hybridfree/eevblog-posts huggingface dataset:
[UK] hamfest followed by TNMoC? - Page 1
Forum section: electronics / rf-microwave

author: tggzzz
author_rank: Super Contributor
timestamp: April 29, 2018, 07:59:44 am
content: Why not go to the large and good Dunstable Downs hamfest in the morning of17th20th May, and then TNMoC (or Bletchley Park if you insist) in the afternoon? I will.The National Museum of Computing is one of the few museums where the attendants really know about the exhibits, e.g. they are more than happy to whip out the circuit diagrams and discuss them with you. *Highly* recommended!You can also see he world's oldest operating computer (WITCH), Colussus, and horrify yourself that your treasured childhood possessions are now museum pieceshttp://www.ddrcbootsale.org/http://www.tnmoc.org/

author: KJDS
author_rank: Super Contributor
timestamp: April 29, 2018, 11:10:28 am
content: I'll be selling off the last few bits and pieces I have left to hopefully finally clear out my house at the DDRC boot sale.

author: philpem
author_rank: Frequent Contributor
timestamp: April 30, 2018, 06:32:55 am
content: The DDRC website suggests it's on the 20th of May:http://www.dunstabledownsradioclub.org/(which makes sense - 17th is Thursday, 20th is a Sunday)It's in Luton, at Stockwood Park

author: tggzzz
author_rank: Super Contributor
timestamp: April 30, 2018, 06:42:30 am
content: Quote from: philpem on April 30, 2018, 06:32:55 amChanged.Iknew what I meant.

author: SNGLinks
author_rank: Regular Contributor
timestamp: May 02, 2018, 09:45:39 pm
content: I'll be there at the British Amateur TV Club stand.

author: High_vacuum_house
author_rank: Newbie
timestamp: May 02, 2018, 09:58:54 pm
content: I will be going as well. I will be the one heaving the heaviest and probably the most useless bit of test equipment I could find especially if it has lots of valves inChristopher Capener

author: tggzzz
author_rank: Super Contributor
timestamp: May 04, 2018, 03:54:04 pm
content: For those that might be wavering, consider this Gary Larson cartoon:

author: KJDS
author_rank: Super Contributor
timestamp: May 19, 2018, 02:33:06 pm
content: I've found a red hat to make it easier for those that don't know me to find me.

author: tggzzz
author_rank: Super Contributor
timestamp: May 19, 2018, 04:45:40 pm
content: Quote from: High_vacuum_house on May 02, 2018, 09:58:54 pmIt is a long walk across grass to the cars; take a trolley for heavy items
Difference between tekbox TBWA vs TBDA models - Page 1
Forum section: electronics / rf-microwave

author: julianhigginson
author_rank: Frequent Contributor
timestamp: May 16, 2018, 11:37:56 am
content: So, I was looking at these tekbox RF amps.they sell a range of them nowdayshttps://emcsupplies.com/collections/rf-amplifiersone pair, with either 20dB gain, or 40dB gain are called the TBWA (Wideband AMP) serieshttps://www.tekbox.com/product/TBWA2_Manual.pdfthe other pair with 12 dB gain, 24dB gain are called the TBDA (Driving Amp) series...https://www.tekbox.com/product/TBDA1_Manual.pdfthe thing is though, there only seems to be 1-2 dB difference in the output level...TBWA goes to +20dBm for 1dB compression point, and TBDA goes to 21 or 22dBm depending on frequency..In this case - what's the point of the TBDA models? yes they are called driving amps, but if they don't drive noticeably higher than the normal wideband amps, what do they actually do? it seems to me that you can do almost the everything the same with the TBDA, but they have nicer gain amounts.It's possible I'm missing something here, in which case I'd love to know what.

author: julianhigginson
author_rank: Frequent Contributor
timestamp: May 17, 2018, 11:58:10 am
content: I'm still wondering what the difference is meant to be here (other than the obvious gain and bandwidth specs) And would really appreciate it if someone would like to help explain?It seems to me that if you have one amp that will get to +20dBm output at it's 1dB compression point and another amp that will get to +22dBm at its 1dB compression point, there's really not that much difference in terms of what each of them could drive.Or is there something else that I'm not seeing with these "Driving Amp" models?

author: CopperCone
author_rank: Super Contributor
timestamp: May 18, 2018, 02:38:00 am
content: Not sure but old hp microwave power/signal amplifiers had this peculiarity. I looked at the specs and I was surprised to see it was only a few dB difference.Something you missed: 3 vs 6 GHzbut the driver one seems alot worse in general? also a bit cheaper. Would love some one with experience to do a detailed analysis.

author: julianhigginson
author_rank: Frequent Contributor
timestamp: May 18, 2018, 05:51:59 am
content: Yeah I saw the bandwidth, but it's the relatively tiny output level difference for 1db compression that is the bit I really don't get.But yes, the bandwidth makes the DA models even less relevant.
Stolen SDRplay RSP1As on eBay - Page 1
Forum section: electronics / rf-microwave

author: tsman
author_rank: Frequent Contributor
timestamp: May 16, 2018, 03:03:13 am
content: Careful about buying SDRplay RSPs on eBay.Somebody stole a batch of units and some of them have been put up on eBay. The serial numbers have been blacklisted.

author: xaxaxa
author_rank: Regular Contributor
timestamp: May 16, 2018, 03:40:50 am
content: I don't think they are doing themselves a favor by blacklisting these devices in software and punishing the users who happened to have bought these devices; does this sound familiar to anyone?

author: Wirehead
author_rank: Regular Contributor
timestamp: May 16, 2018, 07:20:55 am
content: Quote from: xaxaxa on May 16, 2018, 03:40:50 am*cough* FTDI *cough*

author: CJay
author_rank: Super Contributor
timestamp: May 16, 2018, 08:04:10 am
content: Quote from: xaxaxa on May 16, 2018, 03:40:50 amThis is hardly the same thing though, for starters it's only a few devices and users who might have bought one unwittingly have bought stolen goods, actual, physical stolen goods which don't belong to them and could well be siezed by law enforcement. If those users become aware that they have a stolen device and don't hand it back then they are committing an offence too.The clone serial chips I think you're referring to weren't actual, physical clones, they were/are completely different silicon programmed to be protocol compatible which is not illegal, the use of the trademark, USB VID/PID and, enabled by the VID/PID, the drivers is where it gets dodgy.To legitimise the clone parts 'all' that need be done is to assign a new VIP/PID and write some drivers (I appreciate that's a big 'only' but even so), there is no way to legitimise those stolen radios without paying the company they were stolen from.

author: julianhigginson
author_rank: Frequent Contributor
timestamp: May 16, 2018, 11:40:02 am
content: physically stolen units are way different to bootlegged/copy parts!if I was buying one of these, I'd want to be sure it wasn't stolen, as already described by CJay. So some people might get burned - they are getting burned by whoever sold them the stolen gear, knowing full well the serial numbers are known, and now blocked..
Videos: How to measure complex impedance with the MFJ-259B Antenna Analyzer... - Page 1
Forum section: electronics / rf-microwave

author: w2aew
author_rank: Super Contributor
timestamp: May 14, 2018, 01:22:54 am
content: ...or any other analyzer that gives you the R and X components, but doesn't tell you the sign of the reactive component.Smith Chart to the rescue!Presented in two parts (less than 5 minutes each):
avoiding interference in the CC1101 reception - Page 1
Forum section: electronics / rf-microwave

author: natiya
author_rank: Newbie
timestamp: May 24, 2018, 11:48:17 am
content: I'm trying to get signals in the 433MHz band (specifically, at 433.8MHz), but I keep capturing interference, which makes the reception of the wanted signal very slow and incomplete (therefore, incorrect).I set up an RX filter of 200KHz, and the following values for the registers:AGCCTRL2=0x03 to 0x07AGCCTRL1=0x00AGCCTRL0= 0x91 to 0x93I also configured the IF values shown here:http://www.ti.com/lit/an/swra215e/swra215e.pdfIn addition, I tried to set up some thresholds to make sure I capture the signal when its RSSI is inside a valid range, but the interference is still there. I don't mind if the interference is recorded, the problem is the effect when it's transmitted at the same time as the wanted signal because the receiver can't deal with itany hint please? thank you!
Rohde Schwarz HE302 Active Antenna Info - Page 1
Forum section: electronics / rf-microwave

author: eb4eqa
author_rank: Regular Contributor
timestamp: May 21, 2018, 07:58:05 pm
content: Hi all,I have the main body of a HE302 active dipole antenna. It has a few parts missing, most importantly both arms of the dipole. By the pictures on the internet I can guess the rough dimensions but I fear it has coils on the arms too, they don't look just simple elements. I have enough info to bias it (18 V to 30 V DC (170 mA (typ.)) but I do need more info about the elements.I have found the datasheet and the references to it from the antennas catalog.Please, if you have any more information on this antenna, I am very interested.Thank you,Roberto EB4EQAhttp://www.rbarrios.com
Where to shop for ham radio stuff? - Page 1
Forum section: electronics / rf-microwave

author: hammy
author_rank: Unknown
timestamp: May 04, 2018, 03:04:07 pm
content: Hello radio hamsWhich online shops do you visit for amateur radio stuff, particularly antennas?I'm looking for a selling platform outside EU and want to ask about your preferences.Any ideas are appreciatedhammy

author: Lord of nothing
author_rank: Super Contributor
timestamp: May 04, 2018, 05:19:08 pm
content: If you would say where you are from maybe someone could give you an hint.I would say Ebay but it realy depend how much Tax and other things you pay.

author: hammy
author_rank: Unknown
timestamp: May 04, 2018, 11:07:08 pm
content: I don't think eBay and Amazon are the only ones left.

author: Ghislain
author_rank: Regular Contributor
timestamp: May 10, 2018, 10:22:02 am
content: Quote from: hammy on May 04, 2018, 03:04:07 pmWhat kind of antennas are looking for (SHF/VHF/UHF/HF)?I bought my HF 6 band Yagi from Optibeam in Germany, Tom is shipping his antennas world wide and will be more than happy to helphttp://optibeam.de/

author: stj
author_rank: Super Contributor
timestamp: May 10, 2018, 08:51:10 pm
content: 409shophttp://www.409shop.com/

author: Bud
author_rank: Super Contributor
timestamp: May 10, 2018, 10:13:00 pm
content: Dxengineering.comHamradio.comAlphadeltacom.com
Accuracy of 774 ABC Melbourne frequency? - Page 1
Forum section: electronics / rf-microwave

author: Circlotron
author_rank: Super Contributor
timestamp: May 12, 2018, 11:26:11 am
content: Trying to zero beat the function generator by ear to the above station. Fades to a minimum every 1 minute 8 seconds with f/g set to 773,999.832 Hz. That set frequency is about 0.2ppm difference from the nominal 774KHz. How accurate might that particular station have it's carrier frequency set to?

author: dave_k
author_rank: Frequent Contributor
timestamp: May 12, 2018, 11:48:41 am
content: Broadcasting Services (Technical Planning) Guidelines 2007, Appendix 1"Unless otherwise specified, the frequency of the carrier shall be maintained within ±10 Hz."Seems as though they are well within spec...

author: German_EE
author_rank: Super Contributor
timestamp: May 13, 2018, 08:12:16 am
content: 10 Hz, try harder, I can measure down to 0.1 millihertz at home.
Amplifying a VHF Square Wave - Page 1
Forum section: electronics / rf-microwave

author: jgalak
author_rank: Regular Contributor
timestamp: May 01, 2018, 11:06:35 pm
content: A discussion on another thread got me thinking. I am building an APRS tracker using a clock chip as my rf source and modulator. The output is an FM modulated square wave at 144 MHz and 3.3v (biased to 0-2.5V). Obviously it will be low pass filtered veloce going to the antenna to kill the odd harmoics. But it needs to be amplified - I'd like around 250-500mW, ideally,My original plan was to use an off the shelf MMIC IC, but some comments on the other thread mentioned Class E amplifiers and amplifying the square wave itself. I started reading about them (can't say I understand most of it yet), and it looks like a lot of the work and components needed for a Class E are specifically for dealing with the harmoincs. It's almost like they are taking the input sine wave, turning it square, and then back to sine. Which got me wondering:Is there a good way to just amplify the square wave to begin with? Seems like it should be easier and more efficient than amplifying a sine. Maybe a push-pull with no worry about crossover distortion? Obviously low pass filtered afterwards.I've thought about using a logic level shifter, but the ones that go to 144MHz seem to be limited to 5V, which is a bit lower than I'd like.Thoughts? Are there standard ways to amplify a square wave?

author: rf-fil
author_rank: Regular Contributor
timestamp: May 02, 2018, 02:15:47 am
content: A well designed class C will usually give you something like 60% to 70% efficiency. With Class E, you can get up to 90+%. But, at your power level, the actual improvement, in absolute terms, is probably not worth it. Unless it's a learning exercise. You'd be reducing the heat dissipation by something like 100mW.Class E amps have less gain compared to a class C amp with the same device. They are harder to design. And they need a good match at the output - so they are only suited to situations where the load impedance is well controlled. This might not the case for a mobile APRS tracker.Btw, RF Power Amplifiers for Wireless Communications by Steve Cripps is one good book to learn about RF PA design.

author: jgalak
author_rank: Regular Contributor
timestamp: May 02, 2018, 06:48:42 am
content: I'm wondering if a real amplifier topology is overkill altogether. It's a signal that moves between 3.3v and 0v. Can I amplify with a single transistor (bjt or fet) acting as a switch? No need for linearity, it's on or its off. Only needs to switch about 10V. Just need one that's fast enough to handle 144MHz.Wpuld that work?
Reading raw WiFi beacon frames - Page 1
Forum section: electronics / rf-microwave

author: m3g4by73
author_rank: Contributor
timestamp: April 30, 2018, 11:33:09 am
content: Hi guys, I'm using WiFi fingerprinting on an IoT tracking project and I'd like to reduce the power usage.Currently my project uses an ESP8266 to:1. Scan for local WiFi networks and read the BSSIDs.2. Transmit the BSSIDs to my cloud server using LoRaWAN, Sigfox or NB-IoT.3. My server queries Google's Geolocation API with the BSSIDs to obtain the location of the sensor.I don't use GPS is because there is no signal where my tracker spends the majority of its life.Unfortunately the ESP8266:-is an absolute power hog,-takes a while to start up,-drains large current spikes on boot to calibrate its Rf circuits.I feel the ESP8266 is way too complicated for sniffing a few frames and I was wondering if there's a way to use a 2.4GHz Rx-Only IC to read the raw WiFi data and then I could just decode the beacon frames. If so, can anyone recommend a chip that would be suitable or other plan of attack?

author: llkiwi2006
author_rank: Regular Contributor
timestamp: April 30, 2018, 11:59:41 am
content: Unfortunately wifi uses quite a large bandwidth and quite complex modulation schemes, so you are pretty much stuck with ICs designed for wifi. From what I could find online, I don't really see any wifi modules that uses much less power than esp8266.Keep in mind you will want to capture for at least a few seconds at a time (maybe even more), since beacons are sent only (by default) every 100ms, and you need to hop between the 13 channels. You should measure how much power is spent powering up vs during the capture to decide if it's actually a problem.

author: tmbinc
author_rank: Frequent Contributor
timestamp: April 30, 2018, 08:39:57 pm
content: The interesting thing though is that Beacon frames will always be modulated with the lowest supported modulation scheme (MCS-0 I think?). But the bandwidth is still 20 MHz, so there's most likely not a great reduction of power required (as opposed to demod complexity, but that's just logic).Active probing is slightly faster since you don't need to wait for the default 100ms per channel.
where can I get a 145MHz helical filter these days? - Page 1
Forum section: electronics / rf-microwave

author: bd139
author_rank: Super Contributor
timestamp: April 08, 2018, 10:40:22 pm
content: Attempting desperately to revive a project I've been working on for a few years, which is a simple 100MHz SA for use on HF. Nothing exciting - just enough to see 2nd/3rd harmonics, IMD, carrier suppression etc. The 1st IF is 145MHz. I was planning on grabbing a canned Toko 145MHz helical filter for this but as usual, they completely disappeared off the market immediately when I worked on that part of it. I spent today respinning the log amp and video filter from an NE604 RSSI (which I blew up) to an AD8307 based on a power meter design I already threw together. This is working nicely.Options are to build my own helical filter or buy one. Preferably the latter. Does anyone know any sources for these? If not, any design information on how to build one worst case. I don't have a swept generator other than the first mixer on this thing, an NE602 so aligning it is going to be a dick if I build one. Was hoping to avoid thatHopefully if I can solve this I can throw a 2nd IF together (12MHz) and actually finish the damn thing.

author: eliocor
author_rank: Unknown
timestamp: April 09, 2018, 12:44:34 am
content: Maybe this can help:https://www.rf-microwave.com/en/tunable-helical-band-pass-filters/418/

author: phenol
author_rank: Regular Contributor
timestamp: April 09, 2018, 06:34:48 am
content: Temwell-Taiwan. They have toko replacement parts and their own models.

author: bd139
author_rank: Super Contributor
timestamp: April 09, 2018, 07:53:19 am
content: Quote from: eliocor on April 09, 2018, 12:44:34 amAhha perfect! Reasonable prices too. Thank you for this. They do ones which bottom end is 144 which is a bit tight but I can push the 1st IF to 170 which will do the job. Will change 2nd LO to 160 (multiplied up from 20Mhz) and then use cheap crystals for the 2nd IF filters.

author: GerryBags
author_rank: Frequent Contributor
timestamp: April 26, 2018, 10:17:37 pm
content: I found a couple of domestic options, I think:https://www.ebid.net/uk/for-sale/telonic-tubular-tba-140-17-4ab1-140mhz-centre-freq-rf-bandpass-filter-bncs-150054037.htm"TBA 140-17-4AB1 140MHz centre freq 131.5-148.5 MHz 3dB Bandpass 4 section 50 OhmBNC male to female"I'm not sure if you're familiar withwww.radwell.co.ukbut they can be useful for parts, particularly obsolete stuff. You really need to enter p/n's to find much, though. I managed to get a replacement tek P6137 probe tip from them, had no luck finding any others in the UK.

author: Karlo_Moharic
author_rank: Regular Contributor
timestamp: April 27, 2018, 09:05:46 pm
content: This guy made one, and it doesn't seem like a hard project, so

author: bd139
author_rank: Super Contributor
timestamp: April 27, 2018, 11:11:57 pm
content: I can’t be bothered with thatQuote from: GerryBags on April 26, 2018, 10:17:37 pmThanks for the link. Appreciated. Will find some specs. That might do the job.
Looking for a UK/USA  supplier of RF VHF/UHF baluns, torroids, ferrites - Page 1
Forum section: electronics / rf-microwave

author: dazz1
author_rank: Frequent Contributor
timestamp: April 27, 2018, 11:05:03 am
content: HiI want to make/buy some Rx antenna baluns. There are no suppliers of suitable rf baluns/ferrites in my country.I found this site in Italy:https://www.rf-microwave.comthat has what I want but the shipping cost is horrendous.I am looking for a UK/USA supplier of RF components. I have a freight forwarder in those two countries that provide sane shipping costs.Dazz

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 27, 2018, 11:14:54 am
content: http://www.amidoncorp.com/is expensive but the old go-to. They have powder cores and rods, as well as everything else.More conventional parts (ferrites and EMI, transformer cores, but not usually powder cores) are available and cheaper at the usual distributors, like Digikey, Mouser, maybe Farnell or RS Idunno.Tim

author: dazz1
author_rank: Frequent Contributor
timestamp: April 27, 2018, 11:33:44 am
content: HiMurata and Toko make the parts I want but I can't find a seller.(Edit) Digikey seems to have a reasonable range so I will look closer there.Dazz
Converting magnitude ratio to complex form - Page 1
Forum section: electronics / rf-microwave

author: chamathkv
author_rank: Newbie
timestamp: April 10, 2018, 05:43:57 pm
content: Greetings,I recently acquired an AD8302 modulehttp://www.analog.com/media/en/technical-documentation/evaluation-documentation/AD8302.pdfwhich reads to signals and provides an analog reading showing the magnitude ratio. I want to convert this to complex form in order to create a touchstone file (.s1p)http://na.support.keysight.com/plts/help/WebHelp/FilePrint/SnP_File_Format.htm. What is the formula to convert a magnitude ratio (dB) to complex form? (x + iy)

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: April 10, 2018, 07:32:08 pm
content: Magnitude is just that - magnitude. Without any information of phase, you cannot turn this into a real-imaginary format.

author: hagster
author_rank: Frequent Contributor
timestamp: April 10, 2018, 08:45:37 pm
content: Thats an interesting chip. It measures both magnitude ratio and phase difference.I do note that the pgase measurement has a 180degree ambiguity. Not sure if there is an easy way to resolve that.I dont see the problem in taking those and writing to it a touchstone file.

author: chamathkv
author_rank: Newbie
timestamp: April 11, 2018, 05:54:59 am
content: Sorry, I forgot to mention that the phase is also provided.

author: hagster
author_rank: Frequent Contributor
timestamp: April 11, 2018, 06:45:23 am
content: You only need to convert the polar notation to cartesian. Google will help you.Or touchstone files can have log amplitude phase data.

author: kerrsmith
author_rank: Regular Contributor
timestamp: April 15, 2018, 10:05:58 pm
content: I have been using this chip (AD8302) myself for the last week or so and have also been hunting for this kind of information. The most useful site I have found so far is the 'HF Arduino Vna' one:https://hamprojects.wordpress.com/2016/02/21/hf-arduino-vna-english-version/This site explains a lot about creating your own VNA but as far as equations go their Github page is really good:https://github.com/f4goh/VnArduinoTake a look at the file 'VnArduino.ino' starting at line 549, just after this point there is a list of all the equations needed to calculate things such as reflection coefficient, return loss, SWR and the real and imaginary parts of the impedance.

author: Bud
author_rank: Super Contributor
timestamp: April 16, 2018, 06:49:57 pm
content: Quote from: chamathkv on April 11, 2018, 05:54:59 amYou can make a Touchstone file directly using mag(db) and phase, just make a right header for it, search for more information on Touchstone file format.

author: kerrsmith
author_rank: Regular Contributor
timestamp: May 07, 2018, 01:54:17 pm
content: I have been working with the AD8302 for a while now and have created a handy equations sheet to help me remember what I did to work out how the various calculations are derived.This sheet shows how return loss, reflection coefficient, SWR, complex load impedance and mismatch loss are calculated using data from the AD8302.I have attached the PDF to this post as a reference in case anyone else is interested in this.
Lets build a spirit radio  - Page 1
Forum section: electronics / rf-microwave

author: Sebzy
author_rank: Contributor
timestamp: April 25, 2018, 10:07:42 pm
content: I've been inspired by the works of Nikola Tesla and mrfixitrick over on indestructibleshttp://www.instructables.com/id/Spooky-Tesla-Spirit-Radio/and have set myself the goal of constructing a large Spirit Radio for this years Maker Fair here in Dublin to teach people about vintage radio. Well I think I'm going to need some help in scaling this thing up.Sure it's not as simple as bigger aerial and capacitorWell off to read some patentshttps://patents.google.com/patent/US649621

author: Sebzy
author_rank: Contributor
timestamp: April 25, 2018, 10:11:53 pm
content: Eyeing up this old junker (1958 Philips Bi-Ampli) for parts...https://imgur.com/a/79lLqiq
RF source for product testing/verification tool - Page 1
Forum section: electronics / rf-microwave

author: MatjazB
author_rank: Newbie
timestamp: April 23, 2018, 07:06:06 am
content: Hello all,I'm developing some products in ISM band (868 MHz). The part of the development is also testing the products (reception parameters, transmission parameters). Currently they are done using a classical spectrum analyzer (for Tx parameters). Reception parameters are done with our custom tools.But I want to throw our custom tools out of the system.Therefore I would need a RF generator.Typically I'm measuring:reception bandwidth (changing frequency with fixed amplitude)sensitivity level (estimation)packet handling (transmitting different test packets)burst testing (transmitting large amount of data - multiple telegrams transmitted successively)I have few hard requirements - it must be programmable (via USB/LAN), and amplitude must be stable.I'm quite sure, that SDR is a way to go, but I'm worried about amplitude stability.I can not find any (good?) information about SDR (Ettus USRP for example) amplitude stability.I do not needextremeamplitude stability - for my cases it is enough that amplitude does not change for more than +/- 0.5 dBm. Actual amplitude value is not as much important to me, as stability over time.How do SDRs preform? Any experience? Which device would you suggest?Or do you think using a "real" RF generator (something from big players) is a better way to go?Currently I'm looking at LimeSDR mini, and it seems to have everything I would like to have. But - I can not find any data about amplitude stability.What do you think? What are your experiences?

author: Ice-Tea
author_rank: Super Contributor
timestamp: April 23, 2018, 08:27:31 am
content: Would a R&S CMU200 or CRTU-RU do?
Characterizing a discrete MOSFET for RF front-end LNA design - Page 1
Forum section: electronics / rf-microwave

author: beeboopbeep
author_rank: Contributor
timestamp: April 26, 2018, 01:19:07 am
content: Hello,I wanted to get into LNA design for somewhat low-band frequencies (less than ~200 MHz) using simple off the shelf and hobby designed PCBs. However, my background for LNA design is limited to IC design using Cadence and I wanted to find out how I can characterize a discrete MOSFET that can be purchased off the shelf in order to design an LNA using the characterized model on software like ADS. I'm assuming the characterized MOSFET will be in a file providing s-parameters or something similar so that it can directly be placed as a modeled component in something like ADS.I have access to some of the more expensive lab equipment like network analyzers and such which I plan to learn over the summer and I thought this project may be a great way to learn how to use the equipment.

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 26, 2018, 02:01:07 am
content: S21 plot?

author: CFLBob
author_rank: Newbie
timestamp: April 26, 2018, 02:59:56 pm
content: If you're trying to design for noise figure, I think what you're looking for is a NF meter or analyzer. The old HP 8970 or a newer model like the 8973 (now Keysight or Agilent, of course) If you have access to test equipment for HF/VHF my guess is you probably don't have one.It has been a while since I did this, but I think ADS had linear and nonlinear modeling. Linear was like an S-parameter file with a NF column, and nonlinear was something more like a SPICE model.Small signal FETs are usually characterized for NF, or at least they give yousomeinformation.

author: rfeecs
author_rank: Frequent Contributor
timestamp: April 26, 2018, 04:38:03 pm
content: Look up "noise parameters" or "gamma opt". Here's an example:https://www.microwaves101.com/encyclopedias/noise-parameter-extraction-using-source-pullIt requires a quite expensive specialized setup. Not worth it for 200 MHz.You might just try using the manufacturer provided SPICE model for simulation. It might get you in the ball park and close enough to tune on the bench.

author: KJDS
author_rank: Super Contributor
timestamp: April 26, 2018, 07:44:19 pm
content: Most FETs designed for low noise use have S-parameters and Noise parameters available.You'll need both, if you just match to 50 ohms from the S-parameters the noise figure will be terrible.
LMR400 vs DX Engineering 400Max for 2M and 70cm - Page 1
Forum section: electronics / rf-microwave

author: jgalak
author_rank: Regular Contributor
timestamp: April 22, 2018, 09:18:03 pm
content: Anyone have thoughts on these two cables? I need to do a run of, at most, 60'. Mostly for sattelite and FM work, maybe some weak signal eventually. LMR600 seems overkill for this.Outdoors, so needs to stand up to weather and sun.

author: Howardlong
author_rank: Super Contributor
timestamp: April 22, 2018, 09:49:51 pm
content: Quote from: jgalak on April 22, 2018, 09:18:03 pmLMR400 seems perfectly reasonable.I ran a pair of 180’ of Westflex 103 (roughly equivalent to Belden 9913 in performance terms) for my rooftop satellite setup, this was back in the days of HEOs like AO-10 and AO-40. I did have pretty decent preamps and polarisation switchers at the feedpoints of the antennas, which included 2m, 70cm, 13cm and 23cm, plus a multiband vertical for HF. This was on an Az/El rotator at the top of a seven storey building: I had about 20’ of more flexible RG213 from the preamps/antennas to a weatherproof box holding ~100W HPAs for 70cm and 23cm plus duplexers.This was very successful, but being in a city location it suffered a lot of local noise particularly closer to the horizon.For today’s LEOs, you don’t need much power, but you do need a decent receive setup. Having decent feedpoint mounted preamps addresses the receive side.
Small wideband recieve active loop antenna/h field probe performance vs large?  - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: April 17, 2018, 02:01:52 pm
content: So i have a loop antenna i made that has a 1 meter diameter loop and a built in matched transistor differential amplifier type circuit at the base, along with an off switch relay, powered by phantom power.Its rather large. Looks like a hoola hoop.For active loop antennas, how would its performance look like if i made it say 1/3 the size, so that it could be portable?The design i made is supposedly good for low khz to 30MHz.What can i expect from this smaller loop? From cursory research i am lead to believe the results will be suprizing and not what i expect (shift in bw 3db points on both ends being uniform)I basically built this with a matched transistorhttp://www.pa1m.nl/pa1m/wp-content/uploads/2012/09/Loop-schematic.gifShort; what is the effect of keeping the preamp the same but changing coil diameter from 1 meter to one foot
Testing an antenna change over relay question - Page 1
Forum section: electronics / rf-microwave

author: Chris Wilson
author_rank: Super Contributor
timestamp: April 16, 2018, 01:19:57 pm
content: After an expensive accident whereby my home brew antenna change overrelay put nearly a kW of RF up the RX antenna jack of my KenwoodTS-590 i want to safely long term test the relay. It may have been mylack of foresight in using two identical N type sockets for the ampinput and the antenna on the relay box and they got reversed...Therelay is Russian:http://qro-parts.com/product_info.php?products_id=102It needs 24V to reliably change, that is sourced from 12V via a DC toDC converter that is energised via a safely long delay from my U3Sexciter so TX is delayed 100mS It's connected like this:The output of my 1 kW amplifier to NO connection and receiver to NCconnection of the same relay, with COM port to antenna), thende-energized I'd always be in RX mode and energized I'd be in TX modeand there's no way the TX should ever be connected to the RX nomatter what failed. (Theoretically! I am not sure what reversing theamp and antenna connections may have caused, but I am concerned someother issue caused the RF to appear on the RX port....) I don't thinkthe pre LPF voltages from the amp would be too high for this relay,but can't be 1005 sure of this given what occurred. In any casethere's also a 40 Amp 24V automotive "safety relay" that grounds the RX output jackwhen in TX mode. The failure of this to protect the TS-590 furthersuggests I might have had the antenna and amplifier connectorsreversed, although it all worked fine until the early hours when theWSPR spots ceased and I found the bad news.Anyway, I need a "something" to put across the RX antenna output BNCsocket that wil blow or somehow tell tale if RF is injected there. Idon't have a high power enough dummy load other than a huge watercooled 10kW Bird one which means flowing mains water through it to anoutside gutter overnight or longer. My none water cooled one won'ttake high power for long at all. If a FET blows in the amp I canswallow that, rather than my current Red Pitaya receiver getting RF upitSo what could I put across the jack instead of a receiver thatwill tell tale anything nasty happening during a prolonged testplease? Thanks.

author: dmills
author_rank: Super Contributor
timestamp: April 16, 2018, 03:13:13 pm
content: 50 ohm low power resistor wrapped in a bit of fireproof material, you will be able to tell if it gets a kW up it, and if the amp has decent protection it should survive the reflected power when the resistor explodes.Sticky relays are a thing, and there is something to be said for running some DC thru the contacts (choke on each side) and using that to gate the amplifier keying (So the amplifier cannot be keyed unless the relay contacts have really changed over).On the RX side, you are usually going to be sky noise limited anyway (on HF) so a modest pad (3dB or so) helps robustness quite nicely (But will not make the RX survive a kW), sensitivity is seldom a limiting factor on a modern HF set!Regards, Dan.
Hacked DPMR (like TYT MD-390)? - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: April 07, 2018, 09:54:59 am
content: HiI search for hours but could not find anything.Is there an Hacked dpmr (FTMA) who allow to hear anything who is unencrypted?THX

author: usagi
author_rank: Frequent Contributor
timestamp: April 09, 2018, 11:50:52 pm
content: you want something like "open squelch" DMR mode. anytone AT-D868UV explicitly supports it with the standard firmware.

author: Lord of nothing
author_rank: Super Contributor
timestamp: April 10, 2018, 06:56:14 am
content: Which Audio Codeq does the use?

author: usagi
author_rank: Frequent Contributor
timestamp: April 12, 2018, 10:19:33 am
content: DMR uses AMBE+2. better audio quality than d-star.

author: Lord of nothing
author_rank: Super Contributor
timestamp: April 12, 2018, 10:39:52 am
content: The Problem with the different PMR446 dPMR Device is the are not compatible with each other.
VHF/UHF antenna using THREADED ROD - Page 1
Forum section: electronics / rf-microwave

author: tkamiya
author_rank: Super Contributor
timestamp: April 10, 2018, 03:07:12 pm
content: On sleepless night, I was thinking about antennas for a weather satellite reception. Then this question come to my mind. It also has to do with me seeing large quantity of threaded brass rod, about 3mm in diameter available at a local store.Say there is a round brass rod.Say there is a round brass rod that is threaded.Are there any electrical difference between the two?As this is RF, skin effect is "in effect". If I think longitudinally, a threaded rod has about a double surface distance to travel (going up and down the thread) when compared to a simple rod. How does this work in terms of wave length? Is the size the object (rods) occupy in space more important or the how materials present electrically at micro level?I know I can go zig-zag on a dipole and reduce the length but this is at a macro level.Does anyone have a theory or a practical experience?My usual mode of research is to think throughly first, then try it out.

author: CopperCone
author_rank: Super Contributor
timestamp: April 10, 2018, 04:05:59 pm
content: The cut finish of the threaded rod will also make it have a much rougher surface texture then the normal rod.Probobly frequency range you listed is too low for the surface roughness to matter
What is the benefit of the 273 MHz - 328,6 MHz Band?! - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: April 03, 2018, 12:58:34 pm
content: HiHere in Austria the freq. 273 MHz - 328,6 MHz is for (FSB-LS013) Commercial Radio (+ non Civil.I never saw quite no Radio who is for that Freq Range and specially no Digital one.So what is the Benefit of that freq Range? Who would use it for?If I would get some Business Radio why would I choose that Freq range?!Thanks!
Swan Mark II dual 3-500z amp question  - Page 1
Forum section: electronics / rf-microwave

author: cncjerry
author_rank: Unknown
timestamp: April 18, 2018, 09:20:12 pm
content: I have the subject amp, replaced both of the 3-500Z tubes a while back with the ZG graphite after I popped one. I recently hooked it back up to my IC-7610 for the heck of it, don't know why as I hardly ever transmit except for rare DX.For some reason I need more capacitance on the load cap to tune the high-end of my loop. I was thinking of just adding some fixed capacitance right at variable cap. See any drawbacks? I guess I would need a high voltage cap, around 5KV?I could always just fix my antenna or use an external tuner, which I have, but get tired of tuning everything. I am only using a short piece of coax between the amp and a remote balun that then feeds the antenna with ladder line so I'm not overly concerned about SWR either if the amp tunes it.I also have an EL-80B bipolar amp I've been building for 15yrs, just need a power supply.So what would I need, maybe 100pf at 5KV?Thanks,Jerry
How to use the Balun?! - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: February 10, 2018, 03:06:35 pm
content: HiHow to use this:https://www.ebay.de/itm/NooElec-Balun-One-Nine-Tiny-Low-Cost-9-1-Balun-Long-Wire-HF-Antenna-RTL-SDR/151514474355?hash=item2346f76773:g:bI4AAOSwiCRUjbOO?!Nobody could give me an answer who was understandable.Thanks

author: madires
author_rank: Super Contributor
timestamp: February 10, 2018, 04:37:14 pm
content: I'm not sure, but a ratio of 9:1 and the long wire antenna would indicate a unun which is used for impedance matching a random long wire to a 50 Ohms antenna input. One of the wire terminals is for the long wire and the other one is ground (same as the SMA's ground, the antenna's ground isn't used usually). For a dipole you would need a 4:1 balun.

author: chris_leyson
author_rank: Super Contributor
timestamp: February 10, 2018, 04:58:52 pm
content: Looks like a Mini Circuits TC9-1 transformer, or similar.https://ww2.minicircuits.com/pdfs/TC9-1.pdf

author: Damianos
author_rank: Frequent Contributor
timestamp: February 11, 2018, 07:54:03 am
content: http://www.nooelec.com/store/downloads/dl/file/id/40/product/192/balun_one_nine_schematic.jpg... so, it depends on what you have to connect on it. As it is shown, it is configured for a symmetrical high impedance antenna (dipole). If you have to connect a monopole (like a random wire) a modification is needed: open the jumper R1 and connect the ground to one of the input terminals.

author: Lord of nothing
author_rank: Super Contributor
timestamp: February 11, 2018, 10:30:12 am
content: Its just inside the box who got shipped with because I never get run it.Now I want play around with <30mhz Stuff. I have just that thing with an Upconverter (who work with my CB Antena) and an LNA.

author: Lord of nothing
author_rank: Super Contributor
timestamp: April 01, 2018, 05:27:04 pm
content: now the weather get better and i could put and sdr temporary outside the house.For what are the 2 Clamp things are there and what should i put into them?!

author: medical-nerd
author_rank: Regular Contributor
timestamp: April 01, 2018, 07:11:21 pm
content: HiyaA review:http://www.radioforeveryone.com/p/review-balun-one-nine.htmlFrom this you can put a long wire into one of the clamps - or use 2 long wires .Cheers
Impedance matching for an RF circuit - Page 1
Forum section: electronics / rf-microwave

author: madhu.wesly01
author_rank: Regular Contributor
timestamp: March 30, 2018, 08:58:49 am
content: Can anyone please tell me what happen when we change the Shunt capacitance value shown in a dotted rectangle in provided image?Thanks in advance.

author: KJDS
author_rank: Super Contributor
timestamp: March 30, 2018, 10:29:39 am
content: Yes I can, but I won't.Instead, have a look for Randy Rhea's Yin and Yang of Smith chart matching. It's a straightforward exercise to put the equations into a spreadsheet then it will tell you everything you ever need to know about component values for RF matching.

author: ericj
author_rank: Newbie
timestamp: March 30, 2018, 04:12:04 pm
content: Absolutely the most useful response I've seen to a question of this type. I've used AE6TY's SimSmith for several years, but have never seen Randy Rhea's two-part article. Thanks.
Anritsu MS2721B Opinions Sort - Page 1
Forum section: electronics / rf-microwave

author: charliedelta
author_rank: Regular Contributor
timestamp: March 24, 2018, 08:47:42 am
content: Hi GroupAnyone have any negative opinions about the Anritsu MS2721B. I am considering purchasing a 7ghz unit with tracking generator. I like this unit because it has demod including SSB and EMC bandwidths and quasi peak as standard. I could blow the same money on a Rigol but would have to spend a lot on the options.Any comments good bad or ugly about this unit would be appreciated. I know its not longer supported and dealing with Anritsu can be like dealing with a secret society.

author: DaJMasta
author_rank: Super Contributor
timestamp: March 24, 2018, 04:34:45 pm
content: I've had one without a TG and it is a nice unit, but the sweep speed performance of a benchtop SA is way different from a handheld. I believe the cap is 10 sweeps per second on the MS2721B with current firmware, and I believe the default full span sweep time is something like 1.5 seconds. Compare this to a benchtop unit and there is no comparison... you can expect 2-3 times the maximum update rate and probably a quarter or less time per sweep in most cases. The buttons always respond (no missed inputs), but when the sweep time is long it can take extra time for the buttons respond.At one point I contacted Anritsu for a replacement part and they were actually quite friendly to work with, I was buying a replacement kickstand and the rep I spoke with called me back and said they found a used one lying around and sent it to me for free. They were also willing to sell software options for it, still, but I believe they were full launch price, so hardly worth it when buying secondhand and an option or two would be 50% of the total price.Great for making measurements, good low noise performance, smaller footprint and portable anywhere, but much slower overall to work with, as I think probably goes with most handheld units. I found that most of my work was at the desk and was sort of scanning around for stuff, so I swapped over to a benchtop unit and enjoy having the extra update rate.

author: slurry
author_rank: Regular Contributor
timestamp: March 24, 2018, 08:53:31 pm
content: If the purpose is pre-compliance tests on the bench, you would be way better off with a cheap Siglent SSA3021,adding the option for EMC and i also suggest the software EMCview.For really narrow band checks and portable interference hunting, yes, the Anritsu would do the job quite well.

author: charliedelta
author_rank: Regular Contributor
timestamp: March 30, 2018, 05:18:37 am
content: Thanks all who replied. I will digest this information and consider my options.The Siglent looks like a good buy and i like the screen size.Thanks

author: metrologist
author_rank: Super Contributor
timestamp: March 30, 2018, 02:01:15 pm
content: These units are built and serviced in the US. Quality unit ruggedized for field use. I'd sure like a spec an with TG.
Cool minicircuits blocks - Page 1
Forum section: electronics / rf-microwave

author: daqq
author_rank: Super Contributor
timestamp: February 09, 2018, 01:22:42 pm
content: This looks practical:https://www.minicircuits.com/WebStore/x_mwblock.htmlSomewhat expensive I suppose, but great for experiments.

author: Gribo
author_rank: Frequent Contributor
timestamp: February 09, 2018, 02:14:55 pm
content: That is one great idea. I wonder, how do they connect these together? Do I have to solder edge mount connectors, or do I have to solder one module to the other?Edit: Nevermind, found it. That reminds me of an optics lab.

author: daqq
author_rank: Super Contributor
timestamp: February 09, 2018, 02:25:12 pm
content: QuoteSee:https://www.xmicrowave.com/x-mwsystem/why-mwsystem/I'm pretty sure that you could hack some kind of "good enough" interconnect though.

author: Gribo
author_rank: Frequent Contributor
timestamp: February 09, 2018, 04:16:02 pm
content: Those modules could have saved me so much time (and lost hair) doing past projects.

author: ericj
author_rank: Newbie
timestamp: February 11, 2018, 05:32:52 pm
content: Sparkfun BoBs meet metal Legos.https://www.xmicrowave.com/x-mwsystem/why-mwsystem/

author: 1design
author_rank: Regular Contributor
timestamp: February 11, 2018, 06:18:24 pm
content: To be honest, I don't see that many uses for this. The 67GHz screw connectors cost an absurd amount of money, so enthusiast are out of the equation. I would assume all the other components are not any cheaper. For what 95% of the industry needs, a simulation tool and good models do the trick for less and quicker. By the time you want to test performance, you want to test it on your board with your layout with manufacturing quotes and correct budgeting.BR

author: daqq
author_rank: Super Contributor
timestamp: February 11, 2018, 08:52:18 pm
content: They do actually offer SMA versions of the RF connectors. That said, I'm pretty sure you can just use the boards as individual modules.The other components (modules), well, they aren't particularly cheap, but they are on serious RF boards and such, with full parameters included. As to the pricing, see:https://www.xmicrowave.com/products/x-mwblocks/...also, I don't think that anyone who's dabbling in that areas of RF is expecting to come away with a full pocketDunno, I like this system. That said, I'm a total newb when it comes to this kind of RF magic - which is exactly what I find appealing about the modules - they take some of the nasty away.

author: eluther
author_rank: Newbie
timestamp: March 29, 2018, 03:08:38 pm
content: Here is how the interconnect works... board to board interconnect is less than $25. Good beyond 50 GHz, but works great at low frequencies too.
Smith chart spotted in Suicide Squad movie - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: March 20, 2018, 11:55:43 pm
content: given how she was in the movie, they should have displayed a middle finger on the smith chart.

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 21, 2018, 12:11:40 am
content: in galaxy far far away, you have to do frequency sweep to get to the rebel bass (Rogue One 1:41:52)

author: Tomorokoshi
author_rank: Super Contributor
timestamp: March 21, 2018, 02:39:20 am
content: Quote from: Mechatrommer on March 21, 2018, 12:11:40 amIf that display is a CRT, then it has a trap.

author: KD4PBS
author_rank: Contributor
timestamp: March 22, 2018, 08:55:57 pm
content: Quote from: Mechatrommer on March 21, 2018, 12:11:40 amBut the def beats be worth it.