hybridfree/eevblog-posts huggingface dataset:
PTT stuck down by APRS device - Page 1
Forum section: electronics / rf-microwave

author: @rt
author_rank: Super Contributor
timestamp: August 07, 2021, 03:27:15 am
content: Hello,I made one of these pic TNC circuits for mobile. It worked fine on the bench, and mobile for a couple of days.Ever since improving the grounding of my antenna (which indeed lowered the VSWR),The device holds down the PTT line until the radio’s transmit timeout setting, which ties up the APRS frequency.I have tried cutting R9 (don’t know what it does, but another diagram has a jumper next to it.I also tried holding PTT line high with 8k2 resistor to no avail. The circuit still works, but PTT is still held down after the first beacon.I’m planning to try an opto-isolator for the PTT line, but am aware that this isn’t the problem the opt-isolator here is usually trying to solve.Any ideas on this would be appreciated.BTW putting my antennas ground back to the higher impedance connection as it was originally did not restore the usual function.

author: bob91343
author_rank: Super Contributor
timestamp: August 07, 2021, 04:35:19 am
content: What is the signal at pin 6 of the processor supposed to do? It's obviously your problem. I have no idea how this all works but my analog background tells me that the PTT is controlled by that pin.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 07, 2021, 04:36:39 am
content: Check that the transistor pulling down the PTT line hasn't gone leaky. Might also want to try putting a 1n or so capacitor from base to emitter as close as possible to the transistor to increase immunity against EMI triggering it on.

author: @rt
author_rank: Super Contributor
timestamp: August 07, 2021, 05:50:07 am
content: Ok, thanks for replies, but opto-isolator did fix it.I’m not using that transistor anymore. The PTT signal from the chip is fed to opt-isolator via the 1K resistor, and radio’s PTT is shorted by the device to the radio’s own and in the mic cable.BTW @ NiHaoMike, The PTT LED on the APRS chip was working (turning on & off as expected even when the radio stayed in transmit.

author: bob91343
author_rank: Super Contributor
timestamp: August 07, 2021, 11:17:58 pm
content: You have given me an idea to redesign a keying circuit using an optoisolator. For some reason it never occurred to me.Thanks.

author: @rt
author_rank: Super Contributor
timestamp: August 08, 2021, 07:30:29 am
content: This is how I did it.At home I have another TNC that has isolated AFSK lines with transformers as well.
Ebook recommendation covering ZigBee 3.0 - Page 1
Forum section: electronics / rf-microwave

author: davorin
author_rank: Unknown
timestamp: August 06, 2021, 09:21:08 am
content: Good morning (o;For a new project I have to dig into ZigBee 3.0...meaing how I can connect several ZigBee 3.0 thermostats onto a Linux gateway with a ZB module via UART/USB...Is there a good ebook covering ZigBee 3.0 specs and preferably real life examples?Googled for ZigBee ebooks...but all those are rather old...thanks in advancerichard

author: ahbushnell
author_rank: Frequent Contributor
timestamp: August 06, 2021, 10:42:22 pm
content: https://www.digi.com/xbee
clansman 320 mods - Page 1
Forum section: electronics / rf-microwave

author: m3vuv
author_rank: Super Contributor
timestamp: August 10, 2021, 09:37:25 am
content: hi chaps.if any of you guys use one of these check out the vid,certainly makes one of these more user friendly on the fingers i imagine when scanning the bands,i feel another project on the horizon,enjoy,73 de m3vuv.
Confused, RFM69H change frequency in software? - Page 1
Forum section: electronics / rf-microwave

author: onesixright
author_rank: Frequent Contributor
timestamp: August 01, 2021, 09:02:24 am
content: Hi All,I'm a bit confused. Complete noob when it comes to RF. Looking at this IC (RFM69H), the datasheet explains it can run on 433, 868 and 915 Mhz.from:http://www.dnsj88.com/UploadFiles/File/2015-09/6357818882544922622782838.pdfQuoteDoes this mean each part is designed specifically for a frequency rains? So a 433 <hz IC can not work on 858 MHz (looks like it)?I'm asking since on the last page it gives different P/N:QuoteThanks.

author: CJay
author_rank: Super Contributor
timestamp: August 01, 2021, 10:41:19 am
content: Looks like the chip is capable of operating on several bands but the modules will need to have filtering on them and that will determine the frequency range so yes, the modules are band specific even if the chip isn't.
Attenuator failure mode? - Page 1
Forum section: electronics / rf-microwave

author: robert1111
author_rank: Newbie
timestamp: July 25, 2021, 11:24:04 am
content: If a low powered (example 1 watt) SMA coaxial attenuator is subjected to power levels exceeding its rating (example subjected to 5 watts continuous), what is the mode of failure? Does it fail "open" or "short"? Thank you.

author: dl6lr
author_rank: Frequent Contributor
timestamp: July 25, 2021, 12:36:33 pm
content: I would expect open. All attenuators that I measured failed with high impedance after overload. Additonally they are also sensitive to static discharge.

author: Joel_Dunsmore
author_rank: Regular Contributor
timestamp: July 31, 2021, 01:00:23 am
content: Yup, in general they are Pi type structures (shunt R, series R, shunt R) although higher frequency ones look more like a patch of resist material with ground on the side and contacts on the ends. Most over power tends to heat the resist and raise it's ohms per square, until it becomes quite high. It can sometimes overpower so much it sputters off the material to a full open. I've never seen on fail by shorting.

author: rfclown
author_rank: Frequent Contributor
timestamp: August 01, 2021, 03:40:26 am
content: Nice to see you on the forum Dr. Joel. You helped my years ago (on some other forum) in fixing an 8753 of mine.
DMR with DSD+ errors - Page 1
Forum section: electronics / rf-microwave

author: veedub565
author_rank: Frequent Contributor
timestamp: June 07, 2021, 03:54:44 pm
content: I've got SDR# setup and working ok, I've installed the VB cable and DSD+, all configured correctly as far as I can tell. When I try to decode DMR though I I get a lot of digital noise through the speakers, interspersed with garbled voice. There's a snippet of the log below (full log attached)I know it says "DATA" a lot, but it does say "VOICE" too, along with lots of errors. Any idea's whats going on ? Screenshot also attachedSync:+DMR+DMR CACH ERR slot1 BS DATA ERR1 DCC=1 Idle+DMR slot1 BS VOICE e:124r+DMR slot2 BS DATA ERR2 DCC=1 Idle+DMR slot1 BS VC2 e:16r7r+DMR slot2 BS DATA ERR1 DCC=1 Idle+DMR CACH ERR slot1 BS VC3 e:25r5r+DMR slot2 BS DATA ERR2 DCC=1 Idle+DMR CACH ERR slot1 BS VC4 e:4r36r+DMR slot2 BS DATA ERR2 DCC=1 Idle+DMR CACH ERR slot1 BS VC5 e:5r37r+DMR slot2 BS DATA ERR2 DCC=1 Idle+DMR CACH ERR slot1 BS VC6 e:5r4r4mSync:+DMR+DMR CACH ERR slot1 BS DATA ERR2 DCC=1 IdleSync:+DMR+DMR slot2 BS DATA DCC=1 IdleSync:+DMR+DMR CACH ERR slot1 BS DATA ERR3 DCC=1 Idle+DMR CACH ERR slot2 BS VOICE e:6r33+DMR CACH ERR slot1+DMR CACH ERR slot2 BS VC2 e:7r6r7r+DMR CACH ERR slot1+DMR CACH ERR slot2 BS VC3 e:6m7r6r+DMR slot2 BS VC4 e:6r6e6r+DMR CACH ERR slot1+DMR CACH ERR slot2 BS VC5 e:6r6r6m+DMR CACH ERR slot1+DMR CACH ERR slot2 BS VC6 e:6r7r6rSync:+DMR+DMR CACH ERR slot1 BS DATA ERR2 DCC=1 Idle+DMR CACH ERR slot2 BS VOICE e:6m7r3

author: vsboost
author_rank: Contributor
timestamp: June 27, 2021, 10:46:26 am
content: Signal is not strong enough.

author: eb4fbz
author_rank: Regular Contributor
timestamp: July 02, 2021, 09:47:07 pm
content: And set bandwidth to 12.500

author: veedub565
author_rank: Frequent Contributor
timestamp: July 07, 2021, 09:19:13 am
content: Working now on a proper antenna, thanks for the replies

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 22, 2021, 09:17:17 pm
content: Do you want a Antenna recommendation?
IEC 61000-4-3 Spot frequency test - Page 1
Forum section: electronics / rf-microwave

author: Psi
author_rank: Super Contributor
timestamp: July 13, 2021, 01:50:40 am
content: Hi,For IEC 61000-4-3 EMC testing can someone please explain to me the reasoning behind the frequencies used in the "spot frequency test" (if there is a reason)80 MHz, 104 MHz, 136 MHz and 165 MHz, 200 MHz, 260 MHz, 330 MHz, 430 MHz, 560 MHz, 715 MHz, 920MhzWere these selected simply to provide nice coverage over the 80M-1G band,Or do they have some special significance? (e.g. Are they frequencies that often cause problems in devices so they get more attention in testing?)The RF Field part of IEC 61000-4-3 that does a sweep from 80-1000mhz would cover all frequencies, including these.So I'm trying to figure out what the spot test is trying to achieve and am not having much luck googling.Thanks.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: July 19, 2021, 01:24:02 am
content: I'm not finding a reference to that in my copy of 61000-4-3. Which edition do you have? Which section is it from?

author: Feynman
author_rank: Regular Contributor
timestamp: July 22, 2021, 05:33:53 am
content: I don't know what product types you are referring to. Every time I've been to a EMC lab a full sweep from 80 to 1.000 MHz was performed. I don't have the 61000-4-3, but I never came across those spot frequencies. Since they all are about a factor of 1.3 apart, I don't believe these are some special frequencies.
Control line feed thru suggestions? - Page 1
Forum section: electronics / rf-microwave

author: rhb
author_rank: Super Contributor
timestamp: July 17, 2021, 08:44:55 pm
content: I have a bunch of RF eval boards from China which I want to connectorize in shielded enclosures. I don't want to spend $20 packaging a $8-15 board.I make the enclosures from scrap 28 gauge galvanized steel scrap from a local HVAC shop. Quarter inch copper foil tape on the seams soldered to the zinc plating provides an RF tight seal.For power connectors I've standardized on 2.1 mm coaxial power sockets. All Electronics has them for under $0.20 so I bought 100. For prototyping I epoxy them to SS FR4and use copper foil on the epoxy side for pads and microstrip. This works great for Manhattan style construction. Even a small amount of epxoy goes a long way, so I make them up in batches of various size boards that use up all the epoxy I've mixed.For obvious reasons I don't want to use the same connector for control lines. I'd like to find a cheap option for feed thrus. Ideal would be the connectors HP used in the 8601A, but I've never seen those for sale anywhere.Does anyone have suggestions?Have Fun!Reg

author: richard.cs
author_rank: Super Contributor
timestamp: July 19, 2021, 08:59:19 am
content: How about D connectors? Cheap, lots of pins, ribbon-crimp options available. Also you can get bulkhead ones with feedthrough capacitors built in which are cheaper than buying lots of individual feedthrough capacitors.

author: rhb
author_rank: Super Contributor
timestamp: July 19, 2021, 10:08:45 pm
content: I just ordered 10 sets of these:https://www.mpja.com/Pack-of-4-Capacitor-Feedthru-1000pF/productinfo/36701+CF/Have Fun!Reg

author: langwadt
author_rank: Super Contributor
timestamp: July 19, 2021, 10:16:24 pm
content: filtered d-sub 9 connector ?

author: rhb
author_rank: Super Contributor
timestamp: July 20, 2021, 02:27:48 pm
content: The referenced feed thrus are what I was looking for. I have lots of things that only need 1-2 pins. RF is SMA because they are cheap and convenient.I've got a slew of DB-9s among others. RS232 is very useful. But doesn't really belong in an analog RF world.Have Fun!Reg

author: langwadt
author_rank: Super Contributor
timestamp: July 20, 2021, 03:37:19 pm
content: Quote from: rhb on July 20, 2021, 02:27:48 pmDB-9 doesn't have to be RS232. And filtered DB's have filters like the feed-throughs just more pins so convenient when you need multiple control/power signals

author: richard.cs
author_rank: Super Contributor
timestamp: July 20, 2021, 03:53:55 pm
content: Quote from: langwadt on July 20, 2021, 03:37:19 pmMore than that, they can be had with shunt capacitors just like the feedthroughs (most common), but also with series ferrites, or CLC pi filters. It's a cost effective way to get the filtering if you need more than a couple of pins.
Gigatronics 848x Power Meter Cable - Page 1
Forum section: electronics / rf-microwave

author: ignilux
author_rank: Unknown
timestamp: July 18, 2020, 01:14:55 pm
content: Hi, all-I'm in need of an affordable, reliable way to measure RF power output from 2 GHz to 18+ GHz. HP meters are dirt cheap, but the sensors and cables are freaking ridiculous. As in, they cost more than I paid for my spectrum analyzer. Anyway, it looks like the Gigatronics 8481B/C is affordable, and the compatible sensors are much more reasonable. The only left is the cable, which I can't seem to find anywhere. I'm sure when I find one, it won't be cheap. Does anyone know of a source for the male connectors found on the cable ends? Female end is in the attached image, and looks different than the HP sensors.Cheers!.

author: ignilux
author_rank: Unknown
timestamp: July 19, 2020, 03:42:27 am
content: I guess I spoke too soon... Just won an auction for an HP 8484A with 5 ft cable for 100 USD

author: kipp
author_rank: Contributor
timestamp: July 01, 2021, 02:40:08 pm
content: I know you say you've found a solution, but that connector appears to be a standard 14 pin DIN connector with a threaded lock. The thread lock is standard, but it is one of two options when buying a connector, the other being a bayonet style locking mechanism, so watch for that. The HP sensors use a standard 11 pin DIN connector, also with the threaded lock.The cables are easy to make, everything about them is completely standard and well stocked, but the connectors are a bit over $20 US each, so two of them plus a length of shielded multi-conductor cable, plus shipping, and it will end up costing maybe $80 to make your own cable from scratch, plus your own time, plus when you're done you've got a DIY cable of dubious robustness, which I think is the calculus that keeps the cables up around $100 even on the used market. (it's certainly why I haven't bothered making my own).

author: croma641
author_rank: Regular Contributor
timestamp: July 02, 2021, 12:06:37 am
content: ... but is the Hp 8484 compatible with the 8541-B/C Gigatronics Power Meter ?

author: ignilux
author_rank: Unknown
timestamp: July 24, 2021, 06:05:21 pm
content: I'm surprised to see there is still a discussion happening here!No, the 8484A is not compatible with the Gigatronics meter. At least I don't think so. At the time of writing I did not own a power meter, but leapt on that HP sensor because the HP power meters are cheap and readily available. Shortly after I purchased the sensor I picked up a 437B with recent cal date for around 50 USD.
Is a Common Mode Choke Even Necessary at QRPp Power Levels?  - Page 1
Forum section: electronics / rf-microwave

author: Jeff Weinmann
author_rank: Contributor
timestamp: July 20, 2021, 12:18:36 am
content: Hello,I'm using an SI5351a clock generator to generate a WSPR signal at 10-100 milliwatts. An antenna design, theMicroVerthttps://www.dc4fs.de/microvert.pdfsuggests using a common mode choke to keep current off part of the coax used as a counterpoise.Now I understand that common mode current may be troublesome in the shack, affecting the radio electronics and giving the operator a shock if the radio is touched in the wrong place, but I will be operating only 10-100 milliwatts out in the field with an arduino and an Low pass filter connected to a Microvert.Is there really a need for a CMF at such low power levels?I realise that with this antenna design part of the coax is used as a counterpoise, but does it matter at 10mw?73 Jeff

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 20, 2021, 05:17:09 am
content: As I said in theother thread, it's part of the antenna. Omitting it will change the tuning, radiation pattern, sensitivity to nearby things, etc. Doesn't depend on power, it's about the fields themselves.Tim

author: radiolistener
author_rank: Super Contributor
timestamp: July 20, 2021, 07:46:44 am
content: Quote from: Jeff Weinmann on July 20, 2021, 12:18:36 amThe power doesn't matters. The antenna geometry matters.Common mode choke affects your antenna geometry, because it prevents to use feeder, equipment chassis, mains line and other things as a part of antenna.So, it doesn't matter if it's TX with 1000000 W, 0.001 W or 0.0000000001 W, or if it's RX signal.In any case you're needs RF choke to keep proper antenna geometry.
Draw two L1 line on a FR4 PCB - Page 1
Forum section: electronics / rf-microwave

author: namster
author_rank: Regular Contributor
timestamp: July 01, 2021, 12:55:39 am
content: Hi All,i am currently finishing a Dev Board for GPS Receiver that have two MMCX connector that i want to connecte them to BNC output Connector , the frequency of the Signal if in the L1 Band '' 1575.42 MHz '' , i have never designed a RF strip for PCB so i want some help for that , i think that i have to use the via fence along the the two line ? and also a GND polygone on the bottom ?

author: purpose
author_rank: Frequent Contributor
timestamp: July 01, 2021, 05:08:00 am
content: Mr. namster,I was once given this advice from a chap on here, but am yet to put it into practice.* dual layer* 1.6mm nominal PCB thickness* continuous gound plane bottom under the trace that goes to the antenna* polygon filling on top layer (where the antenna trace is)* antenna trace is 0.8mm wide* 150µm polygon to trace clearancethis will get you around 50 OhmsPeter

author: namster
author_rank: Regular Contributor
timestamp: July 08, 2021, 12:22:19 am
content: I really apologize for responding too late , i have finished the PCB by taking in consideration all that you said , for calculating the GCPW i used the soft implemented calculator of altium designer , i also used the impedence control by setting it to 50 Ohm , i think that the result are pretty good
Which Malahit-DSP SDR is worth getting? - Page 1
Forum section: electronics / rf-microwave

author: gardner
author_rank: Regular Contributor
timestamp: July 01, 2021, 04:41:54 pm
content: I would like to acquire one of these Malahit-DSP stand-alone SDR radios.https://www.qsl.net/n9ewo/malahit.htmlClones are readily available that, I suppose, can run the official software. But there must be 100 different ones on Aliexpress and at least 40 on Amazon.ca to choose from. Looking at reviews on Amazon and folks comments on youtube and so forth, there seem to be a lot of dogs out there, with many reports of DOA or incompatible hardware. I'm in Canada and a lot of US-based vendors will flat out not ship here. So there's mainly a forest of fly-by-night Shenzhen market sellers to deal with.Can anyone point at a specific ebay or amazon seller that would be reliable?Any experience with using one of these clones and putting official/upgraded software on it with good results?Thanks.

author: radiolistener
author_rank: Super Contributor
timestamp: July 04, 2021, 05:16:47 am
content: Malachite-DSP has a nice feature - waterfall display with compact size. But radio performance of Malachite-DSP is not great.If you want better performance and more compact DSP receiver, I can recommend receiver "Belka-DX". It doesn't have color display with waterfall, but it's sensitivity and reception quality is much better.Here is comparison of Malachite-DSP with Belka-DX.

author: gardner
author_rank: Regular Contributor
timestamp: July 04, 2021, 10:13:29 pm
content: Interesting. I am not hung up on the display of the Malahit radio in particular, but I would like to be able to use it in VHF. The Belka only goes to 31MHz and I can do that with a normal shortwave set. It also looks difficult to source -- certainly there isn't a deluge of random Chinese clones like the Malahit.

author: radiolistener
author_rank: Super Contributor
timestamp: July 05, 2021, 05:30:28 pm
content: As I know, Chinese clones have issue with encoder. The encoder is cheap and buggy. And it works in the wrong direction and this cannot be fixed with settings. You can read it in people feedback. But I don't have it to test. May be it can be fixed with more new firmware.
HP 8596E Strong signal at 150Khz - Page 1
Forum section: electronics / rf-microwave

author: edumopedu
author_rank: Newbie
timestamp: July 01, 2021, 08:31:24 am
content: I have an HP 8596E SA and I have noticed that for some time it displays a strong signal (-2dBm) with a peak at 150Khz.I am not able to figure out if the signal it's coming from outside (I have a feeling that it is not) or if there is something "leaking" from inside of the SA.Does any one has any hints..? That would be much appreciated.

author: rf-messkopf
author_rank: Regular Contributor
timestamp: July 01, 2021, 08:49:00 am
content: That's the LO feedthrough at 0 Hz. Every swept frequency spectrum analyzer does that. Your marker reading of 150 kHz is due to your unfortunate sweep setting (from -57.9 MHz to 100 MHz). Check the marker readout accuracy in the datasheet and set up a narrower span.
Si5351A conundrum - Page 1
Forum section: electronics / rf-microwave

author: WimWalther
author_rank: Regular Contributor
timestamp: June 25, 2021, 06:17:55 am
content: Howdy folks,The Si5351 is out of stock everywhere I know to look, with leadtimes almost into next year. So unless someone knows of a source...What's the word on the Chinese copy MS5351M? They're not particularly cheap, with prices for the MSOP-10 exceeding the list price of the Si part. But I'm not finding much if any commentary on them.. similar to the situation with the Logic Green upgrade / replacement for the Atmega328P.Any thoughts? Dare I use these MS5351M?Thanks, Bill

author: cadr
author_rank: Contributor
timestamp: June 26, 2021, 02:15:42 am
content: I have no experience with them, but saw some people on various groups.io groups saying they worked for them, such ashttps://groups.io/g/BITX20/message/87189You might search around on there for other reports.Good luck!-Benkc9dlm
Specialty coaxial surge protectors sought - Page 1
Forum section: electronics / rf-microwave

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: July 02, 2021, 04:42:57 pm
content: Has anyone ever seen coaxial surge arresters / overvoltage protectors for the connector series HN and/or SC? All hints would be welcome!

author: coppercone2
author_rank: Super Contributor
timestamp: July 03, 2021, 06:38:11 pm
content: can you provide more detail on frequency range and stuff like that

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: July 04, 2021, 06:22:28 pm
content: ca. 1GHz, +10dBm max. preferably non-shorting to DC
how to remove noises in superheterodyne receiver - Page 1
Forum section: electronics / rf-microwave

author: tariq
author_rank: Contributor
timestamp: June 13, 2021, 12:24:49 pm
content: hii want use 433 Mhz remote and superheterodyne receiver.when i connect receiver data to microcontroller pin that pin becomes high and low continuously for i think every mili second or maybe less.when i press remote button i don't have any problem to determine requested rising edge and falling edge period time but in microcontroller i want to use interrupt when Rising edge comes and because of these noises my microcontroller send interrupt for every 1 mili second or even less.I'm looking for a way to remove that Rising edge noises.all the libraries i found in internet using interrupt to determine rising edge in receiver but i can't use the amount of interrupt in my code so is there any way to remove all that noises?thank you

author: radiolistener
author_rank: Super Contributor
timestamp: June 13, 2021, 01:40:04 pm
content: you can use filter. Narrow bandwidth = less noise power. Narrow bandwidth means that you will needs more time to transmit the signal. If noise is too strong, you can use very sharp filter and transmit signal for several seconds in order to filter it from noise on receiver side. It requires several seconds to transmit the signal, but allows to work in noisy environment.

author: Integrol
author_rank: Newbie
timestamp: June 21, 2021, 07:24:49 am
content: radiolistener,Can you explain why a Narrow bandwidth means that we will need more time to transmit the signal ?I thought it depended only on the upper frequencies of the continuous band of frequencies and not on its width.Thank you,

author: bob91343
author_rank: Super Contributor
timestamp: June 22, 2021, 06:17:38 am
content: Narrow bandwidth restricts data rate. See Mr. Nyquist.

author: radiolistener
author_rank: Super Contributor
timestamp: June 22, 2021, 11:06:22 pm
content: Quote from: Integrol on June 21, 2021, 07:24:49 amBecause narrow bandwidth means that the signal should change slowly (at low frequency).You cannot change signal at a quick speed, because bandwidth is limited. Shorter rise/fall time means higher frequency components in the signal, they require wide bandwidth.When you use narrow bandwidth filter (in order to reduce noise influence), you will needs to use low frequency signal for the carrier modulation. So, it needs more time to detect it on receiver side, just because low frequency has longer period and needs more time to detect one period.Quote from: Integrol on June 21, 2021, 07:24:49 amAbsolute frequency value doesn't matter. Bandwidth matter.
EL504 as a "QRP" RF amp - Page 1
Forum section: electronics / rf-microwave

author: A.Z.
author_rank: Super Contributor
timestamp: June 12, 2021, 03:29:52 pm
content: Hello folks, a friend has quite a bunch of EL504 (Ok PL504) recovered mainly from old TV sets, now he asked me if it may be possible to use some of those tubes (say 2 or 4) to put together an RF amplifier which, driven by a 5W QRP transmitter, could offer some "QRO" output; seeking on the intertubes, I found this schematichttp://www.cqham.ru/projects/25w_qro.pdfbut my friend told me that, while he likes it, he would like a two or more tubes amp, so here I am asking for pointers

author: TimFox
author_rank: Super Contributor
timestamp: June 12, 2021, 03:34:13 pm
content: I’m concerned about the mains feed to the HV supply: is there a transformer not on the schematic page?A 240V to 240V toroidal isolation transformer would be a good idea.

author: A.Z.
author_rank: Super Contributor
timestamp: June 12, 2021, 03:50:01 pm
content: Hi TimYes, noticed it, but aside from that schematic, which apparently is the only one around (didn't find much for 504 tubes as RF amps), what I'm asking is if there are other schematics using two or more tubes; to say it all, I suggested going for PL519 or even 813 tubes in grounded grid, but my friend insists about trying to use the 504...
synchronous demodulator - Page 1
Forum section: electronics / rf-microwave

author: xzswq21
author_rank: Frequent Contributor
timestamp: June 08, 2021, 07:07:23 pm
content: HelloActually I want to apply a single tone signal into a system and analyze the output response by a synchronous demodulator as following:(I have updated the below pics, Mr David Hess helped me to modify the pics)Excitation frequency is from 100KHz to 10MHz.Do you know any IC to do it for me? (Zero Crossing Detector + PLL + quadrature demodulator) now I don't want to work with the FPGA or something similar.Thanks

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 09, 2021, 01:32:08 am
content: 74HC4046 for the PLL, Tayloe mixer for the downconversion.

author: xzswq21
author_rank: Frequent Contributor
timestamp: June 09, 2021, 03:51:01 am
content: The overall detector (PLL+Mixer) is good in a 14Bit system? Actually I want to build a setup to analyze a signal in my research project at university, What do you think about AD8333 for the IQ demodulator?

author: David Hess
author_rank: Super Contributor
timestamp: June 09, 2021, 05:10:59 am
content: The delay and zero-crossing detector need to operate on the excitation signal and not the output from the device-under-test. As shown it does nothing useful.

author: David Hess
author_rank: Super Contributor
timestamp: June 09, 2021, 05:23:08 am
content: Quote from: xzswq21 on June 09, 2021, 05:15:02 amYes, but as shown, nothing is being measured because the output of the delay is being compared to the output of the delay. The zero crossing detector needs to sample the excitation and not the output from the DUT.

author: David Hess
author_rank: Super Contributor
timestamp: June 09, 2021, 05:33:28 am
content: Quote from: xzswq21 on June 09, 2021, 05:29:12 amThe output from the DUT is poorly defined so the delay should drive either the DUT or the zero-crossing detector. There is no advantage to delaying the output from the DUT and usually many disadvantages.

author: xzswq21
author_rank: Frequent Contributor
timestamp: June 09, 2021, 05:42:13 am
content: Quote from: David Hess on June 09, 2021, 05:33:28 amonly forget the delay box, I mean this:as you see the excitation signal and DUT output signal are out-of-phase, I want to use a PLL+IQ Demodulator to get I and Q components.
Catronics CT100 RTTY TU - Page 1
Forum section: electronics / rf-microwave

author: jmh
author_rank: Contributor
timestamp: June 08, 2021, 03:42:17 pm
content: A long shot - does anyone have any info (preferably connector pinouts) for a Catronics CT100 RTTY TU? All I can find on the web is adverts from way back and no tech info. I am tracing the circuit out (slowly - dunno what's wrong with me it's just a bunch of discrete components and TTL chips!) - I'll figure it out but any info would be handy.ThanksJeremy
EMI probe - Page 1
Forum section: electronics / rf-microwave

author: xzswq21
author_rank: Frequent Contributor
timestamp: June 07, 2021, 04:25:36 pm
content: Hello, I have an old HP spectrum Analyzer, these days I want to measure magnetic and electrical fields around an inductor by using a probe and my Spectrum Analyzer, I apply a signal with 10Vpp and the frequency from 100KHz to 10MHz into the inductor, Do you know a good suitable probe for my application?

author: richnormand
author_rank: Unknown
timestamp: June 07, 2021, 04:33:58 pm
content: Dave did several videos about these probes and how to use them.For example:
Methods for generating single-sideband signals from LO and audio? - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: June 03, 2021, 11:49:12 pm
content: I have a Sofrock Ensemble III and I am wondering if it might be possible to also use it for transmitting with modifications. It has an internal oscillator to produce the VFO signal which is at four times the frequency of interest. And of course also the audio signal.(what is the practicality of a ring modulator?https://en.wikipedia.org/wiki/Ring_modulation)Does anybody know of a good source/summary of methods to generate a weak SSB signal? I am trying to get an idea if it might be practical to retrofit my cheap softrock receiver into a transceiver. (Its a great receiver, BTW, for the price)My computer has a nice sound card that can do 24 bits. I am just asking, not doing anything. Of course I would also make sure any operation complied with all applicable laws and licensing reqts)

author: bob91343
author_rank: Super Contributor
timestamp: June 04, 2021, 03:06:20 am
content: There are two basic, classic methods to produce an SSB signal. One is the phasing method and the other the filter method. With modern techniques, however, the field has become more cloudy with innovative methods appearing often.You would do well to consult the Radio Amateur's Handbook for some basic information, especially any edition in the 1960s. You might also look at the schematic diagrams of transceivers, especially for amateur radio, built in the 1960s through the 1980s. Some construction projects are shown in the Handbook as well.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 04, 2021, 03:22:41 am
content: Quote from: cdev on June 03, 2021, 11:49:12 pmHistorically, there were three methods of obtaining SSB signals.(1) The filter method.With this method, a balanced modulator was used to create a DSB signal.This signal was then passed through, typically, a crystal filter to remove one sideband.Most such transmitters did this at a fixed IF frequency, which was then converted to the frequency of interest using a mixer.(2) The "phasing" method.In this method , both the audio in & RF from the local oscillator were split into two signals 90 deg out of phase.They then were fed to separate mixers, & the two resultant DSB signals were passively mixed, resulting in the cancellation of one sideband.(Sorry if this is vague, but it is too long since I last read anything about it)(3) "The third method".This is a very complex extension of the phasing method, & what Idon'tknow about it would fill a book!The most modern designs use DSP to obtain SSB----whether by digital filtering, or digitally performing thehard part of one of the "phasing"methods, or some other method, I know not!

author: LaserSteve
author_rank: Super Contributor
timestamp: June 07, 2021, 01:55:09 am
content: See the Philips AN1981 application noteN8VKD
Smith Chart Tool - Page 1
Forum section: electronics / rf-microwave

author: RoGeorge
author_rank: Super Contributor
timestamp: June 05, 2021, 06:41:14 pm
content: Found this webpage Smith Chart tool/calculator (not mine), and liked it a lot, for being very clean and easy to use:https://www.will-kelsey.com/smith_chart/The webpage works offline, too, when saved locally, thank you Will Kelsey (the author, I think).When offline the webpage needs one more folder that is not automatically saved at the "Save as" webpage. The missing folder is called "icons" (or else the networks icons will be missing). The folder icons needs to be placed at the same level with the "Smith Chart Tool.html" file, then open the saved .html and use it like it would be an online page. The missing icons files can either be saved one by one as .png files inside the folder named icons, or just unzip the 'icons' attached folder. All copyrights, if any, belong to their authors.
Circuit question (Softrock Receiver) - Page 1
Forum section: electronics / rf-microwave

author: cadr
author_rank: Contributor
timestamp: June 05, 2021, 01:30:37 pm
content: Hello,I'm looking at the circuit diagram of the Softrock receiver, and I had a question about a particular connection. Specifically, in the attached diagram and labeled with the red arrows, what is the connection between pin 3 of U4 and the transformer for? Normally I see opamps in this configuration have that leg tied directly to ground, but here they are AC coupled to ground. What is the purpose of doing that, and what is the result?Thanks!-Benkc9dlm(For reference, original page athttp://www.wb5rvz.org/softrock_lite_ii/index/projectId=8)

author: DL2XY
author_rank: Regular Contributor
timestamp: June 05, 2021, 03:50:57 pm
content: R3,4 and C7 are building an artifcal ground at 2.5V for biasing the opamps.

author: cadr
author_rank: Contributor
timestamp: June 05, 2021, 05:05:00 pm
content: Quote from: DL2XY on June 05, 2021, 03:50:57 pmOk, I feel silly now. I completely didn't see that the line I was talking about was connected between R3 an R4. Thank you!!
DH1AKF_Wolfgang  - Page 1
Forum section: electronics / rf-microwave

author: halfwave
author_rank: Newbie
timestamp: May 02, 2021, 05:26:50 pm
content: Saw this over on the Analyzer-EU1KY at groups.io, just a fyi for everyone here, Wolfgang passed away:Quote

author: chrisl
author_rank: Regular Contributor
timestamp: May 03, 2021, 05:12:08 am
content: Wow, RIP.

author: radiolistener
author_rank: Super Contributor
timestamp: May 06, 2021, 05:50:36 pm
content: I know him by his firmware for EU1KY antenna analyzer. He also had some SDR projects. He was a good and friendly guy, RIP

author: cdev
author_rank: Super Contributor
timestamp: June 03, 2021, 01:56:28 am
content: How sad, I didn't even know he was sick.Well, now a contact with him is the ultimate DX! Farewell Wolfgang!

author: cdev
author_rank: Super Contributor
timestamp: June 03, 2021, 01:59:40 am
content: Thank you for letting us know.So many people are dying these days their loss represents a big loss to the world. My heart goes out to their families.Quote from: halfwave on May 02, 2021, 05:26:50 pm

author: HB9EVI
author_rank: Frequent Contributor
timestamp: June 03, 2021, 08:16:36 am
content: from the QRPForum I got know, that he was another victim of Covid-19

author: cdev
author_rank: Super Contributor
timestamp: June 03, 2021, 11:25:36 pm
content: Quote from: HB9EVI on June 03, 2021, 08:16:36 amresveratrol may help prevent new covid infections in people. Now its been over a year and we still dont know for sure why not? It comes from japanese knotweed, an invasive plant that gardeners in the UK often pay to have removed. (Latin name polygonum cuspidatum) This plant has been used medicinally for over 2000 years in East Asia.. and its roots, which also contain emodin, are being used to treat covid-19 in China as "Huzhang". Huzhang looks a bit like rhubarb, color wise. But it contains a number of related and unrelated compounds in its natural form. One, emodin being mildly hepatotoxic while resveratrol is not , And as purified resveratrol is already in the supply chain that makes a safe thing to take daily, while taking all the other precautions. I know that if I was a doctor or nurse, I would be careful to get vaccinated as well as take both resveratrol and n-acetylcysteine, an amino acid that I also suspect might be useful..A lot of studies have pointed out the possibility of its usefulness in Covid-19 for various scientific reasons. These papers can be read on PubMed.
Duplexer interconnect cables  - Page 1
Forum section: electronics / rf-microwave

author: Jesset1996.5
author_rank: Regular Contributor
timestamp: June 02, 2021, 01:41:41 am
content: Hello, I am in the process of finalizing my 6m duplexer that I had made out of some old hardline a broadcast engineer had saved from the scrap pile for me. I'm currently making patch cables for it out of some RG-400 I had around but im a bit confused on the frequency I should cut them to. I would assume you would cut them for the rx and tx frequencies? In my case being 52.6 and 52.1 mhz. Please excuse my ignorance as I have never made 1/4 wave cables (using my VNA) for anything other than an array that I had built.

author: xmo
author_rank: Regular Contributor
timestamp: June 02, 2021, 03:59:58 pm
content: http://www.repeater-builder.com/antenna/heliax-6m-filter.html
Firmware for RF generator 35-4400 MHz - Page 1
Forum section: electronics / rf-microwave

author: fant
author_rank: Contributor
timestamp: May 29, 2021, 01:15:12 pm
content: Good morning;some time ago I have bought a RF generator that was working well.After some time of power off, I have turned it on again, but the display is completely blank and no command is accepted from keyboardThe unit is the one here below.The unit now as soon as is with power is all with the screen white.Anybody has the firmware to re-flash the STM32 that is inside?Thank you in advance
JFW 50DR-082 Manual Attenuator teardown - Page 1
Forum section: electronics / rf-microwave

author: doktor pyta
author_rank: Frequent Contributor
timestamp: May 23, 2021, 04:54:00 pm
content: JFW 50DR-082 is a manual attenuator DC-2000MHz 0-110dB in 1dB steps.The attenuator began to behave slightly unstable at some positions.It was the time to give it some cleaning.I haven't found any photos over the internet so I'm posting mine.Steps for disassembling (not so obvious when attempting for the first time):0. use permanent marker to mark positions of all the critical components. Set the attenuator to a known position (say 0,0)1. remove the knobs2. remove the connectors and small aluminum square part placed between the connectors.3. remove all remaining screws except of two located near the center of rear side.4. gently slide and rotate rear section and remove shielding gasket through the hole made for the connector.5. repeat step above for the front section. There are 3 shielding gaskets inside.More info and the datasheet:https://www.jfwindustries.com/product/50dr-082-dual-rotary-attenuator/
TV TESTS RECEIVER Rohde & Schwarz - Page 1
Forum section: electronics / rf-microwave

author: jean françois
author_rank: Contributor
timestamp: April 16, 2021, 01:07:15 pm
content: Hello, for an R&S EMFP tv test receiver, 2022.6004.02Many searches on the web did not yield anything,moreover nothing generally found on the TV TEST RECEIVERS rohde & schwarz.maybe there is a site that I don't know.I am looking for the operating manual of the EMFP and the service manual of this device, which I recovered broken down.thanks in advance,if manual purchases, a paypal payment is possible.Thanks in advance,Jean François.

author: A.Z.
author_rank: Super Contributor
timestamp: April 17, 2021, 07:40:06 am
content: did you try searching here ?https://www.rohde-schwarz.com/us/manual/search-for-manuals-general_251441.html

author: jean françois
author_rank: Contributor
timestamp: April 21, 2021, 04:45:02 pm
content: Bonjour,Merci pour les informations j'ai essayé sur "manual rohde & schwarz", mais malheureusement je ne trouve absolument rien.j'ai verifié les tensions d'alimentation sur les points de tests internes , toutes le tensions sont presentes et bonnes il n'en manque pas.Et pourtant sur la face avant les leds "failure sont toutes allumées en rouge.il semblerais pourtant que l'appareil fasse tous ces test de départ.Je vous remercie pour toutes toutes les informations , elles sont les bien venues,Merci,.Jean françois.

author: A.Z.
author_rank: Super Contributor
timestamp: April 21, 2021, 05:15:50 pm
content: Did you try contacting R&S support ? Maybe they'll point you to some useful info/manualThat said, english is not my native language, but I use it here for respect to others, so please, stop posting in english and replying in french, thank you

author: jean françois
author_rank: Contributor
timestamp: April 23, 2021, 08:15:42 am
content: Hello, I'm going to see the R&S side.sorry but i didn't pay attentionI would therefore answer in English.thank you anyway.

author: A.Z.
author_rank: Super Contributor
timestamp: April 23, 2021, 12:18:56 pm
content: please post about R&S replyas for the english, thank you, I've no problems with it, but others may, so I think being polite to other forum members is a good idea

author: jean françois
author_rank: Contributor
timestamp: May 16, 2021, 07:15:21 pm
content: Good evening,I am very sorry for the delay in responding.unfortunately my health means that I am only on the pc occasionally, that's why the radio is important to me.still no information, I haven't had the time to ask for the R&S yet.Thank you for your answers.this time I answer in English.regards,jean françois
Signal R-535 Airband - Page 1
Forum section: electronics / rf-microwave

author: veedub565
author_rank: Frequent Contributor
timestamp: May 15, 2021, 07:18:59 am
content: I recently got ripped off for a Signal R-535 reciever described as brilliant condition... but actually appears to have been stored outdoors in the garden for 30yrs.Anyway, it works but I've noticed that if I leave it monitoring a frequency. When I key up the HF rig I get a loud buzzing through the speaker of the airband reciever. None of my other scanners or transceivers do this. I have a pair of amplified speakers in the shack and they don't do it either.Connecting the metal case of the R-535 to RF ground reduces the buzzing, but doesn't eliminate it entirely.I'd have thought these recievers would be a bit better shielded than that.After all the rave reviews I'm not that impressed with this reciever I have to say. It feels quite cheap, more like radio shack own brand £14.99 in 1990 than an expensive quality item. Doesnt help of course that my "brilliant condition" example is actually corroded.Also, the ticking sound it makes when it scans. Is that normal?Oh and the on off switch. It clicks when switched on, but then doesn't click when switched off. Is that normal too?

author: jmh
author_rank: Contributor
timestamp: May 15, 2021, 08:13:33 am
content: Can't answer the screening as when I had mine I wasn't licensed so no tx anywhere. Mine did tick when scanning and the on-off was similar to yours, physical click for on, no click for off.

author: veedub565
author_rank: Frequent Contributor
timestamp: May 15, 2021, 08:35:38 am
content: Thanks, thats good to know they are all like that with the scan ticking and on off switch. At least I won't be chasing a fault that isn't there. It does seem a bit cheap and poorly designed compared to my Yaesu's of a similar vintage.That said It does recieve better than the broadband scanner.
Mystery SUHNER RF-Connector for an AOM - Page 1
Forum section: electronics / rf-microwave

author: DH7DN
author_rank: Regular Contributor
timestamp: May 10, 2021, 11:12:51 pm
content: Greetings fellow nerdsI totally did not steal this phrase from YT/NurdRageMaybe anyone from the RF forums may help me with this matter. I have bought a vintage acousto-optic modulator (AOM, Tpye Crystal Technology 3070-10) for experiments with lasers. AOMs are piezoelectric crystals excited by RF in the range from ~27 MHz to 200 MHz. Inside of the piezoelectric material, standing waves are generated which act as a diffraction gratings for the laser beam. Typical excitation RF power is in the range of 1-5 W.Since I have no information about this AOM, I wanted to test its properties (transfer function) with my test gear. Unfortunately I cannot attach it to my frequency generator unless I cut the cable and solder a BNC connector. I wanted to avoid this, just to prevent experimental mistakes (impedance mismatch, standing waves)According to the attached pictures, there is a LC-circuit in the proximity of the crystal, probably tuned to a resonance frequency which matches the properties of the AOM crystal. The RG174 cable has a mystery HUBER+SUHNER connector which is really hard to identify. It's not the standard SMA connector since its inner diameter is 4.3 mm (SMA = 6.0 mm) and I'm not sure if it's SSMA or MMCX. I've put some pictures of it, maybe you have an idea which kind of connector this might be? I'd appreciate your help!Few hints- The right angled connector is labeled 50 - SUHNER, the inner diameter is 4.3 mm, outer hexagon diameter is 6.0 mm- The cable is labeled as: Suhner Switzerland RG 174/U 50 + 2 Ohm- Different parts of the cable are labeled: Belden + <unknown> 8216 RG-174/U KF <unknown>- The mid part is encased with a rigid heat-shrinking tube- The AOM was probably produced in the 1990's, its origins and applications are unknownI surely am curious and I would like to take it apart but if it is possible to test it without greater intrusion, that would be my first choice :-)

author: mjs
author_rank: Regular Contributor
timestamp: May 11, 2021, 05:33:22 pm
content: SMC connector ?

author: DH7DN
author_rank: Regular Contributor
timestamp: May 11, 2021, 06:58:20 pm
content: Quote from: mjs on May 11, 2021, 05:33:22 pmCheers, thanks for the hint. SMC is highly possible, looks like we got a winner... I'll order a SMC jack and test itEdit 2021-12-19: I bought a SMC jack to BNC jack and it worked perfectly.