hybridfree/eevblog-posts huggingface dataset:
glue to bond dielectric lens back into horn? - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: November 21, 2019, 11:05:17 pm
content: I noticed one of the dielectric lens in my horn antenna was actually just press fit, the bonds failed. The interior looks plated with something, maybe gold (bright yellow).Anyway, is there a special RF transparent glue I should use to glue it back in, or is clear epoxy the standard?its designed to fit into the horn's interior taper spec is 1-10GHz

author: coppercone2
author_rank: Super Contributor
timestamp: November 22, 2019, 06:01:05 am
content: in another development, I noticed there is tarnish on the inside end launcher of the horn. It seems difficult to get to in order to polish.I think a custom dremel tool needs to be made to get in there (along the lens of putting the buffing pad on a long rod).

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: November 22, 2019, 04:33:00 pm
content: I would advise against any dremeling.We have used cyanoacrylate to glue lenses at 670 GHz. I imagine it works at 10 GHz just as well. If you get the really runny kind that has no thickneners the glue film will be on the order of tens of micrometers

author: coppercone2
author_rank: Super Contributor
timestamp: November 22, 2019, 10:16:21 pm
content: Quote from: TheUnnamedNewbie on November 22, 2019, 04:33:00 pmhow would you clean tarnish out of an end launcher of a horn?

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: November 25, 2019, 11:43:29 am
content: Could you show a picture of this tarnish? IF it is leftover from the last adhesive, consider trying some solvent like IPA to clean it out.

author: coppercone2
author_rank: Super Contributor
timestamp: December 02, 2019, 02:01:05 pm
content: I just left it alone after trying mild scrubbing on a stick non scratch brillo padtarnish means metal oxide
Es'hail 2 band plan and guidelines - Page 1
Forum section: electronics / rf-microwave

author: TheBay
author_rank: Unknown
timestamp: October 07, 2018, 05:11:20 pm
content: Just come across this and thought I would share, some may be interested:https://amsat-dl.org/p4-a-wb-transponder-bandplan-and-operating-guidelines

author: msimunic
author_rank: Contributor
timestamp: November 30, 2019, 10:10:40 am
content: HiI'm trying to find Es'hail-2's out of band emission specifications.The only information I found is basically saying "No transmissions should be made beyond the nominal edges of the transponder passbands."OK, this is obvious, but in real life there is no brick-wall filter.Es'Hail-2's band plan says nothing about out of band emissions.What I'm trying to find is specifications on how much emission is allowed in neighbor channels.Is this in the order of -20 dBm, -30 dBm, .... -60 dBm (hard to achieve) relative to passband (or carrier freq)?I can't find ITU specs for 10.45 - 10.50 GHz (amateur band) for satellite transmitter (downlink).Such a specifications are defined for ie. mobile communications and DTV channels in the spectrum below 1 GHz.Please, can anyone help me understand?I would appreciate some references to the documentation and/or standard specifications.
Adjustment of nanoVNA Freq. increment steps - Page 1
Forum section: electronics / rf-microwave

author: vinlove
author_rank: Frequent Contributor
timestamp: November 28, 2019, 02:07:46 pm
content: When the thumbwheel is pushed to the right once, the Freq. in the VNA increments by 9Mhz.Can you make it to increment by 1Mhz or 100KHz .... set it as you want?Sorry for newbie question, but just got it, and trying to check SWR of my HF antennas.

author: xrunner
author_rank: Super Contributor
timestamp: November 28, 2019, 03:24:23 pm
content: Quote from: vinlove on November 28, 2019, 02:07:46 pmYou must be using it full scale (50 kHz to 900 MHz). It has 101 steps across the display. You have to zoom in to have smaller steps (should be doing that anyway to be more accurate). Also you can calibrate it at a smaller span too, if you want to be really accurate.I don't even cal mine up to 900 MHz because I don't have any need to go above 500 MHz. I also have other cal ranges for several ham bands for more accuracy.

author: vinlove
author_rank: Frequent Contributor
timestamp: November 28, 2019, 10:44:15 pm
content: I have changed the screen scales, so it looks larger, but when trying to move to 7Mhz and 3.5Mhz, using the thumbwheel, the freq. moves by 9Mhz at one push. So it goes 50hz -> 9Mhz -> 18Mhz -> 27Mhz .......... like this.I wanted it to go like 50hz -> 1Mhz -> 2Mhz ->3Mhz ... 7Mhz ... like the, and even in smaller steps.Does it have to be set in the calibration? Or is there menu item setting this freq. increment steps in nanoVNA? Or does it have be done in the PC software for the nanoVNA? I hope it can be done very quickly and simply, not having to install the software to PC, or having to go through the calibration.

author: xrunner
author_rank: Super Contributor
timestamp: November 28, 2019, 11:23:04 pm
content: Quote from: vinlove on November 28, 2019, 10:44:15 pmWhat you are describing is a stimulus set to start at 50 kHz and go to 900 MHz. That results in steps of ~9 MHz ... (900 MHz - 50 kHz) / 101 = 8.91 MHz steps. The step size is set by the stimulus range.QuoteThen you need to set the stimulus to a smaller range such as for example - Start=5 MHz and Stop=10 MHz. When I do that on mine I get steps of 50 kHz.QuoteIt isn't set in cal it's set by the stimulus range: Step = (Fhi- Flo) / 101I have several calibrations set up in the available Cal Recalls (0,1,2,3,4) though, because calibrating over a smaller range will give a better result over that range. For example, one cal range I have is for HF from 3 to 30 MHz, another for 2 meter ham band, and another for UHF ham band. Like I said, even for the full sweep I do not cal it above 500 MHz because I have no use or interest in that, so my cal is better because it's for a smaller range 50 kHz to 500 MHz and has less span between cal points.But even if you cal for a range from say 3 to 30 MHz, you can still narrow the sweep range with the stimulus Start and Stop, and thus it will still follow the equation Step = (Fhi- Flo) / 101

author: vinlove
author_rank: Frequent Contributor
timestamp: November 29, 2019, 08:04:50 am
content: Great info & advice. Got it working the now.Thank you
Mixers impedance - Page 1
Forum section: electronics / rf-microwave

author: Miti
author_rank: Super Contributor
timestamp: November 27, 2019, 04:59:27 am
content: Hi,I was looking at the attached Minicircuits mixers and I cannot see the input/output impedance anywhere in the datasheet.Are these mixers, or mixers in general, characterised at 50 ohms or they need matching circuits if used with 50 ohms circuits?Forgive me if this should be common knowledge, I'm still learning RF.Thanks,Miti

author: awallin
author_rank: Frequent Contributor
timestamp: November 27, 2019, 05:30:46 am
content: for most mini-circ parts it's safe to assume 50 Ohm impedance (unless the part specifically is named '75' or similar).The termination of the IF port can be 'special' - see for example mini-circ phase-detector parts where they suggest 500 Ohm termination on IF.

author: coppercone2
author_rank: Super Contributor
timestamp: November 27, 2019, 06:27:13 am
content: http://www.hp.woodshot.com/hprfhelp/4_downld/lit/diodelit/an963.pdf

author: Miti
author_rank: Super Contributor
timestamp: November 28, 2019, 01:25:39 am
content: Thanks for the answers!@coppercone2Very interesting AN, I saved it in my list of technical documents. However, I don't have a VNA and I'm not sure if it applies to a double balanced mixer? It's over my head anyway, I'd have to admit.For now it's enough to know that "it's safe to assume 50 Ohm impedance".
M830120 GPS Chip Antenna and usage of ground - Page 1
Forum section: electronics / rf-microwave

author: kamtar
author_rank: Regular Contributor
timestamp: November 27, 2019, 07:26:34 pm
content: Hello,Not sure if my question doesn't belong to the beginner category but I will try it here.I'm trying to play around with the M830120 chip antenna for GPS (http://datasheets.avx.com/ethertronics/AVX-E_M830120.pdf) mainly because its only reasonable chips antenna I can get for cheap from EU Farnell.My RF knowledge is almost nonexistent but I'm really curious about one thing:As you can see in an attached image the red pad is the feed pin and it's connected to ground. I would like to get some rough idea of how it works if it's possible to simplify to comparison with a dipole or simple ground antenna. Is it just that in 1.5Ghz it behaves like significant impedance?
EPE/Practical Electronics/Silicon Chip Mag GPS frequency reference - Page 1
Forum section: electronics / rf-microwave

author: g0mgx
author_rank: Regular Contributor
timestamp: November 24, 2019, 05:45:55 pm
content: Hi GangWondering if anyone has had a look at, or is building the GPS reference oscilator featured recently in Practical Electronics (and also Silicon Chip Magazine)http://www.epemag3.com/proj/1119.htmlThe project uses the "MicroMite backpack" and has source code (available at the link above) in MMBasic. It looks quite a nice project so I've built one using their shop PCB.I've got lots of issues with noise on the signals and what looks like decoupling issues; As soon as I make the connection to pin 24 of the micromite the VCO output becomes extremely noise, I note they recommend soldering wires between ground points thus "reducing the impedence of ground tracks on the PCB" which smells a bit fishy to me.Just wondering if anyone else has looked at this?Mark
Oscillator kills transistors? - Page 1
Forum section: electronics / rf-microwave

author: szoftveres
author_rank: Regular Contributor
timestamp: November 25, 2019, 05:53:28 am
content: Hi All,I built the below circuit, which is a standard tunable UHF Colpitts-oscillator for the 70cm (~450MHz) band.The inspiration came from herehttps://www.instructables.com/id/UHF-remote-control-Transmitter/and the whole build is largely identical to what is posted on this website (I made small changes, e.g. I run the circuit from 9V and use a voltage divider bias instead of the base-leak type).The oscillator works and produces high frequencies, as expected, however I cannot keep the transistor current under control, even with a standard bias circuit. Biased for approximately 10mA, the oscillator runs between 20mA at 50mA and I've already killed two transistors. I measured the base voltage, which is around 4.5V when the oscillator current is 50mA. I also noticed that the current (and the base voltage) is dependent on the frequency, which makes me think that probably the c-b junction breaks down at the positive peaks at certain frequencies (probably because the high Q of the tuned "tank"), charging the base capacitor to a higher voltage, and thus shifting the bias up.Is this behaviour expected? I haven't seen any literature about Colpitts oscillators with this issue, what is the standard best-practice mitigation in this case?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: November 25, 2019, 06:02:46 am
content: Hi,The 2SC3358 is a low voltage transistor, like many RF transistors.Vcbo = 20VVceo = 12VBecause of the resonant circuit in the collector you are probably violating the Vceo or Vcbo ratings.Try operating the circuit at lower voltages.Regards,Jay_Diddy_B

author: iMo
author_rank: Super Contributor
timestamp: November 25, 2019, 09:57:47 am
content: Simulation.. 25V p-p at collector (18V p-p Vce)..

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: November 25, 2019, 11:20:13 am
content: Imo,Good work!Can you attach the LTspice model?Thanks!!Jay_Diddy_B

author: iMo
author_rank: Super Contributor
timestamp: November 25, 2019, 11:32:20 am
content: Model of what? the Q1?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: November 25, 2019, 12:45:11 pm
content: Hi,I have entered the model into in LTspice:These are the results with a 3V input:oscillator.asc(1.96 kB - downloaded 61 times.)I have attached the LTspice file for those playing along at home.Regards,Jay_Diddy_B

author: szoftveres
author_rank: Regular Contributor
timestamp: November 25, 2019, 08:37:17 pm
content: Thanks to all, a 1.2k resistor between the 9V terminal and the 100p bypass capacitor seems to be a working solution.
PCB technologies to stack microwave signals (soldered) - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: November 23, 2019, 08:38:24 am
content: What methods are used to stack PCB in the microwave region (to 10GHz)?I know they have the mini-connectors that are mechanically fit, but what options are there for soldered connections? Like a one time fit thing with a solder ring that is reflowed and melted together or something (modified high speed interconnect).if its a little pipe that needs to be heated, perhaps with resistance soldering equipment?I have seen the ones that solder to the PCB with a little lid, so you solder the outer coax to the edge and then solder the wire, then solder on the lid. But its at right angles.

author: rfdave#gmail.com
author_rank: Contributor
timestamp: November 23, 2019, 03:12:32 pm
content: I've never seen RF interconnects like you're looking for. Sounds like it would be tough to repair/troubleshoot. I've used Corning-Gilbert connectors GPO and GPPO for a similar application, but they're not cheap. One of the datasheets here.https://www.corning.com/catalog/coc/documents/brochures/CRR-687-AEN.pdf

author: coppercone2
author_rank: Super Contributor
timestamp: November 23, 2019, 04:52:06 pm
content: do those actually work, I was never impressed with stacking connectors (if only headers). I am distrustful. Usually you need to push on them once in a while.

author: rfdave#gmail.com
author_rank: Contributor
timestamp: November 24, 2019, 02:47:10 am
content: They work pretty well, but you have to screw both boards together with standoffs to make sure they are compressed appropriately.

author: coppercone2
author_rank: Super Contributor
timestamp: November 24, 2019, 03:28:09 am
content: makes me wonder if you put pressure plates ontop of DIP sockets, would it hold forever?
Installation info for Mutek in Icom 271 - Page 1
Forum section: electronics / rf-microwave

author: sidspop
author_rank: Contributor
timestamp: November 20, 2019, 06:23:21 pm
content: As it says above.Anybody got a copy they could scan and email please?No info on the web I can find.Andy

author: sidspop
author_rank: Contributor
timestamp: November 20, 2019, 08:04:11 pm
content: I thought they had just used the details. Not aware that they were still being sold, I thought Mutek went years ago.It does not fill me with confidence that the board pictured next to 271 blurb is not a 271 board.

author: YU7C
author_rank: Regular Contributor
timestamp: November 20, 2019, 08:35:24 pm
content: PM sent!73 Voja/YU7C
Polyfet F1003 VDMOS project ideas - Page 1
Forum section: electronics / rf-microwave

author: _Wim_
author_rank: Super Contributor
timestamp: November 17, 2019, 08:23:04 pm
content: Hi,I came across a bunch of these Polyfet F1003 (http://www.polyfet.com/Dsheet/F1003.pdf) VDMOS transistors, and thought it would be fun to play with. I am an RF noob, and it seems very hard to find circuits online that use these exact devices (or Polyfet devices in general). So any ideas what to do with these? Are these still useful?Many thanks,Wim

author: CJay
author_rank: Super Contributor
timestamp: November 17, 2019, 10:31:40 pm
content: Nice find, yes they're useful, they'd make a great 2M amplifier for ham use, I'd be really happy if a box of those landed in my lap

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 18, 2019, 01:21:44 am
content: Do you really need a circuit..? Any MOSFET circuit will do, it's just a pair of bias tees and something to set gate bias. Add in a pair of 180° hybrids (aka transformers) for push-pull.(Circuits -- with layouts -- would be rather useful at high frequencies. Which, maybe it's good up to a GHz, who knows? But lacking those, and s-parameters, for the transistor in question, you'd be on your own it seems.)Tim

author: _Wim_
author_rank: Super Contributor
timestamp: November 18, 2019, 05:59:58 pm
content: Well I have been experimenting on my own a bit in the past (see pictures of my ugly testbed after lots of experimentation), but I was hoping to get some wider bandwidth or higher frequency designs, or maybe other good ideas what to do with these. S-parameters are available from the Polyfet website, but as I said, RF design is new to me, so I was looking for some ideas here.

author: _Wim_
author_rank: Super Contributor
timestamp: November 18, 2019, 06:04:51 pm
content: Quote from: CJay on November 17, 2019, 10:31:40 pmHi CJay,I can mis one of the boxes I have. Would 25€ + shipping be ok for a box with 10 of these?Wim

author: CJay
author_rank: Super Contributor
timestamp: November 18, 2019, 07:21:35 pm
content: Well I'd find it very hard to refuse that offer, I'll PM for more details
Fujitsu MB506 prescaler, other comparable replacement parts? - Page 1
Forum section: electronics / rf-microwave

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: December 22, 2019, 04:50:52 am
content: Greetings RF people,I have been looking at designing a front end for a two or three channel frequency counter. I am a know-nothing so it is appropriate to address me as one would a retarded child. The cheap china frequency counter modules all include what looks like a shanzhai clone of an obsolete fujitsu prescaler, the MB506. These are easily purchased on aliexpress for a dollar or two.see:https://www.aliexpress.com/wholesale?catId=0&initiative_id=AS_20191221202851&SearchText=mb506https://www.qsl.net/n9zia/900/mb506.pdfAre there good alternatives to this chip in current production? And do the fake MB506's work well enough that using them in a hobby project make them the viable preferred choice due to low cost?Thanks

author: OwO
author_rank: Super Contributor
timestamp: December 22, 2019, 06:09:35 am
content: ADF4113 can output a divided signal on MUXOUT, with divider programmable in steps of 1. You can find it for under $1 on aliexpress.

author: awallin
author_rank: Frequent Contributor
timestamp: December 22, 2019, 08:06:21 am
content: if 1.1GHz is enough then something like MC12080 is cheap and cheerful, has reasonable input/output-levels (not ECL), and might be available in /256 variant also..https://www.onsemi.com/pub/Collateral/MC12080-D.PDFI've also used MC12093 with good successhttps://www.onsemi.com/pub/Collateral/MC12093-D.PDF(there might be more in this series, haven't looked very much)

author: German_EE
author_rank: Super Contributor
timestamp: December 22, 2019, 09:36:46 am
content: Seconded for the MC12080, it's a damn useful chip and easily available.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: December 22, 2019, 10:31:41 pm
content: Thank-you all for responding. I should have added my requirements are not strict, simply would like to have a third high speed channel that can cover the 2.4Ghz ism band, which the MB506 does at its upper limit. This gives me extra possibilities to compare to.Some other choices:Duplicate the option board designed by forum member saabFAN which uses nxp BGA2869 and MC12095 - which is also obsoletehttps://www.eevblog.com/forum/testgear/replacement-for-the-pm9610-prescaler-for-philips-pm6654-high-precision-counter/Or buy or duplicate the Agilent 53131A OPT-030 board sold by a Polish ebay vendor. This uses the obsolete MC12079, also available on ali.Which leads me to the question why are all these pre-scalers obsolete with no substitute?option board is beautifully described in a signal path video:

author: ThomasDK
author_rank: Regular Contributor
timestamp: December 23, 2019, 08:33:59 pm
content: Quote from: chickenHeadKnob on December 22, 2019, 10:31:41 pmAs OwO mentioned, ADF4113 can do the job. It works up to 4 GHz.
Testing Quality of RFID Tag - Page 1
Forum section: electronics / rf-microwave

author: snx
author_rank: Contributor
timestamp: November 18, 2019, 12:40:20 pm
content: When using RFID Technology, there can be a simple test of functionallity by placing the tag on the reader and check if a tag is read or not. This gives a binary testing result "yes" or "no".Imgine a large amount of tags, and a large amount of readers. Statistics show the following cases:Reader A can read Tag A but not Tag BReader B can read Tag A and Tag BReader C can read Tag B but not Tag BReader D cannot read Tag A and B but can read other tagsReaders A-B can read Tags 001 to 999, excluding 200, 345,567,879This results in the case that some tags are bad, some readers are bad, and some combinations does not match up.My goal is to create a non-binary result tag-testing fixure.Imagine a application that is depending on some resitort, you could either have a result "good" or "bad" or a result of "100.52 Ohms". The same result i want to get in my testing application. Since the quality (readability) of a tag depends on alot of features (tag placement in part, tag quality itself, tag material issues), i need to have a result representing a value. I would build a reader that has the same mechanical proberties and a tag could be inserted. Then i want to measure the quality by an analog measurement.Can anyone here provide information how this could be solved to identify "excelent" "good" "not so good" tags?
Vintage Radio Restoration Tips - Page 1
Forum section: electronics / rf-microwave

author: Radio Tech
author_rank: Frequent Contributor
timestamp: November 13, 2019, 11:18:53 pm
content: In the below video I share my thought process on restoring vintage radios.

author: German_EE
author_rank: Super Contributor
timestamp: November 17, 2019, 11:19:11 am
content: Number one tip, use an isolation transformer. Some of those live chassis rigs can bite!

author: vk6zgo
author_rank: Super Contributor
timestamp: November 17, 2019, 11:54:13 am
content: Quote from: German_EE on November 17, 2019, 11:19:11 amWe don't have that problem much in Oz, because we maderealradios with power transformers!
Hi ive just ordered some of these SGA-3486Z - Page 1
Forum section: electronics / rf-microwave

author: m3vuv
author_rank: Super Contributor
timestamp: September 27, 2019, 02:26:37 am
content: would these be any use to make an antenna preamp for 2mtrs?

author: yl3akb
author_rank: Regular Contributor
timestamp: September 27, 2019, 04:49:30 pm
content: Depends on the loss between your antenna and the receiver and NF of receiver itself. But in general I would not call an amplifier with NF=3dB a LNA, especially at 2m band

author: m3vuv
author_rank: Super Contributor
timestamp: September 28, 2019, 12:15:25 am
content: well ive an old kenwood ts-700g,its pretty deaf,i wondered if one of these in the front end would help things,as ive 10 ordered for a vna project,only needed one but ordered 10.

author: yl3akb
author_rank: Regular Contributor
timestamp: September 28, 2019, 10:24:27 am
content: If we assume sensitivity of 0.5 uV @ 3KHz (SSB) to get 10dB SNR (http://www.rigpix.com/kenwood/ts700g.htm), then it translates to noise figure:NF = (10*log10(((0.5e-6)^2)/50)+30-10-10*log10(3e3))+174 = 16 dB. So, yes there would be an improvement - by ~13 dB, but even more if You also have cable loss!!

author: m3vuv
author_rank: Super Contributor
timestamp: September 29, 2019, 10:03:38 am
content: Quote from: yl3akb on September 28, 2019, 10:24:27 amSo would it be worth doing do you think? its simple to make an amp by the looks of it just from what i can tell just an input ground and output plus 3.5v to bias it and a couple of caps and an inductor,ive a fox delta 0-30 mhz antenna analyser that uses one ,the one in mine is dead so ordered them to replace that with a few spare to play with,only downside is i couldnt find them in the uk so ordered from china suppose ill get fakes on a slowboat!! 73 m3vuv.

author: m3vuv
author_rank: Super Contributor
timestamp: November 11, 2019, 12:34:50 pm
content: sounds like a plan then,any ideas what inductor and cap values to try with for a start,going by the data sheet?,as nothings listed for 144-4mhz.

author: Teledog
author_rank: Regular Contributor
timestamp: November 13, 2019, 06:34:33 am
content: Basic MMIC calc here;https://www.changpuak.ch/electronics/mar_era_bias.phpGot a fistful of SGA-4586 MMICs.. tweaking components for these boards (1000pf coupling caps, etc. for VHF/UHF DTV)https://oshpark.com/profiles/W7PUA(amp boards)http://www.janbob.com/electron/RFAmp1/RFAmp1.htmG'luck!

author: m3vuv
author_rank: Super Contributor
timestamp: November 13, 2019, 08:55:14 am
content: the calculator would be good if it listed the SGA-3486Z as it doesent,it looks like guess work,pity realy.

author: yl3akb
author_rank: Regular Contributor
timestamp: November 15, 2019, 12:33:27 pm
content: Just use 470pF..1nF series caps and 100...200 nH in bias T and it will work.I would do the linear simulation (using RFsim99 fro example) using S-parameters of device, which are available at manufacturer web-page to verify and optimize, but I have a suspicion that You are not interested in that kind of stuff...
Op Amp Gain Bandwidth - Page 1
Forum section: electronics / rf-microwave

author: vk4ffab
author_rank: Frequent Contributor
timestamp: November 25, 2019, 05:35:23 am
content: Say I wanted to use an op amp with a gain of 10 from 3 to 30mhz how much unity gain bandwidth would I require from an op amp to meet those desires?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: November 25, 2019, 05:54:06 am
content: Quote from: vk4ffab on November 25, 2019, 05:35:23 amYou would need a minimum of 30MHz x 10 = 300MHz.You also need to check that you have enough slew rate, depending on the amplitude of the signal.Normally at the these frequencies an rf amplifier is used.Regards,Jay_Diddy_B

author: vk4ffab
author_rank: Frequent Contributor
timestamp: November 25, 2019, 08:36:46 am
content: Quote from: Jay_Diddy_B on November 25, 2019, 05:54:06 amCheers, i thought i read 10 x somewhere once before and just wanted to confirm i was right. I know an rf amp would be a better option, but parts that are easy to hand solder start around the $3 mark and I was given a pile of 350mhz rail to rail op amps that are a 40 cent part begging for a use. I probably do not even need 10x gain out of them, 5x should get me in the ball park. Time tp prototype up a circuit and see if they will cut the mustard.

author: iMo
author_rank: Super Contributor
timestamp: November 25, 2019, 09:39:34 am
content: Doublecheck the noise of your opamps when you plan do RF with them..

author: RadioNerd
author_rank: Regular Contributor
timestamp: November 27, 2019, 06:57:09 pm
content: if you have several of these opamps you can also build a two stage amplifier. By setting the gain to sqrt(10) for each stage you could relax the GBW requirement of each amplifier by the same factor (= 3.16).Keep in mind that the GBW is the 3dB bandwidth, i.e. with a single stage design the gain of the amplifier will already be reduced by 3 dB at 35 MHz and is likely to produce a considerable amount of harmonic distortion.

author: Yansi
author_rank: Super Contributor
timestamp: November 27, 2019, 06:59:36 pm
content: That way you'll get much worse resulting noise.

author: Yansi
author_rank: Super Contributor
timestamp: November 27, 2019, 07:01:58 pm
content: Quote from: vk4ffab on November 25, 2019, 08:36:46 am$3 what? No frigin way. Even the multi-GHz RF MMIC amplifiers (MSA0x86, MAR-x, ERA-x, and others) cost peanuts from china. Still in a very hand solderable packages.30MHz 10x shall be also easy enough for a transistor cascode to achieve. Also cost of few cents.

author: w2aew
author_rank: Super Contributor
timestamp: November 27, 2019, 08:40:07 pm
content: Just in case you're interested, here's a video I did on op amp gain-bandwidth product and slew rate:
Digital PMR446 experts here? - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: November 08, 2019, 03:41:53 pm
content: HiDoes anyone here is an expert for Digital PMR446 Radios?Yesterday I figured out my "local" Supermarket use Analogue PMR446 Radios.Even when the use a Sub Audio Channel or what ever everyone could legally talk to them and disturbed them until the turn it off.So we guessed why the not use a Digital PMR446 Radio with Encryption. Even the weakest Encryption if good enough to keep 99,9...% of everyone out.So does anyone have practical experience with them?Thanks

author: Dave_PT
author_rank: Frequent Contributor
timestamp: November 08, 2019, 05:07:02 pm
content: I think it is illegal to use any kind of encryption.Any voice scrambler, for example, is not allowed.But let's wait for any expert on this subject ...

author: Yansi
author_rank: Super Contributor
timestamp: November 08, 2019, 05:22:51 pm
content: No encryption or voice scrambling is allowed on free-licensed civil bands.That is what CTCSS and DCS is for.

author: Lord of nothing
author_rank: Super Contributor
timestamp: November 08, 2019, 05:30:27 pm
content: QuoteSay who?QuoteNo its not its a different think.QuoteFell free to think about what you want but the question is did you know Austrian Law? I dont read anything why encryption is not legal.The Law say about PMR446: fixe Antenna, 0.5W Pep, "mobile" and (i guess) 300s max. Transmission.QuoteLink?

author: Dave_PT
author_rank: Frequent Contributor
timestamp: November 08, 2019, 05:40:20 pm
content: Quote from: Lord of nothing on November 08, 2019, 05:30:27 pmWell ... with that kind of answer I'll say this is a job for you ...In Portugal, with our laws, this is not legal.I think there is an EU law on that, in agreement with IARU for sure ... but I can think what I want

author: Lord of nothing
author_rank: Super Contributor
timestamp: November 08, 2019, 05:45:47 pm
content: since I not in Portugal.Hytera UK (and Germany) offer this:https://hytera.co.uk/products/pd505lf#technicalwith a Basic encryption as standard (10, 32 & 64 character keys).So if the in the hole EU not legal why should the produce them and sell it?

author: Yansi
author_rank: Super Contributor
timestamp: November 08, 2019, 08:18:33 pm
content: If you are that much smart ass, go and find for yourself.
HP csv to smith chart program - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: November 08, 2019, 06:16:38 am
content: is there a program that will take a CSV file and make a smith chart that you like to use?not requiring excel or snake language? don't know what parsing HP uses I need a floppy drive to access the data.

author: Lord of nothing
author_rank: Super Contributor
timestamp: November 08, 2019, 04:18:30 pm
content: Depend if you can some script language look for some code.If not play around with Open Office and Notepad++ the can record a Macro and I did some insane stuff with.

author: hagster
author_rank: Frequent Contributor
timestamp: November 08, 2019, 05:06:01 pm
content: Most smith chart programmes take touchstone files(*.S1P). This is just a tab separated format. You can use Excel to get the data into the touchstone format.
Transmitting 125khz signal with coil antenna - Page 1
Forum section: electronics / rf-microwave

author: filthyfrank
author_rank: Newbie
timestamp: November 10, 2019, 05:52:19 pm
content: Alright guys,I need a bit of help with a project I've been working on for a while. I need to make a circuit which can amplify a 125 kHz sine wave signal and place it on a magnetic loop antenna (big coil of wire). This is basically an RFID amplifier; I want to boost the 125 kHz signal and have it make a large magnetic field so it can excite a receiving circuit several feet away.I'm using TLE2301 power-amp as antenna driver. It receives input from Arduino and output is connected to series* resonant tank. Am I doing this correctly?Please see attached image for a better view of what I'm trying to accomplish. Any thoughts are greatly appreciated.Link for TLE2301:http://www.ti.com/lit/ds/symlink/tle2301.pdf

author: Audioguru again
author_rank: Regular Contributor
timestamp: November 11, 2019, 05:29:51 am
content: The high frequency opamp can produce some power into a low impedance but your parallel LC is a high impedance which will produce a very low output power. The tuning of the LC might produce higher output voltages that will damage the opamp.Maybe the opamp can drive some power into a series LC tuned circuit because a series LC is a low impedance.The IC maximum allowed heating is only 2.1W which will probably limit your range.

author: filthyfrank
author_rank: Newbie
timestamp: November 11, 2019, 06:09:55 pm
content: I agree, using series LC sounds like a better idea. I uploaded detailed schematic with series LC tank, does it look right to you?

author: profdc9
author_rank: Frequent Contributor
timestamp: November 12, 2019, 08:37:07 pm
content: Typically the coil is a LC resonant circuit with a very high Q which is achieved by using a wide conductor and a low loss capacitor.To couple to this, either a second loop is used or a coupling transformer. But for a tuned loop, a second loop is easier. You move the second loop between the center and the edge (and can tilt it) to adjust the amount of coupling.

author: Teledog
author_rank: Regular Contributor
timestamp: November 13, 2019, 04:58:13 am
content: Did the same sort of thing for a company I worked for a few years back..used the 125kHz as exciters for RFID monitoring.had 2 to 4 large high-Q inductors/caps, placed with the exciter board, in plastic boxes near the monitor areas.I don't recall the caps, but the inductors were 4x ~1x10CM ferrite rods, evenly spaced in a group, wrapped with ~14 ga. enameled copper.Have one kicking around here ..somewhere(?)..don't recall the inductance or Q..sorry.
Wanted: Kenwood TM-241 Display Board Communication Protocol - Page 1
Forum section: electronics / rf-microwave

author: sundance
author_rank: Regular Contributor
timestamp: November 05, 2019, 01:34:32 pm
content: Does anyone have the details for the communication protocol for that module at hand?I know, it's not going to be very complicated to reverse engineer this since only three pins are involved (CE, clock and data).But maybe it's not necessary to reinvent the wheel since this trx is very popular.Thanks in advance
RF transmission line 50ohm (CC1101 868MHz) - Page 1
Forum section: electronics / rf-microwave

author: zokir
author_rank: Newbie
timestamp: November 20, 2019, 11:06:53 am
content: Hi,I am designing a transceiver board based on CC1101 (868MHz). I have a question regarding a RF track. The general rule of thumb says that if the track length is less than 1/10 of the signal wavelength that the track is not considered as a transmission line. For 868MHz, it is 0.345m, so track shorter than 34.5mm ‘should’ be safe.In my case, I have a track length of 10mm. Does this mean that I don’t have to take care about an impedance at all? Schematic and design for the 1st approach are attached. I am using Johanson Tech. Balun 0868BM15C0001E.If we disregard this rule and I want to have 50ohm track on Top Layer on 4-layer board.Which solution is better?1. Cutting internal layers (Poly pour cutout on 2,3rd layer) below the track in order to reference the track on top layer to GND plane on bottom layer. This increases the track width and using a calculator (https://chemandy.com/calculators/coplanar-waveguide-with-ground-calculator.htm) we have for example the following setup:Track width = 30milsGND-Track-GND gap = 5milsHeight = 60mils2. Referencing track on top layer to GND on the next first internal layer (2nd layer).This gives a smaller track width and does not require GND plane so close on top layer.Track width = 12milsGND clearance > 25milsHeight = 6milsWith the first approach, PCB design is not dependent on PCB stack-up, as different CM are using different default stackups. It also works on 2-layer boards with no changes needed. The design looks like this:Thank you for your feedback and comments.Cheers,Zoran

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: November 20, 2019, 12:37:31 pm
content: Actually the wavelength at 868MHz would be 345mm in air. On the dielectric it gets scaled down by a factor of roughly sqrt(Er). So you can divide that number by 2. That yields a wavelength of 170mm.lambda/10 = 17mm and you are very close to that. But I would not worry about it much as it is not going to add a large mismatch. You can always tune that out with the LC components.

author: radiolistener
author_rank: Super Contributor
timestamp: November 20, 2019, 02:05:52 pm
content: Quote from: zokir on November 20, 2019, 11:06:53 amI suggest to use at least criteria "length shorter than lambda / (10 * 2 * pi)"For your case 868 MHz, it will be 0.005 meters = 5.5 mm.But again, it depends on your requirements.Also note, if you will use soldering mask, the polymers used for mask has unstable parameters. It may affect line impedance and even worse - different instances of the same PCB may have different impedance.
Modeling of a digital PLL - Page 1
Forum section: electronics / rf-microwave

author: Mrt12
author_rank: Regular Contributor
timestamp: October 28, 2019, 10:40:59 am
content: Hi,I am working on a new GPSDO project as some of you may have read on the time-nuts mailing list.This time I plan to use a PLL and for that I would like to make a detailed analysis of the PLL in Matlab to find the optimum values for the PID controller and the EFC digital filter.I am currently thinking about the model of the OCXO to be used. The PLL is almost an all-digital PLL, the only analog component being the OCXO, so I wonder how I should take that into account. Perhaps it is fine to model it as an ordinary NCO? But then what is my NCO gain?when I apply 0V to the EFC input, the OCXO has frequency approx. 10MHz - 3Hz and with 10V at the EFC input, the OCXO has approx. 10MHz + 3Hz. And since I use a 16bit DAC, the numerical value for 10V is 65535. Is it correct then to say that the VCO gain, KVCO, is 6Hz / 65535 = 91.55e-6?However, this model herehttps://upload.wikimedia.org/wikipedia/en/0/04/Generic_NCO.pngseems not to be appropriate since with a control word of 0, the phase doesn't increase.

author: iMo
author_rank: Super Contributor
timestamp: October 28, 2019, 12:27:57 pm
content: The OCXO's gain is usually something like 1-10Hz/Volt around a certain EFC value, say 3-4V (where at that EFC the output freq is near the "exact" 10MHz). That values may change with time, however.PS: For example my oldish Trimble's DOCXO gain is 1.53Hz/Volt at EFC=1.6543V where it is 10.000.000,0xx xxx Hz. Its internal Vref is 6.2V, thus it certainly moved a lot in last 30 years (as I would expect the EFC for 10MHz was around 3-4V at the beginning)
SW Radio Dead? - Page 1
Forum section: electronics / rf-microwave

author: nvidia
author_rank: Regular Contributor
timestamp: October 09, 2019, 11:01:29 am
content: looking at getting a nice SW radio from a friend but not sure if there are any SW radio stations that i could pickup in new zealand anymore

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: October 09, 2019, 11:14:51 am
content: There's still quite a few shortwave stations around.These are some band scans.http://home.alphalink.com.au/~parkerp/shortwave.htmSample shortwave for yourself with a NZ-based web receiver eghttps://sdr.hu/?q=new+zealand(set to AM mode and look for signals in the shortwave bands - lower frequency at night, higher frequency during the day)

author: TheMG
author_rank: Frequent Contributor
timestamp: October 11, 2019, 05:51:44 pm
content: I don't know how it is in your area but here in Canada anyways, any SW stations we can receive are pretty much all DX (all local SW broadcasts have ceased), and the major challenge these days with the low solar activity and generally poor propagation conditions that result from it, is that the signals are mostly so weak that they are buried in local electrical interference.Plan to have to install a decent outdoor antenna if you want a chance at hearing anything, or if you get a portable radio, take it outside away from buildings and power lines as much as possible.

author: babysitter
author_rank: Frequent Contributor
timestamp: October 11, 2019, 10:14:51 pm
content: Why is there no bot that responds to "dead?" topics with "No"? (Insert Bugs Bunny meme here)I am going to book some hours of shortwavey goodness in a few weeks.

author: Lord of nothing
author_rank: Super Contributor
timestamp: October 27, 2019, 03:15:40 pm
content: How about this silly guy -> The Overcomer Ministryhttps://www.short-wave.info/index.php?station=The%20Overcomer%20MinistryThere are Wold Wide many Station still up there. Even Digital one!
antenna anti static spark gap - Page 1
Forum section: electronics / rf-microwave

author: m3vuv
author_rank: Super Contributor
timestamp: October 30, 2019, 10:36:41 am
content: just wondered if anyone has used a petrol engine spark plug for this application? seems a ready made solution to me,nice porcalain insulator etc.

author: bd139
author_rank: Super Contributor
timestamp: October 30, 2019, 10:59:35 am
content: Wont do a lot to be honest. Anything that can jump a few micrometres is enough to blow a receiver which is way less than the average spark plug gap (0.6-1.8mm). That's not a lot of volts (500-ish). If it's static you want to get rid of, shoving a low inductance 100k resistor across your ATU output (carbon comp will do the job) is good enough. That will keep the DC potential across the feed low and seep off any static.On mine I don't usually bother with that. The antenna doesn't stay connected and I just short it before I plug it into the radio.

author: TheMG
author_rank: Frequent Contributor
timestamp: November 01, 2019, 01:24:30 am
content: If it's just static you're worried about, a high value resistor to ground will work fine to bleed off any static charge before it can build up, without adversely affecting antenna performance or tuning.When it comes to lightning-induced transients, I would use GDTs (gas discharge tubes). They are inexpensive and will provide significantly more repeatable results than an open-air arc gap of any type. They are available in a wide range of different spark-over voltages.https://www.digikey.ca/products/en/circuit-protection/gas-discharge-tube-arresters-gdt/142?k=GDTNote that many commercially manufactured antenna tuners are already equipped with these.You will not get reliable results from a spark plug. The spark-over voltage will vary significantly depending on a large number of variables such as atmospheric pressure, humidity, temperature, corrosion on the spark plug surfaces, any other contamination of the electrodes, etc. The electrodes on a spark plug also have pointed or sharp edges which makes it even more difficult to get repeatable results. Ignition coils in a vehicle can produce a much higher voltage than is necessary to arc across the gap, making several of these variables a non-issue.GDTs are sealed devices filled with controlled mixture of gases (typically inert) at a controlled pressure, specifically engineered to get the desired spark-over voltage characteristics and repeatability.Note however that the only surefire way to avoid damage to radio equipment is to physically disconnect antennas during lightning storms and/or when not in use.
Looking for advice on 2,4GHz free running beacon - Page 1
Forum section: electronics / rf-microwave

author: IconicPCB
author_rank: Super Contributor
timestamp: October 25, 2019, 06:29:08 am
content: As the title says, need a 2,4GHz source capable of providing 10 to 20 mW at 2.4GHz. Needs not be crystal locked so long as it remains within the 2.4 to 2.5 GHz band..I would rather not use one of the "modem" transmitter receiver chips as they are in need of a micro.

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 25, 2019, 06:58:10 am
content: Can you use something like this?https://www.aliexpress.com/item/32868476979.html

author: IconicPCB
author_rank: Super Contributor
timestamp: October 25, 2019, 08:04:15 am
content: Yes I could in fact i need to get familiar with the chip in order to see if I can "program" it without a micro.I am also looking at a combination of the Nordic chip and RFAXIS power amplifier to increase the power in line with a process requirement ( materials behavior investigation experiment).There is a module which combines an ST micro, Nordic RF chip and RFAXIS PA Rx Tx switch for about 9US dollars in qty of two pieces.I shall have to investigate the product to see what it really offers.Would prefer oldfashined ON OFF keying and perhaps analog power setting rather than these digital behemoths.

author: ogden
author_rank: Super Contributor
timestamp: October 25, 2019, 08:32:08 am
content: Quote from: IconicPCB on October 25, 2019, 08:04:15 amThere is solution which I do not suggest actually.https://www.maximintegrated.com/en/products/comms/wireless-rf/MAX2753.html. If you use simple trim pot or DAC for voltage control, it may drift out of 2.4GHz ISM frequency band. Beware of using high frequency RF generators without crystal-referenced PLL. 100ppm frequency drift due to thermals at 27MHz is one thing but at 2.4GHz - completely another. BTW you need >=3GHz spectrum analyzer. So better take already suggested Nordic RF IF + MCU solution.

author: IconicPCB
author_rank: Super Contributor
timestamp: October 25, 2019, 10:47:59 am
content: Thanks Ogden,I have had a lookk at this option.I suspect it will not be possible, I think it is difficult to source this component.
9:1 unun - Page 1
Forum section: electronics / rf-microwave

author: m3vuv
author_rank: Super Contributor
timestamp: October 22, 2019, 05:55:01 pm
content: Hi all ive made a 6:1 unun from the binocular pa ferrite matching transfo from an old ts-850 pa,as i guessed the ferrite mix would be good for hf,i found a diagram on the net how to wind it,there are plenty of diagrams for trifilliar winding a 9:1 unun on a torroid,cant see how to wind it on a binockular ferrite,anyone know of a diagran or sketch how to wind it,i cant figure it out from the schematics,cheers m3vuv.73
Behavior of Electrolytic Capacitor  - Page 1
Forum section: electronics / rf-microwave

author: vinlove
author_rank: Frequent Contributor
timestamp: October 18, 2019, 12:25:26 pm
content: If you put in an Electrolytic cap. say 33uF into a circuit, then could you still measure and read the value of the cap. 33uF in the circuit?Because when I did this, the cap reads as a resistor of 0.4 ohm.I thought the cap is gone off, so cut the + end of the leg, and read the Farad value, and it was 33uF.I soldered the leg back into the circuit, and it reads as 0.4 ohm, and OL in capacitance.Is this normal behavior of an Electrolytic cap? Or something doesn't sound right here?

author: vk6zgo
author_rank: Super Contributor
timestamp: October 18, 2019, 01:19:57 pm
content: The proper way to measure capacitance is with the device out of circuit.With the capacitor disconnected, measure the resistance of the circuit between the points where it is normally connected, using the normal resistance range of a DMM.If it still looks like 0.4 Ohms, you either have an inductor, or a transformer winding across those points, or the circuit is faulty.If, as is more likely, you get a reading of several kOhm, your capacitance meter does not like seeinganyvalue of resistance in parallel with the capacitor under test, & produces a "nonsense" reading.

author: vinlove
author_rank: Frequent Contributor
timestamp: October 18, 2019, 01:31:36 pm
content: Yeah, on the + end of the cap. the circuit has an inductor.So, the cap is behaving normally in the circuit then?It is a HF Transceiver, PA circuit. When powered on, the cap has DCV 13.5V, and when the rig is Txing, the cap's DCV goes down to 12.5V.Is this normal?

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: October 18, 2019, 01:50:37 pm
content: Also keep in mind that electrolytic capacitors when measured reverse polarity can in fact look like a load as they don't charge and just puff up and go boom.

author: vinlove
author_rank: Frequent Contributor
timestamp: October 19, 2019, 09:02:19 am
content: Yeah, polarity is critical in electrolytic caps. But even measuring with DMM in wrong polarity could cause them go bang?

author: vk6zgo
author_rank: Super Contributor
timestamp: October 19, 2019, 11:50:14 am
content: Quote from: vinlove on October 19, 2019, 09:02:19 amNo!