hybridfree/eevblog-posts huggingface dataset:
ESP32C3 Chip-Antenna Matching - Page 1
Forum section: electronics / rf-microwave

author: Fredric
author_rank: Newbie
timestamp: July 06, 2023, 08:20:22 pm
content: Hi there,i've designed a little PCB with an ESP32C3 to transmit some sensor data over wifi. However, I'm having a few questions regarding the matching of the antenna.Now I only have a nanoVNA to do the matching with, so I don't expect a perfect match and it's just a one off board. This is also the first board I'm trying this with, so I really don't have a lot experience with RF and could very well be wrong on some things.So, to my question:According to posts from the Espressif forum, the ESP32C3 has an RF output impedance of 35+j10 Ohm. So I understand that I can't just connect the VNA in place of the ESP32C3 on a blank board with just the RF components on it and match the antenna, since the VNA has 50 Ohms. Because when I then put the ESP on, the match will be off, because of the difference in output impedance, correct?If you look at the attached image, I have a pi-network to match the 35+j10 Ohm to 50 Ohm and then another matching network for the antenna.In order to match the antenna, I would just remove the components from the pi-network and attach the vna right after it (image 2).But then how would I figure out what components I need for the pi network to match the 35+j10 Ohm to 50 Ohm and vice versa?I mean I assume I can't just calculate them, since the real world will be very different from ideal calculated values.All the resources I've looked at always assume 50 Ohms output impedance of the RF transceiver, but I haven't found anything that would help me here. Would be great if someone could give me some hints or tell me if I'm completely wrong on my assumptions...

author: RFDx
author_rank: Regular Contributor
timestamp: July 11, 2023, 07:51:54 pm
content: Quote from: Fredric on July 06, 2023, 08:20:22 pmYes, you can connect the VNA instead of the chip. Technically you have two separate matching networks. The first matching network transforms a 50 Ohm load to the complex conjugate value of the chip, namely 35-j10 Ohm. This is the impedance your VNA would show you. As an example see the attached file.The second network transforms the unknown impedance of the antenna to 50 Ohm. You need to measure the unknown antenna first, devise a suitable matching network and then measure again at the input of the second matching network to confirm you now got 50 Ohms.
Technical, DE5000 vs Ohmmeter DC measurement. - Page 1
Forum section: electronics / rf-microwave

author: Qmavam
author_rank: Regular Contributor
timestamp: August 12, 2023, 04:33:06 pm
content: A little background, Making an electrostatic treatment vessel with an emulsion to be treated. First tests were with a test tube and a wire inserted in the center as one electrode. The test tube was inserted in a metal tube as the other electrode. Test have shown the emulsion has enough conductivity that the electrodes must me insulated from the emulsion. To that end we made to aluminum plate 2" x 5" and dipped them in fiberglass resin epoxy, twice just to make sure. The plates have a nylon spacer holding them 1" apart. After it was all cured we set the plates in 4" of tap water connected a DE-5000 and set it for DCR the reading was 1.4MΩ. I expected much higher or higher than the meter measures, or maybe not because it will measure 200MΩ. This being confusing, I got my Bryman BM235 and measured the plates in the same 4" of water. It read an open as OL on the screen, which is what I would expect. I connected my DE-5000 to the scope and it does output DC when measuring DCR (I had to verify). So why the difference between the two measurements?Additional info; in air the plates measure 4pf, in 4" of water, that jumps to 2.2nF.
R&S SML03 display failure - Page 1
Forum section: electronics / rf-microwave

author: oh4mvh
author_rank: Newbie
timestamp: December 26, 2020, 03:31:22 pm
content: Hello,I have R&S SML03 signal generator with some stripes on its display. I have seen the same problem on some other R&S devices before having the same size of display.Do somebody know whether this is a display (LCD or TFT?) or display driver issue normally?thanks for any hint.

author: Radiosonde
author_rank: Contributor
timestamp: January 07, 2021, 03:47:56 pm
content: Thats a *classic* problem for some Rohde & Schwarz gear, I had it too.You can buy a new display for 100-200 Euros.For example:https://www.ebay.de/itm/For-original-4-8-HITACHI-SP12N002-100-NEW-LCD-LED-Display-Screen-Panel/272087929583?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649My display was delivered with a different cable, so I had to swap the cable from the old display...Regards

author: oh4mvh
author_rank: Newbie
timestamp: July 06, 2023, 06:59:02 pm
content: Thanks, found this first now. Link is still valid per today.BR Petri

author: Qw3rtzuiop
author_rank: Frequent Contributor
timestamp: July 06, 2023, 07:05:12 pm
content: The Wandel & Golterman PF-140 is using the same screen. They are very cheap sometimes because they are obsolete.
How to get the RSSI calibration constant for a si4463 - Page 1
Forum section: electronics / rf-microwave

author: kml183
author_rank: Contributor
timestamp: June 28, 2023, 07:28:46 pm
content: Hi there!I have been playing with the rf4463 1W G(FSK) 433Mhz module from nicerf recently. I am trying fetch/compute the RSSI after each rx packet. From the datasheet:QuoteI don't have a signal generator, is there any way I can figure out that RSSIcal constant with another module?lets say I connect two modules with a coax and use a 30dB attenuator, as well as setting the power to be max (1W). On the reciever I am testing, would the RSSIcal be:RSSIcal = (RSSI_value / 2) - 36 + 30?Thanks!

author: kml183
author_rank: Contributor
timestamp: July 02, 2023, 10:24:47 am
content: So I contacted the NiceRF which makes the RF module that I am using (RF4463F0) that wraps the si4463. They were able to give me some test data to use to determine the calibration constant, see attached. From this data I was able to draw a best fit line using matlab's polyfit function, and then determine the y intercept of that line to be 133.765.I mistakenly added another screenshot that was unrelated, and I am not sure how to delete it!
Ebay PLL synthesizer with ADF-4106 and RFMD UMX-1349 VCO anyone knows it - Page 1
Forum section: electronics / rf-microwave

author: prutser
author_rank: Regular Contributor
timestamp: July 25, 2023, 07:34:02 pm
content: I bought some relatively cheap PLL synthesize modules, which probably are designed for the 4GHZ range. Trying to reverse engineer the module, which seems not too difficult.It is relatively straight forward:ADF-4106, LT1677 as loop filter amp ( probably to get to the VCO tuning voltage range) MMIC output stage. Some buffer amps between VCO and PLL and 2 small 6 pin devices (probablyvoltage regulators or switches)PCB has one 20 pin connector.The only thing which is bothering me, is that I cannot find where the VCO power is supposed to come from. VCO is powered with 150 ohm resistor from a tantalum cap. But using multimeter I am so far unable to find where the cap get its power from. (In the mean time I found it, but still leaves the question)Anyone here who happens to know this module by coincidence ?
Coax connector identification  - Page 1
Forum section: electronics / rf-microwave

author: Oh-No
author_rank: Newbie
timestamp: June 28, 2023, 09:14:56 am
content: Hi,I’ve got what looks like a U.FL connector, but it’s about 2/3rds of the size.The SMT stud for it is about 1.8mm in diameter. It’s on a PCIE 4G modem board.Any idea what it’s called as I’m looking to run external antennas from the board.The Router is a Sercomm LTE2122GR. I can’t see the make of the PCIE board due to the heat sink.Thanks.

author: Oh-No
author_rank: Newbie
timestamp: June 28, 2023, 10:49:53 am
content: Looks like M.2 connectors.Found the name of the board and then some docs:https://fccid.io/ZMONL952NA/User-Manual/User-Manual-4940860.pdf

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: June 28, 2023, 11:48:20 am
content: The M.2 connector is the connector on the PCB for digital data, not the RF connector. I think the RF connector is an MHF4 connector.

author: Oh-No
author_rank: Newbie
timestamp: June 28, 2023, 10:37:53 pm
content: Thanks - yes. I’ve now ordered some MHF4 to SMA leads.

author: biastee
author_rank: Regular Contributor
timestamp: July 01, 2023, 06:36:41 am
content: At 2/3 the width of the UFL connector is the WFL.
Amphenol Signal Commander - anyone have a manual for this? - Page 1
Forum section: electronics / rf-microwave

author: stellavox
author_rank: Newbie
timestamp: June 26, 2023, 02:39:52 pm
content: Was a Field Strength Meter (from the 70's maybe). Had plug-ins for various frequencies. Got one at a flea market and would like to get it going.THANKSstellavox1@aol.com
Updated database of radio frequencies - Page 1
Forum section: electronics / rf-microwave

author: glradio
author_rank: Contributor
timestamp: June 25, 2023, 04:47:42 pm
content: Hi everyone, I am experimenting with the TinySA Ultra spectrum analyzer and was wondering if there is a web database or software, even for a fee, that will help me understand the origin of the signals the device receives.Something that tells me what gsm operator uses a given frequency or, for fm radio transmissions, what broadcaster broadcasts on that frequency in a given location.I hope you can help me with that. Thanks.

author: srce
author_rank: Regular Contributor
timestamp: June 25, 2023, 07:46:08 pm
content: For FM:https://www.fmlist.org/

author: radiolistener
author_rank: Super Contributor
timestamp: June 26, 2023, 02:48:06 am
content: https://www.sigidwiki.com
Wifi UNII-3 band United States - Page 1
Forum section: electronics / rf-microwave

author: singeo
author_rank: Newbie
timestamp: June 20, 2023, 11:08:08 am
content: Hi,Hope anyone can provide an answer to this question, or at least point me to the right direction of information.In the United States the UNII-3 and UNII-4 band frequencies (5735 - 5895 MHz, channel 149 - 177) are allowed to use for 5 GHz wifi. How common are these frequencies used? I have not been able to find statistics of channel usage, are there any such statistics available? Background: These frequencies are rarely used in EU and to prevent two different SKUs (and additional compliance testing by the standard ETSI EN 300 440) we are considering blocking these frequencies both for EU and for US but we need to know the precentage these frequencies are used in US in order to make a decision.- Sindre

author: RoGeorge
author_rank: Super Contributor
timestamp: June 22, 2023, 02:48:34 pm
content: Quote from: singeo on June 20, 2023, 11:08:08 amNot sure where from did you get that info. AFAIK, 5GHz Wi-Fi routers were a fact since 10 years ago, or so. At least here, in Romania/EU, one can buy a 2.4/5GHz Wi-Fi router from any supermarket:https://www.emag.ro/search/wireless+wifi+2.4ghz+si+5ghz

author: singeo
author_rank: Newbie
timestamp: June 23, 2023, 06:41:45 am
content: Quote from: RoGeorge on June 22, 2023, 02:48:34 pmYeah, I did not mean the entire 5 GHz band is rarely used, only the channels 149 and above. And, I must admit that I did make an assumption, based on the app Wifi Analyzer that does not show channels above 149, that these channels are rarely used. That is sort of the problem, I cant find any statistics on channel usage, neither for US or EU. That is what I am looking for.I found this:https://www.netally.com/wifi-tech-today/wifi-post-3/, and this:https://ctrfantennasinc.com/5-8ghz-wireless/but they dont tell me much.I have triedwigle.netbut I cant seem to find statistics there.I also found thishttps://extremeportal.force.com/ExtrArticleDetail?an=000087263stating that the UNII-3 bands are not allowed in Europe, but that is wrong.
thingy91 GPS matching network - Page 1
Forum section: electronics / rf-microwave

author: okw
author_rank: Frequent Contributor
timestamp: June 19, 2023, 12:02:55 pm
content: I am looking at the GPS matching network from Nordic thingy91 (development kit based on nRF9160).What function does L4/C87 have? And do they only have purpose when used with external active antenna (C13 not assembled)? I.e. if external isn't needed, L4/C87 can also be eliminated from the design?How would I calculate their values?If this same circuit was to be used, but redrawn without external antenna (remove parts J2/L3/L4/C11/C87). Would I replace the DC block C12/C13 with one 20pF, 39pF or even 82pF? Or does two identical (or differently sized) capacitors block wider/better? Like decading the bypass capacitor values to spread out the noise suppression frequencies.Is is common practice to use capacitor C13 like this, to disconnect the radio from the on-board antenna like this, instead of a 0R resistor?

author: nali
author_rank: Frequent Contributor
timestamp: June 19, 2023, 12:55:59 pm
content: Have you looked at Nordic's Infocenter? Their example shows the LNA directly connected to the GPS pinhttps://infocenter.nordicsemi.com/index.jsp?topic=%2Fnwp_033%2FWP%2Fnwp_033%2Fnwp_033_gps_lna_ex.html&anchor=nwp_033_gps_lna_ex__fig_jtl_sgx_43bThe whole bias network on the thingy seems just to allow an active antenna on J2 as it's fed 3v3 via L3.

author: okw
author_rank: Frequent Contributor
timestamp: June 19, 2023, 08:21:01 pm
content: Quote from: nali on June 19, 2023, 12:55:59 pmYes, I've read most of the references.It's not really what I asked. I asked what is the purpose of L4/C87?I have two different designs, one with onboard antenna, much like the Nordic schematics, and another with only external active antenna.The Nordic DK has very poor GPS reception. I've compared it side to side with my own PCB, and mine gets fix after 23-25 sec (cold start), while the DK really struggles, if it even gets fix.PS. Title was misleading. It first said thingy91, but the attached schematics it in fact nRF9160DK.

author: nali
author_rank: Frequent Contributor
timestamp: June 19, 2023, 08:53:50 pm
content: Quote from: okw on June 19, 2023, 08:21:01 pmTo be fair you asked several questions... My guess about L4/C87 maybe a 2.4G notch filter? Without values it's just a guess.
Smith Charts - Page 1
Forum section: electronics / rf-microwave

author: OneofTheMichaels
author_rank: Newbie
timestamp: June 17, 2023, 09:52:21 am
content: Hey all,At some point in 2020 I took a crack at writing a better Smith chart tool, then got distracted by shiny things and forgot about it. Anyway I dug it out and its in going condition, the TXLine code wasn't finish, but eh, not strictly needed. The party tricks are displaying bandwidth and Monti Carlo style tolerance.If anyone feels like giving it a try I'd be interested to hear if it looks useful, or into the dustbin of history.https://www.tlasystems.xyz/-Michael
Klayout simulation issue - Page 1
Forum section: electronics / rf-microwave

author: buttercutter
author_rank: Newbie
timestamp: June 15, 2023, 05:25:34 pm
content: I am trying toreplicateFigure A ofhttps://www.nature.com/articles/s41566-023-01193-1usingKLayouttool.What step did I miss other than "export netlist" ?

author: zrq
author_rank: Frequent Contributor
timestamp: June 16, 2023, 06:21:50 pm
content: What you are doing here?You want to draw a illustrative figure like the A on the paper or simulate the four wave mixing process and filtering?KLayout has almost nothing to do with either goal.The illustrative figures on my papers are usually created by rendering some 3D CAD model.
Satellite Dish Skirts  - Page 1
Forum section: electronics / rf-microwave

author: jonovid
author_rank: Super Contributor
timestamp: June 16, 2023, 07:02:38 pm
content: why did this 1960s dish antenna have this skirt?this antenna is of a satellite navigation system or first generation Global Positioning System1967 Navy Satellite Navigation; IBM 7094; AN_UYK Computer History Archives12:46 on the video to see the dish antenna with its skirt

author: A.Z.
author_rank: Super Contributor
timestamp: June 16, 2023, 07:43:43 pm
content: wild guess: mechanical reasons ?

author: Bicurico
author_rank: Super Contributor
timestamp: June 16, 2023, 08:24:18 pm
content: My guess is that this is a shield against background noise.https://www.bell-labs.com/about/history/innovation-stories/confirming-big-bang/

author: jonovid
author_rank: Super Contributor
timestamp: June 17, 2023, 03:34:16 am
content: In the meantime I did some more research.looks like this is an attempt at weatherproofing the dish.at a time before the use of weatherproof radomes.by adding a roof or skirt to keep the weather out of the underside of the dish were the elevation & azimuth tracking geared motors areso seems to have nothing to do with theradio frequencyfunctionality of the dish.its a type of weatherproof skirt.
85719A on an HP PCMCIA card for 8596E - Page 1
Forum section: electronics / rf-microwave

author: dominitech
author_rank: Contributor
timestamp: June 08, 2023, 11:12:22 pm
content: Anyone have the 85719A Noise Figure Measurement Personality on an HP PCMCIA card that I can purchase or borrow? I repaired an 8596E which required a couple boards to be replaced and there went the Noise Figure software.Thanks in advance!

author: max-bit
author_rank: Frequent Contributor
timestamp: June 12, 2023, 05:09:21 pm
content: I've seen them on ebay, but they're getting harder to find
Pulse RF Amplification - Page 1
Forum section: electronics / rf-microwave

author: Revky27
author_rank: Contributor
timestamp: June 16, 2023, 05:10:06 am
content: Hi All,I am looking into using some RF Amplifiers to amplify very short duration pulses (think 50-100pS width with 200MHz repetition rate).This leads to frequencies in the range of 10-20GHz.Does anyone have a recommendation for any literature or application notes to see some practical implementations and some theory background on how to best handle these pulses using standard RF MMIC amplifiers?Thanks
TC209V13A Funpack Basic. Tx function stuck - Page 1
Forum section: electronics / rf-microwave

author: jorgemef
author_rank: Regular Contributor
timestamp: June 01, 2023, 07:51:05 am
content: Hello,I have a pair of Funpack Basic Radio with board number TC209V13A, on which one of the units is always transmitting. Intermitently it stops.I tracked the circuit and could see it is keyid by a group of resistors in series that when key not pressed should stay at 3.2V.In the "damaged unit" the series stays at 0.1-0.5V. When unsolder Volume up that is very close to TX key, it seems to stay at normal 3.2V.Measuring the resistance when powered off seems to have normal resistance.Unfortunately this is a multilayer board with a microchip as a blob. Searched on the network and could not find a schematic for it so I am not sure of the configuration of the keying circuit. Where the 3.2V cames from or how the resistor network is interconnected.Any hint or do you know where I can find the schematic?From this page:https://ukspec.tripod.com/446/indexp.htmlTC-209 EXTERNAL PIC (OR LOCAL)Updated TC-109. "FM radio" ?(black or silver) 38 CTCSS, vox / baby call, key bleeps, monitor, auto power offBatts: 3AA or 4AAA?!Seen as Zodiac Me2You Radio, Commodore Fun Pack 40, Alecto FR-30BR,Jorge

author: jorgemef
author_rank: Regular Contributor
timestamp: June 01, 2023, 08:56:27 pm
content: Solved it by reverse engineering. Seems PTT key was presenting a low resistance even not activated (2.5K). After unsoldering/resoldering it was working fine.Schematic and component positions attached.
Guidance for sniffing a Medtronic BLE loop recorder - Page 1
Forum section: electronics / rf-microwave

author: Digital Corpus
author_rank: Contributor
timestamp: May 30, 2023, 09:57:46 am
content: I have a close friend with a curiosity streak who’s approached me about a unique topic. They have a loop recorder, aka an ICM or insertable cardiac monitor. Specifically the LINQ II manufactured by Medtronic. It has a 4.5 yr rated battery life, 1 mW antenna, iirc, and connects to a base station or phone to upload once a day. Additionally, a neck worn dongle allows for live output of the patient’s ECG, though company reps are the only ones in possession of the device.He’s not so much interested in the live output but the daily reports if any events are reported. As such, I’m only looking on how to sniff these packets and determine if the data is able to be interpreted as it isn’t available to the patient directly. Currently his ICM is setup through pairing with a bedside base station connected through a mobile/cellular uplink to Medtronic. The pairing is controlled by Medtronic and no SIM card is accessible. Theoretically the station can be connected to the home WiFi, but these instructions haven’t been attempted or inquired as to if the patient can do so w/o speaking to the company rep.Looking for advice or guidance on helping him out. I visit him at least once a week and doesn’t mind some experimentation, so as long as it’s passive. At the time, please consider the base station as tamper evident though I’ve not looked up FCC filings for it directly just yet.I’m not aware of if this is in violation of forum policies, but again, just looking to passively read/copy the nightly upload for my friend. I do realize personally identifiable information may be contained in the transmissions.
Superregen AM BC band receiver? - Page 1
Forum section: electronics / rf-microwave

author: Circlotron
author_rank: Super Contributor
timestamp: June 01, 2023, 06:26:37 am
content: Made a number of ordinary valve-based regenerative receivers 50 years or so ago and they worked remarkably well. Never dabbled with superregen receivers though. Looking on the interwebz the only ones I found were for VHF and above. Is there any fundamental problem with building one for the AM broadcast band? Other than maybe radiating on the same frequency as being received? Currently this is more of a thought experiment than a practical project.

author: RoV
author_rank: Regular Contributor
timestamp: June 01, 2023, 06:59:39 am
content: Toy walkie-talkies on 29.7 MHz were quite common in the 70s. They used a single RF BJT as a superregen receiver and an XTAL transmitter. I remember my first experience on CB (Citizen Band) radio was with one of them, by replacing the XTAL with one for channel 2, 26.975 MHz and adjusting the tune coil. The problem was that electivity was very poor in reception: I received all CB channels at the same timeThe practical problem in going down with frequency is the ratio between the carrier frequency and the quenching frequency, which must be kept high to get a good performance. But the quenching must be ultrasonic, otherwise the audio would be disturbed, so the carrier frequency can't be too low.I suppose there is a relationship between quenching frequency and selectivity, but I'm not sure.There are several academic papers on the subject of superregen receivers, you may look at them.
Help identify microwave transistor logo - Page 1
Forum section: electronics / rf-microwave

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: May 28, 2023, 05:10:45 am
content: Does anyone recognize this manufacturer's logo on microwave transistors? Can't seem to find anything.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: May 28, 2023, 10:41:16 pm
content: Exodus Advanced Communications

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: May 29, 2023, 12:29:53 am
content: Thanks! Was looking for it for a long time. But it seems they sell only microwave systems, not individual transistors. The actual amplifier module is from IFI. I wonder what are my chances of getting a datasheet or replacement for that transistor.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: May 29, 2023, 12:36:41 am
content: Maybe someone (experienced sales and/or application engineer) at RFPD (Richardson) or another specialised distributor could help you. Or ask at everythingrf or mwrf.com whether anyone knows who took that product line or who made them really..

author: coppercone2
author_rank: Super Contributor
timestamp: May 30, 2023, 01:58:45 am
content: I wonder how hard it would be to find a new one that you can put in there.Are they that different from each other? I would expect maybe some noise figure irregularity or something.. I wonder how tuned the circuits are to the transistors. Sometimes I wonder how different it is from hacking a toilet flush system (like a transistor it goes into 'latchup' (permaflush) if you don't bound it etc..

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: May 30, 2023, 03:22:07 am
content: I am far from microwave expert, in fact this is the first module I popped open. Here are some pictures of the module. It is labeled as IFI, but it looks very similar to AMP1124 from EAC, which would explain the transistors.The symptom is that there is no output and no significant current draw. My current plan is to turn it on and probe with a high impedance scope probe around the input section. But having never opened one of these I wonder if there is a danger of feedback with cover open, so maybe I should screw down the cover so it covers the output section. Also can check the bias voltages, but first I need to learn what they are supposed to be...

author: coppercone2
author_rank: Super Contributor
timestamp: May 30, 2023, 04:03:46 am
content: well it might not be the transistor.. you know it can be a capwith solder tweezers I really think that checking every single cap on complex stuff is the way to go lolpull test mark with sharpie resolder and go through the whole thing, cleaning after you test a cluster of components.maybe its just me, but the soldering on some of those passives looks kinda dodgy...IDK the deal with the PCB though, is it copper metalization, or silver? In that case silver or copper bearing solder would help. So you don't dissolve traces
Cut steps when tuning a 2.4g meander antenna length. - Page 1
Forum section: electronics / rf-microwave

author: Psi
author_rank: Super Contributor
timestamp: May 18, 2023, 12:00:13 pm
content: When cutting a 2.4ghz meander antenna shorter and shorter to tune the length, how much length should I be cutting/grinding off each time to avoid missing a good antenna length? eg 1mm? less?I'm using this coil layout, except without the exact FR4 edge positioning that they spec.Also I have a longer feed line to the antenna, 4mm or so surrounded by GND plane and via stitching.https://www.st.com/resource/en/application_note/an5129-low-cost-pcb-antenna-for-24ghz-radio-meander-design-for-stm32wb-series-stmicroelectronics.pdf

author: geggi1
author_rank: Frequent Contributor
timestamp: May 18, 2023, 04:52:44 pm
content: 1mm is almost 1% of a full wavelength and that will give a big difference in in the resonant point of the antenna.I would recommend to trim as short lengths as possible.Another way to get it into resonance is to use a trimmer cap in the matching capacitors see page 4.Option one is to use one trimmer capacitor 60pF or something and trim for the highest output.Option two is to use a fixed 120pF and a trimmer at the same size, trim for the highest output.The last potion is to play around with fixed caps.

author: Psi
author_rank: Super Contributor
timestamp: May 22, 2023, 12:00:39 pm
content: Is it better to do length tuning with the RX or TX antenna?

author: coppercone2
author_rank: Super Contributor
timestamp: May 23, 2023, 12:46:18 am
content: do strokes of a file

author: geggi1
author_rank: Frequent Contributor
timestamp: May 23, 2023, 04:10:33 am
content: Quote from: Psi on May 22, 2023, 12:00:39 pmNormaly it is better to tun the lenght but on higher frequencies it is hard because just tiny changes will give large changes resonant frequency.One way to get around this is to make the antenna wide band to simplifie the tuning.

author: Hamelec
author_rank: Regular Contributor
timestamp: May 28, 2023, 02:57:55 pm
content: take a tiny piece of sheet metal e.g aluminium foil, put it on your FR4 board near the antenna and move it around for tuning with a toothpicker, always watching the s11. Glue it with some silikon (and readjust it).
si5351 at 200 MHz - Page 1
Forum section: electronics / rf-microwave

author: bb1
author_rank: Regular Contributor
timestamp: May 26, 2023, 02:44:47 pm
content: si5351, being very inexpensive, is very popular as VFO.For each output it uses two fractional dividers: One in fractional PLL, and the other to divide PLL frequency for the output.Fractional dividers create spurs in the output. To decrease them, output divider is usually used in integer mode.However, to provide enough frequency resolution, fractional divider should be used to set PLL frequency.It is interesting to find how significant the spurs can be.At low frequencies, such as around 7 MHz, spurs are low and difficult to observe.To make them more visible, high si5351 output frequency around 200 MHz may be used.If the PLL reference frequency is set to 25 MHZ, and si5351 output is set to 200 Mhz, then the output divider is set to 4,and PLL divider is in integer mode with value of 32. In this case there should be no spurs.200.0MHz_8mA_wide2MHz.png,which is screenshot of the Tek Spectrum Analyzer, confirms that.The absolute frequency on the Spectrum Analyzer screen is not exactly 200 MHz because the si5351 reference frequency is about 100 ppm above 25 MHz.However, small increase of the output frequency to 200.1 MHz leads to fractional PLL divider of 32.016, and radically changes the picture:200.1MHz_8mA_wide2MHz.pngshows a lot of spurs, the largest ones being only about 25 db below the carrier.It is interesting that 1GHz Tek scope infinite persistence does not show any significant jitter even at 200.1 MHz:ts_si5351_8ma_200.1MHz_AC_infPers_7.5usDelay.png

author: radiolistener
author_rank: Super Contributor
timestamp: May 26, 2023, 07:03:16 pm
content: In order to reduce spurs, keep PLL frequency as high as possible. Many si5351 instances can run stable PLL above 900 MHz, but there is possible issues with PLL reset, if you overclock it it too much it may stuck in some state and require full power off to reset it (sofware reset and rewrite all register doesn't help). There is also some magic tricks to write some registers several times in order to keep it running stable in overclocked modes.The problem with high frequency (above 100-140 MHz) is that it requires PLL reset so you can't sweep frequency smoothly. At low frequency you can change frequency without PLL reset and it allows smooth frequency sweep.
RF Interference to Metal Detector - Page 1
Forum section: electronics / rf-microwave

author: DarrenC
author_rank: Newbie
timestamp: May 24, 2023, 02:08:43 pm
content: Hi All,I have a Analogue Metal Detector that is false tripping constantly, the receiver is set to 32Khz. I have tried replacing the transmitter boards and receiver boards and rebalancing the coils to different frequencies, I have isolated equipment in the near vicinity that could be causing interference to no avail. Before I replace the unit with a replacement I need to rule out noise interference before installing the new unit.My question is that if there is radiating noise interference what would I need to analyse this and pinpoint the source of the interference? Any information would be extremely helpful.Thanks,Darren

author: coppercone2
author_rank: Super Contributor
timestamp: May 24, 2023, 10:07:57 pm
content: modern metal detectors have a frequency hop features so its very possible, but its designed so that crews can work together close by without disturbing each other, otherwise its a lonely experience. (the idea is to block interference from fellow metal detectors by changing frequency)Hard to say if its 30KHz interference or other interference getting into it anyway because its not made well. Kind of hard to deal with low frequencies. It might work at 30Khz but be effected by any frequency like any other device.www.vlf.ithas designs for sensors / antenna in that frequency rangeIf you want radio quiet, go out into a big field, or possibly deserted valley.I know walkie talkies (FRS) can trigger them nearby.

author: DarrenC
author_rank: Newbie
timestamp: May 25, 2023, 07:13:19 am
content: Thanks for the information.This Metal Detector is attached to a conveyor system, the unit also has a side frequency intended for if there was two side by side but even when switching to the side frequency the detector is still going crazy. Having done some research myself I have found out that if there is indeed interference it would have to be the same harmonics as the detector and also be multiples of 32Khz, also I have found out that I would need a spectrum analyzer and a directional antenna to try and find the source and pinpoint it. But what spectrum analyzer I would need I don't know.
Spaceview Satellite Systems, Model SR-2000A - Page 1
Forum section: electronics / rf-microwave

author: TheRuler8510
author_rank: Regular Contributor
timestamp: May 22, 2023, 05:00:57 am
content: RE: Spaceview Satellite Systems, Model SR-2000AHas anybody heard of these units? Or, does anyone know what it is used for exactly?I could not find a shred of info on the internet. It looks like a 1960s to 70s type of gear. I thought it might be worth something due to rarity.Picture below.Regards,TheRuler8510
Best SO-239 style for outdoor box? - Page 1
Forum section: electronics / rf-microwave

author: elroy
author_rank: Regular Contributor
timestamp: May 29, 2023, 05:14:24 am
content: I'm winding a transformer that will go in a small ABS box outdoors near an antenna's feed point. The box will need an SO-239 socket.I've seen a couple of different styles of SO-239. Some are a basic barrel, held onto the box or panel by a large-diameter nut, and maybe a washer. The other type is on a square plate, with holes at the corners for four small screws.From a weatherproofing point of view, what's the better choice? Also, is there a best sealant to use, and a best way to apply it?

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: May 29, 2023, 07:42:08 am
content: Avoid the type with a large nut. I use the square flange type with 4 bolt holes. It helps to buy the more expensive types, as some will literally fall apart. I use these from M0MAT on eBay, see item 153363155392Seal the inside connections and coax tails with “704 silicon”, or liquid electrical tape (rubber dissolved in strong solvents). Do not use ordinary silicon that is found in hardware stores and smells of vinegar, it corrodes metal. 704 silicon can be sourced from China on eBay, one example is item 175402647347It is the white stuff that is also used to secure electrolytic caps in transistor radios.Drill a small (1mm) vent/drain hole in the lowest side of the box.Job done.73 SJ

author: elroy
author_rank: Regular Contributor
timestamp: May 29, 2023, 03:29:50 pm
content: Thanks, good suggestions.The SO-239's from M0MAT look good, but I'm hoping to get one fairly quickly, and international shipping would be a factor. So I might go with an Amphenol from a U.S. source.Likewise the 704 silicone from China will take a while to get here. I wonder if 3M marine-grade silicone sealant would be an alternative?

author: elroy
author_rank: Regular Contributor
timestamp: May 29, 2023, 03:34:35 pm
content: Also, just to clarify, would the square flange mount on the exterior surface of the box? Or inside?

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: May 29, 2023, 03:35:44 pm
content: “ I wonder if 3M marine-grade silicone sealant would be an alternative?”I’m not sure. Liquid Electrical Tape is manufactured in the USA, so should be easy to obtain. It comes in various colors and is in a jar with a brush in the lid. Beware, it dissolves rubber self amalgamating tape.You want the flange on the outside. Otherwise the plug won’t fully seat.SJ
Pairing of remote with switch relay reciever - Page 1
Forum section: electronics / rf-microwave

author: TorOlavHE
author_rank: Newbie
timestamp: May 19, 2023, 01:20:52 pm
content: Hi!Do someone know what one could do to pair the switch relay receiver and the remote in the links below? I have a 8 channel remote and switch, but only some of the buttons are working - and not channel 1 to port 1, channel 2 to port 2 etc, but more random pairing. In addition, there is a relatively high beeping sound when the relay operates from input from the remote - slight oscillating mismatch maybe? Both devices use 433 MHz. Looks like the encoding on the relay is PT2264 and on the remote PT1527 (assuming PT although eV1527 is imprinted physically on a board chip?).Is there a chip or something I could replace somewhere?Pictures of the circuit board of the remote attached, and video of the internals of the switch here:https://drive.google.com/file/d/1ulsJ-kCfhv6O4_napJFBwDTYWU-IFz_A/view?usp=drivesdkhttps://drive.google.com/file/d/15ULho27OSmIEEcpwP-ShWtcXDsCmZ1fl/view?usp=share_linkhttps://www.aliexpress.com/item/400...716594670968963435e7446!10000000434084947!seahttps://a.aliexpress.com/_mNWeH6GBest regards,Tor Olav
RF amplifier CMX90A004 problem - Page 1
Forum section: electronics / rf-microwave

author: just5554
author_rank: Contributor
timestamp: May 12, 2023, 10:59:23 am
content: I'm designing UHF RFID reader using ST25RU3993 IC, which has 0 dBm output. I'm using CMX90A004Q7-R710 RF amplifier, which should output 30 dBm signal.The problem is, that I'm getting same 0 dBm signal on the amplifier output as in input (checked using spectrum analyzer), therefore achieving only half a meter working distance (using 8 dBi antenna).Few details about testing:It is designed based on datasheet application example;Amplifier consumes current stated in datasheet (1A);Soldering quality was inspected using microscope and multimeter in continuity mode with needle probes;Amplifier supply voltage does not drop below minimum specification.How likely is that amplifier was damaged after accidentally powering it without load (antenna) connected due to standing waves? Or is it designed wrong?Thank you for your answers in advance.

author: Marsupilami
author_rank: Frequent Contributor
timestamp: May 12, 2023, 07:49:07 pm
content: Powering it on in itself is not necessarily a problem but if you also fed full power input into it it can be easily damaged with a full reflect on the output.I would expect change in its current draw though.What are we seeing on the scope screenshot?Are you sure that the input level is correct?
I want to know current and voltage of a matching circuit - Page 1
Forum section: electronics / rf-microwave

author: LM21
author_rank: Regular Contributor
timestamp: May 06, 2023, 02:34:18 pm
content: I have a impedance matching circuit of a transistor amplifier, How can I calculate current and voltage of each component. I think I could start from power and reactance, and solve U*U/XL=P and U*U/Xc=P. Is that all, what about for instance the circuit Q.I attach a simple output matching circuit for VHF and 4W, for an example, but there are plenty of circuits and powers.

author: yl3akb
author_rank: Regular Contributor
timestamp: May 06, 2023, 04:16:29 pm
content: These formulas cant be used like that. The power source must be converted to voltage source with series resistor and then standard AC circuit theory applied. See example 2.1. calculation here:https://wiki.math.ntnu.no/_media/tma4120/2021h/forkurs/ex_circuits.pdfBut yf You are lazy (like me), just use circuit simulator, lieke LTspice.

author: TimFox
author_rank: Super Contributor
timestamp: May 06, 2023, 06:14:24 pm
content: I would also use a Spice analysis, using the ".AC" mode in regular Spice..AC mode is just a convenient analysis of the algebra, and is useful for either true linear models or linearized models.Note that each reactance has a parasitic component (series inductance parasite for capacitors, shunt capacitance parasite for inductors), where the parasites are not exactly independent of frequency.The parasitic resistance for each reactance (ESR) does depend on frequency.However, the Spice analysis with reasonable models for each branch should work well for a narrowband calculation.

author: RoGeorge
author_rank: Super Contributor
timestamp: May 07, 2023, 01:39:37 pm
content: If you need only the numerical values (and you don't need to know how to solve that manually, on paper), then use a simulator, e.g.: LTspice, QucsStudio, QUCS, TINA-TI, etc. all free and can solve the posted example.QUCS and QucsStudio have some extra RF goodies, like Smith chart representation, PCB structures calculator, RF filters design, etc. LTspice is probably the easiest to use. QucsStudio has dragging sliders (called Tune), in case you want to see live what happens when a component value varies.
Varactor voltage in high performance VHF VCO? - Page 1
Forum section: electronics / rf-microwave

author: rf-fil
author_rank: Regular Contributor
timestamp: May 01, 2023, 09:49:13 pm
content: I'm working on a thing, and got to modeling VCOs, to find one that would be good for VHF, specifically a few MHz around 124MHz. All of the topologies have one thing in common. Fundamentally, low phase noise VCO requires high loaded Q resonator. Which means high voltage across it. which would mean, high RF voltage across the varactors. I've attached one example circuit. In my example, the voltage across the top of the resonator is ±20V (!!), and about ±4V across the varactor.So it seems like my only choice is to reduce the voltage across the resonator either by reducing the loaded Q, or by using smaller DC bias current. am I right?

author: paul@yahrprobert.com
author_rank: Regular Contributor
timestamp: May 02, 2023, 11:43:12 pm
content: So that capacitor C4 in series with your varactor drops some of the RF voltage. If you make that smaller you can reduce the voltage on the varactor. That might reduce your tuning range, so further information is needed.

author: duak
author_rank: Super Contributor
timestamp: May 03, 2023, 04:00:31 am
content: You might be able to make two varactors work in a push-pull configuration where the bias voltage across one increases while it decreases across the other.One way is something like the attached screen shot from page 47 of Turner's ABCs of Varactors:https://worldradiohistory.com/BOOKSHELF-ARH/Author-Groups/Rufus-Turner/ABC%27s-of-Varactors-Rufus-Turner.pdf.I envisage something a bit different - see PP varactors.jpg attached file. The 100k resistor isolates the control voltage driver from the resonant circuit. The two 1M0 resistors balance the average bias voltages. This requires a higher bias voltage but it offers a greater capacitance because the varactors are in parallel.I think I've seen a circuit using two varactors and a center tapped inductor, but I doubt it could be applied here.Cheers,
awr  port - Page 1
Forum section: electronics / rf-microwave

author: Nahim
author_rank: Contributor
timestamp: May 01, 2023, 03:24:24 pm
content: Comrades, please tell me how to display the second output from the PORT? There are various structures , coaxes, microstrip lines , you need to connect directly WITHOUT EARTH ..As far as I can see, the ground pin is hidden by default on a regular port ..

author: yl3akb
author_rank: Regular Contributor
timestamp: May 01, 2023, 03:49:48 pm
content: You may want to use ideal 1:1 transformer component.

author: Nahim
author_rank: Contributor
timestamp: May 01, 2023, 03:59:27 pm
content: Thanks a lot !!!
Hytera PD6 Pinout? - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: February 13, 2023, 07:01:21 pm
content: Thanks I know:https://www.wildtalk.com/hytera-x1-and-pd605-curly-cable/But sadly how about the other Pins? I know Pin11 is for custom thinks but the other?Does anyone know?Thanks!EDIT: Here is a possible Pin Layout:Pin 11 is from the Manual.The Top 3 Connector are for Audio Devices. The Bottom left is a Cable to a Bodycam and the right is the Programming Cable to the PC.So... the main Question is are the Pins use only for one typ of Transmission like Audio or do the serve multiple purpose?!Thanks

author: Lord of nothing
author_rank: Super Contributor
timestamp: April 10, 2023, 05:38:32 am
content: No idea?Thanks

author: eb4fbz
author_rank: Regular Contributor
timestamp: April 29, 2023, 06:59:02 pm
content: Check the PD60X service manual

author: eb4fbz
author_rank: Regular Contributor
timestamp: April 29, 2023, 07:13:36 pm
content: Pin 11 is TD output. I guess it’s a square wave synchronized to the TDMA slots.

author: Lord of nothing
author_rank: Super Contributor
timestamp: April 29, 2023, 08:35:07 pm
content: Quote from: eb4fbz on April 29, 2023, 06:59:02 pmI dont have access to them. Where can I find them?Thanks
P-type semi from adding In to Ge crystals - Page 1
Forum section: electronics / rf-microwave

author: biastee
author_rank: Regular Contributor
timestamp: May 02, 2023, 05:29:11 am
content: Local ham exam has a question on adding indium atoms to germanium crystals to produce P-type semiconductor (fig. 1). I suspect the local authority cribbed the question from the FCC/US ham question bank. I am wondering if the described process refers the obsolete Ge transistor? My thought is that contemporary npn/pnp BJTs are all silicon, i.e. devoid of Ge material. Or am I wrong?A website says that p-type semiconductors are produced by diffusing Boron into Si material; i.e. it didn't mention Ge at all(fig. 2).So, is the above question describing an obsolete process - e.g. Ge BJT? Thanks!

author: RoGeorge
author_rank: Super Contributor
timestamp: May 02, 2023, 09:01:14 am
content: Probably a question from decades ago, when transistors and diodes were based on Germanium.If you are curios for the very beginning of manufacturing Ge transistors, this documentary series is called "A video history of Japan's electronic industry":Birth of The Transistor (Part 1)Circuits in stone (Part 2)The Calculator Wars (Part 3)The technologial giant of the micron world (Part 4)

author: iMo
author_rank: Super Contributor
timestamp: May 02, 2023, 09:48:53 am
content: The question is probably related to the number of valence electrons Ge and In have got.Ge has got 4 valence electrons, Indium 3 valence electrons thus you get P-type of semiconductor (as In adds the 'holes' because of the missing electron). A pretty difficult question for the ham exams, however..