hybridfree/eevblog-posts huggingface dataset:
The Testing Fixture for 6-Lead QFN SPDT RF switch - Page 1
Forum section: electronics / rf-microwave

author: neilhao
author_rank: Regular Contributor
timestamp: October 26, 2021, 07:44:36 am
content: I purchased several SPDT RF switches which manufactured by a Chinese listed company. The chip’s footprint is 1.0mm x 1.0mm x 0.45mm 6-lead QFN package. The manufacturer did not provide S-parameters. Thus, I had to design the fixture and measure the S-parameters by myself.The measurement data conform to the Insertion loss and Return loss specifications in datasheet. Unfortunately, the measurement data exceed the isolation specifications in datasheet. However, for $0.04/pcs, I should not complain to much...This article could also be fetched from the project’s wiki if the screenshot of this article is not comfortable for reading. Project's Wiki:https://uniteng.com/wiki/doku.php?id=rfmeasurement:testing_fixture_6_lead_qfn_spdt_rf_switch

author: 3isenhorn
author_rank: Contributor
timestamp: October 26, 2021, 09:00:51 am
content: HiGood measurement!I was wondering if the switch could be directional for insulation? Since they call the pin Ant(enna), they could only consider isolation when power flows into that port.So maybe it is worth repeating the first measurement when the switch for the S34 part is open sit? (Second RF port matched with 50ohm)

author: RadioNerd
author_rank: Regular Contributor
timestamp: October 26, 2021, 02:39:58 pm
content: Before putting down the switch as not compliant to the specifications, bear in mind that performing isolation measurements at several GHz can be quite tricky and pose high demands on the design of the test fixture.I n general, good isolation is achieved by1) providing lowest inductance between the IC GND and PCB ground (lots of vias under the GND pad of the IC)2) miminizing direct RF coupling between the traces on the PCB.I cannot see the details of the PCB layout but at least point 2) could be improved in your test fixture. It might help to take a look at the layout of evaluation boards of the most important RF switch IC manfacturers. Skyworks for example has several Switch IC with very similar characteristics. Often there is also a drawing of the corresponding evaluation PCB in the datasheet. As an example:https://www.skyworksinc.com/-/media/SkyWorks/Documents/Products/1901-2000/SKYA21012_203021D.pdf

author: neilhao
author_rank: Regular Contributor
timestamp: October 26, 2021, 04:21:32 pm
content: Make sense! Just similar as mmwave radar design, better GND plane design between TX and RX can improve isolation, sometimes a GND via between TX and RX can improve the isolation by several dB.However, for the fixture design, it seems it is not easy to measure the isolation of the IC itself. No De-embedded algorithm can work with crosstalk problem..

author: neilhao
author_rank: Regular Contributor
timestamp: October 27, 2021, 10:35:39 am
content: Quote from: RadioNerd on October 26, 2021, 02:39:58 pmUpdate:I did the EM simulation for isolation between the traces RF1 and RF2 on the PCB. The isolation is not perfect but still far better than the measurement.
Highest-Q 25pF-40pF variable capacitors for VHF? - Page 1
Forum section: electronics / rf-microwave

author: szoftveres
author_rank: Regular Contributor
timestamp: October 17, 2021, 07:51:04 am
content: Hi All,What are the recommendations for high-Q variable capacitors in the 25pF-40pF range?So far I've found the old style ceramic trimmer to work the best, but I'm curious if there are any other good options. Anything else I should try?Thanks!

author: radiolistener
author_rank: Super Contributor
timestamp: October 17, 2021, 09:23:42 am
content: Quote from: szoftveres on October 17, 2021, 07:51:04 amКП1-4, 5-100pF, 25 kV vacuum variable capacitor:it cost about 75 USD on internet.Very good for magnetic loop antennaUps... didn't notice you're needs it for VHF, КП1-4 max frequency is 30 MHz...

author: David Hess
author_rank: Super Contributor
timestamp: October 17, 2021, 05:41:30 pm
content: Piston trimmers achieve Qs in the 1000s.

author: TimFox
author_rank: Super Contributor
timestamp: October 17, 2021, 07:26:27 pm
content: Piston trimmers are great.Most have one terminal to the mounting bushing (normally grounded) but some have two leads for non-grounded operation.More expensive ones have sapphire dielectric between the internal moving piston and the outside cylindrical electrode; cheaper ones use glass. Others are PTFE or air dielectric.If this be a onesie (not manufacturing) project, Surplus Sales of Nebraska has a good selection of pistons.https://www.surplussales.com/Variables/PistonTrimmers/index.htmlFor example, on the "high-Q" page, their catalog no. CTP5452 is a Johanson 1.0 to 16 pF panel-mount unit, air dielectric, withQ> 3000 at 100 MHz, for $18.99.On the "standard" page is CTP MPT62004A from JFD, Q not specified, 0.8 to 18 pF for $6.00Both of these have enough change in C to reach your 25 to 40 pF range with a suitable fixed capacitor. Higher capacitance units are available there.

author: szoftveres
author_rank: Regular Contributor
timestamp: October 18, 2021, 08:32:02 pm
content: Thanks all, the piston trimmer seems like a good choice. I'm building a coaxial type resonator filter for low power level on vhf.

author: TimFox
author_rank: Super Contributor
timestamp: October 18, 2021, 08:34:32 pm
content: A piston trimmer with grounded bushing is also a good mechanical fit for a coaxial resonator.

author: David Hess
author_rank: Super Contributor
timestamp: October 18, 2021, 09:43:23 pm
content: Quote from: szoftveres on October 18, 2021, 08:32:02 pmOh really? Many years ago I built a helical resonator. The first version used plastic film trimmers, which was marginal, but the second used pistol trimmers and performed superbly. Piston trimmers down below. They have little screw on caps with a gasket so the external slotted screw for adjustment is not visible.I made the coupling window too large, so mine is over-coupled, but that also means very low loss so it worked out well enough.
Dielectric Constant Measurement Using Microstrip Ring Resonator Method - Page 1
Forum section: electronics / rf-microwave

author: neilhao
author_rank: Regular Contributor
timestamp: October 21, 2021, 01:48:31 am
content: In this article, a HTCC substrate is measured by using the Ring Resonator method.The Ring Resonator method has following advantages :1. A closed ring with no gaps eliminates much of the fringe effect.2. Resonator rings ensure minimal or negligible loss by radiation, so that Er can be calculated more accurately.3. The results refer to very narrow band ranges/widths (resonance); this avoids issues connected to spurious modes.Project Wiki:https://uniteng.com/wiki/doku.php?id=rfmeasurement:ringresonatormethod
Labsat 3 Wide band noise level GPS position  - Page 1
Forum section: electronics / rf-microwave

author: man_marius
author_rank: Contributor
timestamp: October 13, 2021, 01:10:39 pm
content: HiI have a problem with a labsat,I have a GPS receiver that I want to verify. I have a scenario on the labsat recorded. When I play this scenario for my DUT gps receiver, I do not get signal acquisition. I know the scenario I recorded is okay, because some time back I was able to get a PVT solution.My speculationsAfter checking the datasheet of the labsat I was to see that they use 3 bit quantization (best case scenario). This raises the noise level by around 20dB. Reducing my SNR can this explain the acquisition problems?Is there a why to improve the SNR with the Labsat?One way of doing that will simulate the antenna patterns, is it possible to do with the Labsat?

author: ConKbot
author_rank: Super Contributor
timestamp: October 15, 2021, 08:45:49 pm
content: If you have a 20db receiver noise figure, and a 2db n.f. LNA, then you are going to need at least 24db of gain on your LNA before the system noise figure drops below 3db.https://www.pasternack.com/t-calculator-noise-figure.aspxNote that cable loss/passive splitters between the LNA and receiver(recorder in this case) count against your LNA gain. So make sure your (LNAgain)-(cable loss) figure is over 24db, preferably 30db.Also, when you start throwing high gain preamps at things, you're going to want band limiting also, either in the antenna passband, or a dedicated filter. With 30dbm of gain at 1575, a cell phone at 1800 can drive an LNA non-linear pretty easily without a bit of pre-selection.
Video - basics of the superheterodyne receiver - Page 1
Forum section: electronics / rf-microwave

author: w2aew
author_rank: Super Contributor
timestamp: October 15, 2021, 02:07:00 am
content: My latest video discusses and demonstrates the basics of the superheterodyne receiver:

author: andy3055
author_rank: Super Contributor
timestamp: October 15, 2021, 04:08:46 am
content: I just watched it an hour ago! Great presentation. Thanks.

author: BrokenYugo
author_rank: Super Contributor
timestamp: October 16, 2021, 12:56:48 am
content: Good presentation, concise and well illustrated as always. I already knew the basics of how a superhet worked, but had never seen it in action as presented.
Please help to identify this SMA connector - Page 1
Forum section: electronics / rf-microwave

author: SKPang
author_rank: Unknown
timestamp: October 14, 2021, 08:34:08 pm
content: There is a PCB mounted SMA connector I want to use on my board. It is flush to the PCB edge and has a slot cut out to make it low profile.Do anyone know the correct name for this SMA connector ?

author: langwadt
author_rank: Super Contributor
timestamp: October 14, 2021, 08:57:10 pm
content: edge mount, edge launch, cut out, ...https://www.digikey.de/product-detail/en/samtec-inc/SMA-J-P-H-ST-EM3/SAM9950-ND/6678687

author: SKPang
author_rank: Unknown
timestamp: October 14, 2021, 08:58:27 pm
content: Wow that is great.Thank you.
Can too much pre/post emphasis worsen the BER and why - Page 1
Forum section: electronics / rf-microwave

author: Noah
author_rank: Newbie
timestamp: October 14, 2021, 12:11:28 pm
content: I am working on an FPGA <-> FPGA link using the GTY transceivers in an Ultrascale+ Virtex FPGA. Two transceivers are connected through a QSFP direct attach copper cable of 1.5m length with ~15dbm insertion loss. Using the IBERT in the Xilinx FPGA I can measure a statistical eye diagram and change different settings of pre/post emphasis.I noticed that the eye diagram gets worse if I enable either pre or post emphasis. The link has a line rate of 25Gbps and 390mVpp swing and DC coupling with floating 100E termination.The Tx driver is documented in this PDF starting page 167.https://www.xilinx.com/support/documentation/user_guides/ug578-ultrascale-gty-transceivers.pdfCan someone explain the observed effect to me or point me to some good resources on high speed serial links and why this might happen?

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: October 14, 2021, 12:58:05 pm
content: Not an FPGA guy, but am a high-speed-serial guy - How do you train the equalization? Improper settings will make things worse, rather than better.

author: Noah
author_rank: Newbie
timestamp: October 14, 2021, 01:34:15 pm
content: The receivers have a DFE with discrete-time adaptive high-pass filter and AGC that continuously runs an MMSE adaptive algorithm (linked datasheet p. 197 ff). The data stream is scrambled so the DFE should have enough data to continuously be trained. I can reset the receiver and watch ~90 bit errors reported until the DFE settles and the BER goes to zero.Could it be that at 25Gbps my cable just can't support the precursor? The datasheet:https://www.molex.com/pdm_docs/ts/1002970003-000.pdfDoes the transmitted signal with applied pre-curser have a faster rise time?
Microwave / RF behavior of SMT component hold down adhesives ? - Page 1
Forum section: electronics / rf-microwave

author: EE-digger
author_rank: Frequent Contributor
timestamp: October 10, 2021, 05:39:46 pm
content: ** sorry for dupe, cannot fix at the moment **To replace an inadequate interconnect method between two tiny assemblies, I need to place a U.FL connector on an existing PCB, it will have an excellent gold surround and signal to solder to, but no footprint since it's an afterthought. Solder paste is auto deposited and pick and place no problem, but I need to restrict movement during reflow. Frequencies are all under 3GHz. Signal is a 50 ohm path.Does anyone have experience with the high frequency / dielectric / loss tan characteristics of the adhesives used to hold components down (when needed) for reflow? Any experience with particular brand or product?Thanks !

author: Andrey_irk
author_rank: Regular Contributor
timestamp: October 11, 2021, 09:00:01 am
content: The best way to get the loss tanget of a material is to ask the manufacturer. But, you may not need it.What laminate do you use for your PCB? If it is FR4, then the adhesive will hardly make any differrence.The lack of a proper footprint can harm your VSWR much more than the presence of the adhesive. And, what parameters do you want to get from that interconnect?Still, my rough estimate will be Eps = 3 ... 4 and tanD about 0.05 (maybe more, but not muchl). Based on my experience.

author: tszaboo
author_rank: Super Contributor
timestamp: October 11, 2021, 11:37:58 am
content: Quote from: Andrey_irk on October 11, 2021, 09:00:01 amThey will not have this info, they never do. When you ask them for dielectric constant, you get 50Hz, or if they are really scientific, 10KHz.

author: EE-digger
author_rank: Frequent Contributor
timestamp: October 11, 2021, 01:51:07 pm
content: Quote from: tszaboo on October 11, 2021, 11:37:58 amMaterial is FR4. The plan is to eliminate 3 very bad serial inductances caused by cantilever spring contacts.True, they seldom have this info, always 50/60Hz related. Got lucky once while potting a BLE antenna for a medical device. Mfgr still had no numbers but a long successful track record with their compounds. Took a few extra iterations but worked out well.Looking at the jacks some more, I think two diagonal placed dots can grab it without touching the signal pin. Plus I have low impedance of the signal on my side.ATEX, heh? I've designed two small products to meet it. Can be a challenge when you need a 0402 size part and the ATEX rated version is a half inch/cm cubeWhat can be more of a challenge is labeling it properly.

author: Andrey_irk
author_rank: Regular Contributor
timestamp: October 12, 2021, 02:23:09 am
content: Can't say about 50/60Hz, but the dielectric constant value measured at 1MHz (which is pretty much standard) is usually very close to that at 3GHz. If it isn't, then the loss at 3GHz will be over the roof (in other words, huge loss affects epsilon value).FR4 itself is very lossy, so you will unlikely notice any difference with the adhesive.
PCI wifi board (Ubuntu OS) to experiment with microwave signals - Page 1
Forum section: electronics / rf-microwave

author: mpradio
author_rank: Newbie
timestamp: September 06, 2021, 09:02:55 pm
content: Hi I would like to use a PCI wifi board (Ubuntu OS) to experiment with microwave signals. I would like to be able to access the board through the software driver and be able to turn on or turn off the carriers of the Wi-Fi channels without modulation. In other words, use the board as a microwave signal generator in the Wi-Fi band (2400Mhz-2500Mhz). I have no idea where to look for information to achieve this if at all possible. Basically I would like to be able to access the records of the chip of the wifi board by looking at its data sheet (if there is this possibility).

author: MartinL
author_rank: Regular Contributor
timestamp: September 11, 2021, 07:10:53 pm
content: You're probably looking for a software defined radio board, not a wifi card, and unless you want to spend a lot it will have a USB rather than PCIe interface. Something like theHackRF.Wifi chipsets do have CW test modes for compliance testing and factory use, but only the manufacturer will know how to activate them and they don't publicise that information.If you look at MCUs with built-in wifi though, the test software is more likely to be publically available. E.g. for a very cheap signal generator you could use an Espressif ESP32 dev board and run the RF test firmware availablehere. It should be able to do constant-carrier at selected frequencies in the 2.4-2.5GHz range, although you may not have a great deal of control.

author: EE-digger
author_rank: Frequent Contributor
timestamp: October 10, 2021, 06:54:13 pm
content: If you can find sample code for a radio test, you may be able to put the radio into compliance test mode. For a Bluetooth radio, you can turn a signal on/off, CW/modulated, set power level, set data speed, etc., on a selected channel. Typically, this would be example code for the chip you're working with. I've never done this on WiFi, however.Keep in mind that when you are transmitting, you should be in a screen room or RF test box to avoid radiated signals.

author: radiolistener
author_rank: Super Contributor
timestamp: October 11, 2021, 12:38:23 am
content: If you're want just enable/disable carrier, then you're needs RF generator and use USB or Ethernet to control it from PC.If you're want more (for example transmit and receive signals), then you will needs more complicated setup. You can tryADALM Pluto. But wifi needs to deal with a very wide bandwidth 40 MHz and more, so probably it cannot cover all cases. But at least it will be the most cheap and easy startup for transmit and receive signals on 2.4 GHz

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 11, 2021, 01:43:55 am
content: Raspberry Pi 3+ and 4 support using the onboard Wifi as a SDR.https://github.com/seemoo-lab/nexmon
Playing around with amplifiers, looking for a source for enclosures - Page 1
Forum section: electronics / rf-microwave

author: 3isenhorn
author_rank: Contributor
timestamp: October 16, 2021, 04:21:10 pm
content: Hello forum,I like to tinker with MF to RF (100kHz to 3GHz) and would like to test different amplifiers. I already ordered some from China, one of them had a nice metal case, unfortunately the mmic died quite fast.So I reused the case and board for an MSA-0335 I still had, not an LNA but good as an amplifier for my signal generator:And it works exactly as expected from the data sheet:So starting a thread just for this little tinkering is not my intention. I would like to play around with more different amps, just for fun. The mmic are easy to find, butdoes anyone know a source for RF enclosures and unpopulated boards? The enclosures are more needed as I still have some ESD damaged amps on the board.Of course I could design it myself, but I hope the price is more reasonable for high quantities, unfortunately I only found design kits for mixers.I wonder if I'm the only one who needs this, or am I just using the wrong search terms?
Repurposing old  RF power amplifiers - Page 1
Forum section: electronics / rf-microwave

author: veedub565
author_rank: Frequent Contributor
timestamp: October 05, 2021, 04:24:07 pm
content: I recently rescued a couple of old RF power amplifiers from the dumpster (permission was obtained) one works perfectly and the others are faulty.Microwave Amplifiers Ltd (working)50W, 1.78-1.81GHzGeneric RF power amp100w, 930-960MHz(Faulty PSU, just a generic open frame 18v job)Varian TWT amplifier35dB gain, 4-8GHz(Faulty, high helix current)Before I strip these for parts, and project cases. Is there any possible use for them as they are. Or could they somehow be repurposed for other frequencies.The TWT amp may be useful for amateur microwave communications. Although I don't fancy cooking myself messing about with it. And its no dead cert that the tube is at fault.The other two only appear useful for cellular comms (UK). I can't see any amateur uses at those frequencies. And I suspect they can't be retuned to a wider bandwidth or different freq without substantial redesign.I thought I'd ask here tho, before I strip them down. See if there is anything useful or interesting I might be able to do with them. They are decent amps, they would sit there all day at 50w/100w continuous power. The heatsinks are massive !

author: veedub565
author_rank: Frequent Contributor
timestamp: October 05, 2021, 09:13:03 pm
content: I've been having a read about this. The design of the 930MHz and 1.8GHz amplifiers is very modular. And I've discovered there's such a thing as a pallet amplifier module. So I can ditch the RF modules, and replace them with something more usable. The rest of the hardware can be carried over, or easily altered to suit.May be a nice project.

author: geggi1
author_rank: Frequent Contributor
timestamp: October 06, 2021, 05:05:56 am
content: The 930-960 might be able to be tuned to the HAM 23cm band depending on the transistors. It might also be possible to tune it for the 70cm band.The 1.78-1.81 Ghz might be tunable to the ham 23cm or 13cm bands depending on the output transistor.Open the units and find the type of transistor, google and se what comes up.The TWT is covering several ham bands un modified and can probably also be tuned to the 3cm ham band.Google the tube and se what you got.
Checking uni assignment - Page 1
Forum section: electronics / rf-microwave

author: faust1002
author_rank: Contributor
timestamp: September 28, 2021, 01:27:21 pm
content: Hello guys,I have just started my MSc degree and one of mandatory modules I have to take is RF. Provided that I have hardly any background in this area I feel a little bit insecure about this subject. Furthermore, the lectures doesn't seem to be super student-friendly.So I wonder if any of you could check my first assignment. It is related to basic things like transmission line paramaters and S paramaters. Please find questions and answers (except for the last question as it is trivial even for me) for them attached.Kind regards

author: Joel_Dunsmore
author_rank: Regular Contributor
timestamp: September 30, 2021, 04:00:00 am
content: Problem 1: correct final but -1 out of 10 points for (10+j10)/110 (missing imag part in the denominator, though you got the right answer numerically)1b: 0 marks (hint, Pdel=Pincident*(1-mag(gamma)^2) here power is linear (watts)1c: -1 of 10 (SWR is always above 1, can't be below; swr less than 1.2 is "good" low standing waves; 1.2<swr<2 "moderate", SWR>2 bad.1d: full marks2a: -3 of 10 (s-parameters are sqrt of power, always use 20 log10( bn/an). You did on s11, s22, but not s12, s21.final grade: 37/50=C+

author: faust1002
author_rank: Contributor
timestamp: September 30, 2021, 08:48:58 am
content: Thanks for help!
corrugated magnetic shielding? - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: September 24, 2021, 08:03:57 pm
content: Has anyone done any experiments with corrugated steel and wiring to see what the effect is on low frequency noise, as a way to shield a cable other then twisted pair for that frequency range?I only have aluminum spiral, and it seems you need a helmholtz setup to test this, but has anyone seen the results of this type of shielding?not a bad project to make the tester either.. I just want to see if there is a reason not to do so more then if there is a reason to do so

author: radiolistener
author_rank: Super Contributor
timestamp: September 27, 2021, 10:23:50 pm
content: it depends on what kind of field you're want to shield. You can calculate attenuation level from known material properties and distance from the source. The most complicated is a shielding from magnetic field within near field zone from a source.
Anyone know what binary FSK modulated quadrature data is? - Page 1
Forum section: electronics / rf-microwave

author: beandigital
author_rank: Contributor
timestamp: September 22, 2021, 07:50:21 am
content: Someone asked me to design a demodulator for binary FSK modulated quadrature data. What exatly is this kind of modulation scheme? Thanks

author: srce
author_rank: Regular Contributor
timestamp: September 22, 2021, 09:45:04 am
content: If it's binary FSK, the signal shifts between two frequencies, one for a 0 bit the other for 1. The "quadrature data" part probably means that you will have I and Q data streams from your receiver.Have a look at something like:https://www.allaboutcircuits.com/technical-articles/digital-signal-processing-in-scilab-how-to-decode-an-fsk-signal/https://www.allaboutcircuits.com/technical-articles/how-to-use-i-q-signals-to-design-a-robust-fsk-decoder/

author: beandigital
author_rank: Contributor
timestamp: September 22, 2021, 10:36:25 am
content: You are probably right. It was the quadrature part that threw me. Thanks
Signal waveform from rtl-sdr - Page 1
Forum section: electronics / rf-microwave

author: mariolucas75
author_rank: Contributor
timestamp: September 15, 2021, 01:12:58 pm
content: Dear Forum,Can you advise me please if it is possible to get the signal waveform from rtl-sdr....For example I recently started using rtl-sdr and sdr# to scan radio frequencies.On FM frequency line i see some FM stations. I want to investigate a particular FM station.If FM signal bandwidth is +/ - 75 Khz from carrier frequency, and if carrie frequency is 100 Mhz it means that my signal is within 99.925 Mhz till 100.075 Mhz. So i want to investigate this 150 khz widith.When using sdr# fft pane i noticed that there are some spikes within this 150Khz widith... therefore i want to view their waveform to find out what they might be ....Pls correct me if i am wrong in my understanding.

author: kahe40
author_rank: Contributor
timestamp: September 15, 2021, 01:49:16 pm
content: maybe you want this ?https://www.sigidwiki.com/wiki/FM_Broadcast_Radio

author: srce
author_rank: Regular Contributor
timestamp: September 15, 2021, 02:03:46 pm
content: Do you mean the time domain waveform?If so, you can use the Channel Analyzer plugin in SDRangel to view it:https://github.com/f4exb/sdrangel/blob/master/plugins/channelrx/chanalyzer/readme.md

author: rfclown
author_rank: Frequent Contributor
timestamp: September 15, 2021, 02:26:05 pm
content: I don't have my notes with me now, but in the past I used one of the PC command line programs, I think it was called rtl_tcp, that caused I/Q data to be streamed in via TCP. I used LabVIEW to read in the data which came in as interleaved 8 bit I/Q pairs. That's the way the dongle works. It streams out a baseband waveform. Everything from there is software.

author: mariolucas75
author_rank: Contributor
timestamp: September 17, 2021, 07:50:35 pm
content: Dear all,Thks so much that is exactly what i wanted ... All of your responses (kahe40, srce and rfclown) greatly help me....Best Regards

author: mariolucas75
author_rank: Contributor
timestamp: September 17, 2021, 08:18:36 pm
content: Dear srce,Could you please advise me how to install that plugin -https://github.com/f4exb/sdrangel/tree/master/plugins/channelrx/chanalyzer.As understood there are many plugins and one of the plugins is "chanalyzer"....I am a bit poor with compiling from source and installation afterwards.Right now i am using ubuntu with pre-installed SDRangel and as i assume i have to add that plugin.If you know by any chance could you advise me how to install that plugin from the source files given in the link.Thank you so much

author: srce
author_rank: Regular Contributor
timestamp: September 18, 2021, 06:55:01 am
content: That plugin should be installed by default.Just add it as a channel, by pressing the + channel button.If you want to compile from source to make sure you have the latest version, see:https://github.com/f4exb/sdrangel/wiki/Compile-from-source-in-Linux
Impedance matching of bidirectional amplifier - Page 1
Forum section: electronics / rf-microwave

author: e.sotillet
author_rank: Contributor
timestamp: September 28, 2021, 01:31:57 pm
content: Hi folksRight now I'm working with a board that has a bidirectional amplifier: one for 172MHz and other for 152MHz. The initial designer not take in account to make a good in-out matching to 50ohm, so i need to add a matching network (in an external board) that can be operative in both frequencies.I tried with the usual LC network but it worked for only one frequency. I used the VNA to measure the impedance and I got he follow results:** 119- j13 @ 152MHz** 36,8- j50 @ 172MHzWhat kind of method can I use to make the impedance adaptation to 50?Best regards

author: UR5FFR
author_rank: Contributor
timestamp: September 28, 2021, 05:24:34 pm
content: HiTry myImpedanceMatchingfree software. Some results for your case in attachment

author: e.sotillet
author_rank: Contributor
timestamp: September 29, 2021, 10:41:19 am
content: Hi Andrey, thanks a lot. I will test and comment the results.Best regards

author: e.sotillet
author_rank: Contributor
timestamp: September 29, 2021, 01:22:51 pm
content: As attachment is the measurement of the builded adapter, I think it could be improved a lil bit.

author: UR5FFR
author_rank: Contributor
timestamp: September 29, 2021, 01:48:59 pm
content: What circuit did you use in the adapter?

author: e.sotillet
author_rank: Contributor
timestamp: September 29, 2021, 04:43:56 pm
content: I used the option 3, with air coils and variable capacitors. The adjustment with the VNA help alot.I think that the improvement will come putting everything in a PCB.In the other hand, using smd inductor instead of air coil can degrade the behaivor?Best regards
what does the kd vector mean; - Page 1
Forum section: electronics / rf-microwave

author: Dinos Tsakalakis
author_rank: Newbie
timestamp: September 05, 2021, 03:25:13 pm
content: Hallo ,i was studding about antennas when I suddenly find the kd term that is a vector as shown at the following file ,that is and it is describing a Linear array antenna, so i was find difficult to understand what is the meaning of k in front of d, that represents the distance between an initial point of antenna and the calculation point.Thank,you

author: Joel_Dunsmore
author_rank: Regular Contributor
timestamp: September 05, 2021, 06:54:27 pm
content: Ok, I'll be the first to say it (but I can't be the first to think it)...."It's all Greek to me"

author: Joel_Dunsmore
author_rank: Regular Contributor
timestamp: September 05, 2021, 07:05:27 pm
content: But to give a serious answer: I guess k would be the wave vector and d would be the magnitude of the position. I found this resource for wave vector:https://www.antenna-theory.com/definitions/wavevector.phpand this link (https://www.antenna-theory.com/arrays/arrayfactor.php) appears to use rifor the value d in your drawing.
Attenuator switch repair - Page 1
Forum section: electronics / rf-microwave

author: tkamiya
author_rank: Super Contributor
timestamp: August 31, 2021, 05:01:03 am
content: I'm not sure if this topic is better suited in amateur radio forum or repair forum.Over the last few years, I've been repairing over a dozen of 1980 to early 2000 HF radios, mostly Kenwood and Yaesu. Oldest if FR/FL101. Newest is TS940S. They all have a common fault. RF attenuators switch! As you know, typically a rotary switch is located right after the T/R relay and before front end. It switches in and out various register networks. Incoming power is off the antenna so it is extremely weak.Most switches have sufficient voltage across terminal so self-cleaning action happens but not here. Deoxit or similar contact cleaner and repeated operation often fixes it but it's only temporary. New exact replacements are long out of production. I thought of using mercury wetted relay or something but I'd very much like NOT to modify the circuit.Have anyone seen isssue? Have anyone solved it?To me, the band is unusually quiet means RF ATT switch is oxidized again.

author: D Straney
author_rank: Frequent Contributor
timestamp: September 05, 2021, 03:54:29 pm
content: If it is definitely oxidation and not dust etc. getting into the contacts...Going for minimal modifications, I wonder if a bit of DC (a volt or less maybe) through an RF choke on the switch's common terminal would give enough of a quick current spike to be useful. This depends on the following stages being AC-coupled up-front though (probably need a large resistor from each output terminal to gnd just to bleed off the series caps), and the front-end being able to tolerate a large-enough temporary spike to be useful. Or as an alternative, if the downstream stages have a DC path to ground but there's some capacitance on the common side of the switch, an RF choke/1M resistor can just charge up the common-side capacitance for a nice discharge when you rotate the switch.Or since it sounds like the switch contacts are sitting out in the open, maybe there's a decent way to remove the switch without too much trouble, and electro-plate the contacts with gold?

author: tkamiya
author_rank: Super Contributor
timestamp: September 05, 2021, 06:40:36 pm
content: Thank you for your suggestion. Attenuators are between TX/RX relay and first input stage, so it is possible to add a capacitor if it is not already there and apply some bias current. Gold plating is a good idea though if I can find a place that can do it. I think gold plating uses potassium cyanid, so not something I'd want to do at home....
How to measure isolation db between parallel wires. - Page 1
Forum section: electronics / rf-microwave

author: mattf
author_rank: Newbie
timestamp: September 02, 2021, 10:43:58 pm
content: Hello all,First off, I am not that experienced when it come to all thing RF and microwave. I am a electronics test tech. and the most I have had to do when it comes to RF and microwave is take S parameters using a network analyzer.I recently had a cable assembly to test that contained multiple shielded pairs and some coax cables that not only needed the to have insertion loss and VSWR tested, but required a minimum of 70db isolation between some of the coax and twisted pairs. I have no idea how to measure isolation. I have googled, youtubed, and read manual for hours. I did looked at some old test records and whoever tested them last time isn't around anymore, but did list an Agilent E5062A as the equipment used, which is the same equipment I use for S parameters. I just can't figure out how its done. If anyone could please help it would be much appreciated.Thanks- Matt

author: radiolistener
author_rank: Super Contributor
timestamp: September 02, 2021, 10:51:56 pm
content: You can put one cable into output port and load other piece of cable with terminator. And use the same config with a second cable and terminator for input port. Now place bodies of cables close to each other and measure S21, it should be more than 70 dB for your needs.

author: mattf
author_rank: Newbie
timestamp: September 03, 2021, 12:07:29 am
content: Thank you. I will give it a go tomorrow.

author: Joel_Dunsmore
author_rank: Regular Contributor
timestamp: September 03, 2021, 03:01:42 am
content: It can be a bit complicated. There are actually two isolation between pairs of cables, one is call near-end cross-talk and one is called far-end cross talk. For near end, if you have a pair of cables, you inject signal into one of the coax pairs, loads on the other end of both, and measure what comes out of the near end of the other coax. It is an S21 measurement. Far-end is similar but you put the VNA port 1 into one of the cable inputs, and a load on the other; then you put a load on the cable far-end of the cable that has port 1 going into it, and you connect port 2 of the VNA to the other cable (which has a load on the near end), and measure S21.If you are measuring differential cables (that have two-wires, often twisted together) it gets a bit more complicated.
Question about x-ray tubes - Page 1
Forum section: electronics / rf-microwave

author: Ben321
author_rank: Frequent Contributor
timestamp: August 29, 2021, 11:48:10 pm
content: I don't mean incidental x-rays given off by the operation of other types of vacuum tubes. I mean actual medical x-ray tubes. However I'm posting here, because I figure that people in the radio section of this forum might be able to apply their knowledge of other types of tubes to my question about x-ray tubes.My question is how are electron beam voltage and current controlled separately in an x-ray tube? I know that the electron beam's voltage and current can be controlled separately, because of the fact that I've read that these 2 separate adjustments can be useful for setting up the x-ray equipment for taking various kinds of medically useful x-ray images. Voltage controls the wavelength of the x-rays (energy per photon), while current controls the amplitude of the x-ray beam (photons per second). But how does this work? Every device has a certain resistance, and for a given resistance, the current is controlled by the voltage across the device. When you change the voltage across an x-ray tube, you also change the current through its electron beam. So how do medical x-ray machines allow separate voltage and current adjustments?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 30, 2021, 12:19:15 am
content: Ben321,Most medical x-ray tubes, those used for general radiography and fluoroscopic are operated like this:There is a high voltage power supply for the Anode to Cathode voltage. This is symmetrical about ground. So if the machine is set for 70kV, the power supply generates +35kV on the Anode and -35kV on the cathode.The voltage is regulated like most switching power supplies with voltage dividers on the output. The voltage is adjusted using a DAC and and a microprocessor.The Anode current is controlled by setting the filament temperature. There is a control loop to adjust filament current to get the desired Anode current. The x-ray tube is a diode that is emission limited.Because the x-ray exposures are short, there is normally a calibration routine that preheats the filament based on the desired anode current.Here is a link to a typical medical x-ray tube:https://www.vareximaging.com/sites/default/files/datasheets/vic/G-292pds_0.pdfPage 11 shows the relationship between Anode current and filament current for various kV.In use, the tube is placed in an oil-filled housing.Regards,Jay_Diddy_B

author: Ben321
author_rank: Frequent Contributor
timestamp: August 30, 2021, 01:00:44 am
content: Quote from: Jay_Diddy_B on August 30, 2021, 12:19:15 amCOOL! Thanks for that info. That makes sense. The temperature of the cathode determines the rate at which electrons detach from the atoms in the cathode, and that determines the current. I was just thinking about standard TV or computer monitor CRTs that have a fixed filament current, and use several variable voltage grids to set the per-pixel brightness (to display the image) and overall brightness/contrast of the image (as well as to focus the electron beam).
Tv antenna LTE 5G filter covers 4G? - Page 1
Forum section: electronics / rf-microwave

author: sdancer75
author_rank: Frequent Contributor
timestamp: August 28, 2021, 09:37:50 am
content: HiI am gonna buy a new televes antenna dat 45 boss tforce with 5G filter.I would like to ask if this filter covers also the established wide cover 4G LTE frequencies.If not, do I need to install an extra 4G filters?Thanks
deaf rig and high vswr - Page 1
Forum section: electronics / rf-microwave

author: m3vuv
author_rank: Super Contributor
timestamp: August 23, 2021, 09:44:09 am
content: hi all,i have an old ts-700 multimode,ive replaced all of the front end fets with lower noise modern items,i join a net most sat mornings 0n usb 144.310MHZ,recently its been like noone is on air,the rig seems totaly deaf!,checked the swr on 2mtrs and the lowest it reads is 4.5-1,about 6 months ago i had a fire that burned thru the outer of the rg213 feed line,the ant is a triband co linear up at about 35ft,i suspect water has got into the coax and ruined it,would that cause these symptons?,the antenna is a bstard to get down,in a small court yard on a big pole,i want to know if i need too lower it as will have to get a few ppl to help,its sorounded by low roofs all with slates so dont want an expensive disater!.

author: geggi1
author_rank: Frequent Contributor
timestamp: August 23, 2021, 10:44:54 pm
content: Water in the coax will give you high SWR.Try to check the SWR against a dummy load. Do also check any jumpers to ensure that there is no faults on them.

author: m3vuv
author_rank: Super Contributor
timestamp: August 24, 2021, 03:22:16 am
content: what do you mean by jumpers?,do you also mean put a dummy load on the other end of the coax?,if so i cant as its 30+ feet in the air,i just measured radio end of the coax with a nano vna.

author: geggi1
author_rank: Frequent Contributor
timestamp: August 25, 2021, 10:00:39 am
content: Quote from: m3vuv on August 24, 2021, 03:22:16 amJumpers are the short coax cables used between things like SWR meter, wattmeter, tuner, linear and other shack equipment. You will have to disconnect the antenna to be able to check the coax. The best way to check the coax is to disconnect the antenna and connect a 50ohm termination (dummyload) at the end.Most of the time its the connectors that will give high SWR on the coax.You should also test the antenna with in case there is something wrong there.But as you wrote in the post you had a fire the burned through the outer insulation of your coax. You will most likely have to replace the coax so in any case you will have to get up there and disconnect the coax form the antenna.

author: m3vuv
author_rank: Super Contributor
timestamp: August 25, 2021, 04:06:05 pm
content: Ahh i see what you mean by jumpers,never heard them called that,we call them patch leads here in the uk,may get the antenna down when we have a nice day and stick my vna on it,cheers,i suspect its water ingress in either coax or antenna.73 de m3vuv

author: Joel_Dunsmore
author_rank: Regular Contributor
timestamp: August 25, 2021, 04:58:28 pm
content: Yes, in the US, what you in the UK call jumpers we call sweaters, oddly enough.
Who makes this shield? - Page 1
Forum section: electronics / rf-microwave

author: jayk
author_rank: Regular Contributor
timestamp: August 17, 2021, 04:51:39 pm
content: Does anyone know who manufactures the shielding on this Xilinx eval board? This is the first one I've seen with clips that solder down to the board and then a cover you can install/remove.Thanks!

author: langwadt
author_rank: Super Contributor
timestamp: August 17, 2021, 04:54:15 pm
content: https://www.harwin.com/connectors-hardware/emc-shielding/?

author: chrisl
author_rank: Regular Contributor
timestamp: August 17, 2021, 06:13:43 pm
content: https://leadertechinc.com/product/tech-clip/

author: eb4fbz
author_rank: Regular Contributor
timestamp: August 18, 2021, 02:14:45 pm
content: https://www.we-online.com/catalog/en/WE-SHC-CLIPhttps://hollandshielding.com/PCB-shield-mounting-Large-clip-LCLaird has a better option for high frequency shields using two pieces: frame (soldered) and a cover which is clipped over the frame.https://www.laird.com/products/enclosure-solutions/board-level-shielding-bls/two-piece-board-level-shields
NE32584C at 8 GHz - Page 1
Forum section: electronics / rf-microwave

author: benkm
author_rank: Newbie
timestamp: April 25, 2021, 01:00:55 pm
content: Hi,I like to optimize the NE32584C for minimum noise, found on this board for 8 GHz:https://www.rf-microwave.com/en/nbp/nmp/10-ghz-amplifier-24ghz-doubler/su-02/The microstrips I don't get. Are the stubs marked with a star capacitors?The track-width is also not clear to me. Two tracks come together in the 50 Ohm. So the track should be 100 Ohm, but it is much wider.Hopefully someone can help me with these basic questions.Thanks in advance.

author: zach05
author_rank: Newbie
timestamp: August 16, 2021, 11:58:23 am
content: The microstrips I don't get. Are the stubs marked with a star capacitors?search "tuning stubs". In your case, these very short stubs more act like capacitor at operating frequency.The track-width is also not clear to me. Two tracks come together in the 50 Ohm. So the track should be 100 Ohm, but it is much wider.these not necessary to be 100 ohm. This is a satellite TV receiver down convertor, perhaps X or K band, at this frequency range better use the transmission line calculator.www.microwaves101.comwill answer most your questions
Dielectric coaxial resonator vco circuits topology? - Page 1
Forum section: electronics / rf-microwave

author: mpradio
author_rank: Newbie
timestamp: August 06, 2021, 07:22:52 pm
content: I came across this VCO that uses a dielectric coaxial resonator, I understand how the resonator works, what I don't know is the oscillator topology, Colpitts, Clapp, et. Also I do not see any circuit element that is feeding back the output to the input, I suspect that it does so through the internal capacity of the transistor but I am not sure. The transistor is an at42086 and the VCO frequency is 1450Mhz.

author: neilhao
author_rank: Regular Contributor
timestamp: August 07, 2021, 01:34:17 am
content: I wrote a article about the VCO topology before:https://uniteng.com/index.php/2021/05/02/2-45ghz-to-2-85ghz-vco-design-with-infineon-bfp420-wideband-silicon-npn-rf-bipolar-transistor/

author: mpradio
author_rank: Newbie
timestamp: August 07, 2021, 04:15:34 pm
content: OK thanks neilhao but what is the topology of this coscillator and how did you calculate the components of your design, in the document you mention only the finished circuit is present.

author: neilhao
author_rank: Regular Contributor
timestamp: August 07, 2021, 04:30:43 pm
content: It is just a combination of a LC Resonator (L1 and C1) and an unstable amplifier in desired freq band. Thus you just need to calculate the resonant frequency of L1 and C1 and then, making the transistor to be unstable around the resonant frequency.The calculation could determine the initial values of the circuit, we still need to tune it by using simulator.The design process:1. Design an amplifier that S11>1 (Base side) for the required range of working frequencies.2. Design the LC resonator, the Varactor Diodes may be used in this module.3. Connecting an idea transformer between the Amplifier and the Resonator, try to make the mag(Z(1,1)) to be closed to 0 by turning the L or C in the Resonator module.4. For nonlinear design, replacing the idea transformer with OscPort, Sweep the VturnP of VCO. The Output Spectrum should be similar to the expected result.5. Double check the Freq vs VtuneP which should be linear. The Pout should be almost same across the working band.6. Double check the phase noise.

author: WideBandwidth
author_rank: Contributor
timestamp: August 08, 2021, 02:48:26 pm
content: Is there not a downside to relying on the device parasitics to create the negative input resistance, since those parasitics (at least the junction capacitances) are nonlinear? Just curious.