hybridfree/eevblog-posts huggingface dataset:
OpenEMS and far field radiated emissions - Page 1
Forum section: electronics / rf-microwave

author: KlausKragelund
author_rank: Regular Contributor
timestamp: July 09, 2024, 07:29:15 am
content: HiI am working on a project, where large currents are running on cables inside a cabinet. We are exceeding the radiated EMI limits.So I am looking for a way to determine the impact on moving cables around, and the impact of the shielding effectiveness of the cabinet enclosure, for example distance between screws that fix the cover plates to the cabinet.I have very little experience with OpenEMS, Ansys seems to have an easier flow, but cannot afford Ansys tools.Is it possible, and if so, how hard is it to do a layout of placement of cables, define a current waveform in the cables, and then getting results that could correlate to a 3m measurement in an anechoic chamber?ThanksKlaus

author: selcuk
author_rank: Frequent Contributor
timestamp: July 09, 2024, 08:10:13 am
content: If you have necessary equipment, it may be faster to do shielding effectiveness tests on the prototype for a single project. It will take time to have satisfactory results with openEMS. But it can be helpful if you are doing this occasionally.I don't know how to define current waveforms. But for the cable design you can use FreeCAD to do the layout. There is a good project in the below link to show you the steps from 3D design to EMS simulation:https://github.com/toammann/Multilayer_SMA2MicrostripYou can enter dimension parameters into spread sheets in FreeCAD. For example you can define variables like "cable_length" or "screw_spacing" in the table, then export your geometry to openEMS and do simulation. Then you edit the "screw_spacing" in FreeCAD and it will update all 3D design with the new parameter. Then you can export and simulate again.

author: ftg
author_rank: Frequent Contributor
timestamp: July 09, 2024, 12:31:51 pm
content: Quote from: selcuk on July 09, 2024, 08:10:13 amThat is an excellent find.I also agree with the author on this:QuoteSo much potential squandered by the lackluster documentation.But writing it and maintaining it is a thankless job. So very understandable that there is not that much of it.

author: KlausKragelund
author_rank: Regular Contributor
timestamp: July 09, 2024, 08:26:16 pm
content: Thank you for the comments and the excellent linkWith respect to documentation, OpenEMS has great potential and if it was easier to use, some companies could use OpenEMS instead of Ansys. Some kind of donation could be good to keep the project going...
Best RF field strength meter - Page 1
Forum section: electronics / rf-microwave

author: jashugan
author_rank: Regular Contributor
timestamp: July 02, 2024, 09:35:19 pm
content: Hello,I need to test the electrical field inside a GTEM for radiated immunity testing (10 V/m). The frequency range is from 30 MHz to 6 GHz. I found this: EMF RF HF-B8G, which is around three hundreds bucks. What do you think about? Is it suitable for my needs, or do you think it is just a piece of crap?

author: pdenisowski
author_rank: Super Contributor
timestamp: July 03, 2024, 12:22:37 am
content: I could be wrong, but it's hard for me to take any RF detecting device seriously when its description includes things like:- "Spy camera, wireless bug finder"- "Cellular /Cordless phone radiation safety level"- "Personal living environment EMF safety"I guess the question I would ask is what your budget is. Our (R&S) field strength measurement solutions are excellent, but I'm pretty sure they are well outside of your price rangehttps://www.rohde-schwarz.com/us/products/test-and-measurement/radiated-testing/rs-ts-emf-portable-emf-measurement-system_63493-8174.htmlIf you're trying to do this on a limited budget, the best bet would probably be to get a good isotropic antenna and connect it to an RF power sensor. You would need to correct for the frequency response of the antenna, but a reputable manufacturer should supply this information.

author: radiolistener
author_rank: Super Contributor
timestamp: July 03, 2024, 02:56:44 am
content: Quote from: pdenisowski on July 03, 2024, 12:22:37 amWhere I can buy isotropic antenna?

author: jashugan
author_rank: Regular Contributor
timestamp: July 03, 2024, 11:28:42 am
content: Yes, you're right, and you're correct for the doubts that arise reading that description. I'd like to stay within 500 €, but I don't know if this is a correct budget.Do you think that object like Tenmars TM-196 or the above EMF RF HF-B8G are useless for my application? I don't need to be extremely precise, even an error of 0.3 V/m is acceptable for me.

author: pdenisowski
author_rank: Super Contributor
timestamp: July 03, 2024, 12:22:11 pm
content: Quote from: radiolistener on July 03, 2024, 02:56:44 amAs I mentioned above, we (R&S) sell calibrated isotropic antennas (TS-EMF series)https://scdn.rohde-schwarz.com/ur/pws/dl_downloads/pdm/cl_brochures_and_datasheets/specifications/3608_9918_22/TS-EMF_dat-sw_en_3608-9918-22_v0300.pdfbut I'm sure they are well outside of the OP's price range

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: July 05, 2024, 08:32:18 am
content: I had the loan of one of those 3 axis EMF meters, it was another "brand" but looks identical to the B88G. The meter was complete cr*p, the readings were all over the place, indoors it showed I should be cooking in the level of RF it showed and outdoors it was very variable and nowhere close to the real readings from a spectrum analyser and dipole antenna. And I had turned off my phone too... A spectrum analyser is easy to use to calculate the field strength, which is why R&S, Keysight, etc. offer the option on some spectrum analysers.
Remote Control with 2 Receivers (IC solution) - Page 1
Forum section: electronics / rf-microwave

author: Scutarius
author_rank: Regular Contributor
timestamp: July 03, 2024, 12:41:58 pm
content: Hi,I am not familiar with the low-cost ICs for remote controls, I am looking for a transmitter than can pair with two receivers, i.e. activate both (or more) with the same button.What should I be looking for in the specs? I am looking for a chip so I stated looking on aliexpress RF modules to have a better idea of what chips are using, no surprise datasheets are basically non-existentideally I need a receiver that can pair with an OTS remote control, but the remote should be able to pair with two or multiple receivers (do the pairing at the same time?) having a custom remote is OK.Most of the modules don't mention the pairing process or capability, does that mean they are factory locked to each other?Thank you,Edit, I am turning different lights on and off, no microcontroller involved.
ADF4351 as radio beacon - Page 1
Forum section: electronics / rf-microwave

author: YU7C
author_rank: Regular Contributor
timestamp: June 18, 2024, 11:09:44 am
content: Hello,recently I bought ADF4351 module with STM32F103 microcontroller for my simple project of Radio beacon for 23cm band:Unfortunately it came without any documentation.But it works, and generate 500MHz CW signal with default SW into STM.The programming sequence between STM and ADF is recorded, and I'll make a complete new SW for beacon purpose.But, I would like to try to get schematic, especially for STM part, before going into reverse engineering.Also would like to make some testing with PC software, if it's available.73 de Voja/YU7C

author: ftg
author_rank: Frequent Contributor
timestamp: June 18, 2024, 02:39:17 pm
content: I guess the seller was unable to provide you with any documentation when asked?That particular type is new to me, so cannot comment much about it.I don't know how much about the SPI connection between the synth and the MCU needs to be reused, at most the PFD freq and charge pump settings.The rest can be figured out from the programming manuals.Planning for the beacon to be CW only or something fancier like PI4?For example,OZ2M's Pi4unoADF4350 and ADF4351 synthesizers.

author: YU7C
author_rank: Regular Contributor
timestamp: June 18, 2024, 07:09:45 pm
content: That was really strange, what happened with a purchase. The parcel was stuck for more than one month, and I reported to ebay, and a seller totally refund me, without any questions. I forgot about it, But after three month I received the parcel. I contacted the seller and inform him about the situation and ask him how do i pay for goods. No answer from him, and now he doesn't have any obligation to technically support me.For now I have plan to implement F1A modulation, but PI4 would be challenge.73 de Voja/YU7C

author: YU7C
author_rank: Regular Contributor
timestamp: June 21, 2024, 06:58:04 pm
content: Here is STM32 digital board:Unfortunately, it seems that MUXOUT is not provided from RF board, so basicaly there is no feedback about lock detect.I don't want to diassaseble RF board, so will not add that.Next, BOOT0 is fixed to GND, so only tool programming is option.73 de Voja/YU7C

author: radiolistener
author_rank: Super Contributor
timestamp: June 22, 2024, 02:26:53 pm
content: is that STM32 PCB is glued to ADF4351 shielding enclosure?

author: YU7C
author_rank: Regular Contributor
timestamp: June 22, 2024, 07:05:59 pm
content: Quote from: radiolistener on June 22, 2024, 02:26:53 pmNo, STM32 board is attached with few screws. On the cover of the RF part, there is a slot for the STM32 board.

author: YU7C
author_rank: Regular Contributor
timestamp: July 03, 2024, 05:24:08 am
content: There is a problem with original STM32 board. It cannot be programmed, so I tested it with standard board.Regards,Voja/YU7C
Calculator for branchline 90 degree hybrid coupler (microstrip, not lumped) - Page 1
Forum section: electronics / rf-microwave

author: wb0gaz
author_rank: Frequent Contributor
timestamp: August 11, 2024, 01:07:10 am
content: I have need to implement branchline 90 degree hybrid coupler (to be used for RF power splitting/combining) for use at low microwave frequencies (right now 1.3 and 2.3 GHz - a separate design for each frequency, not a coupler intended for use at both frequencies).I see these things implemented on PC boards (typically an ellipse-sort shape), and there's an article (https://www.microwaves101.com/encyclopedias/hybrid-couplers) that provides useful (to me) background information.What I'm looking for is a (preferably online) calculator that can spit out the geometry for one of these things, given inputs such as expected operating frequency and port impedance (and ideally properties of the PCB laminate to be used; I expect to be using one of the Rogers laminates.)Have you run into such a calculator of any sort?Thanks for any suggestions (or of course any requests for clarification!)
Connectors used in old Kenwood radios - Page 1
Forum section: electronics / rf-microwave

author: alan.bain
author_rank: Regular Contributor
timestamp: June 27, 2024, 10:16:12 pm
content: Can anyone help me identify these connectors seen in photo which are used in many old Trio/Kenwood ham transceivers. They are similar to JST-XH (and pitch is around 0.1in or 2.5mm) but the bodies are physically smaller which means even replacing both the connector and socket is not an option (I tried for the 3 pin one and had to move two resistors for clearance). I need to replace some of the crimped connections where brittle wiring has fallen off.Kenwood tell me that they have not been available for years.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: June 28, 2024, 02:32:16 pm
content: Since no one has responded, here goes:These same connectors are used on CB Radios, so I use parts from broken radios to replace these connectors. Just resolder to the wires and use heat shrink. Perhaps find a CB shop and help them recycle an old radio or two. I have not purchased any of these new, You can remove the pin socket by pushing on the side (the little metal showing on the side of the connector) with a small screw driver and pulling the socket out then resoldering but this is messy and it is easy to damage the removed metal socket. If you have the recycled connectors, you can usually get one out intact without removing the attached wire and install it into your connector though.Perhaps join groups.io and join a group that deals with your radio there are several Kenwood groups, 930-940 TS 440 etc...https://groups.io

author: alan.bain
author_rank: Regular Contributor
timestamp: June 28, 2024, 11:26:52 pm
content: Yes, I have removed the contacts with a screwdriver and resoldered the wires to the contact but as you say this isn't massively reliable (as the solder makes the joint liable to fracture). I didn't know about their use on old CB rigs, I'll have to hunt out a dead example.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: June 29, 2024, 11:49:14 am
content: Yea, the little connectors do not like to be soldered. I usually take a replacement wire and connector from an old connector and use that. Sometimes I can find an entire connector that fits and use that, soldering the wires and not messing with the connectors in plug, but most of the time I just need to fix one connector.
Designing low-Z (10, 12, 16, 18, 25 ohm etc) coax transmission line transformers - Page 1
Forum section: electronics / rf-microwave

author: wb0gaz
author_rank: Frequent Contributor
timestamp: June 25, 2024, 02:04:44 pm
content: VHF (50 and 144 MHz) push-pull ham radio power amplifiers often use pairs of short length (10-20 cm seems common) low impedance (often 10, 12, 16, 18 or 25 ohms depending on design) coaxial cable to transform the low impedance device drains to 50 ohms.My question is this - given frequency, Vp (velocity of propagation) and the relevant impedances (drain, coax, and system), how is the length of the pair of low-impedance coax cables calculated/determined? Over what frequency range (say as % of center frequency) can these be expected to work properly (or conversely, what precision is required when actually preparing the coaxial cable pair?)I am not able find any description of how the length of the (typically) short lengths of low impedance coaxial cable are calculated. When alternate impedance coaxial cable is used in radio antenna impedance transformation, a quarter wavelength (inclusive of Velocity of Propagation) is often chosen. At 144 MHz, quarter wave would be about 30-40 cm (assuming Vp of ~60-70%), yet the lengths used in these transformers seem to be much shorter (10-20 cm).Any advice, references, or requests for clarification greatly appreciated!

author: ZigmundRat
author_rank: Regular Contributor
timestamp: June 25, 2024, 05:48:28 pm
content: As I recall, it’s a quarter wave where the characteristic impedance is the geometric mean of the two impedances to be matched. The physical length may change due to capacitance. For example I n tube amps with stripline tank circuits, 1/2 of the theoretical length was in the tube itself. Similar idea. Whether the actual length is determined empirically or just calculated I don’t know. If you have a real example you could calculate it backwards and see just how shortened it is.See if you can find a copy of “Reference Data For Radio Engineers”. You should be able to find more related info in there.

author: wb0gaz
author_rank: Frequent Contributor
timestamp: June 25, 2024, 06:58:16 pm
content: Thank you ZigmundRat, that provides very valuable clues - mainly that 1/4 wavelength would be an upper limit (length), which also lights the path towards the other question (what is the operating frequency range?) If I then begin with 1/4 wavelength sections and sweep the amplifier, I'd suspect I'll end up with a cut-off problem at the intended frequency, but would then work backwards (shortening the sections).Reference data for radio engineers - thanks for the pointer!

author: LM21
author_rank: Regular Contributor
timestamp: June 25, 2024, 07:53:15 pm
content: Old Motorola had some push-pull amplifiers, and instructions how to build their coaxial transformers. That data is on the net today. By the way, 25 coaxial is 2 50 ohm coaxials in parallel and so on. But this my own knowledge. Motorola used a different idea.
can you make some kind of RF thing with the Nutube dual triode "IC" - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: June 23, 2024, 12:25:36 am
content: https://diyaudiostore.com/products/korg-nutubeIts for audio. But do you think there is a RF circuit I can try to make with it? As interesting as their app notes are, I don't need another audio amplifier.

author: szoftveres
author_rank: Regular Contributor
timestamp: June 23, 2024, 12:53:07 am
content: Regenerative receiverPart 1https://youtu.be/KjNrrIEZJss?si=ilcOIKNbHsASx66OPart 2https://youtu.be/NjFVtD6rxGg?si=bK9Ouk6u5AVeBm0s

author: coppercone2
author_rank: Super Contributor
timestamp: June 23, 2024, 10:04:53 pm
content: he does not have a schematic some where for someone that just wants to get their hands dirty implementing a design does he? i wanted to have some fun

author: coppercone2
author_rank: Super Contributor
timestamp: June 23, 2024, 10:06:16 pm
content: 12:21 if you just want the schematic

author: joew
author_rank: Newbie
timestamp: June 24, 2024, 04:45:13 am
content: Interesting device. I am not sure I would mess with it, but it is interesting. When I was a kid my father told me, probably apocryphal stories of troops during the was using dual beam headlights as very make shift triodes by burning one beam out and using that as the plate and grid, and the good beam as a directly heated cathode.

author: coppercone2
author_rank: Super Contributor
timestamp: June 24, 2024, 04:52:15 am
content: where is that like the korean war or ww2?it sounds like something from the french resistance lol

author: coppercone2
author_rank: Super Contributor
timestamp: June 24, 2024, 04:55:36 am
content: https://hackaday.io/project/9108-poor-mans-triode
FM receiver antenna made of a single (insulated) wire - Page 1
Forum section: electronics / rf-microwave

author: VinzC
author_rank: Frequent Contributor
timestamp: June 19, 2024, 06:11:55 pm
content: Hi.I'm currently designing an FM receiver module based on aSi4705. The receiver will be placed in a device that is made of an aluminium enclosure, about 10-20cm long and 5-6cm diameter. Not all faces might be metallic but let's assume they'll all be, which rules out the possibility of an embedded antenna inside the device.Unfortunately Skyworks design guidelines do not seem to provide any hint about using a single wire as an antenna, like many portable radio receivers I've seen that are designed that way. I imagined several possibilities, which includes piercing a whole in the enclosure and let the (insulated) antenna wire pass through it but I don't like that idea very much as it would damage the wire in the long run (unless I mount some protective ring/gasket around the wire).I am also considering a connector; but then what? A panel-type connector that is mounted onto the enclosure? If so, what connector type makes sense? And how about the path between the connector and the PCB? I guess another connector on the PCB is overkill, right? On the other hand, soldering a wire between that connector and the PCB might make the whole device a little bit more fragile, e.g. when tearing it apart. Or would it?So I'm a bit out of ideas. Or maybe I'm just overthinking it, I don't know.What kind of practical options are available?Thanks in advance for any hint/suggestion.
Automatic bias for RF  power fets - Page 1
Forum section: electronics / rf-microwave

author: LM21
author_rank: Regular Contributor
timestamp: June 11, 2024, 05:27:05 pm
content: RF power fets need positive gate voltage to function well. That causes some drain current and idle power consumption, even without RF input.How about rectifying some of the input RF power to get that positive bias voltage to gate. Less or no power consumption when there is no signal. And of course some delay in power output.

author: rfclown
author_rank: Frequent Contributor
timestamp: June 12, 2024, 01:23:37 pm
content: You could try that; I've not seen it done. An RF detector is usually used to switch the bias voltage. Response time can be less than 1 usec.

author: radiolistener
author_rank: Super Contributor
timestamp: June 12, 2024, 01:31:50 pm
content: how you're planning to rectify RF voltage? The diode has some forward open voltage about 0.3-0.7V, so it's not easy to properly rectify it.

author: mag_therm
author_rank: Frequent Contributor
timestamp: June 12, 2024, 01:35:34 pm
content: Wsjt-x emits PTT via Rig_Control, then, with {user adjustable delay, default 200 ms}, baseband starts.I have homebrew Linear Amp with bias and antenna switching.The FET driver has asymmetrical +/- supply rails so that zero cross is adjustable relative to gate threshold .During receive, the driver (+) rail (adjustable +9 to +13V), is clamped to 1.2 V dc with Vg at -2.0 V .The Hermes 14 SDR Txcvr has an open drain that pulls low at PTT.Initiation of Tx sequence:Receiver reed relays (fast) open antenna and short the receive input.The 13.8V to 200 V drain converter is started and ramps up.The Tx contactor is energised, to close.The driver (+) rail clamp is released and ramps up in few ms.By the time the RF starts, the 200V supply has already ramped up (about 150 ms)If you sense RF instead of using Rig Control PTT, I think it should work OK.Take care that the TX antenaa switching is before RF starts.The loss of 200 ms or so should not affect wsjt-x decoding, and should be OK for ssb too.CW might need some extra consideration...

author: LM21
author_rank: Regular Contributor
timestamp: June 12, 2024, 02:05:15 pm
content: This wouldn't work on a low power transmitter/fet, you need a certain input voltage to get some DC out of it. But yes, using RF detection to turn on the bias, would work.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: June 16, 2024, 11:44:22 am
content: If you have a VOX Unit perhaps the output from that could be used to turn on the mosFET BIAS??? Somehow?
About Crystals, cutting / type / drive / series / parallel / overtone / tempco - Page 1
Forum section: electronics / rf-microwave

author: BrianHG
author_rank: Super Contributor
timestamp: June 12, 2024, 03:02:44 am
content: This vid goes over everything mechanical and electrical about crystals:

author: EEVblog
author_rank: Unknown
timestamp: June 12, 2024, 07:04:50 am
content: Edit for title spacing for word wrap.

author: BrianHG
author_rank: Super Contributor
timestamp: June 12, 2024, 02:49:50 pm
content: OK, done.
Model RF Power Meter By Bird - Serial Communication Problem - Page 1
Forum section: electronics / rf-microwave

author: Yad
author_rank: Newbie
timestamp: June 12, 2024, 01:57:30 am
content: Hi. I need help regarding my project. So basically, I have problem with my 4421 RF Power meter which they can communicate with my laptop via RS232 port even all the setting is right from the DIP switch to DB25- DB9 Cable. The 4421 Power meter is a new version (Darker frame). I have tried everything but still not working and I also verify the 4421 RF Power meter with the older version (Lighter frame) which can communicate with my software but after I switch to newer version of the meter, my software crash. I'm not sure why. If anyone have any idea, please let me know. Thank youI've attached the 4421 RF Power Meter (Newer version)
Active FM antenna amplifier circuit revision - Page 1
Forum section: electronics / rf-microwave

author: mustafayilmaz
author_rank: Contributor
timestamp: June 10, 2024, 07:36:39 am
content: Hello,What changes should I make to use this circuit with a 4V/4.5V radio?Would halving the resistors R3 and R2 help?https://www.learningelectronics.net/VA3AVR/circ/activefm.html

author: wasedadoc
author_rank: Super Contributor
timestamp: June 10, 2024, 08:07:52 am
content: Start by reducing R3 to 390. Do not alter R2 as that affects the RF gain.
antenna trap - Page 1
Forum section: electronics / rf-microwave

author: boful
author_rank: Contributor
timestamp: June 07, 2024, 02:34:33 pm
content: Greetings..Reyco KW-40 Trap from back in the day ..Notice on the attached picture.. There is a metal band around the coil.Any comments as to the purpose ? Could not find any mention oftraps that included a band. Trap seems to work at 7.150 Mhz (+/-)as it is pictured.My guess is it could be to use at different frequencies, but that could be so so wrong :-=)Thanks
Push on RF connector ID - Page 1
Forum section: electronics / rf-microwave

author: DaJMasta
author_rank: Super Contributor
timestamp: June 02, 2024, 03:15:22 am
content: Removed this cable from an Advantest signal analyzer after determining it couldn't be fixed and can't for the life of me figure out what it is. Probably in the few GHz rated frequency as they're on semirigid coax and connected to SMAs or SMBs on the other end. Push on, no threading, a seemingly wide dielectric with a relatively thin recess for the shield around it.Any good guesses that will save me another half hour inefficiently browsing connectors?

author: DaJMasta
author_rank: Super Contributor
timestamp: June 07, 2024, 04:31:40 am
content: I feel a little better that it seems like it is an unusual one, but it still would be nice to know. From the shallow depth and from scrutinizing some of the very few, far away pictures of the boards they were once on - I think it could be a surface mount connector, possibly one that connected to the board with the BNCs on the back (among others, there are too many ends terminated with this connector to just be those.)
80Ghz Radar Compliance in Australia - Page 1
Forum section: electronics / rf-microwave

author: ryanm
author_rank: Newbie
timestamp: May 22, 2024, 06:52:04 am
content: Hi All,Long time reader first time poster. I've just ordered some 80Ghz radar units off Aliexpress to have a play with to see if they work better than ultrasonic sensors for monitoring levels. Since they operate using EM waves instead of sound, I assume integrating them into a product would require certification as an intentional radiator with the ACMA down under?Cheers, Ryan.

author: CaptDon
author_rank: Super Contributor
timestamp: May 23, 2024, 01:51:04 pm
content: I don't know the specifics for Ozi rules, however many of those modules fall below the power level where licensing or certification is required. It may also depend on how much of the radiated signal 'escapes' beyond the container who's fill level is being measured. An example, can you transmit 1KW at 2.45GHz? probably not, but you can legally generate 1KW or more in a microwave oven although it does have to meet leakage certification because it operates above the minimum power threshold which in the states is 100mw D.C. input power to the final amplifier. I wonder if the rules governing R.F. radiation levels and standards for certification can be found online for your country?

author: vk6zgo
author_rank: Super Contributor
timestamp: May 25, 2024, 07:02:18 am
content: Quote from: ryanm on May 22, 2024, 06:52:04 amIf you intend making it as a saleable item, you will probably have to jump through whatever hoops ACMA require, but if you are basically experimenting with them you may find they accept the original approvals from the country of origin, the FCC or whatever.In either case, you should "do your homework" by asking ACMA.

author: coppercone2
author_rank: Super Contributor
timestamp: May 26, 2024, 10:15:38 am
content: I thought this kind of thing would be in the ISM band. But 80GHz is not in the ISM band. 60GHz and 120GHz are

author: vk4ffab
author_rank: Frequent Contributor
timestamp: May 27, 2024, 01:18:19 am
content: Quote from: ryanm on May 22, 2024, 06:52:04 amGive ACMA a call, if you have concerns, but here is the relevant class license.There are restrictions in there for 80ghz radar, cant be operated near a radio astronomy site, the emissions need to be pointed at the floor or a wall. Must comply with some ETSI standard. Not sure what you want to do with them, but seems some things are doable within the class license.https://www.legislation.gov.au/F2015L01438/latest/text

author: ryanm
author_rank: Newbie
timestamp: May 31, 2024, 02:29:47 am
content: Thanks for the replies.My closest neighbour is a few kilometers away so I don't think my prototypes will bother anyone. If it works well I might integrate it into a saleable product which is why I was trying to look ahead for problems. If I have to put it through a compliance lab sorting by lowest price first on Aliexpress might not be the best way to pick a module.
Power sensor: 8481D or 8484A - Page 1
Forum section: electronics / rf-microwave

author: HalFoster
author_rank: Frequent Contributor
timestamp: May 29, 2024, 04:40:49 pm
content: I have one of each of these, both with a current calibration but only need one and am trying to decide which one to keep. The only practical differences I'm seeing is in the maximum average power (8481D: 100mW, 8484A: 200mW) and the worst case linearity from 1uW to 10uW (8481D: 2%, 8484A: 1%) Both of the units are fairly comparable in the CF values.At first glance the 8484A would be better but only slightly. Does anyone know of factors that I may be missing or have advice?Thank you,Hal

author: M0HZH
author_rank: Regular Contributor
timestamp: May 30, 2024, 11:05:35 am
content: There are two versions of the 8484A:1. the original larger one in black metal casing, with more thermal drift (see attached picture)2. the revised one, where thermal drift has been fixed so the double-insulated large case has been replaced with the standard (smaller) oneIf you have the first one, get read of it. If you have the second one keep that, I think it's slightly newer (and better) than the 8481D.

author: HalFoster
author_rank: Frequent Contributor
timestamp: May 30, 2024, 11:39:20 am
content: I had no clue that there was a later revision of the 8484A - I actually have two and both are of the evidently earlier series in the larger black cases. I'm not really concerned with any drift as it will only be used on my home bench with a fairly stable temperature - and I tend to re-zero often as it is so that takes care of any minor drift. I've been thinking about it and I've pretty much decided to keep one of each, along with a 8482A and just use attenuators as needed. By keeping both, I have a spare in the event of the probably "Oops" moment ;-)Thanks,Hal
receiver antenna input protection - Page 1
Forum section: electronics / rf-microwave

author: istovit
author_rank: Contributor
timestamp: June 13, 2024, 01:44:02 am
content: My Kenwood R-1000 went hard of hearing recently and I suspect q1,a 3sk74,was taken out on a longwire. what type of diodes can I put at the input so I only do this once. and at what point does their C value affect HF reception?

author: Teledog
author_rank: Regular Contributor
timestamp: June 13, 2024, 03:56:25 am
content: A lot of people use 1n914 silicone (or oddball germanium) back to back.it seems the standard now is the BAV99.I took them out of my preamp, as there's more loss in VHF/UHF zone.Tech Note here;https://www.ti.com/lit/an/slva898/slva898.pdfG'Luck!

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: June 13, 2024, 07:28:45 am
content: Also make sure you have a static drain on your "long wire", as antenna wires of any reasonable length are very prone to picking up static electricity. While it hasn't happened to me, a friend has damaged the input to his transceiver more than once due to static building up on a large wire antenna.SJ

author: A.Z.
author_rank: Super Contributor
timestamp: June 13, 2024, 07:08:46 pm
content: deep sighhttps://www.kk5jy.net/rf-clipper/make an educated decision

author: iMo
author_rank: Super Contributor
timestamp: June 13, 2024, 09:55:38 pm
content: Also the 1N5711 could be a good candidate too. Btw a storm with lightnings in aprox 40km distance from my QTH created 5-6mm long sparks against ground every 5-8 seconds off my 22m long wire antenna.. An unun at the input might be good solution as well (the unun grounded).

author: Teledog
author_rank: Regular Contributor
timestamp: June 14, 2024, 01:55:18 am
content: Thought of it at 5:00 AM this morning..We used to use a plethora of SMD bi-directional TVS suppressors in VOIP boards.There are a LOT out there.. for voltage, leakage, frequency, etc.A study in itself..G' Luck!

author: biastee
author_rank: Regular Contributor
timestamp: June 14, 2024, 06:31:04 am
content: The front end, i.e. 3SK74, could have been damaged by RF overdrive / indirect lightning strike / static - take your pick.If it is the latter two, then a unun with a ground connection may help.Some suggested PN diodes, e.g. 1N914, BAV99, Ge, etc., but they will also act a mixer to bring down the IMD performance. A PIN diode limiter would be a better protection for RF overdrive as it is more linear than a PN diode. The package and configuration are important as you want to minimize loss at higher freq. A good reference:http://www.hp.woodshot.com/hprfhelp/5_downld/lit/diodelit/an1050.pdfAs for the suggestion to use a silicon transient voltage suppressor (TVS), most of them don't have low enough capacitance to be inserted into the RF path.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 14, 2024, 07:20:27 am
content: Or your 3SK74 could have just died of old age, FETS are not immune to aging.
ROHDE & SCHWARZ SMDU and SMDU Z1 test set owners!  - Page 1
Forum section: electronics / rf-microwave

author: py1dkw@yahoo.com
author_rank: Contributor
timestamp: April 29, 2024, 12:51:33 am
content: I had worked with this nice test set from 1984 to 1999 and now I could get the same unit here in Brazil. The R & S Support gave the available manuals, but my SMDU is changing its frequency in RF generator mode fast, but only in the lower band, the upper bands are ok and not out of lock. Does any owner of SMDU knows where I could start looking for the defective part? I had the SMDU Z1 unit restored and works fine. Many thanks, 73s Sam Rocha, PY1 DKW

author: py1dkw@yahoo.com
author_rank: Contributor
timestamp: May 22, 2024, 09:29:02 pm
content: Does anybody knows where to find the coaxial relay used in Rohde Scwharz SMDU, SMDU Z1, ESU2 and many other equipment? I noticed they can be disassembled and cleaned with Freon.

author: Harry_22
author_rank: Frequent Contributor
timestamp: May 24, 2024, 08:31:21 pm
content: Hi!Could you possibly attach the photos of the relay.
test equipment search:  Network analyzer with remote front end - Page 1
Forum section: electronics / rf-microwave

author: aaronlow
author_rank: Newbie
timestamp: May 21, 2024, 05:29:21 pm
content: Hello all,I am looking for a potentially unique piece of test equipment. I need a network analyzer where the one of the ports can be remotely connected over fiber optics.I thought I remember seeing an Agilent network analyzer with this feature several years ago, but I can't find anything like this now.What I need is a spectrum analyzer with a tracking generator that can be remote (and connector over fiber optics) and can sweep very quickly. If I limit myself to using fiber optics, I would have to use something likehttps://aaronia.com/en/shop/signal-generator/spectran-v6-eco-150xa-18with the source located remotely using RF over Fiber.Thanks for your help. I am looking to put together a portable shielding effectiveness test set.Aaronp.s. I recently got a quote for essentially what I need for ~$100k USD, which is way too expensive for what I am willing to attempt to justify.

author: zrq
author_rank: Frequent Contributor
timestamp: May 21, 2024, 06:24:16 pm
content: Is these what you are looking for?https://www.keysight.com/us/en/products/modular/pxi-products/pxi-optical-extenders-for-instrumentation.html(I got a reasonably cheap 50G M9405A off ebay recently so I happened to know this series.)Or probably just get a RFoF link and a capable SA if the dynamic range is enough for you.

author: jjoonathan
author_rank: Frequent Contributor
timestamp: May 21, 2024, 07:19:34 pm
content: You can do this with FieldFoxes -- I think it used to go under the name "FoxTrot" but now goes by the name "ERTA." It wants LAN and two trigger wires, which you could probably Macguyver to work over optical. Not sure it's going to save much on budget though, and if you're already going to the trouble of optical LAN you can probably find more economic options.

author: pdenisowski
author_rank: Super Contributor
timestamp: May 22, 2024, 12:16:09 am
content: Any reason you can't use Ethernet with an electric-optical converter / extender? That would make things a lot easier.

author: Odysseus
author_rank: Regular Contributor
timestamp: May 23, 2024, 04:20:18 am
content: Anritsu sells a so-called "Distributed Modular VNA":https://www.anritsu.com/en-us/test-measurement/products/me7868aProbably not much cheaper.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: May 23, 2024, 08:08:21 pm
content: I think Anritsu is your best bet here. They have some fancy rf-over-fiber based synchronization to do modular VNAs where each port is phase locked to the other over fiber.

author: tautech
author_rank: Super Contributor
timestamp: May 24, 2024, 08:22:23 am
content: Quote from: aaronlow on May 21, 2024, 05:29:21 pmFrequency of interest ?Can the analyzer be connected remotely and monitored/controlled over LAN/WLAN ?Any analyzer with a webserver can be used in this way.
Any extra considerations for different wavelength same band antennas on car? - Page 1
Forum section: electronics / rf-microwave

author: K5_489
author_rank: Regular Contributor
timestamp: May 23, 2024, 05:34:32 pm
content: I know when having multiple same band antennas on a vehicle that you want a minimum of 1/4 wave separation between the two, with more is better, and this is based on the wavelength of the frequencies being used.Does this get altered with using different length antennas on the same band, or any other things that should be kept in mind if I were to install a 1/2 wave 2M, 5/8 wave 70CM antenna together with an existing 1/4 wave 2M antenna?In my head, it doesn't seem like it should make a difference as 1/4 wave of 2M is the same regardless of antenna length, but I keep thinking of different radiation angles, confusing myself, and Google isn't helping... I'm pretty sure I'm just overthinking this, but wanted some confirmation either way.Oh, and in case someone wonders why - I currently have a FT-100 in the truck. I'm adding one of my Kenwood TM-D710 radios, and I figure two antennas better than one, and no worries about a failed duplexer back feeding the other radio. Plus a 2nd antenna is cheaper 😅
Beam Lead PIN Diode up to 40 GHz - Page 1
Forum section: electronics / rf-microwave

author: Harry_22
author_rank: Frequent Contributor
timestamp: May 16, 2024, 10:09:33 am
content: Hello!I would like to ask what model of beam lead PIN diodes are used in the following diplexers?

author: Harry_22
author_rank: Frequent Contributor
timestamp: May 21, 2024, 03:20:20 pm
content: I found GC4902-GC4906 and GC4801-GC4802 from Microchip but they are written to be suitable for applications through 26 GHz.https://www.microsemi.com/document-portal/doc_view/8714-gc4900-series-pdfhttps://www.microsemi.com/document-portal/doc_view/8713-gc4800-series-pdf

author: jjoonathan
author_rank: Frequent Contributor
timestamp: May 21, 2024, 04:16:15 pm
content: Oh hey, I worked on a R&S diplexer much like that one the other day!https://www.dropbox.com/s/8v5ghwzexq4pybw/Rohde%20Diplexer.pdf?st=9t2fgilb&dl=0Unfortunately, while my replacement diode of choice (Skyworks DSM8100) had acceptable insertion loss in the ON state, it had poor isolation in the OFF state, leading to issues with the low band (which could still "see" the reactive stub behind the reversed biased PIN diode). It's still on my todo list to evaluate other PIN diodes and find one with better isolation.

author: Harry_22
author_rank: Frequent Contributor
timestamp: May 21, 2024, 07:36:16 pm
content: Hi Jonathan!Your research is very interesting.I greatly appreciate your help!Harry
464 MHz Power amplifiers - Page 1
Forum section: electronics / rf-microwave

author: Cicada
author_rank: Regular Contributor
timestamp: May 13, 2024, 07:00:22 pm
content: HiPlease help me identify the power connector. See photos attached. I can't find any datasheets on this amplifier. Can someone perhaps point me to the datasheets please. This company seems to be out of business for a long time.I have no RF experience. I would like to ask colleagues at work in our RF lab to test these amplifiers.What would be the equipment needed to test these amplifiers?Will it be a lot of work to test 3 such amplifiers?

author: Paul Price
author_rank: Super Contributor
timestamp: May 13, 2024, 08:40:41 pm
content: If you have access to the RF lab at work, why aren't you asking them to help you with your questions???

author: geggi1
author_rank: Frequent Contributor
timestamp: May 16, 2024, 04:53:14 am
content: The power connector looks like a XLR connector but with more pins than used for audio.

author: ftg
author_rank: Frequent Contributor
timestamp: May 20, 2024, 10:31:38 am
content: Yep. Definitely looks like an XLR connector. If no datasheets for it can be found, you get to open one up and reverse engineer the pinout.In addition to power there might be some diagnostics like reflected power or temperature.To test them you need to figure out the pinout and possible keying.Then a signal generator with enough power to drive the amp, a power meter to measure the output power and likely some attenuators to protect the power meter.If your employer has an RF lab, go ask the engineers there if they have equipment suitable for testing them.But don't expect them to know the power pinout or other DC details like that.
Using NRF24L01+ as a spectrum analyzer - Page 1
Forum section: electronics / rf-microwave

author: JamesMaxwell
author_rank: Newbie
timestamp: May 19, 2024, 02:59:07 am
content: Hi this is my first time posting so apologies if I am not up to standard!I am trying to make a 2.4GHz radar and looking at using the STM32L4 as a controller to the NRF24L01+. I am looking at the MakerFocus 3pcs NRF24L01+PA+LNA Wireless Transceiver that uses the NRF24L01+ and was curious if there is a way to get the raw unmodulated sampled signal from the NRF24L01+? Or if just using the Received Power Detector (RPD) but is enough for something like this?Thanks!

author: MarkF
author_rank: Super Contributor
timestamp: May 19, 2024, 05:00:11 am
content: 1) No. You can not get the raw unmodulated signal.2) I have never been able to get the received power level to work.Following the RF24 library sample code for the Arduino never worked for me.Don't know what the trick is.3) The nRF24L01+ will not work as for radar. It does not detect itself.Even if you used two, the power detect is line-of-site between them.There is no bounce/echo detection as you see in a normal radar.(Welcome to the forum.)
using a mobile phone as a signal strength meter - Page 1
Forum section: electronics / rf-microwave

author: phred01
author_rank: Contributor
timestamp: May 27, 2024, 10:23:27 pm
content: Hi allI have used a android phone to measure signal strength using Android apps. Do know that the radio methodology uses digital spread spectrum so using a spectrum analyser is futile However I can only measure a specific carrier as embedded in the sim card. Say a Telstra will only test Telstra towers. Is there away to make the phone pretend as universal unit that enables the signal strength apps to measure any towers signal
I am confused about my drone signal - Page 1
Forum section: electronics / rf-microwave

author: xincheng
author_rank: Newbie
timestamp: May 28, 2024, 09:05:45 am
content: Why does the drone's remote control interfere with the image transmission system

author: darkspr1te
author_rank: Frequent Contributor
timestamp: May 28, 2024, 12:54:38 pm
content: Could be many reasons like cheap drone , incorrect setup, using 2.4ghz radio along with analog 2.4ghz video.Without know what exactly you "drone" is with maybe some information we can help but we cannot mind read you and know what equipment you are using.help us help you by providing some info other than just"my drone"darkspr1te

author: radiolistener
author_rank: Super Contributor
timestamp: May 28, 2024, 08:39:33 pm
content: Quote from: xincheng on May 28, 2024, 09:05:45 amMost of all, this is because your image transmission system has a cheap radio receiver which has low dynamic range, so strong signal from remote control affects it's reception. It is also possible that your remote control uses cheap radio transmitter, which has out of band emission which falls into image transmission system band.You can check what is the root of cause with spectrum analyzer. If there is unwanted emission from remote control on band of image transmission system, then this is due to low quality transmitter of your remote control.But I bet this is due to low quality radio receiver (low dynamic range) in your image transmission system. This is because it's hard to build cheap and compact receiver with high dynamic range. You can try to fix it by using high directivity antennas for remote control and for video placed at some distance from each other in such way to avoid direct reception of remote control signal on video receiver antenna.
Please help with understanding RF amplifier (tekbox TBMDA3/B) - constant Pout - Page 1
Forum section: electronics / rf-microwave

author: Warhawk
author_rank: Frequent Contributor
timestamp: May 15, 2024, 07:03:03 pm
content: Hello everyone,I have a reasonably strong background in electronics but RF is new to me. I am re-doing some tests at work for per-compliance radiated immunity test. I use a TEM cell and TBMDA3 from TekBox as my predecessor did. It is a great learning exercise. I mainly do comparative measurements.First, I wanted to make sure that the signal from the RF power amplifier matched what I expected. I used a spectrum analyzer for measuring the output power. (through 30dB atenuator). I somehow expected that the TBMDA3 amplifier (link) would take whatever is on the input and add +37dBm to it. Of course, within some reasonable range.Example:Pin=-10dBm, Pout = 27dBm,Pin=0dBm, Pout = 37dBmHowever, the output stays around 37dBm without regards to the input power change. This matches the datasheet for the amplifier. Only when I go for very low input power, the output power starts dropping. To me it seems that the amplifier is designed with variable gain/constant output power in mind.Q1: What is the name of such amplifier? Is there a special keyword?Q2: What is the typical construction? Is it a common emitter type of an amplifier where impedance in the emitter path generates the negative feedback?To my surprise, there is also asuccessor called TBMDA3B. This unit acts differently. At least when reading the datasheet. Reducing the input power by 5dBm results in decrease of the output power by ~5dBm.There is a chance that couple colleagues took measurements with the constant output power when just blindly expecting the output power changes too... However, more likely, I am a fool and do not understand how it works. That's why I kindly ask for education on this subject :-)PS: When I connect the signal generator (some R&S model) directly to the spectrum analyzer (MSX?) through various atenuator I am getting reasonable and repeatable results when it comes to reading power.Regards, Jiri

author: BigBoss
author_rank: Regular Contributor
timestamp: May 15, 2024, 10:50:44 pm
content: This phenomena is called as "Compression".Typical Compression curve is as follows.
Inside a Tektronix sampling module - Page 1
Forum section: electronics / rf-microwave

author: EggertEnjoyer123
author_rank: Frequent Contributor
timestamp: May 14, 2024, 05:24:10 am
content: I bought this "bad" 80E03 sampling module from a hamfest last month. This is what the insides of the plugin look like under a microscope.