hybridfree/eevblog-posts huggingface dataset:
"minipa" HF linear amp - Page 1
Forum section: electronics / rf-microwave

author: djacobow
author_rank: Super Contributor
timestamp: January 21, 2020, 09:19:12 pm
content: So, I've got my mcHF up and running and with massive 5W power, I'm not having all that much fun, since nobody hears me. (I suspect it would work fine as a CW or "JT" machine but I'm actually interested in SSB voice.)I'm thinking of building one of these "minipa" 70-100W HF amplifiers. Aside from a lack of quality docs, they look seem legit.https://www.ebay.com/itm/13-8V-6-10A-70W-SSB-linear-HF-Power-Amplifier-For-YAESU-FT-817-KX3-DIY-Kits/112803983302?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D20131003132420%26meid%3D34b510baf70349b79100635e16fa2743%26pid%3D100005%26rk%3D1%26rkt%3D12%26mehot%3Dpf%26sd%3D333397556500%26itm%3D112803983302%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100005.m1851Anybody have experience with them? Looks like I'll need a heatsink and, to not be evil, an LPF to go with.

author: on7yi
author_rank: Contributor
timestamp: January 21, 2020, 11:04:22 pm
content: Hello,I don't have experience with that specific PA but I do with with PA as I have build mine.The key point I would like to draw your attention on is that to avoid killing your PA at the first overdrive or first high output swr event you will need to protect it.The protection unit is essential otherwise unless you are especially gifted in controlling the drive and the output swr, you will spend your time replacing your finalsWhy don't you have a look at the products of eb104.ru , you can buy everything you need over-there, weter it is the PA or the protection unit or both, assembled or in kitRegardsPeter

author: radiolistener
author_rank: Super Contributor
timestamp: January 21, 2020, 11:07:50 pm
content: these kits usually come with fake transistors. There is also a lot of reports that these fake transistors has incompatible pins with PCB, so you're needs to bend it's pins to solder it in reverse. Also I hear that this amplifier is unstable and transistors burn out very quickly.
MORPHEUS half price sale - Page 1
Forum section: electronics / rf-microwave

author: medical-nerd
author_rank: Regular Contributor
timestamp: June 07, 2018, 11:06:10 pm
content: HiyaCheck out rtl-sdr latest blog entry :MORFEUS HALF PRICE SALE: $99 SIGNAL GENERATOR AND FREQUENCY MIXERmoRFeus is a low cost wideband signal generator and frequency mixer. It can be used to generate a tone anywhere from 85 MHz to 5400 MHz, and can also be used as a frequency mixer, allowing you to implement upconverters and downconverters. In past posts we've reviewed and seen it being used as a PC based signal generator with open source GUI's, downconverter, CW generator, and most recently as a tracking generator for measuring filters and antenna VSWR.Currently Outernet are having a half price sale on the moRFeus. Normally it's US $199, but now with the coupon code "rtlsdrblog" it's only US $99. The sale only lasts until Saturday 09 June 2018, so get in fast if you want one.moRFeus can be purchased from the Outernet store.I couldn't resist so naturally have ordered one.Cheers

author: 9aplus
author_rank: Regular Contributor
timestamp: January 19, 2020, 06:56:06 pm
content: Just one information about user experience...MoRFeus is able to mix 10.7 IF! // on spec. 30 MHz and upTested on ICOM PCR1000 10.7 MHz IF outRF Generator on 350 MHzSDR LimeNET micro on 350 - 10.7 RX, Soapy Remote, CubicSDRNote:Standard LimeNET micro is not able to receive 10.7 IF or 7 MHz without external HF LNA

author: 9aplus
author_rank: Regular Contributor
timestamp: January 22, 2020, 12:18:58 pm
content: Here example, mid day, 20 MHz loop antenna almost on ground:ICOM PCR 1000 remote operated, set on 7.000 MHz10.7 IF OutmoRFeus 85 MHz - 10.7 = 74.300 => 7.000LimeNET micro sample rate 500 kHz, remote over Soapy Server2 x CWsome FT 82 x SSBand 3 x band intrusions & local QRM
ARRL CEO fired... - Page 1
Forum section: electronics / rf-microwave

author: worsthorse
author_rank: Super Contributor
timestamp: January 19, 2020, 08:20:34 pm
content: ... with a one paragraph announcement on the ARRL website, published on Sunday morning. The announcement says, "details to follow". The clown show begins a new episode...

author: coppercone2
author_rank: Super Contributor
timestamp: January 20, 2020, 03:45:29 am
content: at least provide some political analysis I have no idea whats going on with them

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 20, 2020, 04:05:46 am
content: My vague recollection was that he wasn't very well upholding the interests and values of the ARRL. And also that there was skepticism that this would actually happen, because bureaucracy, apathy. So I guess it's good news.Tim

author: worsthorse
author_rank: Super Contributor
timestamp: January 20, 2020, 04:45:22 am
content: Political context? Okay, here's my take... over the last few years the ARRL board has really gone off the rails, culminating in a shitstorm that led to the creation of Radio Relay International and the collapse of the National Traffic System. The whole sorry episode has its roots in a choices made by the board - the last two CEOs chosen by the board, the "board confidentiality" fiasco, the Parity Act lobbying - which is comprised largely of old time corporate guys who forgot that the ARRL exists to serve its members.Their treatment of a group of long time contributing members involved in the National Traffic System, censuring of board members that spoke out, and opaque management of the election process finally pissed enough people off that a group of reform candidates were elected last year. The departure of the new CEO -- the official line is "his contract wasn't renewed -- after a year is a continuation of this turmoil. On a positive note, one can hope that it is a sign that the reform candidates are winning the battle to re-make the ARRL into an organization that better serves it members.As an aside, the board has *always* run the ARRL, no matter what they call the guy in the corner office.

author: Marco
author_rank: Super Contributor
timestamp: January 20, 2020, 06:33:20 am
content: 200k$ corner office though. The directors do it for free.
PRS10 - Page 1
Forum section: electronics / rf-microwave

author: chris22
author_rank: Newbie
timestamp: January 17, 2020, 10:54:25 am
content: Hello SRS PRS10 user need help !!!My PRS10 v.3.21 sends TT values ​​greater than approx. 999999640 "SYNTAX ERROR" in the TT string. Therefore, no negative TTs are displayed in LH. Only when the TT gets smaller does LH also show values ​​more negative than approx. -360ns, otherwise 0 or positive. When displaying the other parameters, you notice that TO = 0 and TS = 12000, PS = 200 (unlikely that these round values ​​are correct ??). If 1PPS output and input are connected, TT = 1855 is output. This value should be saved as TO -1855. A complete recall (RC1) also brought no change.One way to compensate for the low TS value should be to extend the interpolate pulse (??) by reducing the charging current through Q501.Does anyone have any insights or secrets on how to correct the problem, or is someone known to the factory acess (will be treated confidentially, of course) to write the correct values ​​into the device.For direct answers, I can also be reached at verochris@web.de.

author: tkamiya
author_rank: Super Contributor
timestamp: January 20, 2020, 05:45:36 am
content: There is no negative values for TT. Manual page 31 says: Returned values range from 0 to 999999999. It also says only valid negative value is -1 which is "not available"https://www.thinksrs.com/downloads/pdfs/manuals/PRS10m.pdfDoes that help?
RD16HHF1 for mcHF - Page 1
Forum section: electronics / rf-microwave

author: djacobow
author_rank: Super Contributor
timestamp: January 19, 2020, 06:03:41 am
content: I've built a M0NKA mcHF. It receives well, but I'm seeing some wonky behavior on transmit. I think I might have screwed up some of the magnetics winding, but I'd also like to try replacing one or both PA transistors.So, it seems a popular tranny for HF experimenters, but typing that into mouser or digikey, it's like they've never heard of it.They are available on eBay, but would prefer legit supplier if possible.Where to buy?

author: German_EE
author_rank: Super Contributor
timestamp: January 19, 2020, 11:11:03 am
content: A number of amateurs have had good results purchasing from Ebay seller polida2008https://www.ebay.com/usr/polida2008?_trksid=p2047675.l2559As for the device itself, it appears to be obsoleteEditOne devicehttps://www.ebay.com/itm/1PCS-RF-VHF-UHF-Transistor-MITSUBISHI-RD16HHF1-RD16HHF1-101-100-Genuine-and-New/362255976407?hash=item54582387d7:g:eqgAAOSwuLZY42cxFive deviceshttps://www.ebay.com/itm/5PCS-RF-VHF-UHF-Transistor-MITSUBISHI-RD16HHF1-RD16HHF1-101-100-Genuine-and-New/362255984104?hash=item545823a5e8:g:eqgAAOSwuLZY42cxTen Deviceshttps://www.ebay.com/itm/10PCS-RF-VHF-UHF-Transistor-MITSUBISHI-RD16HHF1-RD16HHF1-101-100-Genuine-and-New/273089897986?hash=item3f956d2602:g:eqgAAOSwuLZY42cx

author: djacobow
author_rank: Super Contributor
timestamp: January 19, 2020, 04:22:50 pm
content: Thanks, guys!
WW2-era VHF aircraft transmitter in antique store (CT, USA) - Page 1
Forum section: electronics / rf-microwave

author: D Straney
author_rank: Frequent Contributor
timestamp: January 13, 2020, 01:24:10 am
content: Was visiting some friends recently and ended up in an antique store called Rustology in Stafford, CT. I was surprised to come across a box in one of the weird non-obvious nooks on the first floor, about knee-height, that looked very old-electronics-ish, and on closer inspection turned out to be a T-23/ARC-5, which seems to be a VHF transmitter from WW2-era aircraft:https://en.wikipedia.org/wiki/AN/ARC-5(it looked identical to the left-hand box in the main photo there) There was what looked like a directional coupler and some other piece of mystery test equipment nearby, as well as some old tubes in original packaging in the main room (12AX7 and others) which made me think this was the leftovers of some ham's collection. Pretty interesting seeing some almost-80-year-old equipment just floating around!Didn't grab it myself - I enjoy seeing the construction and circuitry inside vintage and aircraft/mil-spec stuff, but have zero interest in starting a collection or anything like that. Just thought since the unique sighting was kind of wasted on me, I'd put out a heads-up in case there's anyone in the area who'd fully appreciate it and actually is interested in restoring a really old transmitter or doing anything else useful with it.
Can I sell a FCC certified 433mhz product in other countries? - Page 1
Forum section: electronics / rf-microwave

author: Day101
author_rank: Contributor
timestamp: January 04, 2020, 02:53:06 pm
content: if I make a product using FCC certified 433mhz RF modules and pay to have the product certified by the FCC, must I also pay for more certification to sell it in other areas of the world?Am I correct in the following?* Europe uses ETSI and self-certification.* South America uses either FCC/ETSI rules.* Canada uses FCC rules.* Australia and NZ are self certification.What about the rest of the world?Any help is appreciated.

author: Gribo
author_rank: Frequent Contributor
timestamp: January 08, 2020, 01:40:48 pm
content: Some countries accept FCC or ETSI, Some have their own certification requirements, it really depends on the specific country. Usually, the stronger the electronics industry in a specific country, the higher certification requirements.

author: Georg - PY5ZSE
author_rank: Contributor
timestamp: January 11, 2020, 08:42:51 pm
content: To be added to Gribo's comment:The more bureaucratic a country is in general, the higher the chance it requires it's own certification. Brazil is such a case. No electronics industry to speak of, but lots of paperwork. They do, however, in many cases accept test results done for an fcc certification as basis for their own. Another issue is, that while in general frequency allocations follow international conventions, there might be national deviations for each country.
Home Brew RF Sampler - Page 1
Forum section: electronics / rf-microwave

author: vk4ffab
author_rank: Frequent Contributor
timestamp: January 07, 2020, 09:18:59 pm
content: Not rocket surgery, but now i can characterize amplifier gain bandwidths with the Nano Vna and not blow the arse out of my spectrum analyzer with a 2V p-p signal HEHE.https://robs-blog.net/2020/01/07/rf-sampler-2/

author: HarryMan
author_rank: Newbie
timestamp: January 10, 2020, 09:34:33 am
content: wow...good work! thanksdo you constantly use?

author: bd139
author_rank: Super Contributor
timestamp: January 10, 2020, 09:45:16 am
content: Ooh now that's a cool idea. Could use that with my AD8307 power meter

author: vk4ffab
author_rank: Frequent Contributor
timestamp: January 10, 2020, 08:34:06 pm
content: Quote from: HarryMan on January 10, 2020, 09:34:33 amIts come in handy, I have used it twice in the last 2 days, once for measuring gain bandwidth of a MMIC and the other the gain bandwidth of a high speed op amp being used at HF. My spec-an has a -30dbm input, 0dbm if i turn on its attenuator, so now i can look at frequency without worrying about blowing the arse out of its front end. LOL

author: vk4ffab
author_rank: Frequent Contributor
timestamp: January 10, 2020, 08:35:43 pm
content: Quote from: bd139 on January 10, 2020, 09:45:16 amYes you could and nice board
homebrew RFID-like - read & write Master & Slave - Page 1
Forum section: electronics / rf-microwave

author: legacy
author_rank: Super Contributor
timestamp: January 07, 2020, 10:00:58 pm
content: "RFID" is probably not the right word to describe it, anyway, considering Mifare 4ktye ISO/IEC 14443 cards, it's about what I'd like to make: a radio frequency couple of devices composed by a contactless reader/writer master and a slave storage device, which should use an i2c EEPROM 24Cxx as nonvolatile memory.I know that around 2008 the company "Coges" used a 24Cxx chip as for the prepaid keys for the coffee.I'd like to reproduce it, and better, I'd like to build it from scratch. What I am looking for is a couple of "internet good keywords" for searching on Google, and/or a GetStarted guide/lecture/theory whatever can teach.Thanks

author: Electro Fan
author_rank: Super Contributor
timestamp: January 07, 2020, 11:34:26 pm
content: NFC (Near Field Communications)NXPhttps://www.nxp.com/video/nfc-reader-design-i-how-to-build-your-own-reader:BUILD-YOUR-NFC-READER

author: Berni
author_rank: Super Contributor
timestamp: January 08, 2020, 06:24:20 am
content: Yep such a thing exists in the form of NFC.Even mobile phones have this functionality now. So all you have to do is buy a NFC RFID tag, put it against the back of your phone and run an app to read and write data to it.To use NFC cards on android no app is even needed as the OS has some built in functionality for reacting to some "magic strings", so you can program a card to do things like show a message on screen, connect to a wifi network(with password and everythyng), open an app, open a webpage... etc

author: legacy
author_rank: Super Contributor
timestamp: January 08, 2020, 03:09:42 pm
content: The N24RF64 device is very interesting. It's EEPROM chip with a dual interface: i2c and RF. It only need an external coil as antenna to operate. I just wonder how the internal circuit is designed to achive this.

author: legacy
author_rank: Super Contributor
timestamp: January 08, 2020, 03:24:54 pm
content: The RF protocol is compatible with both NFC Forum Type 4 Tag and ISO/IEC 14443 Type A, and there is amikroekit with a PCB antenna
Weird AM whistling sound on 1996 RV/camper radio receiver - Page 1
Forum section: electronics / rf-microwave

author: testtube44
author_rank: Regular Contributor
timestamp: December 03, 2019, 02:40:43 pm
content: Way back in 2016 I used to have an RV camper which had a radio receiver in it. Sometimes I would play around with different frequencies and bands and would hear this sound on the AM bands:https://www.dropbox.com/s/6xui8psbal06jr5/wobbletone.wav?dl=0(not a recording, just a recreation). The sounds would even change between day and night, the whistler would disappear the next day/night, then come back, and I was curious about the pattern involved. Sometimes I could even hear two of them at slightly different frequencies. What is it and what causes it?

author: radiolistener
author_rank: Super Contributor
timestamp: December 03, 2019, 03:40:54 pm
content: Looks like noise from some switching power supplyLines at the center are 120 Hz step, may be some harmonics from distorted 60 Hz mains sine?

author: testtube44
author_rank: Regular Contributor
timestamp: December 04, 2019, 08:50:48 am
content: This isn't an actual recording, I just recreated what I heard back then (I remade the sound to provide an example), this was 3 years ago! I know that the hum was mains, but I wasn't really ever sure what the whistling sound was.

author: testtube44
author_rank: Regular Contributor
timestamp: December 04, 2019, 08:51:51 am
content: So it could have been an SMPS or something?

author: radiolistener
author_rank: Super Contributor
timestamp: December 04, 2019, 08:55:41 am
content: yes, sounds like some SMPS, there are a lot of similar whistles at 40 kHz - 4000 kHz range from different home electronics

author: testtube44
author_rank: Regular Contributor
timestamp: January 05, 2020, 05:12:14 am
content: Oh! There was a black box way in the back labeled "power source", maybe it was that? But why does the sound go away sometimes? My power draw in the camper was constant for the most part.

author: SeanB
author_rank: Super Contributor
timestamp: January 05, 2020, 09:32:47 am
content: most common source of that noise would be interior lighting, in most RV's you do still find flourescent lamps used for lighting, or in more modern ones LED lights. both have switching power supplies, cost cutted down to the bare minimum so lacking any sort of RF filtering on inputs and outputs, and injecting this noise into the power supply rails, where the long leads will either radiate it to poorly shielded coax cable (never met car antenna cable that is anything other than poorly shielded, most are either foil with a drain wire, or a 20% coverage braid) or will have it come in direct over the power leads to the radio. If not lighting, then with engine running alternator noise, which is quite distinctive as it varies with engine RPM, and there if you have the engine running to provide AC inside. Connected to external power you can get noise from the SMPS keeping the battery maintained, as it has to provide a large current to run your typical fridge inside the Rv all the time.
baofeng UV-5R Auckland New Zealand  - Page 1
Forum section: electronics / rf-microwave

author: nvidia
author_rank: Regular Contributor
timestamp: January 10, 2020, 12:08:00 am
content: i am kinda new to vhf/uhf radio i have a baofeng UV-5R i got off ebay for 24usd (36nzd) free shipping took 7days to arrive to my house in new zealandim looking for frequencies in auckland nz that people use or that i can use to listen to thingswhen i first got the radio i found a frequency 146.625 and people where talking on itim using the aerial it came with and this channel came in crystal cleari listened for a couple of mins then i did some auto scanning to find other channels then maybe an hr latter i went back to 146.625 but don't hear anybody on iti have tried it off and on every day and never get anything on that channel just a random static for maybe a split second ever couple of minsthanksif you have used this radio what are some good setting to use with it

author: vk6zgo
author_rank: Super Contributor
timestamp: January 10, 2020, 02:16:17 am
content: Quote from: nvidia on January 10, 2020, 12:08:00 am146.625MHz is a Amateur Radio repeater in the "2m band".There are others you could listen to, like:145.775, 146.700, & 146.900 MHz.It might also be worth looking at :438.450, & 439.875 MHz in the "70cm" band.Amateur Radio activity on repeaters is, unfortunately, just a shadow of its former self.I'm not sure if the UV-5R you have can receive NZ UHF CB, but if it is programmed to do so, here is the info needed.https://en.wikipedia.org/wiki/UHF_CBAnother possibility is that it might receive the aircraft bands from around 118MHz up, but they are in AM, & as far as I know, unlike a proper scanner receiver, the Baofeng doesn't include that mode as an option.Listening is OK ----BUT please be aware thatyou cannot legally transmit on any frequencywith this radio, with the exception of those used by Amateur Radio,which, however requires you to hold an Amateur Operator's Certificate of Proficiency, which, from the general tenor of the OP, you do not possess.It does not meet the standards for UHF CB, or any other other service,Don't let anyone kid you!Hams will report you, but if you transmit in the allocations of much more serious organisations like the army, aircraft control, cops or fire service, you will be "up before the beak" so fast, your head will still be spinning!

author: nvidia
author_rank: Regular Contributor
timestamp: January 10, 2020, 02:18:33 am
content: Quote from: vk6zgo on January 10, 2020, 02:16:17 amthanks man

author: hendorog
author_rank: Super Contributor
timestamp: January 10, 2020, 04:49:16 am
content: I would consider getting a ham license if you are at all interested in this stuff. It is very straightfoward in NZ to do so and great for helping to understand it all.Basically a bit of self study then attend a weekend workshop. At the end of the weekend if you pass then you will be registered.If you PM me I can give you a contact to call, they are very helpful people and will point you in the right direction.
Send DMR Text Messages with an Radio over the Pc? - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: January 11, 2020, 05:47:15 pm
content: HiMany People know that is possible to send Text Messages over a DMR Radio.What I know "just" from a Radio to a Radio.Is there any way to send them from a PC?I know my TYT MD380/ MD390 can be communicate with the Hacked Firmware to a Pc but I dont know if the support Text Messages.Is there a hacked FW for the TYT MD-9600? It seem the support DMR - Tier1 who is important.Thanks
Why a better RDS reception with an 50Ohm extention cord? - Page 1
Forum section: electronics / rf-microwave

author: Pluscrafter
author_rank: Regular Contributor
timestamp: December 28, 2019, 10:40:51 am
content: I had wanted to recieve RDS information from FM stations with my rtl-sdr(RTL2832U) and a normal car antenna(https://www.banggood.com/USB2_0-FM-DAB-DVB-T-RTL2832U-R820T2-RTL-SDR-SDR-Dongle-Stick-Digital-TV-Tuner-Receiver-with-Antenna-p-1353904.html?rmmds=search&cur_warehouse=CN) but had no luck. Then ive decided to put the antenna out of the window and extendet the cable with an 50ohm extedtion cord(https://www.banggood.com/USB2_0-FM-DAB-DVB-T-RTL2832U-R820T2-RTL-SDR-SDR-Dongle-Stick-Digital-TV-Tuner-Receiver-with-Antenna-p-1353904.html?rmmds=search&cur_warehouse=CN) The signal was much better eventhough I haven't put the antenna outside. But why is the reception better with te extention cord and has it something to do with the impedance? Should it not stay the same when both cable are 50ohms?

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 28, 2019, 12:02:20 pm
content: When using a car antenna without the car you are missing 1 pole of the antenna: the car. Your extension cord probably works as the counter pole.

author: TheMG
author_rank: Frequent Contributor
timestamp: December 29, 2019, 06:13:46 am
content: Automotive whip antenna is intended to be mounted on the metal body of a vehicle, which acts as the RF ground plane for the antenna.Without the antenna mounted to a vehicle, or at least some other large-ish metal object, the feedline (coax) acts as a counterpoise for the antenna, and changing the length of the feedline by adding an extension changes the length of the counterpoise, resulting in quite a significant change in the antenna characteristics and performance.Also, proper RDS decoding, as you've likely already found out, requires a good signal, since the RDS information in encoded on a 57kHz subcarrier, above the stereo difference signal, so it tends to suffer from poor SNR much sooner than the audio itself.
Analog FM vs. Delta Sigma FSK - Page 1
Forum section: electronics / rf-microwave

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 28, 2019, 01:46:07 am
content: I'm working on a circuit to send two analog signals each with a bandwidth of a few kHz, with low latency and good robustness requirements. I decided on FM and started prototyping a circuit to generate the signal using a 74LV4046A. The problem is the jitter causes a high noise floor of the decoded signal, causing a limited dynamic range. I have some CD4046s on order (which are rumored to have a better VCO section), but until they arrive, I started thinking if there might be a better solution. If I put the analog signal into a Delta Sigma modulator and then send the bitstream using FSK, I would end up with a digital signal with "analog like" properties as far as (not) needing FEC is concerned. (Noise that causes bit errors would merely cause degradation of output SNR just like it would for analog FM, not cause complete corruption of data like a PCM stream would. Also no need for packet synchronization.)But how well would it actually work compared to analog FM? The signal is actually being sent over PLC, but I consider that more like wireless than wired due to the significant and varying noise levels encountered. Each of the signals would be sent as separate streams on different frequencies.
Low-frequency extension for 1-port VNA - Page 1
Forum section: electronics / rf-microwave

author: jmw
author_rank: Frequent Contributor
timestamp: December 23, 2019, 08:19:45 pm
content: I found a QEX article (http://www.arrl.org/files/file/QEX_Next_Issue/2015/Jan-Feb_2015/Audet_QEX_Jan-Feb_2015.pdf) that describes a low-frequency adapter to extend vector S21 measurements down into the AF range. The author writes it is only for through measurements, but is there a topology that would do the same for S11? The lower limit on the FPC-1500 I have access to is 2 MHz, and it would be nice to characterize reflections below that.

author: OwO
author_rank: Super Contributor
timestamp: December 24, 2019, 04:04:18 am
content: I think it would be far easier to just build a reflectometer/impedance analyzer for DC-2MHz. Find a micro with fast ADC/DAC (I think some freescale/NXP ones do), use the same resistive bridge circuit as the NanoVNA, and omit the downconverting mixer entirely.

author: Berni
author_rank: Super Contributor
timestamp: December 24, 2019, 06:26:54 am
content: Yep at 2MHz doing classical TDR (Time Domain Refletromerty) is easy.All you need is a oscilloscope with enough bandwidth for what you need, that's easy since 100MHz scopes are common these days. Then you just need a fast step generator to send the TDR pulse into the device of interest.This TDR generator can be easily built from standard logic chips:http://marcusjenkins.com/tdr-pulse-generator-for-testing-coax/Or if you want to go faster you can do TDR up to about 40GHz with a 30ps rise time step generator that a eevblog forum member sells:http://www.leobodnar.com/shop/index.php?main_page=product_info&products_id=295(Tho you still need to get your hands on a scope that goes that fast, likely a sampling scope)But if you just want to get RF power reflection down to near DC all you have to do is stick a multimeter across your DUT and measure the DC resistance. The closer to 50 Ohm it is on a 50 Ohm system the closer to infinity the return loss will be. Some math can be used to turn the resistance number into actual dBIf you are looking to actually analyze things like filters in the DC to 2MHz range then you might want to pick up something like the HP 89410A (Dynamic Signal analyzer) This is basically a spectrum analyzer that works like a SDR and as a result can go from 10 MHz all the way down to DC. Also includes a tracking generator, so by adding your own resistive reflection bridge (Easy to do at these low freqnecies) you can turn it into a vector network analyzer (But you will need your own software if you want a smith chart out of it). I like to use mine for audio stuff because it has a lot more dynamic range than a typical spectrum analyzer.
low level DC  AO amplifier - Page 1
Forum section: electronics / rf-microwave

author: nenea dani
author_rank: Regular Contributor
timestamp: December 22, 2019, 09:10:30 pm
content: Hi colleagues,I attach my schematic which is part of a 10Mhz sine CW calibrator. A directional coupler at the calibrator output is followed by a Ge diode detector and then a AO repeater and inverter amplifier Q1, so that they can have an automatic adjustment of the amplification. For tests I can adjust from an attenuator to get Udet between a few mV and 800mV DC. The problem is that everything works well for Udet between 800mV and 575mV. Below 575mV AO no longer works. I would like to be able to work down to 300-400mV, so that I have enough range for the automatic adjustment of the U out level. Now I get level adjustment for 3-4dB. If I replace the detector with one with voltage doubling then U det rises to a maximum of 1.7V and the U out changes for an equivalent variation 8-9dB of generator output which is sufficient. However how can I get AO to amplify below 575mV? I did these tests with OP97 and with TL081 nothing works. Tl081 would be best for the detector load.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 23, 2019, 08:55:06 am
content: One has to keep an eye on the common mode voltage and output range of the OP. In this circuit I would prefer a single supply OP, thus an OP that can work all the way down to the negative supply. So something like LM358, LT1006, TLC271 or OPA170.

author: iMo
author_rank: Super Contributor
timestamp: December 23, 2019, 08:59:36 am
content: I would use an AD8307 or similar.

author: nenea dani
author_rank: Regular Contributor
timestamp: December 23, 2019, 07:18:11 pm
content: Indeed the AD8307 is a very good circuit for measuring small RF energies. However I chose AD8317 because it has "on board" possibility for amplification adjustment. As I have a module from e-bay equipped with AD8317 in the "measurement mode" I obtained at the output between 0.5Vcc and 1.045Vcc for a generator level variation at the output between + 10dBm and -15dBm. Between the generator and AD8317 there is a directional coupler with approx. 14.5dB attenuation. I should change schematic a little for the "control mode" so it is in the data sheet. For measurements I used 5O 0HM terminals and the oscilloscope was also set to 5O 0HM. So far it is very good, but I will try to solve a detector in the classic way.
DC to 3GHz differential amplifier - Page 1
Forum section: electronics / rf-microwave

author: OwO
author_rank: Super Contributor
timestamp: December 22, 2019, 10:11:19 am
content: I'm looking for differential amplifier/buffer ICs or discrete solutions for two use cases:1. Extracting a difference signal and rejecting the common mode signal. I need CMRR on the order of 20dB up to 3GHz. The signal level will be on the order of -10dBm. Multiple stages is acceptable. No gain is required. I'm currently using an ordinary surface mount balun. The input signal is not necessarily balanced, so baluns with a third winding to enforce a 180 degree phase relationship are not usable. The balun I'm using is similar to the CX2156NL, which has no good CMRR so I'm using two stages. However, the baluns have physical asymmetry which causes common mode to differential mode transfer, which limits the CMRR that can be had by cascading multiple stages. The baluns are bulky and radiate so I would like to replace this with an active balun solution.2. Fixing the balance of a balanced signal. I am experimenting with a new reflection bridge design that requires balanced inputs, and it turns out the ADF435x doesn't have good enough output balance above 2.2GHz which leads to a Differential to Common-mode Power Ratio of less than 10dB. I need a differential buffer to fix up the balance, maybe by 10dB or so.Is there any good solution for these two cases? Budget is around $1. I've tried differential pairs using MMICs (BGA616), but can't get it stabilized while maintaining CMRR (the common-mode circuit has high emitter impedance to ground, which leads to feedback).

author: Marco
author_rank: Super Contributor
timestamp: December 22, 2019, 01:11:18 pm
content: Quote from: OwO on December 22, 2019, 10:11:19 amNeed to lead with this ...coax and beadsperhaps if a manual soldering step is an option?
push-pull power converter, selecting frequency and core - Page 1
Forum section: electronics / rf-microwave

author: Jesset1996.5
author_rank: Regular Contributor
timestamp: December 21, 2019, 10:27:21 pm
content: Hello all, I am trying to reverse engineer this power converter for a LV-80 amp. I am having difficulty deciding what frequency to run this at and deciding what toroidal core to go with. I do know that I will need a rather large core, around 3 in id or so. The transistor specified is a 2n1146c.Thanks

author: David Hess
author_rank: Super Contributor
timestamp: December 22, 2019, 12:27:12 am
content: The operating frequency is determined by saturation of the transformer core. That is a Royer based inverter.https://en.wikipedia.org/wiki/Royer_oscillator
Wireless Charging EMF - Page 1
Forum section: electronics / rf-microwave

author: jmurphy
author_rank: Contributor
timestamp: December 30, 2019, 07:16:24 pm
content: I’m building a small handheld 3.7V lipo battery operated Arduino project which will be enclosed in a water resistant 3D printed PLA case. I want to build a wireless charger for it. I bought 5V wireless transmitter and receiver coil modules (see photo) on Ali Express.1. Is it OK to leave the transmitter on all the time or should I build a circuit to turn off power when there is no device present?2. Do I need any EMF shielding on the transmitter or receiver side?
WiFi antenna connector "muting" termination - Page 1
Forum section: electronics / rf-microwave

author: ricko_uk
author_rank: Super Contributor
timestamp: December 20, 2019, 11:27:30 am
content: Hi,We need to minimise all RF in a lab for some tests but need to keep internet connection on. One of the wireless routers we cannot switch off the WiFi through any external switches and we don't have the login either. Because of the way it is screwed into the wall we cannot just shift it in a metal can either (and that would also leave some open gaps anyway.Is there a way to mute the antenna? I was thinking about unscrewing the antennas and putting some screw-on terminator of some sort. Do such thing exist? If so what are they called?Is that the best way to remove all RF emitted from that router?Thanks

author: 0culus
author_rank: Super Contributor
timestamp: December 20, 2019, 08:48:29 pm
content: I think the best way is probably going to end up being the solution you don't want: turn it off.Keep in mind that most wifi equipment uses reverse polarity (basically reverse gendered) rf connectors specifically to "prevent" people from installing third party antennas.

author: Bud
author_rank: Super Contributor
timestamp: December 20, 2019, 09:48:57 pm
content: It is called coaxial termination or load termination and you heed to identify what type of connector your router has, i.e. SMA, TNC, and if the termination has to have reverse polarity (pin vs socket). Part suppliers such as Digikey may have them. But conventional routers have plastic casing so some RF may still leak from the box.

author: TheMG
author_rank: Frequent Contributor
timestamp: December 20, 2019, 11:54:16 pm
content: Quote from: Bud on December 20, 2019, 09:48:57 pmI've also seen units that have both external antennas, as well as internal antennas right on the PCB, so terminating the external antennas really wouldn't do much in that case.
Drive level for comb (SRD) mixer? - Page 1
Forum section: electronics / rf-microwave

author: Staffan321
author_rank: Regular Contributor
timestamp: December 15, 2019, 06:20:44 pm
content: Hello,I'm fixing a VNA where the first stage is a comb mixer. The driver PA was off tune and gave only 22 dBm output level. After retuning, it manages 30-31 dBm. Anyone knows whether this may even be too high level for the mixer?The PA seems fairly trivial in design and I don't really know how to limit the output power. Hoping for someone with experience to tell whether this may be OK or that it is on the border of damaging the mixer (?). If the latter, any suggestions on how to control the level? Reducing power supply voltage seems not to do it.The mixer sits in a Wiltron 37247A VNA as first stage and LO input is 360-540 MHz, RF input from 270 MHz to 20 GHz.Regards,Staffan

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: December 17, 2019, 10:09:58 am
content: 30 dBm seems like a lot of power for a mixer, but then again, perhaps for the higher harmonics it is needed.What do you mean when you say the PA was off-tune, and you 're-tuned' it?Does the mixer have any part number you can look for?

author: Staffan321
author_rank: Regular Contributor
timestamp: December 21, 2019, 05:46:54 pm
content: 30 dBm is indeed needed to drive the SRD sampler/mixer. The PA and mixer is part of the 37247A VNA - should have a part number, but haven't really looked. The PA has a couple of trim caps that were seemingly off slightly so that output was reduced to - roughly - 25 dBm. More or less setting all caps to fully on when in serial and fully off when shunting gave 30 dBm over almost the full frequency range, but unfortunately not the last couple of tens of MHz (500 - 540 MHz) so I can't drive the mixer over the complete range which makes the VNA freezing when it's trying to lock the YIG with frequencies in this range (multiple).
null adjustment on my ts-850 - Page 1
Forum section: electronics / rf-microwave

author: m3vuv
author_rank: Super Contributor
timestamp: December 18, 2019, 12:18:34 pm
content: hi all,im doing some work on my ts-850,can someone explain what it means on service manual page 103 section 24 null adjustment,its as clear as mud to me.cheers m3vuv.

author: 9aplus
author_rank: Regular Contributor
timestamp: December 18, 2019, 12:28:10 pm
content: All is clear to me....Adjust all trimers to minimum output... assuming CW mode without key down.If level is as listed or bellow all is good.

author: m3vuv
author_rank: Super Contributor
timestamp: December 18, 2019, 12:37:13 pm
content: firstly what does the "ENT 035" mean?,tbh it still makes no sense,does it mean i have to adjust tc-1 when its in cw mode with the car knob min and the send button pressed,then adjust tc-1 for min rf output?

author: m3vuv
author_rank: Super Contributor
timestamp: December 18, 2019, 12:54:23 pm
content: was there a fault lol,in a word yes,i brought it from ebay as fully working,gave it to a friend to test as at the time i had no hf antennas up,it was only doing 12w max on tx,that was blown pa drivers,when i checked all the memory slots they were all 11m chicken band!,then had bad caps on the car board,low rx sensativity,that was a bad ic on the filter board dad digital transistor on the rf board,pll going out of lock when warm,bad display caps also,its been a lot of work so far,its working fine but,when i renewed the pa board and the other bad parts,i was working thru doing a realignment and cot stuck at the null section as couldnt figure out what it was sayying 100% so stopped there,its been niggling me ever since,it seems fine on air,what would the symptoms be of the null out of whack on air,ie is it worth bothering with?,also would that alter the atu matching range as this seems to match 4-1 swr ratios,thought they were only good to 3-1 max.

author: m3vuv
author_rank: Super Contributor
timestamp: December 18, 2019, 02:46:53 pm
content: i gather then this has an afect on the operation of the atu then?

author: m3vuv
author_rank: Super Contributor
timestamp: December 18, 2019, 02:51:27 pm
content: is the 50mv measured with a dvm on dc or ac range or an rf voltmeter,also is that at the tp 1 or ant jack?
FT-767GX - 70cms module taking off - Page 1
Forum section: electronics / rf-microwave

author: voltz
author_rank: Frequent Contributor
timestamp: December 15, 2019, 11:17:37 am
content: Hi all, I haven't posted on this forum for a long time. Hope someone has had some experience with this.Had a problem with a FT767GX, 70cms keeps going crazy during SSB transmission with PO meter showing full scale intermittently and loss of output. This is an unusual one, traced it down to the 70cms module (the rig is a HF, 6, 2 and 70cms bands). All other bands are fine. Rig is essentially in working order.When i remove the module case lids, the problem seems to clear up but as soon as the lid gets even just close to the unit, its taking off at around 442Mhz with full carrier. Basically going wild. Placing the lids on firmly with screws makes it unstable, sometimes its ok sometimes its taking off. But i have not been able to locate any faulty component or any bad earthing etc. All earth points have been cleaned / re-tinned. Tried supplementing the earthing to lids with copper foil, with no effect. So my conclusion is - is this a design fault?. The PA stages have too much gain and its self oscillating when the lid gets close to the box. Unfortunately, that means having to mod the thing, to stop feedback. But the question is, has anyone out there also experienced this? Nothing showing on google. Result is a time consuming job - thankfully its my own radio not a customers!Things I have already tried:Ferrite rods place inside the 'cavity' areas to de-tune any resonance - no effectFerrite beads placed on internal power lines - no effectExtra screening soldered in sensitive areas on PCB (early PA stages including TX mixer) - helped reduce the effect but problem still persists.Googled too may times - no mention of this anywhere.Thanks.
Input-current noise by DC blocking capacitor? - Page 1
Forum section: electronics / rf-microwave

author: kvd
author_rank: Contributor
timestamp: January 14, 2020, 10:15:20 am
content: Hi,I am trying to improve the noise figure of my FM preamp. I am trying to quantify the noise sources.In Art of Electronics 3rd edition there is an instructive example, in figure 8.36E which is being calculated on page 499. What surprises me is that to calculate the input-current noise for Q1, they do not take the DC blocking capacitor C1 into account. I do not see any reason to omit this cap from the calculations. Only the capacitance of the photo-diode, collector base capacitance of Q1 and wiring are mentioned. But C1 is about 1000 times as large as any of these.What is the reason C1 falls out of the equation?Koen

author: mjs
author_rank: Regular Contributor
timestamp: January 14, 2020, 10:57:05 am
content: C1 is in series with the 10pF, so it has insignificant contribution. 10nF in series with 10pF is still almost exactly 10pF.

author: kvd
author_rank: Contributor
timestamp: January 14, 2020, 09:21:42 pm
content: Ah sure, thank you!
what is the maximum signal strength that is save for a tv? - Page 1
Forum section: electronics / rf-microwave

author: www2
author_rank: Contributor
timestamp: November 23, 2019, 05:27:00 am
content: HiI wand to make an tv transmitter (close loop).But i wand to know what is maximum signal strength that is save for a tv?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 23, 2019, 08:00:22 am
content: Way the hell higher than the legal limit (equivalent to FCC Part 15; I don't know where it's called out in .eu), that's for sure.Most likely 3 V/m, whatever that comes out to at your antenna and distance.Tim

author: donmr
author_rank: Regular Contributor
timestamp: November 24, 2019, 06:16:19 pm
content: A strong tv/radio signal is -70dBm, about 100 pico watts.I looked up the specs for a commercial tv signal preamp. Its maximum input power is about 500 nano Wattsand its maximum output power is about 100 micro Watts. Keep in mind they probably expect the output togo through splitters and cabling which will reduce the power before it gets to a TV.You will probably find that the input distorts badly with much weaker signals that those that will cause damage.

author: TheMG
author_rank: Frequent Contributor
timestamp: November 26, 2019, 02:24:16 am
content: I live so close to a TV broadcast transmitter, that with a simple dipole antenna I get close to 0dBm (1 milliwatt) of signal going into my TV, which it seems to be perfectly happy with.But what is it that you're trying to do anyways? Generate a TV signal directly into the TV? If so, you can always use external attenuation if you need to lower the signal level down some. No need to go crazy with how much signal you put into the TV. 75ohm CATV attenuators are a dime a dozen.

author: coppercone2
author_rank: Super Contributor
timestamp: November 26, 2019, 03:52:06 am
content: the most sensitive RF preamplifiers have something like a 10-20dB maximum limit. thats for devices that go from dc to daylight and cost 2000+. even most spectrum analyzers can tolerate 1W. (30dB).Hard to imagine a transistor so sensitive that 1mW would fry it. Think about how much thermal energy and voltage in a 75 ohm system at 1mW... I think that device would be very mechanically fragile too if it was that sensitive to small thermals and voltages..

author: www2
author_rank: Contributor
timestamp: December 03, 2019, 10:08:58 pm
content: Thanks.@TheMGI wand to build a small TV TX for sending A/V over a cable to my TV and i wand not destroy my old CRT TV.
SMA attenuators - need info - Page 1
Forum section: electronics / rf-microwave

author: Helix70
author_rank: Unknown
timestamp: December 01, 2019, 04:06:41 am
content: Anyone have any data or information on these attenuators? I assume the adjusters are to calibrate, or tube frequency response.

author: DaJMasta
author_rank: Super Contributor
timestamp: December 01, 2019, 04:18:24 am
content: Wouldn't be surprised if they were filters, with tunable caps or inductors to adjust response. Do you have any way to test them and find out? Can you make out the markings on them?

author: ejeffrey
author_rank: Super Contributor
timestamp: December 01, 2019, 04:22:45 am
content: They are marked "3 dB" "5 dB", etc. so are almost certainly attenuators. Never seen one with adjustment screws, all I can imagine is that they are used to tune the return loss in situ.

author: Helix70
author_rank: Unknown
timestamp: December 01, 2019, 05:28:05 am
content: The markings are:1015Z525dB (6dB, 10dB)NECI didn't want to tweak the adjusters until I knew more about them and what it did, and how screwed I could make it, assuming they are ok at the moment.I have a SA at work with a TG, so I can do a simple sweep, but was hoping for a datasheet or something first.

author: TheMG
author_rank: Frequent Contributor
timestamp: December 01, 2019, 06:38:14 pm
content: Being NEC branded I wouldn't be surprised if these were custom attenuators made for a specific application, as far as I know, NEC never sold RF attenuators to the general market. What did they come out of?The screws could simply be setscrews to hold the guts in.Only one way to find out...

author: TheSteve
author_rank: Unknown
timestamp: December 02, 2019, 01:40:12 am
content: I can fully characterize one to 26.5 GHz on a VNA if you want(you need to send it to Canada though).

author: Helix70
author_rank: Unknown
timestamp: December 02, 2019, 10:16:51 pm
content: I used the SA and TG to sweep them, and they are relatively flat (+/- 0.25db) up to 3.2 Ghz. The adjusters did not seem to alter the frequency response, so who knows.

author: ejeffrey
author_rank: Super Contributor
timestamp: December 03, 2019, 12:35:29 am
content: Do you have a directional coupler to measure S11 with the TG /SA vs screw adjustment?

author: Helix70
author_rank: Unknown
timestamp: December 03, 2019, 07:22:11 am
content: No, I don't have one, or a VNA unforetunately.