hybridfree/eevblog-posts huggingface dataset:
Are these microwave absorbers any good? - Page 1
Forum section: electronics / rf-microwave

author: grg183
author_rank: Contributor
timestamp: November 09, 2023, 01:48:54 am
content: I'm looking for affordable microwave absorbers for minimizing reflections during measurements. I don't need many and not necessarily top-of-the-line quality, I need just a few for strategical placement. I've noticed several vendors on Alibaba offering low-cost pyramidal microwave absorber tiles, like this one:https://www.alibaba.com/product-detail/Pyramidal-Microwave-Absorbing-Foam-rf-Absorber_1600306531990.htmlGiven the low-cost I'm quite skeptical of the real specifications of these absorber. Has anyone used these (or from similar vendors) and can share their experience?

author: CaptDon
author_rank: Super Contributor
timestamp: November 19, 2023, 11:03:15 pm
content: Can't tell you if that exact product is any good, but the design is the standard of the industry for E.M.I. test chambers and the ones that have about a 2Ft. square footprint usually run a couple hundred U.S.D. I guess they do share the same fancy blue color with the cheap knock-off stuff. The good absorbers are a conductive foam similar in nature to the foam that CMOS I.C.'s used to be stored on. One company called them 'bug rugs'. Like all foam your multi-thousand dollar investment will crumble and disintegrate over time!! I have brushed so much of that stuff out of my hair when setting up tests in an old lab about 20 miles from my home. Several of the 'blocks' have fallen off the ceiling lately.

author: coppercone2
author_rank: Super Contributor
timestamp: December 02, 2023, 06:19:07 am
content: you know I wonder if that room is bad for you, they found a issue with CPAP machine foam giving people lung problems.
Hot Iron magazine - new issue out - Page 1
Forum section: electronics / rf-microwave

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: November 30, 2023, 04:01:15 am
content: Was an email bulletin, now it's a free quarterly pdf magazine with hints & tips for the homebrewing amateur.A new issue has just come out.Find it and back issues here:https://www.w4npn.net/hot-iron-directory/

author: RoGeorge
author_rank: Super Contributor
timestamp: November 30, 2023, 12:12:51 pm
content: The collection looks interesting, quite a lot of builds and schematics there, thanks!An RSS feed would allow web subscriptions without email, to help reminding about new posts there.

author: p.larner
author_rank: Frequent Contributor
timestamp: November 30, 2023, 01:54:08 pm
content: just started reading these starting from oldest,look very poorly done,ok for free tho.,remind me of old car magazines from the 60's where some of the ideas are cheesy to put it mildly,hope the later ones get better.73

author: A.Z.
author_rank: Super Contributor
timestamp: November 30, 2023, 07:10:06 pm
content: Quote from: vk3yedotcom on November 30, 2023, 04:01:15 amnice, thank you for posting, glazed at the index and at some issues and it seems interesting, thanks again !

author: p.larner
author_rank: Frequent Contributor
timestamp: December 02, 2023, 05:33:59 pm
content: reminds me of a poor version of g3va;s technical topics but just poorly done.still worth a read tho,cheers for te link+73
Is it possible to receive radio with this dongle? - Page 1
Forum section: electronics / rf-microwave

author: avitsur
author_rank: Contributor
timestamp: December 02, 2023, 10:05:28 am
content: [ Specified attachment is not available ] [ Specified attachment is not available ] [ Specified attachment is not available ]I have this dongle, it's main purpose is to receive tv broadcast. I wonder if it can be used as a sdr to receive radio transmissions too. if so, how can I tell the frequency range of it and if you can suggest the adequate software for it.

author: wasedadoc
author_rank: Super Contributor
timestamp: December 02, 2023, 10:18:54 am
content: My crystal ball is broken. I have no clue what dongle you have.

author: avitsur
author_rank: Contributor
timestamp: December 02, 2023, 11:30:02 am
content: Sorry, my fault. I hope that the crystal ball is mended.

author: janoc
author_rank: Super Contributor
timestamp: December 02, 2023, 03:31:14 pm
content: Quote from: avitsur on December 02, 2023, 11:30:02 amWithout knowing what exactly is inside of that dongle one would need a lot better crystal ball to answer that. Some of these can be used because they have the Realtek chips that are supported by RTL SDR. Many others are not.Also depends on what sort of radio are we talking about. E.g. the RTL SDR compatible ones usually can't receive (or only very poorly) anything below about 30MHz. Normal FM and DAB should work with whatever software that thing came with, you have it written right on the dongle.In addition, that USB connector doesn't look healthy at all - I am pretty certain it is not meant to be twisted to one side like that.

author: p.larner
author_rank: Frequent Contributor
timestamp: December 02, 2023, 05:38:37 pm
content: had one for dtv,then got it working as a radio sdr receiver,it was cra then overheated and died,not bothered since,if i remember it was a pita doing it tho!.not worth the effort imho.
Siglent SSA3032X Plus -> SVA1032X Plus VNA RF switch sweeps - Page 1
Forum section: electronics / rf-microwave

author: kj7e
author_rank: Frequent Contributor
timestamp: November 28, 2023, 08:43:18 pm
content: I built an RF switch with the intent of never exceeding 52MHz, I focused on Insertion Loss and VSWR below 6m, not so much on Port Isolation. Came out to less than 0.02dB Insertion Loss at 60MHz. I have a need to switch a Modulation Monitor (Inovonics 551) between three transmitters at at 101 MHz. Not finding an RF switch I wanted to spend lots of money on (I would need 6 of these), I decided to test this switch as proof of concept and just build my own. My recently converted SSA -> VNA came in handy. This one, was designed to handle power in the HF spectrum, my next version will be for low power switching in the VHF range. Going to use some Panasonic high freq reed relays and BNC's rather than the high current relay and UHF connectors seen below.
Comments about radiomobile - Page 1
Forum section: electronics / rf-microwave

author: Marcel_21
author_rank: Newbie
timestamp: December 09, 2023, 10:58:00 pm
content: Hi everyone, i am professional beginner in RF propagation. In my Job i need to simulate coverage of Radio Links in 5 GHz band (PtMP), i choose Radiomobile because is a powerful and free tool, but i encountered problems such as manage private elevation data (Radiomobile support 1 arc DEM data, and i can't use BIL format data). In the other hand i dont see forums in any sites about radiomobile, i saw little information about the software. My question is, what softwares do you use actually to simulate propagation coverage, to manage elevation data, what do you think is the reason why radiomobile is not heard much, or if it is not really so? I read you
g7fek antenna - Page 1
Forum section: electronics / rf-microwave

author: p.larner
author_rank: Frequent Contributor
timestamp: November 23, 2023, 07:07:40 am
content: would it be possible to build a g7fek antenna wth the windowline running horizontaly,would that be better for nvis?

author: ZigmundRat
author_rank: Regular Contributor
timestamp: November 23, 2023, 05:01:56 pm
content: I think it will make little difference as the ladder line portion is only 7.4 meters long. For 80/40 meters this is so low that it will provide NVIS operation. The antenna has both vertical and horizontal components (and consequently vertical and horizontally polarized radiation) and a more complex pattern than one or the other alone.You may find it useful to refer to the article athttps://rsars.files.wordpress.com/2013/01/g7fek-antenna-analysis-iss-1-31.pdfCheers!

author: A.Z.
author_rank: Super Contributor
timestamp: November 23, 2023, 06:07:19 pm
content: Quote from: p.larner on November 23, 2023, 07:07:40 amall is possible, you can modify it as you like, but before doing so, maybe, just maybe, it could be the case to understand why that antenna was designed that way and how the currents flow on it, otherwise I strongly suspect you would be condemned to a failure to achieve what you wantanyhow, go on and modify it, call it as you want (since it won't be a "g7fek" anymore) and have fun
Is this signal FSK or PSK?? - Page 1
Forum section: electronics / rf-microwave

author: emre2blue
author_rank: Newbie
timestamp: November 22, 2023, 11:54:11 am
content: Hello, I'm trying to read my TPMS system with CC1101. Now I'm using URH in windows 11 with RTL-SDR. I'm working on my car with TPMS, I've successfully capture the signal and decoded in UHR. Sensor catalog says that it is FSK modulated 433.92Mhz - 76khz deviation , 9600 baud rate. And Manchester coded. All seems fine . But is this signal really FSK?UHR Decoded the signal without problem. And data is there but how is this a FSK signal. I'm asking because when I want to capture it with CC1101, I get random bits and I could not manage the capture any real data since I started the project. But every time I use UHR it captures perfectly.Here is the data for UHRhttps://drive.google.com/drive/folders/1yoGfmySBvS7HPjrfBjRb0RMwVOsWrdtn?usp=sharingAdditional information :if you look at the wave from of BPSK. it is almost same as the data I've capture from the URH. how can it solve the wave form as FSK??? also I've done a spectrum analyzer in URH. When I check the form it is like FSK this time.I'm so confused. Please help

author: radiogeek381
author_rank: Regular Contributor
timestamp: November 23, 2023, 01:16:30 am
content: It looks to be FSK.But really really really awful FSK. It would be really really awful PSK too.The abrupt changes in phase where the first derivative goes from positive to negative more or less instantaneously is vile. Such modulation schemes went out with polar relays and 88 mH toroids.Civilized FSK is not if (D == 0) x = sin(f1 t) else x = sin(f2 t)The digital waveform is *shaped* with some kind of filter and then converted to a continuous function m(D) between -1 and 1. Then the output is x = sin(f0 + m(D) * delta_F)That’s not what we see here. Instead we see the instantaneous phase changes that cause enormous clicky sidebands. Those are all the spikes in the spectrum.But this may be an artifact of your collection scheme? I see that you’ve limited the RX bandwidth to 9.6 kHz. Am I reading that right? For a signal with a shift of 76 kHz deviation, you really want a sample rate above 100 kHz (higher if possible) and you want to open the filter up to at least 50 kHz on either side of the carrier.Beyond that, one can do a fairly simple FSK demodulator by “beating” the carrier down to baseband with a complex sinusoid tuned to the midpoint between the two tones. This gets you an I and Q representation of the signal. Looking at the IQ values as a vector in the complex plane, the “high” tone is represented by a counter-clockwise rotation of the vector, a “low” tone by a clockwise rotation. This scheme is substantially easier to implement than a BPSK demodulator that needs to track the carrier phase reasonably well. For the FSK demod that I just described, you don’t even have to get the carrier frequency correct, just close.From eyeballing your traces, this is an FSK signal. But a pretty crappy one.
IC RF Attenuator in Rigol DSA832E-TG - Page 1
Forum section: electronics / rf-microwave

author: azemati
author_rank: Contributor
timestamp: November 21, 2023, 12:16:45 pm
content: Hello friendsHope you are doing great.I have a spectrum analyzer from Rigol, model DSA832E-TG, which unfortunately shows 40 dB less power.I checked the device and found these two ICs and two diodes that I specified in the figure.Does anyone know the part number of this IC and diodes? Please help me

author: RFDx
author_rank: Regular Contributor
timestamp: November 21, 2023, 07:14:56 pm
content: The two RF-switches look like PE42551 (discontinued) from Peregrine.https://www.globes.de/weborder/svliste/pdf/pe42551ds.pdf
Rafael Micro R860 sourcing - Page 1
Forum section: electronics / rf-microwave

author: kazam
author_rank: Regular Contributor
timestamp: November 21, 2023, 12:03:23 pm
content: Hi,I'm trying to get a hold of the RTL SDR tuner chip R860. The R820T2 was discontinued as I understand it.I need at least a few IC:s and possibly hundreds. Anyone know where I can buy them?/k
somerkamp ft-767dx/yaesu ft-707 cw mode issue - Page 1
Forum section: electronics / rf-microwave

author: p.larner
author_rank: Frequent Contributor
timestamp: November 13, 2023, 01:09:51 am
content: i have this radio,its a rebadged yaesu ft-707,if i select cw wide or narrow on any band the speaker emits a loud (1khz about.) tone,its loud and the vol control wont change its volume,i can still hear stations in the background but the background hiss can be heard and the vol pot will change that,but the 1kc tone is always comming over the speaker no matter where i set the vol,cw does actualy tx ok tho if i monitor on a web sdr,any ideas where to start?,i have the yaesu ft-707 sm,cant find one for the sommerkamp model tho,will post in the repairs section too,thanks+73

author: Andy Chee
author_rank: Super Contributor
timestamp: November 13, 2023, 04:41:38 am
content: My radio is not the same, FT-757GX, so I may be completely off track.But look for a “marker” switch on the back of the radio. This is basically a tone marker used for frequency calibration and should be turned off in normal use.I just had a look at your FT-707 operating manual. Page 4 describes the MARK switch. This should be turned off.

author: p.larner
author_rank: Frequent Contributor
timestamp: November 18, 2023, 08:16:14 am
content: found the cause was the sidetone pot on the af board was wound to max!.

author: p.larner
author_rank: Frequent Contributor
timestamp: November 20, 2023, 02:17:00 am
content: well,turning the sidetone pot to min cured the symptoms,guess there is still a problem to as i guess the sidetone should not be on in rx only tx?,am i correct in thinking that?.

author: Andy Chee
author_rank: Super Contributor
timestamp: November 20, 2023, 09:00:31 am
content: Try inserting a “dummy” CW key into the keying jack (just a plug with a couple wires hanging off it).Make sure you use the correct plug. Check the FT-707 user manual for wiring diagram.When the key is open, sidetone should be off. When the key is closed, sidetone should be on.

author: A.Z.
author_rank: Super Contributor
timestamp: November 20, 2023, 02:08:17 pm
content: Quote from: p.larner on November 18, 2023, 08:16:14 amsometimes reading the manual (aka RTFM) is useful, isn't it :-6 ?
twisted pair question with transmission - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: November 20, 2023, 07:55:06 am
content: SO kind of related to PCB layout maybe, where its said that higher frequencies tend to follow under the conductor.Which lead me to think of this idea...If you have a twisted pair, lets say a 100 ohm impedance. Of signal + gnd.Then you have a separate ground wire, some distance away from this twisted pair, say 1 inch.If you generalize it to twin lead (I think the math is similar), you get for 16 awg wire, two wires that are basically right up to each other being 100 ohms.Now you have the parallel ground wire 1 inch away, meaning the impedance of this twin lead (red spiral wire segment and the free negative wire) is ~450 ohms.is it correct to think if you give this wire a signal, its a voltage divider? so the majority of the current will flow through the twisted pair black wire and a small portion on the strait wire?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 20, 2023, 08:12:02 am
content: N conductors in constant cross-section gives a symmetrical NxN matrix(?) of transmission lines, yes.For the N=3 case, and for asymmetrical distances (close pair plus one distant), the coefficients end up such that the pair-ness is easily recognizable, and we might express that close-together pair as an equivalent CM+DM representation (assuming for a moment, we have absolute voltages per conductor), where the CM is basically saying the two lines act together as one, which then becomes DM with respect to the remaining (more distant) conductor. We of course have two degrees of freedom (two differential modes) for three conductors. Note that we can convert any three-conductor scenario in this way, it doesn't matter what its relative impedances are; we aren't losing any degrees of freedom by thinking about two different kinds of differences, as long as we have a linearly independent basis using them. And we can have different impedances and velocities for each of these, since in general we could wrap some conductors with dielectric and others not (different, within reason, of course).Because the close-in pair CM acts as a thicker conductor against the remaining one, Z will be a bit lower than the twin-lead case, and also E-field balance at a distance won't be perfect; but yeah, it's actually three wires in a cable, of course it's asymmetrical, and presumably the signals would be balanced in amplitude to reflect that (or if nothing else, by running the cable through a choke core to improve balance).Tim

author: coppercone2
author_rank: Super Contributor
timestamp: November 20, 2023, 08:16:37 am
content: how well does the bootleg impedance calculation stand up though? very error?i am gonna make this with zip ties and measure it on a segment I thinkhow many feet long should it be to see something interesting? I have bootleg PVC wire I HATE
sem transmatch dont. - Page 1
Forum section: electronics / rf-microwave

author: p.larner
author_rank: Frequent Contributor
timestamp: November 19, 2023, 04:50:56 pm
content: i have an sem transmatch with the ezitune+160m option,inside is an abortion of poor design,has anyone ever managed to get one of these abortions to actualy match anything except a dummy load?.

author: A.Z.
author_rank: Super Contributor
timestamp: November 19, 2023, 09:28:21 pm
content: again ?https://www.eevblog.com/forum/rf-microwave/sem-transmatch-variations/msg5174667/#new

author: p.larner
author_rank: Frequent Contributor
timestamp: November 19, 2023, 10:29:56 pm
content: what do you mean by "againe",its a totaly different question ok!.

author: p.larner
author_rank: Frequent Contributor
timestamp: November 20, 2023, 02:14:22 am
content: well finaly got this dog working at least on 80+40,replaced the coupling cap and used the coax input with a 4-1 balun,not tried higher bands yet.
Low level video feedthrough measurement after a delay - Page 1
Forum section: electronics / rf-microwave

author: yuyilibai
author_rank: Newbie
timestamp: November 14, 2023, 11:40:33 pm
content: I heard about another project at work and was curious, and asked about the details. I am new to the field, and do not have a good solution myself, and I wished to ask if anybody had suggestions.We are looking to measure video feedthrough content from a device after switching. Not peak video content, but content after 20-40ns delay after switching.We are interested in video content in 600-1400MHz band, and expect to see <-70dBm content.It seems that the oscilloscopes we have lack the dynamic range for this purpose.I suggested using a spectrum analyzer in zero-span mode, only to realize later that our equipment has limited bandwidth to measure such fast signals.What other measurement options can there be?
SAT(L-Band)+GNSS Combo Antenna - Page 1
Forum section: electronics / rf-microwave

author: madhu.wesly01
author_rank: Regular Contributor
timestamp: October 06, 2023, 05:24:13 am
content: Hello all,I am looking for a smallest possible form-factor SAT(L-Band)+GNSS Combo Antenna. I would like to know if anyone can suggest workable options which are readily available in the market if any for the Combo antenna.Thank you!

author: hamdi.tn
author_rank: Frequent Contributor
timestamp: November 19, 2023, 02:51:21 pm
content: Hi,I suggest ADFGP.60A from TaoglasHamdi
sem transmatch variations - Page 1
Forum section: electronics / rf-microwave

author: p.larner
author_rank: Frequent Contributor
timestamp: November 14, 2023, 02:21:35 pm
content: Hi all,i have a sem transmatch amu,mine has top band,dummy load abd the ezitune option,it is like the pic in view 1,there is another variant with more connections on the rear,can anyone explaine the differences please.

author: A.Z.
author_rank: Super Contributor
timestamp: November 18, 2023, 09:57:56 am
content: https://qsouk.forumotion.com/t1362-s-e-m-tran-z-match-atuit's basically a 100W Z-match unit, some have a noise bridge (called ezTune) to try speeding up the match process
Rohde & Schwarz EZK - Page 1
Forum section: electronics / rf-microwave

author: LUBER41
author_rank: Newbie
timestamp: November 12, 2023, 10:58:12 am
content: Do some body have a service manual for the Rohde & Schwarz EZK frequency controller part of the ET001? I am not looking for an operator manual as I have it.
EMC for Control Area Networks and Automotive Electronic Sub Assemblies - Page 1
Forum section: electronics / rf-microwave

author: Greece2000
author_rank: Contributor
timestamp: September 28, 2023, 02:48:46 am
content: So I can't understand what kind of standard or testing regime is required here.I have an automotive electronic subassembly (ESA) which very clearly goes under UN ECE Reg 10. However Reg 10 doesn't really mention control area networks and how to test them w.r.t radiated emissions.Suppose you have an automotive ESA with a CAN connection. The ESA has a switching converter and it may place noise on the CAN line, a 3m CAN line may emit radiated emissions.There is also to be considered the emissions from the CAN line from normal data communication from your ESA.So how is this to be taken into account?In Australia.

author: Greece2000
author_rank: Contributor
timestamp: September 28, 2023, 11:51:28 pm
content: Please respond.

author: coppercone2
author_rank: Super Contributor
timestamp: October 01, 2023, 05:45:37 am
content: i suspect this regime is not democraticand you should probobly call a test lab or something because this is the depths of paid engineering beurocracy from hellthe engineering time from doing this wrong based on forum advice of basically legal frame work is gonna cost more then possibly a consulting feewatch the guy on the forum that knows this in 2022 gets it wrong because of some addendum from 2023

author: Niklas
author_rank: Frequent Contributor
timestamp: November 09, 2023, 11:09:21 pm
content: The R10 is typically lower in demand compared to what many OEMs require. The emission tests follows CISPR25 and the DUT is supposed to operate during the test and you check all emissions (CAN, power etc) combined. You might need something to simulate communication from other ECUs to make the DUT fully operational.CISPR25 does not explicitly mention CAN, its harness length or placement of the optical interface. For the conducted emissions test, be sure to use the short harness between the DUT and the LISNs as described for the voltage method in CISPR25. Using the longer harness for radiated emissions also for conducted can cause issues with CM around 40 MHz due to resonance. This also applies if you have a short harness for power and a long harness for CAN.
bias t schematic for an atu100 - Page 1
Forum section: electronics / rf-microwave

author: p.larner
author_rank: Frequent Contributor
timestamp: October 16, 2023, 10:48:58 am
content: hi i want to fit my atu100 atu on my mast so need a bias t to power it from the rg-213 coax,has anyone a schematic for building one for a hf 100watt tx,i need component values so i can order the parts,73.

author: A.Z.
author_rank: Super Contributor
timestamp: October 16, 2023, 05:00:05 pm
content: see herehttps://www.hayseed.net/~jpk5lad/K5LAD%20Memories/Vols%2031-35/Memories--Vol33.htm

author: max-bit
author_rank: Frequent Contributor
timestamp: October 25, 2023, 08:40:12 am
content: A good BIAS-T is not that simple.Write exactly what frequencies you will use.

author: p.larner
author_rank: Frequent Contributor
timestamp: October 26, 2023, 10:03:42 am
content: its going to be mostly for 80 but upwards from time to time but hf.

author: radiolistener
author_rank: Super Contributor
timestamp: October 27, 2023, 05:33:39 am
content: How you're planning to protect LNA input on antenna side from high voltage during transmission?

author: p.larner
author_rank: Frequent Contributor
timestamp: October 27, 2023, 09:11:37 am
content: there is no lna,its for an atu.

author: radiolistener
author_rank: Super Contributor
timestamp: October 27, 2023, 09:25:02 am
content: then just try to connect DC through inductor to coax. On ATU side just use inductor with capacitor to extract DC. I think should works ok, just needs to experiment to select proper inductors.But such solution may inject some noise from ATU controller. So, it may needs to add good filtering on ATU side.

author: A.Z.
author_rank: Super Contributor
timestamp: October 27, 2023, 04:51:48 pm
content: Quote from: max-bit on October 25, 2023, 08:40:12 amoh, for the 3 to 30 MHz range it can be that simple, then for sure it would be better running (say) some CAT5 cable and using that to power the ATU and to have spare wires for other purposes

author: p.larner
author_rank: Frequent Contributor
timestamp: November 07, 2023, 04:17:04 am
content: heres the mfj schematic,i have L1 100uh but need to know what wattage to order for L2 1milli henry,can anyone tell me what to order?,there are some 1 watt ones on ebay,would they be ok?.

author: p.larner
author_rank: Frequent Contributor
timestamp: November 08, 2023, 02:53:56 am
content: anyone?.
Power/SWR Meter Not Recognized by Windows 10 - Page 1
Forum section: electronics / rf-microwave

author: ko4nrbs
author_rank: Regular Contributor
timestamp: November 05, 2023, 04:44:17 pm
content: Fox Delta SWM3 Linkhttp://foxdelta.com/products/swm3-0915.htmI keep getting this error code when I plug in the SWM3 power meter.Windows has stopped this device because it has reported problems. (Code 43)andUnknown USB Device (Device Descriptor Request Failed)I have searched online and tried everything recommended but it still shows the same code. I even tried it on a different computer with the same results. I am now thinking maybe the Firmware may be the problem even though it works fine as a standalone device.Any ideas?73,Bill KO4NR

author: CJay
author_rank: Super Contributor
timestamp: November 05, 2023, 05:38:45 pm
content: The website suggests there's a firmware/software update for Win 10, have you installed it?
Harmonic conversion -- Any favorite mixers? - Page 1
Forum section: electronics / rf-microwave

author: ezalys
author_rank: Frequent Contributor
timestamp: November 04, 2023, 03:02:58 am
content: I'd like to have an auxiliary receiver dedicated to IQ mixer balancing -- that is, I want to discriminate three tones about 50 MHz apart with 30 dB of dynamic range at a frequency of 6 GHz to 12 GHz. To do this cheaply and simply, I'd like to alias down from NxLO + RF. Does anyone have experience doing this? Are there some inexpensive mixers that are better suited for this than others? It seems like designs that do this don't use mixers that are necessarily specified for it, so is it a matter of testing and figuring out which ones work best?

author: KE5FX
author_rank: Super Contributor
timestamp: November 04, 2023, 05:25:54 am
content: What's the application, and do you already have RF ADC(s) in the block diagram? If you only need 30 dB of dynamic range, you might be surprised at how well some RF ADCs can work in (very!) high Nyquist zones, well beyond their rated specs.

author: ezalys
author_rank: Frequent Contributor
timestamp: November 04, 2023, 01:54:23 pm
content: No ADC. Just looking for a suitable mixer. Ideally better than 30 dB!
Service manual - Tecsun S-8800 - Page 1
Forum section: electronics / rf-microwave

author: Longines
author_rank: Newbie
timestamp: October 31, 2023, 07:34:14 pm
content: HelloMaybe someone has or knows where to download a free service manual for the Tecsun S-8800 receiver.Thank You for your attention.

author: xrunner
author_rank: Super Contributor
timestamp: October 31, 2023, 10:31:53 pm
content: For those types of lower end consumer electronics I doubt you can get a service manual.Note: I'm saying you can't because as soon as I say you can't, someone will find it, so it's for good luck.
cap types in a bias t for 100watts power tx hf - Page 1
Forum section: electronics / rf-microwave

author: p.larner
author_rank: Frequent Contributor
timestamp: October 30, 2023, 08:05:58 pm
content: can metalized 4kv Metallized Polyester Capacitor types be used in this type of bias t?.

author: coppercone2
author_rank: Super Contributor
timestamp: October 30, 2023, 08:43:55 pm
content: what is the ESR of the capacitor at the frequency of interest. then you can figure out how hot it will get. then you can figure out if the life time is effected

author: TimFox
author_rank: Super Contributor
timestamp: October 30, 2023, 08:59:54 pm
content: For what frequency range?Polyester does not have very highQover its useful range compared with polypropylene or polystyrene, so will have some loss.Also, film capacitors can easily have self-resonant modes (series resonance) in the MHz region, so will look inductive at higher frequencies.I used to use ceramic or porcelain capacitors in this shape, with broad ribbon leads, for high-power RF circuits, but they seem to be hard to find now:https://exxelia.com/en/product/detail/464/spt519-caw-cew-series

author: p.larner
author_rank: Frequent Contributor
timestamp: October 30, 2023, 10:47:36 pm
content: mostly hf 160-10m

author: TimFox
author_rank: Super Contributor
timestamp: October 30, 2023, 11:33:25 pm
content: The polyester capacitors will not work well at 30 MHz (10 m).
Need source for Microdot connector - Page 1
Forum section: electronics / rf-microwave

author: jmelson
author_rank: Super Contributor
timestamp: October 30, 2023, 06:55:04 pm
content: We need to find a source for a Microdot connector. I THINK I have the part # 051-0056-0001. It is a female hermetic connector that is intended to be soldered into a bulkhead which will be under vacuum. The threads seem to be about 1/4" major diameter and maybe 32 TPI. I have searched all the distributors I know of, none of them can come up with that part #. Some web searches do come up with it, but none of them are actually sellers of this part. Anybody know a better place to look?Thanks,Jon
g7fek antenna - Page 1
Forum section: electronics / rf-microwave

author: p.larner
author_rank: Frequent Contributor
timestamp: October 22, 2023, 11:18:13 pm
content: has anyone here tried one ?.

author: p.larner
author_rank: Frequent Contributor
timestamp: October 25, 2023, 07:45:59 pm
content: is there any way to mod this for nvis?,as no room for a low dipole on 80.

author: A.Z.
author_rank: Super Contributor
timestamp: October 27, 2023, 07:06:02 pm
content: Quote from: p.larner on October 25, 2023, 07:45:59 pmthere are other antennas which may fit you NVIS needs, going for an antenna which WAS optimized to keep low radiation lobes, and pretending to "un-optimize" it to do NVIS seems just crazy to me; why are you insisting on such antenna ?Wanna an example ?https://www.nonstopsystems.com/radio/frank_radio_antenna_KGD.htmplace that one horizontal and you'll have NVISOr are you pretending to put up a "magic" antenna giving you the radiation pattern you want when you want it ?

author: A.Z.
author_rank: Super Contributor
timestamp: October 28, 2023, 07:45:56 am
content: and thenhttps://www.w8ji.com/nvis_n_v_i_s_antenna.htmhttps://www.tetech.nl/divers/SmallGarden_80m.pdfhttps://www.dj0ip.de/open-wire-fed-ant/short-antennas/short-80m-antennas/some food for thought
vna load - Page 1
Forum section: electronics / rf-microwave

author: p.larner
author_rank: Frequent Contributor
timestamp: October 25, 2023, 07:42:27 pm
content: My nanovna has bnc connectors fitted,its a pita when doing a cal having to use adapters,cauld i not use a bnc 50 ohm termination,like you get for scopes?.

author: tszaboo
author_rank: Super Contributor
timestamp: October 25, 2023, 08:14:30 pm
content: You would need an open/short 50R cal kit for that. The 50Ohm BNC terminators for scopes are kinda bad, they are not 50R anymore already at a few hundred MHz.It depends what you are using it for. If you want to look at the ham radio antenna, it's probably fine. If you want to match an LTE antenna at 3000MHz+, you need a lot better cal kit for that.

author: metrologist
author_rank: Super Contributor
timestamp: October 25, 2023, 08:36:55 pm
content: https://www.eevblog.com/forum/rf-microwave/diy-short-open-and-load-for-vna-calibration/https://www.sdr-kits.net/600-MHz-BNC-Calibration-Kits/BNC-3pc-Cal-Kit

author: Bud
author_rank: Super Contributor
timestamp: October 25, 2023, 08:56:11 pm
content: @OP what is your question?

author: metrologist
author_rank: Super Contributor
timestamp: October 25, 2023, 09:33:14 pm
content: I think he wants to use something like this for a load standard during OSL cal.https://www.centricrf.com/terminations-loads/bnc-terminations/cft50b-bnc-termination-feedthru-male-female-1ghz-vswr-1-3-2watt/

author: p.larner
author_rank: Frequent Contributor
timestamp: October 26, 2023, 06:31:22 am
content: i was thinking of thishttps://www.ebay.co.uk/itm/125432080487?hash=item1d3455a867:g:AfMAAOSwrkNi3ogl&amdata=enc%3AAQAIAAAA0CbfblyQRdQ8dhVDTU1CZSR2KhET8%2FOy%2FbKw2nx8%2BeYIld2qYz5iflDkuX4IL1JwVosN0h9s1F8l%2Fj0pMai3qvVJPYa4JGXFJIQls%2FegDX%2FAzQ2D52rPHAEJc%2Bw3KvA%2BEQO6umivQf1AOQlVWlY9g132WRpEx6HHt2yH5rOqAqR6ttjkscpXmerE6uEbbfbcQuAcsWXc6vNf6QV4YWDnuSGQlRD6P23HLvPnTvSRiEk2iNGzU40hweAk%2FFAxmEWiQ51IH9EOgjUoqKNKonzVgEI%3D%7Ctkp%3ABk9SR4ix5qrtYg

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: October 26, 2023, 01:31:17 pm
content: Usually you want to calibrate as close to your DUT as possible. No point calibrating with a BNC at the VNA if you then proceed to hook up a cable to an antenna to measure that - you need to calibrate at the end of that cable with whatever connector that cable-DUT interface is.
varistor value in a bias T - Page 1
Forum section: electronics / rf-microwave

author: p.larner
author_rank: Frequent Contributor
timestamp: October 24, 2023, 08:41:33 am
content: any idea what value the varistor should be for this bias t mentioned herehttp://www.ifwtech.co.uk/g3sek/in-prac/best-of.htm#0904it will be to power an atu 100 so 12v+ rf.

author: RFDx
author_rank: Regular Contributor
timestamp: October 25, 2023, 02:44:46 am
content: The varistor type is mentioned in the article.

author: p.larner
author_rank: Frequent Contributor
timestamp: October 25, 2023, 07:47:16 pm
content: ive ordered 2 of at 18v,my god there expensive,about £5 a pop.
CMW500 / LTE Testing - Page 1
Forum section: electronics / rf-microwave

author: jd9197
author_rank: Newbie
timestamp: October 24, 2023, 12:33:59 am
content: Hi all.Does anybody have experience in testing cellular modems with the Rhode and Schwartz CMW500?I'm attempting to force my cellular modem to transmit at its max power level of ~25 dBm, so that I can verify power consumption of the modem itself.I was under the impression I may be able to control this from the CMW500 side.Can anybody give me ideas of how to go about doing this?Thanks in advance.

author: geggi1
author_rank: Frequent Contributor
timestamp: October 24, 2023, 04:07:28 am
content: You could probably use a directional cupler with a known cupling factor and a few attenuators to do this measurement.Cellphone technology is made to scale down the transmitted power when reception good and scale up when bad.By putting a attenuator on the antenna connector before the antenna you will make "bad reception" and force the modem to scale up the power.

author: ComfyChair
author_rank: Contributor
timestamp: October 24, 2023, 08:04:30 am
content: The method describe by @geggi1 will work. Make sure to set the cell power to a level the module can receive though.Assuming you are testing LTE there's another method: just set the desired transmit power in the configuration. See the attached screenshot.

author: jd9197
author_rank: Newbie
timestamp: October 24, 2023, 05:00:02 pm
content: This check box is really what I was looking for, although I definitely agree altering the signal quality itself through a few attenuators can work too.Thanks a lot!
W1GHZ wideband LDMOS amplifier - Page 1
Forum section: electronics / rf-microwave

author: geggi1
author_rank: Frequent Contributor
timestamp: October 26, 2023, 10:22:34 pm
content: I have been looking into the broadband linear amplifier by Paul Wade W1GHZ.The nice thing with tis design is tat it seams to be matched by the feedback ciruit.I'm considering to use the BLP9LA25S from Ampleon because it is reasonable priced at Digikey.Does anybody got any experience with this design?http://www.w1ghz.org/small_proj/Simple_Broadband_Power_Amplifiers.pdf?fbclid=IwAR3YgBK0XcMjm8Pf7RvfS0K1sAYcKH0kOPxq88wlrE-OUwmS_qzDBEkwM8s

author: RFDx
author_rank: Regular Contributor
timestamp: October 28, 2023, 01:41:09 am
content: Quote from: geggi1 on October 26, 2023, 10:22:34 pmIf you are looking for straight 50 Ohm IO impedance then you are limited to certain gm values. The BLP9LA25S has at 100mA almost 1S which makes the gain with a 50 Ohm load very high and the amp prone to instability. The max. output power in class-A would be, depending on the voltage of the power supply, relatively low compared to what the LDMOS can achieve. To get more output power and bandwidth you have to go down with the impedance and put some broadband transformers at in- and output.

author: LaserSteve
author_rank: Super Contributor
timestamp: October 28, 2023, 04:29:13 am
content: Paul Wade had a tray of the transistors ĥe used and kindly sold me a pair. If you choose the right type of feedback resistor, it works well.My gain numbers are somewhat lower then his, but I never saw any inherent oscillation.Yes, The design works.
rsp1a receiving video multiplex - Page 1
Forum section: electronics / rf-microwave

author: bb1
author_rank: Regular Contributor
timestamp: October 21, 2023, 02:17:18 am
content: While GRC has blocks to decode ATSC video, in practice using this block with RSP1A is not easy due to poor sensitivity and insufficient host PC computing power. Attached fileReceiving ATSC OTA video multiplex by RSP1a.pdfdescribes ways to go around problems and shows screenshots of the resulting video.

author: videobruce
author_rank: Frequent Contributor
timestamp: October 21, 2023, 04:40:07 pm
content: Ok, what is GRC?? It's not governance, risk (management)And have to assume RSP1A is this;https://www.anico-hamshop.eu/sdrplay_rsp1a_radio_spectrum_processor_1khz-2ghzBut the question that remains, why is all of this necessary when any recent TV w/ a ATSC1 tuner will 'receive' the TV stations?

author: bb1
author_rank: Regular Contributor
timestamp: October 23, 2023, 01:05:01 pm
content: https://wiki.gnuradio.org/index.php?title=What_Is_GNU_Radio

author: videobruce
author_rank: Frequent Contributor
timestamp: October 23, 2023, 01:21:44 pm
content: That still doesn't tell me what GRC stands for, nor does that link tell me (or anyone else) what those letters GNU stands for.Seems to be a epidemic of using letter terms w/o mentioning what the letters actually stand for. Not much of a 'FAQ' is it?That excludes the more,verycommon and often used letter terms as I just did.

author: bb1
author_rank: Regular Contributor
timestamp: October 23, 2023, 04:53:44 pm
content: GRC is short for GNU Radio Companion, which, as is said on the first page of the What_is_GNU_Radio link, is GNU Radio visual Editor. This editor permits to process data from Software Defined Radio (SDR) receivers without writing code, just by drawing pictures.GNU radio software can be downloaded from several places. Unfortunately, different versions are not exactly compatible and have different bugs. I used this source of the software:https://downloads.myriadrf.org/builds/PothosSDR/RSP1A is moderately priced good SDR receiver:https://www.sdrplay.com/rsp1a/https://www.hamradio.com/detail.cfm?pid=H0-015965There are many YouTube videos about rsp1a, as well as about GNU Radio.

author: pienari
author_rank: Regular Contributor
timestamp: October 24, 2023, 07:35:10 pm
content: I need to test GNU software with RSP1A
Kenwood TS-440S CW Key Splatter / Clicks - Page 1
Forum section: electronics / rf-microwave

author: Palmitoxico
author_rank: Regular Contributor
timestamp: October 08, 2023, 01:08:30 am
content: Hi,I bought an used Kenwood TS-440S HF rig about 5 months ago for a very good price. It is not in a pristine condition (SWR readings are a bit higher than it should be, FM mode doesn't work, squelch doesn't work), but it is usable otherwise. Recently I started getting some signal reports like '597' '588' (one operator used some not very polite words describing my signal...), so I listened to my transmissions on a near public SDR. Here is the recording:So yeah, not pretty. I tried swapping the power supply for a battery, but it made no difference. It occurs on all bands. Reducing the power to about 10W clears the signal though. Is this a known problem with this rigs? Looking at the service manual I could not identify where the CW 'shapping' is done (rising and falling time).Thanks,Augusto.

author: pienari
author_rank: Regular Contributor
timestamp: October 08, 2023, 09:58:36 am
content: Hi.There must be some capacitor failure.I own 3pcs and all units have faulty some parts.

author: Palmitoxico
author_rank: Regular Contributor
timestamp: October 09, 2023, 01:18:49 am
content: Quote from: pienari on October 08, 2023, 09:58:36 amHumm, it might be. I should probably replace all electrolytic caps in such an old radio.

author: pienari
author_rank: Regular Contributor
timestamp: October 13, 2023, 04:58:56 pm
content: Have you check this?.http://www.klimaco.com/HAMRADIOPAGES/440_mods.htm

author: Palmitoxico
author_rank: Regular Contributor
timestamp: October 15, 2023, 11:25:39 pm
content: Quote from: pienari on October 13, 2023, 04:58:56 pmThat is nice! Although the proposed fix for the key clicks adversely affects the full break-in mode, so I'll try to debug the problem further, there is no way that it sound that bad from the factory.
chamelian tactical delta loop clone - Page 1
Forum section: electronics / rf-microwave

author: p.larner
author_rank: Frequent Contributor
timestamp: September 29, 2023, 01:30:40 am
content: the deltaloop mentioned uses a 5-1 balun,any ideas how to make/wind one,see plenty for 1-1 and 49-1 etc but no plans for 5-1,i want to build a copy with wire+ roach fishng poles.

author: coppercone2
author_rank: Super Contributor
timestamp: September 29, 2023, 04:17:02 am
content: yo what

author: RFDx
author_rank: Regular Contributor
timestamp: October 10, 2023, 01:33:36 pm
content: https://reflector.sota.org.uk/t/unun-construction-differences-5-1/22517Looks to me like a 6:1 and not a 5:1 UnUn.

author: A.Z.
author_rank: Super Contributor
timestamp: October 13, 2023, 05:41:06 am
content: https://web.archive.org/web/20230722120127/https://www.g8jnj.net/cometcha250b.htm
Altai gdo mod - Page 1
Forum section: electronics / rf-microwave

author: p.larner
author_rank: Frequent Contributor
timestamp: October 10, 2023, 11:20:19 am
content: have this old altai gdo with all the coils,the dial frequency markings are too course for acurate measurements,can a frequency counter be added to show the exact frequency of the dip?.

author: p.larner
author_rank: Frequent Contributor
timestamp: October 12, 2023, 09:32:41 am
content: anyone?

author: Hamelec
author_rank: Regular Contributor
timestamp: October 12, 2023, 04:28:32 pm
content: ..deleted.because: no response - so help yourself

author: geggi1
author_rank: Frequent Contributor
timestamp: October 12, 2023, 04:54:25 pm
content: Assuming you are a HAM and having a transceiver with CW you can zero-beat the GDO with your transceiver.It is also possible to use a counter but you must be carefull to not overload the oscillator because it might go out of oscillation.

author: Hamelec
author_rank: Regular Contributor
timestamp: October 12, 2023, 05:53:42 pm
content: deleted.
Please explain this RF filter circuit - Page 1
Forum section: electronics / rf-microwave

author: Lino22
author_rank: Newbie
timestamp: October 11, 2023, 12:28:57 pm
content: Guys, this is a circuit you put at the end of a pulser that feeds a radar magnetron. It ensures the leading edge of the pulse has a nicely rounded corner before it becomes the flat top.The idea is that after the zener voltage has been reached, the cap loads the power source and thus the rise time increases (making the corner round).It is fed by a negative pulse, and i have troubles to read it. Could someone possibly redraw it to a positive pulse and explain how it woks? I can't see it ...Thank you.

author: jonpaul
author_rank: Super Contributor
timestamp: October 11, 2023, 08:32:52 pm
content: Magnetrons run with cathode - HV and anode at earth so output waveguide is at earth and not - 3000 V.Flip diagram upside-downj

author: D Straney
author_rank: Frequent Contributor
timestamp: October 12, 2023, 02:05:32 am
content: You can reverse the order of the diode and cap/zener too, if that helps.

author: D Straney
author_rank: Frequent Contributor
timestamp: October 12, 2023, 02:14:40 am
content: Basically, what happens is that after the first pulse, the cap voltage discharges through the zener diode until it reaches the zener voltage (Vz) and stops discharging there. So on each pulse's rising edge, the "fast diode" is reverse-biased until the pulse voltage reaches the cap voltage (= Vz). At this point, the diode starts conducting, and the cap & zener together load down the output and slow/clamp the voltage past this point. The circuit doesn't affect the falling edge of the pulse, because it would involve current flowing backwards through the "fast diode". When the pulse is done, the cap has been charged to a higher voltage than Vz, but it then discharges down to Vz through the zener again, and the process repeats.The reliance on a specific zener resistance value to do more of a "slowing" action from the cap, and less of a "clamping" action from the zener, feels a little shady, along with all the extra power that the zener must be dissipating unnecessarily during this period (personally I'd want to try adding external resistance in series with the zener, but also not familiar with the application so take that with a heaping pile of salt), but I guess it's simple and it works(?).

author: Lino22
author_rank: Newbie
timestamp: October 12, 2023, 07:03:49 am
content: Thank you D. I missed the trick with keeping the fast diodes reverse by the cap voltage comparing to the new pulse voltage. Excellent!