use it again and of course I need to download the PC software for their product since it isn't a simple COM port emulator on USB. Low and behold, their site seems to be gone.Did anyone, who bought this counter, save the software with it?EDIT: It looked like thishttps://web.archive.org/web/20160126111556/http://sonarblue.com/downloads/The file I'm looking for seems to be "USB_Frequency_Counter_SB_FS1_1_9.rar" according to Archive.orgThanks in advance
DMR Hotspot?! "MMDVM Module" - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: December 25, 2020, 04:54:19 pm
content: HiWhen I was searching on Ebay and Aliexpress this come in sight:https://www.ebay.at/sch/i.html?_from=R40&_nkw=dmr+hotspot&_sacat=0&LH_TitleDesc=0&LH_PrefLoc=2&_sop=15&_blrs=recall_filtering"MMDVM Module" who claim to be a DMR Hotspot.And this:https://www.pistar.uk/index.phpSoftware.So does anyone here know more about that?Maybe use one?Well over a long time I looking for an DMR Repeater who could do some special think maybe that is what I was looking for all the time... So if someone know more about that pls tell me.Thanks

author: geggi1
author_rank: Frequent Contributor
timestamp: December 25, 2020, 06:18:34 pm
content: You add a Raspberry pi and a SD card with a Linux set up for hotspot use.Set up the hotspot. There are several description on the internet on how to set up.Connect the antenna and get it on internet and you got a local hotspot.The hotspot is only about 10mW so dont expect that you will be able to access it to far away.I recommend that you get a duplex hotspot because if you want to change from a busy TG you might have to reboot the hotspot.

author: Lord of nothing
author_rank: Super Contributor
timestamp: December 25, 2020, 08:23:49 pm
content: Quotewell that is what I not want to. I just want to run them as Repeater.Quotewell with that its maybe legal to when I glue the Antenna in.What are the freq range of that Modules?Mostly DMR Radio come with a lower UHF 400 - XXX UHF and upper 450 - 520 Mhz Range.With 2x its possible to run then full duplex?What kind of Modules are available?There are some V2 Modules on the Market do you know what difference is:https://www.ebay.at/itm/V2-0-MMDVM-Hotspot-module-P25-DMR-YSF-NXDN-Raspberry-Pi-3B-16G-SD-Case/123282224857?hash=item1cb43176d9:g:HT8AAOSwr85bYCPh?

author: Lord of nothing
author_rank: Super Contributor
timestamp: January 16, 2021, 10:37:18 pm
content: Does anyone here use that?

author: Dwaine
author_rank: Frequent Contributor
timestamp: January 17, 2021, 02:40:35 am
content: I use this one with my Kenwood D74A.. Works great..https://www.ebay.com/itm/2020-Duplex-MMDVM-Hotspot-P25-DMR-YSF-for-Raspberry-Pi-Antenna-Revision-1-3-/142804590100

author: Lord of nothing
author_rank: Super Contributor
timestamp: January 17, 2021, 07:56:35 am
content: What is the Min and Max freq who is possible to set?THX
Starlink Dish Phased Array Design, Architecture & RF In-depth Analysis - Page 1
Forum section: electronics / rf-microwave

author: Hugoneus
author_rank: Frequent Contributor
timestamp: January 12, 2021, 03:50:27 am
content: You may find this analysis interesting:youtu.be/h6MfM8EFkGg

author: 0culus
author_rank: Super Contributor
timestamp: January 12, 2021, 04:05:10 am
content: Oooo! Watching this on the tablet before bed. Been looking forward to this.
Spark Gap flashover of This Variable Air Capacitor - Page 1
Forum section: electronics / rf-microwave

author: jonovid
author_rank: Super Contributor
timestamp: January 04, 2021, 05:50:43 pm
content: this 60pf variable air capacitor came from a 1960s timber moisture content testerthe vacuum tube prob ran at low VHF part of the radio spectrum.this is a junkbox treasure that I hope to re-use if I get the timesee the images.what is the maximum voltage of this 30 yr old variable air capacitor?any ideas are welcome.the plate spacing looks like 0.5mm is it any good for 700v or 1kv? 4 watts power RF?60pf variable air capacitorcan it be re-used in a 1 meter diameter indoor 27MHz magnetic loop antenna made of copper tubing.will it spark over? a compact indoor HF antenna for a HF radio

author: bob91343
author_rank: Super Contributor
timestamp: January 04, 2021, 05:55:40 pm
content: https://ham.stackexchange.com/questions/6293/how-to-estimate-or-measure-the-max-voltage-of-an-air-variable-capacitor

author: LA7SJA
author_rank: Regular Contributor
timestamp: January 04, 2021, 09:13:23 pm
content: Example loop calculations:Magnetic Loop Antenna SpecificationsLoop Circumference 3.20 metersConductor Diameter 22.23 mmOperating Power 5 wattsFrequency 28.00 mHzBandwidth 174.8 kHzCapacitor Value 2.5 pFCapacitor Voltage 0.6 kVConductor Wavelength 0.314 lamdaEfficiency 95.8 %Inductance 2.730 µHInductive Reactance 480.4 ohmsLoop Area 2.5 meters²Loop Diameter 1.0 metersLoop Q Value 160.2 QresRadiation Resistance 1.436 ohmsResistance Loss 0.063 ohmsYour variable capasitor consists of to parts 36pF - 4pF and 24pf - 3pf in serie the resulting capacitor should be 14.4pF to 1.72pF and 1kV. So if you remove the soldered cable bridge that parralel the two capcitors and connect one to each end of the loop this cap should work just fine with your loop.This tip comes with a 100% money back guarantee.

author: ledtester
author_rank: Super Contributor
timestamp: January 04, 2021, 09:24:39 pm
content: I built an crystal radio by wrapping a lot of wire around a cardboard box like this:and my variable air capacitor arced over several times during a thunderstorm.

author: jonovid
author_rank: Super Contributor
timestamp: January 05, 2021, 12:17:02 am
content: Quote from: ledtester on January 04, 2021, 09:24:39 pmi am familiar with arced over in variable air capacitors same type of thing.happed to me. when i was back in the dayalso in old 2MHz 1950s vacuum tube transceivers used by VIC country fire authority as in-truck radios used crystalsBritish designed in-car transceiver antenna output was tunable. with a light bulb, it had a dc to ac HT vibratornot a jokeit buzzzed! finding images of this rig online failed.Quote from: LA7SJA on January 04, 2021, 09:13:23 pmthank you
Matlab and ADS S-param. DeEmbed Technique - Page 1
Forum section: electronics / rf-microwave

author: carvalhoatx
author_rank: Newbie
timestamp: January 11, 2021, 09:52:23 pm
content: Dear Folks,Anyone who already did some De-Embedding S-Parameters using Matlab ( Rf tool box @ deembedsparams tool) and ADS-Keysight with "De_Embed2" ?The get the same results? I doing some investigation and they provided me different results.Regards,
Bird 82 termaline load early version - re-using ceramic resistive element? - Page 1
Forum section: electronics / rf-microwave

author: wb0gaz
author_rank: Frequent Contributor
timestamp: January 03, 2021, 04:10:45 pm
content: I have a very old version of Bird 82 termaline (500W class) load, which has an earlier version main RF connector about size of DIN 7/16 but very different (looks like a big SO-239). After finding a usable adapter (convert to N female), I discovered that the load was actually open circuit (=DOA).Drained coolant, disassembled (finding a hose clamp had been used to attach the far end to the shield cage), and recovered the ceramic resistive element which was fractured through about 1/4" from one end where the hose clamp was (reducing that end's silver plated contact area length, but not intruding into the carbon area length.) The fragment that would have been present is missing, so this load had previous repair attempt or perhaps this is how Bird built them, but that seems very unlikely.I'm interested in trying to re-use the element which still reads 50 ohms at DC as a HF dummy load, perhaps using forced air cooling. To do this I would need to make electrical contact at the silvered ends and work out a mounting arrangement as there are no mounting attachments on the element (just a ceramic cylinder).Before I try anything, wanted to ask here if anyone else has played with this component. My initial thought was to find short length of copper tubing (maybe 1" dia?) and after thorough cleaning, solder a short length of the tubing to each end, providing a mechanical and electrical attachment point, then mounting the thing into a metal cylinder/box with forced air cooling. This wouldn't be used except < 30 MHz. Two risks I can see - (1) the silvered end doesn't "take" to solder, or (2) the thermal gradient in soldering destroys the element.Any other suggestions/ideas for re-use (I can just scrap the whole thing but would like to try to salvage it)?Thanks!
Ladder crystal filter - Page 1
Forum section: electronics / rf-microwave

author: geggi1
author_rank: Frequent Contributor
timestamp: December 27, 2020, 11:37:47 pm
content: How wide is it possible to manke a ladder crystal filter?I'm considering using 10, 12 or 16Mhz crystals.The filter is planed to be used in a tuned field strength meter with modular design.

author: coppercone2
author_rank: Super Contributor
timestamp: December 28, 2020, 12:41:55 am
content: probobly depends on the Q of the thingOne is a “narrowband filter” whose element section consists of a crystal resonator and a capacitor. This filter is designed so that its passband width is 0.005 to 0.6 % of the center frequency. The upper limit of the bandwidth is determined by the capacitance ratio of the crystal resonator (C0/C1), and the lower limit is determined mainly by the Q of the crystal resonator and the stability of the frequency.https://www.fujitsu.com/uk/Images/CrystalFilters-General%20Guidance.pdfSo high quality crystal can extend your upper limit and as for the lower limit I am not sure, I assume capacitance is more fixed because the material and dimensions are similar between different quality parts when thinking about capacitance.
Scrapbook of Radio Frequency's & spectrum chart AU - Page 1
Forum section: electronics / rf-microwave

author: jonovid
author_rank: Super Contributor
timestamp: December 27, 2020, 04:08:25 pm
content: Scrapbook of Radio Frequency's & spectrum chart.made this chart out of an Australian Frequency's & spectrum chart.listed favorite frequency's so its not so confusing.update-not so sure about that Localizer Aviation Frequenciesare only 90Hz 150Hz must be a higher carrier frequency for that.update- 2localizer signalcarrier frequency108.00 MHz to 111.975 MHzyou could go forever down the frequency mapping rabbit hole.but time got the better of me. so I posted as is.one of the ways to show frequencies is by a nonlinear spectrum frequency-linenot shown on this chart.this type of chart artwork magnifies parts of the spectrum list that have many listed frequency's &shrinks parts of the spectrum list show less. this would make for an interesting chart.maybe show dominant and submissive frequency's in a shared slot or band.if anybody is interested please copy and add to it,or remove my text and reuse the chart.with photoshopsee attachment .big jpg