hybridfree/eevblog-posts huggingface dataset:
array solutions vna - Page 1
Forum section: electronics / rf-microwave

author: phenol
author_rank: Regular Contributor
timestamp: September 30, 2017, 01:48:27 pm
content: Any VNAuhf owners out there?Has anyone tried to reduce port A output amplitude and perform a scan accordingly? The software seems to provide couple of 6dB attenuation steps, but I can't get it to perform a custom OSL calibration with anything other than 100% in the amplitude box. The software gives a weird port A gain error message and amplitude gets reset back to 100% (-12...-13dBm).The inability to reduce drive level could be a problem for low input level/high gain amplifiers and some filters.
Unused Ports on RF Test Equipment - Page 1
Forum section: electronics / rf-microwave

author: German_EE
author_rank: Super Contributor
timestamp: October 07, 2017, 08:42:22 pm
content: Those unused ports on your test equipment (or when the equipment is not in use). Do you:a) Use those little yellow or black plastic covers?orb) Use 50 ohm terminators all over the place?

author: dave_k
author_rank: Frequent Contributor
timestamp: October 07, 2017, 09:51:27 pm
content: Use the plastic covers - it's much kinder to the threads on the connector.

author: DaJMasta
author_rank: Super Contributor
timestamp: October 08, 2017, 01:09:27 am
content: I use little plastic covers to just keep stuff out of the ones that I don't use regularly (external triggers and monitoring outputs and whatnot), then cover all the high speed RF ports, even if somewhat regularly used. Terminators for things that are outputting, are high frequency, and are active... but there's usually not too many of those. Plus terminators are expensive and there's the aforementioned wear issue, especially if you're actually using the connection regularly.I think my plastic covers are clear plastic or dipped red rubber, though

author: ChuckDarwin
author_rank: Regular Contributor
timestamp: October 08, 2017, 01:56:30 am
content: Plastic for dust, unless it requires special termination or otherwise susceptible to outside interference--not much in my case. Some metal caps on rarely used ports, just because I have them.I find the the hard plastic top hats easier to use and longer wearing than the rubbery caps, particularly with SMA.

author: bjcuizon
author_rank: Frequent Contributor
timestamp: October 08, 2017, 02:57:42 am
content: The plastic ones are okay for protecting the connectors with dust just like what the others said. There are also metal dust caps (as in its the connector itself without the pin) which chain can be screwed into a hole in the instrument to avoid losing it. They may be used if you want the port open.
New $1,299 VNA China - Page 1
Forum section: electronics / rf-microwave

author: Zebryk
author_rank: Newbie
timestamp: September 28, 2017, 04:02:37 pm
content: Found this on E-Bay:http://www.deepace.net/Seems for real?No USB SW interface:-(

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 28, 2017, 04:24:07 pm
content: Quote from: Zebryk on September 28, 2017, 04:02:37 pmyes its real, the fun is no pc dependency and can do outdoor field measurement, and its been so long that its $1999 KC901V 6.8GHz brother is already out. with the latest 5.8GHz wireless video blooming in china industry, you cant analyze that with the KC901S. and V has some improvement in HW iirc thats not available in S version... ymmv...

author: 4CX35000
author_rank: Regular Contributor
timestamp: September 28, 2017, 04:50:38 pm
content: They can be bought over here in the UK from Martin Lynch amateur radio. Think they have been on sale for while now.https://www.hamradio.co.uk/accessories-test-equipment/mydel/mydel-deepace-kc-901s-plus-3ghz-handheld-network-analyser-multi-rf-meter-pd-5721.php

author: DaJMasta
author_rank: Super Contributor
timestamp: September 29, 2017, 12:31:30 am
content: TheSignalPath has a video review of one, and there is some other info around on the forum. I believe it doesn't do full s parameter testing, but it's got a pretty comprehensive featureset and performance/build quality is quite good given the price.
RF PCB design gurus: Which 2.5D solver can handle thin dielectrics? - Page 1
Forum section: electronics / rf-microwave

author: rf-fil
author_rank: Regular Contributor
timestamp: September 27, 2017, 07:58:00 am
content: I'm trying to extract s-parameters from a PCB. I am evaluating Sonnet right now. What an awesome tool. It's very user friendly. It's super accurate, as far as I can measure, with a thick PCB. Say 1mm.However, when I try to model a thin PCB, say 0.1mm, the results are way off to the point of being unusable. Does any other EM tool / 2.5D solver handle thin dielectrics?Btw, I work at UHF, at few hundred MHz.(Just to be clear, a tool based on circuit theory works well too, but has limitations. Circuit theory tools use manual schematic entry and the PCB has to be modelled as sections of transmission lines or microstrips. What I'm trying to achieve is to get something less labour intensive and more accurate than a circuit theory tool.)

author: hendorog
author_rank: Super Contributor
timestamp: September 27, 2017, 08:03:41 am
content: I'm no RF guru, but for my 2cents, could this be due to the copper not being modelled accurately enough?It seems logical to me that copper thickness and roughness will have more of an effect on the result as the dielectric layer becomes very thin.I seem to remember that Sonnet lite (free version) has limitations on the modelling of copper layers.

author: rf-fil
author_rank: Regular Contributor
timestamp: September 28, 2017, 04:40:13 am
content: It turns out I have forgotten to model the solder mask. The Sonnet output now matches what I measured within 1%.Btw, the actual PCB will be so thin (for EM purposes) because it's a multi-layer board. So this is just the distance of the top layer to the ground plane beneath it. The PCB is much thicker overall.
DIY EPR/ESR spectrometer - general overview+dummy-load? - Page 1
Forum section: electronics / rf-microwave

author: ChristofferB
author_rank: Frequent Contributor
timestamp: September 24, 2017, 01:33:48 pm
content: Hi all!I posted some beginning musings over building my own electron spin resonance /electron paramagnetic resonance spectrometer some time ago.It's kinda like NMR but easier, because it requires lesser magnetic fields, so it can usually be done with permanent magnets and still reach usable results.Now that I've gotten a gunn-diode module, i've gone a bit further with the design, see attached.The main idea is that the lower piece of straight waveguide is a cavity (akin to the resonant coil in an NMR head) in which the sample is placed in the mag. field. and this field is swept by slow AC, and an output in varying energy is siphoned off by the directional coupler and sent to a recorder, as function of field strenght.Does this look sound? I'm a bit concerned that there's no downright load for the energy, and so the gunnplexer might be punished badly by this setup.whatcha think?thanks for the interest!
whats state of the art in microwave noise floor? - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: September 17, 2017, 11:52:32 am
content: What is considered state of the art for a 'experimental' laboratory receiver?I figure that radio astronomy might have the best equipment, but they also have big dishes, so I am not sure what field to look at.If compared to a spectrum analyzer, -? dBm.. I guess like -220dBm?are there cryogenic equivalents to things like squids?

author: KJDS
author_rank: Super Contributor
timestamp: September 17, 2017, 02:49:17 pm
content: Without cooling, I've done LNAs at 2GHz with 0.3dB noise figure. Thermal noise floor in a 1Hz bandwidth in 50ohms is -174dBm. That can be reduced by cooling. Noise = kTBR with T in Kelvin, so you need to get to -120 degrees C to half the noise floor, ie a 3dB improvement.

author: CopperCone
author_rank: Super Contributor
timestamp: September 17, 2017, 07:39:36 pm
content: what kind of LNA is that?

author: retrolefty
author_rank: Super Contributor
timestamp: September 17, 2017, 07:46:22 pm
content: Quote from: CopperCone on September 17, 2017, 07:39:36 pmAn expensive one I bet.

author: CopperCone
author_rank: Super Contributor
timestamp: September 17, 2017, 08:11:30 pm
content: me too. Is it a wideband amplifier you put into a spectrum analyzer with spectrum limited?Are there special coaxial cables? Does a regular good coaxial cable (like rf141) work at -100C? How about liquid nitrogen temps?I would be interested in getting an amplifier setup that uses liquid nitrogen (i have a dewar)... liquid helium is off the budget right now though.

author: DaJMasta
author_rank: Super Contributor
timestamp: September 18, 2017, 04:22:21 am
content: I think in Dave's video to the Canberra DSN comm center they mentioned that they could get a usable signal at -160 to -165dB or so using cryo cooled LNAs directly on the back of the antenna. I'd imagine that in a lab environment you could do better, maybe a couple orders of magnitude, but I think it's a real tall order to get to even -200dBm without a ton of software averaging noise reduction or something.... even then, that's quite a ways below the stuff I've heard of.

author: Antonio84e
author_rank: Contributor
timestamp: September 24, 2017, 04:51:13 pm
content: Once you have a good LNA with very low noise floor then, as KDJS was saying, Noise = kTB. If you want to lower the noise floor, you are going to need a good filter. Do you know the bandwidth you require to cover?

author: CopperCone
author_rank: Super Contributor
timestamp: September 25, 2017, 02:02:40 am
content: I was looking for more a 'near theoretical measurements' graph as a go to. I don't have a specific signal in mind.A case study if you will.
does a directional coupler need to be terminated to work right? - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: September 16, 2017, 02:24:41 am
content: If you have a directional coupler, does it need to be terminated to 50 ohms? Can you leave it floating when sampling is not being done?or I found ithttp://www.scte.org/TechnicalColumns/10-11-01%20why%20use%20terminators.pdfSpigot and feeder were not terms I was familiar with before, but it makes sense.

author: KE5FX
author_rank: Super Contributor
timestamp: September 16, 2017, 04:35:07 am
content: This:https://www.microwaves101.com/encyclopedias/directional-couplers... is a good summary of the operation and theory behind couplers.

author: bjcuizon
author_rank: Frequent Contributor
timestamp: September 16, 2017, 05:15:58 am
content: Sometimes they are already internally terminated like the one shown here: (and watch this video too for basics of directional couplers)

author: bjcuizon
author_rank: Frequent Contributor
timestamp: September 16, 2017, 05:23:39 am
content: Here's another video of The Signal Path. It is about microwave components in general but I linked it to the part where he talks about directional couplers.https://youtu.be/6kwamCh1QkE?t=28m51s

author: Antonio84e
author_rank: Contributor
timestamp: September 24, 2017, 04:41:50 pm
content: If you have a 3port directional coupler and you are not using the coupling port, it's better to terminate it with a 50 ohm load for various reasons:1. Depending on the coupling value, the higher this is (4dB for example), the coupled signal will reflect and couple back to the main line worsening the performance in terms of IL, VSWR, etc.2. most of the coupled signal will reflect if the output port is not terminated and then this will couple back to the main line but most (depending on the coupling value) will go to the internal load. You may need to derate the input power in order not to damage the internal load.
Zeta Laboratories Inc? - Page 1
Forum section: electronics / rf-microwave

author: CNe7532294
author_rank: Regular Contributor
timestamp: September 24, 2017, 11:56:55 am
content: Their code ID is 31260. Anyone know who owns this company's assets now? Checked on the rf sites and they say DRS Technologies but now its LeonardoDRS. Out of curiousity, I have a part from them that I assume is a multiplier and amplifier module that accepts a 10MHz signal with 15V+ DC and spits out 4400MHz (x44 Multiplier). Model # is 5552-02. I wonder what it's other specs are per datasheet if any exist.
Problems with AOR AR8600mk2 receiver (RF switches?) - Page 1
Forum section: electronics / rf-microwave

author: borjam
author_rank: Unknown
timestamp: September 24, 2017, 10:56:59 am
content: HiI have an odd problem, maybe someone can help.Some time ago I purchased a used AR8600mk2 receiver. Turns out it was damaged, its sensitivity was really low.I sent it for repair to a very reputable guy here and indeed when it came back it had improved a lot. He found a damaged RF switch (SPM3204) and a transistor. Seems it was damaged by RF applied to the input (maybe a nearby transmitter, who knows). He also told me that the problem was a real bitch because there was some intermitent problem which he determined to be one of the SPM3204 switches. It uses a lot of them.When it came back I noticed several surprising things: At least one or two more switches are damaged. If I turn on the receiver it takes more than 30 seconds to be able to receive. And if I activate and disengage the input attenuator it takes the same 30 - 40 seconds. Those switches should be fast.I also noticed something odd. There was some kind of impedance adaptation problem. It's difficult to describe, but when running on an attached telescopic whip it was way too sensitive to the whip length. Of course I know that changing the length will tune the antenna to a frequency, but the effect was way too sharp.So I tried to determine if something else was wrong. I attached the receiver to a miniVNA Tiny and begun looking at the RL.I have observed several curious effects.First: The first time I did it I did a wideband scan and, surprisingly, the RL curve came flat. This receiver has (as far as I know) a rather strong front end filtering and I expected to see a dip in RL. There wasn't any and the RL was low, maybe in the order of 4 dB. Bad.Second: After doing several tests it begun to behave differently, like something "woke up". And I begun to see more reasonable RL curves. (More on this later)The surprising thing was, after the "awakening" it worked way much better for a week or so. The "awakening" effect remained in effect despite the fact that I power off the receiver completely when not in use. So it's not a matter of reaching a certain temperature, it can be powered off for 12 hours in between.I also noticed something strange. Some of the front end filters are tunable (75-118 MHz, 118-174 MHz, 174-300 MHz, 300-470 MHz) and indeed, each of these filters has a varicap diode. The thing it, the filters seem to be somewhat detuned. I attach some examples.So, I am wondering. What is the failure mode of these RF switch MMICs? Could it be that they are adding some parallel capacity to the circuit? I guess that would detune the filters. The other scenario, a problem with the control voltage used to tune the filters seems to be more unlikely.

author: borjam
author_rank: Unknown
timestamp: September 24, 2017, 11:24:01 am
content: I forgot, block diagram and schematic of the RF part.
external microphone line levels - Page 1
Forum section: electronics / rf-microwave

author: DrMag
author_rank: Regular Contributor
timestamp: September 21, 2017, 10:19:05 pm
content: I've been working on a project that would send a specified audio signal to my radio (could be hand-held, could be mobile, etc.) microphone line. For the life of me, I can't find anywhere in any radio's manual information on what signal amplitude the radio expects. The only thing that's listed is the microphone impedance (600 ohms seems common). Not wanting to destroy something in the radio by applying too high of a voltage to the microphone line, I'm trying to figure out where the line level should be. Is there a way to find that out or determine it from the microphone impedance, or am I stuck doing it manually by attenuating the signal to zero and gradually turning it up until the audio level sounds right, then measuring the output voltage that gives that level?My current radios are an old IC-V8 (mic impedance not listed in the manual) and a TM-V71A (listed as 600 ohms) if that's of any use.

author: DrGeoff
author_rank: Frequent Contributor
timestamp: September 21, 2017, 10:59:36 pm
content: It sounds like a dynamic mic. The output from the mic is likely to be around 20mV or so, depending on how close you have it and how loud you shout into it.The radio probably will have an ALC circuit as well, to adjust the gain level to compensate for variations in input level. This also helps maintain better signal modulation.

author: DaJMasta
author_rank: Super Contributor
timestamp: September 21, 2017, 11:20:59 pm
content: +1 it's very common to see dynamic mics in radios, so I would expect that as well. You can check to be sure, and see if there's any DC bias coming out of the mic jack, if there is, then it's using a different kind of mic that involves active circuitry (like your typical electret or various condensers).Regardless, if you know what mic would have come with it or some that are known compatible - you could see if they're specified. If you've got a working mic, you can always just tap into the line with a high impedance probe and take a look for yourself too!

author: 4CX35000
author_rank: Regular Contributor
timestamp: September 24, 2017, 08:40:08 am
content: You can measure the voltage output using a oscilloscope with a pair of 1k2 resistors in parallel and speak into the mic. Use the second oscilloscope channel as a marker to show where the peak of the audio output is.If the mic is 600 ohm then it will probably be similar to the mic in the transceiver, so you can probably just add the mic to the transceiver input and adjust the FM deviation settings on the transceiver to adjust the output. Listen on your second transceiver for maximum performance with no clipping.
"Transforming Electromagnetics Using Metamaterials" article - interesting - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: September 23, 2017, 08:01:43 pm
content: This likely is a good example of what "they" meant when they made up that saying about any sufficiently advanced technology would likely be seen by others as magic.http://anlage.umd.edu/06167594.pdf

author: bjcuizon
author_rank: Frequent Contributor
timestamp: September 23, 2017, 09:28:16 pm
content: Hmmm...seems interesting indeed. Thanks for posting. I'll have a full read at it later.
is a tighetened APC-7 connector supposed to be able to twist? - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: September 21, 2017, 09:52:29 pm
content: I have something with two apc-7 connectors, so i got sma to apc7 adapters. One port is tight, and it wont move.The other one is fully tightened, but its acting like a rotary joint. Is this a problem? Only under substantial pressure though. The other one is rock solid.By substantially tighened, i mean it almost hurts my fingers. I did not rotate it more then like 1/8 of a turn when fully tightened.I quite like this connector but this worries me a bit. Mechanically they look the same but I am not familiar with the mechanisms behavior.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: September 22, 2017, 12:13:48 am
content: Center contact might be maladjusted.I cannot locate the instruction at the moment but I could look it up tomorrow.

author: CopperCone
author_rank: Super Contributor
timestamp: September 22, 2017, 01:37:57 am
content: It appsears I have somehow managed to improperly mate it. Now it is tight, if you rotate it it feels like there is some kind of antirotation element with a bit of slack (a few degrees) in either direction.Annoying, since this is my directivity bridge, I guess I need to check the junction with another bridge just incase. The other one does not have that antirotation feel to it, its just super tight (finger tight).I believe the term is 'play'.I'm not sure what axis its rotating about, but the 'seal' looks good. Both joints do this to an extent, one does it a bit more.Pennies on the dollar, so I should count my blessing I suppose.

author: bjcuizon
author_rank: Frequent Contributor
timestamp: September 22, 2017, 09:25:57 pm
content: Thismight somehow help.

author: CopperCone
author_rank: Super Contributor
timestamp: September 22, 2017, 10:22:55 pm
content: Does spining freely count if it spins about 1 degree back and forth between being stuck (it might beless then 1 degree).The simulation could be modeled by having one of those pannel mount devices that has a pin in it, so there is a hole under the bulkhead connector, and the hole is just a wee bit too large, so you can rotate it left and right based on the free space between the center pin and the pin hole (very not much).It goes from free rocation to very gentle rocking with high friction.
ADL5920 - just-add-PCB wide band power log detector and directional bridge - Page 1
Forum section: electronics / rf-microwave

author: daqq
author_rank: Super Contributor
timestamp: September 21, 2017, 06:32:37 am
content: This seems pretty useful:http://www.analog.com/media/en/technical-documentation/data-sheets/ADL5920.pdfA problem - the output function is frequency dependent (has an offset depending on the frequency). Still, pretty neet.David
Discussions/Suggestions on some issues for KC901V Network Analyzer - Page 1
Forum section: electronics / rf-microwave

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 30, 2017, 03:33:20 pm
content: i just got this (Deepace/Kechuang/Measall KC901V Network Analyzer) recently and still learning. its good item i think mainly for its advertised purpose, and shariar's review has persuaded me to get this unit i cant get out the temptation out of my head for months... i've been eyeing 2nd hand VNA in ebay for a lot longer. for the same price, the used working unit mostly only goes 3GHz, calibration status is uncertain. if it goes beyond 3GHz at the price, then it must be either non working sold as is, or we are going to need additional part/unit to make it work as a whole. so i think the KC901V must be it, my benchmark is no lesser than 5.8GHz because i have 5.8GHz antenna and wireless video system to tune and optimize for... and i had experience of mysterious 2.4GHz LNA and transceiver damage on my rc remote controller, so without this kind of thing, i'm just as good as a blind man in the dark... well enough story...but i have some issues (mainly negative) i want to highlight/discuss/suggest. whichever i want to suggest and hope for firmware improvement, i will try to get it through their bbs forum. but first i will post it here for the purpose of learning and discussion in case i did something wrong...first issue: impedance not showing the right thing at very low frequency (DC - 100KHz or 500KHz), my setup is as in the first picture.2nd picture for open load, it should show Inf ohm from the beginning.3rd picture for short load, it should show 0 ohm from the beginning.4th picture for 50 ohm load, ok this one they got it right.5th picture for 100 ohm load., it should show 100 ohm from the beginning.so you see, everything will start from 50 ohm reading no matter what resistance i put at termination, the only right thing they do it if we put 50 ohm terminating resistor, even that it shows a mysterious bump at the beginning. am i missing something? is there any good reason for this? for practical purpose it can be confusing, why cant they do this right? if they cant do this right, my suggestion is that either in firmware:1) cheat in firmware to show flat horizontal line on the screen from say 100KHz or 500KHz (where the line showing false impedance) down to DC.2) or better yet, just dont show (blank line) in the region where they cant do it right.if this is beyond firmware, ie hardware limitation, is it too difficult to do impedance test at DC (or near DC)? in this $2K device? it should be simple isnt it? just a resistive divider and passing Vdc at the test port, and then sense the divided voltage, no? any better suggestion/insight?

author: hendorog
author_rank: Super Contributor
timestamp: September 30, 2017, 07:16:55 pm
content: Perhaps the internal bridge has poor directivity at the extreme end of the frequency range?I see the manual recommends using an external bridge for better accuracy.
British Amateur TV Club convention talks - Page 1
Forum section: electronics / rf-microwave

author: SNGLinks
author_rank: Regular Contributor
timestamp: September 19, 2017, 01:29:11 pm
content: Here are the videos from CAT17.Very interesting talk on using a Goonhilly dish for amateur EME!https://www.youtube.com/playlist?list=PLhLAVxsCvzNBf2DgTV_saLT3bdwFex11b
Scientific Atlanta 4671 Baseband Analyzer Manual - Page 1
Forum section: electronics / rf-microwave

author: kiheiman
author_rank: Contributor
timestamp: September 08, 2017, 05:57:21 am
content: A vendor shipped me a 4671 box by mistake (I was supposed to get a 4661). Does anyone know of a manual for the 4671? I am trying to get it to work with my existing 4661 to measure NPR when the units are back to back. It seems that the NPR is not very good when I set the 4661 to 0 dbm out (about -67 dbm). However, if I set the 4661 to -10 dbm output and the input to the 4671 to -10, then I can get a NPR of about 77 - which seems to be in the ballpark of what I should be reading. Not sure if my control settings are correct. I have a manual for the 4661, but it only briefly mentions the 4671.RegardsClint

author: bjcuizon
author_rank: Frequent Contributor
timestamp: September 10, 2017, 01:50:34 am
content: Do you need a user/operating manual or the service manual?

author: bjcuizon
author_rank: Frequent Contributor
timestamp: September 10, 2017, 01:58:25 am
content: If you need the service manual there are plenty of sites to search from. Just check out this thread:https://www.eevblog.com/forum/repair/repair-documents-and-links-sticky-me-please-mods/Maybe it will help you.

author: kiheiman
author_rank: Contributor
timestamp: September 10, 2017, 04:40:36 pm
content: A service manual or user manual would be nice. I need to figure out how to use the unit with my 4661 noise generator.RegardsClint

author: kiheiman
author_rank: Contributor
timestamp: September 10, 2017, 04:51:08 pm
content: I have done quite a few searches and could not find anything. I did find a manual for the 4661 companion unit and was able to purchase the manual on eBay. The Scientific Atlanta user manuals are very good and include a full set of schematics.RegardsClint

author: bjcuizon
author_rank: Frequent Contributor
timestamp: September 10, 2017, 07:30:49 pm
content: Alright, I'll try to find it then.

author: bjcuizon
author_rank: Frequent Contributor
timestamp: September 15, 2017, 11:44:10 pm
content: The latest I found was this one here:http://www.etestmanuals.com/Search.aspx?Search=Scientific%20Atlanta%09%09IF/Baseband%20Analyzer%20Instruction%20Manual%20w/%20Schematics.%204671It is the one on the top...and unfortunately it costs 100 bucks and they only have one in stock

author: kiheiman
author_rank: Contributor
timestamp: September 17, 2017, 07:21:26 pm
content: Thanks. I contacted the vendor and they cannot find the manual.RegardsClint

author: bjcuizon
author_rank: Frequent Contributor
timestamp: September 18, 2017, 06:16:08 am
content: I'm sorry to hear that. Have you asked the seller if he has the manual or if he knows anyone that has at least a copy of the manual?
spacing for coupled line coupler - Page 1
Forum section: electronics / rf-microwave

author: Cacao
author_rank: Contributor
timestamp: September 12, 2017, 02:58:23 pm
content: does someone here know how can I calculate the spcing of the two transmission line on a coupled line coupler? Thanks in advance.

author: rf+tech
author_rank: Frequent Contributor
timestamp: September 12, 2017, 04:13:08 pm
content: Hello Cacao,Take a look at this Coupled Microstrip Calculator on Sourceforge.net:http://wcalc.sourceforge.net/cgi-bin/coupled_microstrip.cgiThe CGI-Wcalc home page has a nice collection of handy RF calculators, including coupled stripline and coplanar waveguide:http://wcalc.sourceforge.net/cgi-wcalc.htmlRF+ Tech

author: bjcuizon
author_rank: Frequent Contributor
timestamp: September 16, 2017, 09:15:16 pm
content: Here's an article about coupled line couplers and some calculators that might help you too.https://www.microwaves101.com/microwave-encyclopedia/coupled-line-couplershttp://www.hughescircuits.com/index.php/en/support/impedance-calculatorhttp://www.finetune.co.jp/~lyuka/technote/ustrip/https://www.eeweb.com/toolbox/edge-coupled-microstrip-impedanceHave fun with microstrip! ..and hope that helps.
Any experiences with OSH Park + SMA connectors? - Page 1
Forum section: electronics / rf-microwave

author: ThomasDK
author_rank: Regular Contributor
timestamp: September 14, 2017, 09:37:42 pm
content: Just as a sanity checkI'm designing a PLL board to be manufactured on OSH Park's 4 Layer service.I need to get a 2.5 - 8 GHz signal onto the board through an aluminium wall.I'm planning on using these connectors:https://www.digikey.com/product-detail/en/cinch-connectivity-solutions-johnson/142-1701-201/J10153-ND/3587660The connector pin width is 0.25 mm which fits nice on the 50R trace width on pcb (0.37 mm).I'm assuming a standard taper transition should do the trick...Any gotcha's I should be aware of?Thanks,Thomas

author: bjcuizon
author_rank: Frequent Contributor
timestamp: September 16, 2017, 01:56:22 am
content: How about those right angle sma jacks which solder/mount directly to the board.https://www.digikey.com/product-detail/en/rf-solutions/CON-SMA-EDGE-S/CON-SMA-EDGE-S-ND/5845767You can also find a bulkhead type like this one here:https://www.digikey.com/product-detail/en/cinch-connectivity-solutions-johnson/142-0701-871/J610-ND/275095The latter is a bit pricey though.After that, you could then put a transmission line going to your board/device/component.Like this one:

author: ThomasDK
author_rank: Regular Contributor
timestamp: September 16, 2017, 03:46:37 pm
content: Quote from: bjcuizon on September 16, 2017, 01:56:22 amI know and use that type often. They are however a major pain to mount in a milled enclosure (the pcb is mounted flat in the enclosure base for heatsinking)
isolator/circulator non-passband large signal behavior? - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: September 14, 2017, 06:24:01 am
content: So Isolators are rated for some frequency range, so are circulators. What exactly happens if a signal is passed through beyond its range?reflection? pass through? severe attenuation (thermal loss)? for passive types, with active types I can see them passing the signal through, as the op-amps begin to look like capacitors.I can measure small signal behavior, but I am scared to do large signal tests.I might make a transfer function, but I figured I would ask. I don't want to wreck expensive things if someone knows.
can there is a bot in this forum tha t atuoatically posts that you should google - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: September 23, 2017, 01:06:43 pm
content: I think it would make the threads more meaningful.also. some qasia relevant microwave101 reference

author: tec5c
author_rank: Frequent Contributor
timestamp: September 23, 2017, 01:13:18 pm
content: Are you drunk?

author: cdev
author_rank: Super Contributor
timestamp: September 23, 2017, 02:55:23 pm
content: Bots=poison to intelligent conversation in many online contexts.

author: vk6zgo
author_rank: Super Contributor
timestamp: September 23, 2017, 03:05:56 pm
content: Quote from: CopperCone on September 23, 2017, 01:06:43 pmPerhaps there should be!

author: bjcuizon
author_rank: Frequent Contributor
timestamp: September 23, 2017, 11:02:09 pm
content: Quote from: CopperCone date=1506172003I'm not too sure.

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 24, 2017, 01:41:41 am
content: Quote from: CopperCone date=1506172003there is, since the beginning... by keying the right word such as...Code:i <explain your problem here> but i dont know what keyword to look for in google. please helpand you'll get your autoreply bot.. some you may like the answer, some you may not. there are 38906 certified bots over here, turing test passed to 200% with soul in each one of them... but if you are too particular about the accuracy of the words rather than the meaning/semantics of words that are tried to convey to you.. (literalists)... like many bots over here... then you can easily get lost...

author: CopperCone
author_rank: Super Contributor
timestamp: September 25, 2017, 02:08:24 am
content: yes its complete sarcasm because im 99% SURE THERE WILL BE A FUCKING MICROWAVE 101 LINK THRE. ITS THE FIRST FUCKING CHECK i PLACE. I ALSO AM CERTAIN NO ONE WILL READ WHAT I WROTE AND PARROT USELESS INFORMATION.NOT AIMED AT YOU. BUT IF YOU HAD TO ASK.

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 25, 2017, 02:15:51 am
content: Dont watch too much bollywood movies, you'll got sucked up by sentimental crap..

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 25, 2017, 05:27:40 am
content: * T3sl4co1l toasts a bourbon to this thread, sits back quietly to watch
wideband circulator two octaves? - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: June 22, 2017, 04:07:47 am
content: Do these exist? I only find circulators with 1.5 octaves and isolators with two octaves.I wanted a 3 port device that has a two octave bandwidth.

author: rfeecs
author_rank: Frequent Contributor
timestamp: June 22, 2017, 05:10:27 pm
content: Probably not.There are peripheral mode isolators that have an absorber built in as part of the structure and can be multi-octave, but they are isolators, not circulators.From Wikipedia:https://en.wikipedia.org/wiki/Isolator_(microwave)#Field_displacementQuote

author: MikeLogix
author_rank: Contributor
timestamp: June 26, 2017, 04:36:10 am
content: There is a physical limitation to circulators that limits the bandwidth. What I mean is, the part is built with physical dimensions that dictate its frequency of operation. It is just not possible to exceed these limitations.One possible 3 port device that you might look at is a directional coupler. Depending on your frequency you might find multiple octave bandwidth. Power level and directivity will be specs that you should look at when using couplers. Hope that helps ya.

author: CopperCone
author_rank: Super Contributor
timestamp: June 26, 2017, 05:22:25 am
content: I looked. What is the difference between the DC and the Circulator?They seem similar (i.e. 4 port circular to DC).Loss? Power Handling?

author: CopperCone
author_rank: Super Contributor
timestamp: September 12, 2017, 08:10:12 am
content: So I am guessing commercial NLJD use directional couplers instead of circulators (due to cost of multi octave ones which I found were unforgiving)?Does anyone know?That has a 20dB loss though, right? Compared to 0dB.
Calculating/Estimating gain of an in-phase antenna array? - Page 1
Forum section: electronics / rf-microwave

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: September 07, 2017, 11:16:24 pm
content: Im working on a 20 turn quad helix array in the L-Band, I also have 10 24inch parabolic wifi grids. So at 1.42ghz my helix antennas are calculated at 17db of gain, wich I know is much higher than what you get in real life, and at 1.42ghz the parabolic grids are a solid 16db when fed correctly. Im looking in to radio astronomy/satcom, and maybe even EME using arrays of smaller lighter antennas. I have a 3 meter C Band dish with an actuator for tilt, but a real az/el system is way out of my budget. The idea is I can steer arrays of smaller and lighter antennas using unistrut and maybe wheelchair motors with encoders and cheap worm gears, and minimal to no welding.So the real question is how do I figure out how much gain ill get by adding an element in phase with the array. If I could get away with a 2 element array that would be nice but what about a 3x3 array of either helix or dish?
Noisecom NC-4193-G Specs - Page 1
Forum section: electronics / rf-microwave

author: kiheiman
author_rank: Contributor
timestamp: September 09, 2017, 02:50:14 pm
content: Does anyone have a link to obsolete noise test equipment manufactured by Noisecom? I am trying to find the specs for the NC-4193-G module. It appears to generate a usable amount of noise in the 15 to 440 Mhz band. I could not measure above 440. I sent an email to Noisecom but got no response.RegardsClint
Microstrip bending in a transformer - Page 1
Forum section: electronics / rf-microwave

author: i_am_mry
author_rank: Newbie
timestamp: September 14, 2017, 08:55:35 am
content: Hello all,I'm creating microstrip 50-to-75 ohm wideband transformer. Here is my draft:And my questions are:Can i bend quarter-wave parts?Is there any shortening factor for the each bend?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 14, 2017, 11:56:34 am
content: What do you mean "bend"? As in, turning corners, in the PCB layout?Use arc segments (trace length = mean arc length), 45 degree corners (close enough not to worry about), or 90 degree corners with a chamfer (trace length follows the inside path).I doubt the quarter-wave lengths are very critical: your bandwidth is quite large (>50%). Can always design it for extra bandwidth (the result will be a couple extra steps), to get even looser tolerances.Note that the trace edge-to-trace edge distance should be 2-3 trace widths minimum.Tim

author: Yansi
author_rank: Super Contributor
timestamp: September 14, 2017, 12:04:58 pm
content: Why not using a tapered transition instead of the stepped one? Doesn't the taper give more bandwidth naturally?

author: i_am_mry
author_rank: Newbie
timestamp: September 14, 2017, 01:29:00 pm
content: Quote from: T3sl4co1l on September 14, 2017, 11:56:34 amHi Tim, Thanks for detailed answer.Yes, just the turning corner, to make PCB more compact.QuoteAs i understand, in this case "inside path" will be summary length of red edges. Is it correct?Quote from: Yansi on September 14, 2017, 12:04:58 pmThanks for a tip. I'll look on it.
Anyone handy with the GM3SEK pi / pi-L network spreadsheet?? - Page 1
Forum section: electronics / rf-microwave

author: Chris Wilson
author_rank: Super Contributor
timestamp: September 08, 2017, 02:29:41 pm
content: I am hopeless with spreadsheets and want someone to very kindly do the calcs for running a Russian GS35B valve on 137khz as both a pi and Pi-L output format amp. Would anyone have the time and inclination to plug in the figures so I can compare with my feeble attempts please? Spreadsheet is attached (hopefully) and the bumf on the valve (tube) is at:http://www.gs35b.com/gs35b/Thank you!! My direct mail is chris at chriswilson.tv
silver epoxy for microwave frequencies? - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: September 06, 2017, 08:27:07 am
content: Can you use silver epoxy for very high frequencies, like 20GHz? I was looking to join the center pin of a waveguide antenna SMA adapter to a IC (GaN power amplifier). It seems to be used in RF applications, according to microwave 101, but is it appropriate for direct signal path use? At power levels of >10 wattsI ask this because it is relevant to my other thread,https://www.eevblog.com/forum/rf-microwave/gan-amplifiers-home-implementation/, but I feel that it deserves its own topic, because it is relevant to RF repair and possibly RF manufacturing.I have used it before to fix a isolator (only for 1-2 GHz), which had a very unrepairable bent SMA thread. I got a new SMA to waveguide adapter thingy, but getting the center pin to solder in the waveguide was very difficult, it would require a long thin soldering iron and four hands. I'm not sure how they put it together actually, the time constants of the thermal masses appropriate for soldering inside of that thing are tiny... you would need some kind of laser to melt the solder and a mechanical jig to clamp them together... or be a ninja. I have yet to test this repair as it is still curing... but anyway lacking a good VNA or test subject.I have this product:http://www.mgchemicals.com/products/adhesives/electrically-conductive-adhesives/silver-conductive-epoxy-slow-cure-high-conductivity-8331sI considered using hot air, but I noticed if you heat those coaxial connectors too much the dielectric tends to get distorted. Other options also include some kind of special hot air pencil (perhaps heating a needle passing air with a gas torch) and low temperature solder paste...

author: CopperCone
author_rank: Super Contributor
timestamp: September 07, 2017, 08:20:04 am
content: the repaired connector on the isolator reads less the 0.001 ohms of DC resistance. I will maybe try to make a piece of hardline with silver epoxy on the connector and see what the before and after is on the spectrum analyzer with a 10GHz signal.The connection style I made in the repair will be very similar to the connection style I want to make in my amplifier.It should be noted that this arrangement had some mechanical tension on the center pin of the coaxial connector and the conductor inside of the isolator. I might be measuring that instead of the actual epoxy resistance, but so long the mechanical tension is maintained and the epoxy forms a shell over it, I guess it should be ok.I would need to make special adapters to properly connect a 6.5 digit meter to the device with a kelvin connection... but I am not really too worried about DC resistance. What I am worried about is the dielectric epoxy 'sponge' that forms around the conductive particles...
what decides of a microwave band pass filter modes at passband multiples? - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: September 05, 2017, 09:44:34 pm
content: I noticed that a band pass filter I have will let through the harmonic of the pass band through a 'resonance' that is way more then what the slope would indicate. The area at twice the pass band is very spotty, and looks like this /\/\/\/\/\I watched a video online that explained this, but it was relevant to microstrip filters.I looked at some datasheets for bandpass filters, for instance the ones offered by pasternack, and they show a bode plot to about 2.5x their pass band, and this effect is not present.I thought this effect was not present in waveguide filters, it according to my measurement it is.What decides this? The waveguide filter (which I took apart), looked like it had little disks suspended by rods inside of it adjusted by tuning screws.Are there any clues as to what a filter might do? (for 2nd hand purchasing).

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 05, 2017, 09:53:39 pm
content: I suppose a responsible filter would have extra shapes inside, or tuned dampening, to reflect or absorb higher modes. But that's costly.Low frequency filters have the same problem, where component parasitics reduce the stopband attenuation. Solution? Add more filtering, with smaller values, to preserve the stopband.Same idea for distributed filters, but the higher modes are closer to the passband, so the design must be done more carefully.Tim

author: CopperCone
author_rank: Super Contributor
timestamp: September 05, 2017, 10:07:53 pm
content: ok so its a crap shoot

author: CopperCone
author_rank: Super Contributor
timestamp: September 05, 2017, 10:11:47 pm
content: Is the shape of the filter in any way indicative of this? I.e. modified waveguide vs a 'aluminum box' (which indicates milling) with rf connectors on opposite corners?Like manufacturers tenancies?I'm inclined to think that adding some doodads to a piece of waveguide is the 'cost sensitive' manufacturing technique... is it standard to not have harmonic peaking on 'machined' products?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 05, 2017, 10:24:32 pm
content: I doubt it. And all those methods will have higher modes, just in different ways (waveguide vs. cylindrical/coaxial resonator modes, plus oddball modes dependent on the exact positioning of the screws). You have to make smaller features to reflect or divert the upper modes.Tim
Bluetooth stack tutorial beyond basics - Page 1
Forum section: electronics / rf-microwave

author: ah_l
author_rank: Newbie
timestamp: September 05, 2017, 12:52:53 pm
content: Hello,Can anyone suggest a good up-to-date literature, video lectures etc. on the Bluetooth stack that is beyond basic stuff?I have been doing some simple Bluetooth related projects for a while, and have no problem using BT in my embedded projects, for example, to communicate between MCU and some PC app using Bluetooth SPP. However, I get fuzzy as quickly as you can when talking about more in-depth stuff like protocols (RFCOMM, L2CAP, etc.), operation details (pairing, scans, connection invocation, multiple connections), security, packet construction, optimal sending conditions, etc. Also I have very limited knowledge regarding newer implementations such as BLE.In other words, I'm in search for a resource that would help to get information that is required to implement BT in a proper end-user product not just one off prototype.
FT8 - Page 1
Forum section: electronics / rf-microwave

author: xrunner
author_rank: Super Contributor
timestamp: September 04, 2017, 01:44:01 am
content: Anyone using the new FT8 mode on HF? It's a lot faster than JT65 / JT9. It uses 15 second TX/RX intervals. It's also an automated QSO. It seems to have taken the bands by storm ...

author: denverpilot
author_rank: Regular Contributor
timestamp: September 04, 2017, 07:35:33 am
content: Had heard of it but not tried it out yet. JT65 was always extremely slow because it needed to be to achieve performance in an incredibly low SNR.I assume... just because of the usual "tradeoffs" of how these modes work, that FT8 can't quite go that far into a weak single if it's operating faster?Will have to add it to the reading list... and download software for it and try it out on-air.I always found for "fast easy copy" type DX work, the vast majority of foreign and domestic stations were operating PSK31.JT65 and other variants of WSJT were what was used for insanely weak signal work with skeds, and I didn't find myself trolling around looking for that sort of signal much. It was the go-to tool for a skeduled contact that I knew shouldn't really be possible but it might be able to successfully copy well down into the noise floor.Fun stuff. Will check this out.

author: OldDogSleeping
author_rank: Contributor
timestamp: September 04, 2017, 04:07:59 pm
content: yes, been using FT8, but I think I prefer JT65.my license ( UK Foundation) limits me to 10W, and when trying to work DX I find it a fair bit easier with JT65. FT8 works for me when it's quiet, but when it gets busier, I get very few contacts.