hybridfree/eevblog-posts huggingface dataset:
4 axial mode helical antennas in array with common reflector - Page 1
Forum section: electronics / rf-microwave

author: jujun
author_rank: Regular Contributor
timestamp: September 08, 2018, 04:16:58 pm
content: Hello,I want to build an array of 4 axial mode helical antennas. Each antenna have an impedance near 140 ohm, how to match it to a 50 coax ?I feel that there is a very easy way to do it (parallel feed), but I cannot find documents about it, even in the ARRL books.Do you have more information about it ?Thank youJ

author: iMo
author_rank: Super Contributor
timestamp: September 08, 2018, 05:34:45 pm
content: https://slideplayer.com/slide/6987034/#

author: jujun
author_rank: Regular Contributor
timestamp: September 09, 2018, 07:25:57 am
content: Thank you, they seems to use a simple power splitter.I didnt explained well what I'am looking for. It's not really 4 distinct antennas, it's 4 helicals on one reflector.So I dont think it will change a lot of things, but because of the size of the construction in 2.3 Ghz, it would be better to have something embded at the back of the reflector.

author: iMo
author_rank: Super Contributor
timestamp: September 09, 2018, 07:52:53 pm
content: Here is a picture of a power splitter (mid of the page "Rear side of Quad antenna with power divider."http://www.nitehawk.com/rasmit/ras_pics.html

author: Howardlong
author_rank: Super Contributor
timestamp: September 09, 2018, 08:04:26 pm
content: The way I’ve done it in the last is to implement an integrated transformer on each antenna to match down to 50 ohms and then use a four way coaxial power splitter.http://www.g6lvb.com/quadruple_helix.htmYou don’t say what frequency you’re working at, or if it’s wideband. You could indeed match at the characteristic impedance if you can fabricate the right feed, keeping in mind how you’d achieve that in a physical environment (i.e., is it outdoors?).You could certianly transform the impedances up to 200 ohms in each fabricated feed, and then feed in parallel at a star point for example. Remember to keep mind the inherent losses of any method you use.
flush mating connector kinda like APC7 for cheap/lower frequencies between boxes - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: September 09, 2018, 01:46:20 am
content: Is there a type of connector, with similar performance to say BNC or up to say 500MHz, that operates on the same principle as APC7 where you can make a connector of precise length and insert it into a carefully spaced geometry? Like a tight spot between two panels. With a 50 ohm impedance. The APC 7 still has a thread that prevents you from making some kinda flush connection.I imagined it would have maybe a little ball spring loaded that would allow you to mate like a ratchet.I don't know if its mechanically possible to get good RF performance this way.I want to use it with copper hard line. (not the braided one)It does not need to screw on, it can be wedged/snapped in place.
Fun with gunnplexer's - Page 1
Forum section: electronics / rf-microwave

author: TheSteve
author_rank: Unknown
timestamp: September 04, 2018, 05:56:43 am
content: Picked up a pair of Macom Gunnplexer transceivers the other day.Today was the first power on to verify they are working.Next is to FM modulate the supply to transmit tones/audio.After that is is receiver time.Eventually the plan is to have a pair of limited range, very directional 24 GHz walkie talkies - just cause I can!I will update this thread with progress as I go.

author: babysitter
author_rank: Frequent Contributor
timestamp: September 04, 2018, 02:28:07 pm
content: Used simiilar ones together with people from my makerspace to do a model speed enforcement car. Complete with flashing LED in case you're over the threshold and external display. (Converted a pink VW Bus from Dickie to a black and white one, hehe...)

author: TheSteve
author_rank: Unknown
timestamp: September 08, 2018, 08:23:54 am
content: Finally had a chance to build a quick and dirty 5 volt regulator with a LM317. Audio is fed in to its adjust pin via a 0.1 uF capacitor. The output of the regulator is fed directly into the gunnplexer. With 4 mV of audio I am getting roughly 100 kHz of FM deviation @ 24.13 GHz. The audio demodulates quite nicely but there is a lot of frequency drift. When a receiver is built it will need to have a wide front end.
Bad spectrum analyzer setup or out of band emissions? - Page 1
Forum section: electronics / rf-microwave

author: ivan747
author_rank: Super Contributor
timestamp: September 06, 2018, 09:14:49 pm
content: Hi,I was measuring a WiFi signal with a spectrum analyzer and found that it stretches past its 20MHz bandwidth. I was wondering if this is the reality or if this is an artifact of the spectrum analyzer and the way I set it up. If I were to place a filter between the WiFi transmitter and the spectrum analyzer, should I see a reduction in the out of band signals?Best regards,Ivan

author: Ice-Tea
author_rank: Super Contributor
timestamp: September 06, 2018, 09:31:57 pm
content: They have to comply to certain masks. Doesn't mean they are not allowed to radiate anything beyond 20MHz, just that it has to be xxdB less.
telecom hardware Nokia Flexi comprehensive glossary that explain abbreviations - Page 1
Forum section: electronics / rf-microwave

author: zillah
author_rank: Contributor
timestamp: September 05, 2018, 08:14:53 pm
content: Dear folkSorry it might not be the right place to post this questionI am after a comprehensive glossary that explain abbreviations like :ABIS, FIE1, FIYB, FSME, FSMD,,,,,,,etcI already know what each hardware is used forThe one that I found is very limited in the link below :http://www.academia.edu/30905109/WCDMA_BTS_and_Module_OverviewThanks
Q. Vcc, Vee cd74hc4316 Switch IC - Page 1
Forum section: electronics / rf-microwave

author: vk4ffab
author_rank: Frequent Contributor
timestamp: September 04, 2018, 03:33:08 am
content: http://www.ti.com/lit/ds/symlink/cd74hc4316.pdfIf I am not using dual supplies, do i just tie Vee to Gnd? Max signal I will be sending through the switch would be about 1v p-p so i do not nee a 10v swing. The datasheet is not clear to me on this and I can find no use examples anywhere on the net.

author: RandallMcRee
author_rank: Frequent Contributor
timestamp: September 04, 2018, 05:09:11 am
content: Vee sets the lower voltage limit of the switch. A great feature. The datasheet tells us (page 1):the analog inputs/outputs can swing between VCC as a positive limitand VEE as a negative limit. Voltage ranges are shown inFigures 2 and 3So if you don't need negative voltages, tie to ground.

author: vk4ffab
author_rank: Frequent Contributor
timestamp: September 04, 2018, 06:28:51 am
content: Thanks, that is what I thought it was saying. It just was not clear to me
Want to make a 413 MHz receiver and transmitter for garage remote - Page 1
Forum section: electronics / rf-microwave

author: dw8000
author_rank: Contributor
timestamp: September 06, 2018, 08:22:53 pm
content: If I had a 418 MHz or 433 MHz trinary receiver and transmitter and I needed to transmit at 413 MHz would it be possible to Change a capacitor, resistor, etc. combination to get the desired transmit/receive frequency?or is it more complicated than that?Here is a 300 MHz version of the circuit board that I have to work with.Also does anybody know of a way to transmit 413 MHz trinary Via an app/program using an SDR? This would probably be easier.Thanks dw8000Here’s a link to the microcontroller.http://www.sonix.com.tw/article-en-1006-31292
Method of Moments bases - Page 1
Forum section: electronics / rf-microwave

author: rhb
author_rank: Super Contributor
timestamp: September 02, 2018, 12:46:15 pm
content: I've been reading "Antenna Theory" by Balanis, 2016 and the HOBBIES book by Zhang et al. This has made me curious about the choice of basis set. The constant value (aka constant pulse) seems rather a poor choice, at least for wire antennas.The basis set used in HOBBIES seems more sensible, but there is no explanation of the reasoning behind the choice.As neither says anything about the computation of the matrix inverse, I'm assuming that both NEC2/4 and HOBBIES use least squares.Has anyone looked at applying the MoM using a wavelet basis? And more particularly using a sparse L1 solution instead of L2.
RADAR target emulator - Page 1
Forum section: electronics / rf-microwave

author: Kirkhaan
author_rank: Frequent Contributor
timestamp: September 01, 2018, 07:00:24 pm
content: I'm looking for an affordable Doppler emulator.Something likethis, but then for 5.8GHz ISM band.It can also be more simple then the K-DT1. I'm only interested in IF frequencies from 1 to 200Hz.Any idea's or suggestions?
Advice on biasing Marki A2050 (using a negative bias generator) - Page 1
Forum section: electronics / rf-microwave

author: pigrew
author_rank: Frequent Contributor
timestamp: September 03, 2018, 05:00:40 am
content: I want to design a power supply for a pair of Marki A2050 amplifiers. These need -5 V (<20 mA) and +5 V (<450mA), but I need to make sure the negative bias is applied first.How clean of a power supply is needed for a 20 to 50 GHz amplifier? Is it reasonable to use a charge pump (LTC1983-5) to generate the negative rail (with a few uF of capacitance)? I'm planning to use a PMIC supervisor to detect if the negative rail has been established, triggering a pFET to enable the positive bias.I think this will fulfill the power supply ordering requirements.Thoughts?I'll post the schematics (expected to be quite simple) once I make them.

author: pigrew
author_rank: Frequent Contributor
timestamp: September 09, 2018, 01:58:54 pm
content: Short update:I've designed a small board which should delay the positive bias until after the negative bias is established. I've milled it, but not yet assembled it. I ended up not using switched capacitors since their output voltage is a bit under the input voltage. The LTC1983-5 would need a Vin between 5.4 and 5.5 V (or so) in order to achieve regulation with 40 mA output (weird).I'm using an isolated DC-DC converter module instead (though this is also probably a bad idea since I believe it just inverts the voltage, so it'll likely be about as far off since my schematic doesn't have a regulator). I'm going to do some bench testing to see what happens with my circuit later today with some dummy loads.Some of the parts (for example, the FETs) are just based on what I have available in stock already.Summary: My new circuit should work with a Vin of about 5V, but provides no regulation, and doesn't provide a way to control the positive bias for gain control. I also don't know what the switching supply module will do if the input voltage drops.
Use an Wideband LTE Company Network when (quite) Every Freq is in use? - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: September 01, 2018, 12:37:34 am
content: Hmm I will need an Wideband Communication System for our Social Club. Yesteday was an small Tec Fair who Huawei had an small Stand there and present there LTE for Company Radio System.The major problem is a find a freq who is not in use for something.So what to do?

author: coppercone2
author_rank: Super Contributor
timestamp: September 01, 2018, 12:42:42 am
content: use fear and intimidation to accomplish your goals
What is ''Baseband RX DC offset callibration'' - Page 1
Forum section: electronics / rf-microwave

author: sangar
author_rank: Regular Contributor
timestamp: August 31, 2018, 02:32:57 pm
content: Hello All,I have come across the term ''Baseband DC offset calibration'' from the datasheet of AD9361. What does it actually means and why it is required?Thanks,Muthu

author: radioactive
author_rank: Regular Contributor
timestamp: August 31, 2018, 07:32:02 pm
content: In a quadrature based system with I/Q (in-phase, quadrature) signals, any differences between the two 90-degree quadrature signals caused by non-ideal mixers, amplifier offsets, frequency error between tx/rx, etc will cause an offset around DC in the response. The idea of calibration is to adjust the response such that the I/Q have the same gain/offset. This may or may not be important to correct for depending what you are doing. Some receiver systems use a low IF (intermediate frequency) that avoids this DC offset and also helps to improve the negative effects from close-in phase noise in a PLL. The low IF signal can be sampled with a wider bandwidth into a digital system (ADC) and then filtered and downconverted the rest of the way in the digital domain. In higher order modulation schemes like OFDM, the DC bin(s) in the FFT are nulled out and not used, but calibration of I/Q is still important so as not to cause too much distortion in the received/transmitted constellation.

author: radioactive
author_rank: Regular Contributor
timestamp: August 31, 2018, 07:41:16 pm
content: Another important thing I forgot to mention is that uncalibrated I/Q gain/offset will cause undesired sideband emissions in transmit.
RF materials related to Modulation techniques - Page 1
Forum section: electronics / rf-microwave

author: sangar
author_rank: Regular Contributor
timestamp: August 31, 2018, 02:19:05 pm
content: Hello all,I know something about RF modulation but I want to get in-depth knowledge in that. So, I am asking you people to share any material related to this if you have.Thanks,Muthu

author: mark03
author_rank: Frequent Contributor
timestamp: August 31, 2018, 03:30:27 pm
content: Wikipedia? Textbooks?

author: HB9EVI
author_rank: Frequent Contributor
timestamp: August 31, 2018, 03:57:49 pm
content: 'In-depth' is quite general.Are you aiming on how to build modulators/demodulators with electronic components or do you want to dive into the maths of modulationsthese are two quite different things and one doesn't necessarily need the other
Substitute relay OK for RF path, in a Kenwood TS-590?? - Page 1
Forum section: electronics / rf-microwave

author: Chris Wilson
author_rank: Super Contributor
timestamp: August 29, 2018, 01:45:23 pm
content: I fixed up my poor old Kenwood TS-590 that had 1kW of RF at 137kHz shoved up the RX antenna socket and it's been working well for weeks. However sometimes when it is switched on or goes from RX to TX and back again I see little or no signal. I am 95% sure the relay K101 has suffered contact damage and is now suspect. I cannot get the specific part any more, so have looked at spec sheets for an alternative.The original is a Panasonic C Form factor type HY1Z-9V a 9V DC relay, SPDT and the Z bit means it has a coil of 405 Ohms and draws 22.2mA at 9VI have found a relay at RS Components that is physically almost exactly the same size, but the lowest Ohmage coil available is 540 Ohms and it draws only 16.7mA at 9V. Change over times are similar. Current and voltage ratings of its contacts are similar. Closed resistance is similar. Can I substitute this relay please?OE Panasonic relay HY1Z-9V is athttps://na.industrial.panasonic.com/products/relays/mechanical-signal-relays/signal-relays/series/hy-relays/1206/model/HY1Z-5VThe one I am hoping to substitute ishttps://uk.rs-online.com/web/p/non-latching-relays/6839255/?relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D626572266C753D656E266D6D3D6D61746368616C6C26706D3D5E282872737C5253295B205D3F293F2832355C647B387D7C32355C647B317D5C2D5C647B377D7C5C647B337D5B5C2D5D3F5C647B332C347D5B70505D3F292426706F3D3126736E3D592673723D2673743D52535F53544F434B5F4E554D4245522677633D4E4F4E45267573743D3638332D39323535267374613D3638333932353526and its spec sheet is at :https://docs-emea.rs-online.com/webdocs/0dbf/0900766b80dbfca2.pdfThe circuit it has to switch is here:http://www.chriswilson.tv/input-schematic.jpg(Relay K101)Thanks.

author: CJay
author_rank: Super Contributor
timestamp: August 29, 2018, 02:10:25 pm
content: Yeah, that'll be fine.
Vintage Audio FM MPX Adjustment - Page 1
Forum section: electronics / rf-microwave

author: jheatac
author_rank: Regular Contributor
timestamp: August 04, 2018, 06:25:20 pm
content: Hello,I am very much a beginner at electronics.I am working on an old receiver and looking through the service manual at tuning in the FM MPX section and it directs me to connect the vertical and horizonal axis of my scope to different pins.I have a Tek TDS754C... Is this possible with this scope or would I need an analog scope to make this work?Thanks

author: xwarp
author_rank: Frequent Contributor
timestamp: August 29, 2018, 11:26:35 am
content: Should have X-Y mode on your scope.

author: capt bullshot
author_rank: Super Contributor
timestamp: August 29, 2018, 02:08:36 pm
content: Most DSO have an XY mode, e.g. in the Display Menu. This uses two input channels and maps one of them to the X axis.Anyway, the resulting display is often rather poor in comparison to a real analogue oscilloscope.As the description says, you want to to display a sine wave and a derived sawtooth wave that are stationary. You should be able to adjust this by monitoring these waveforms in "normal" XT mode, the goal is to see both stable, not just one of them stable and the other moving.
Where can you buy this stuff? SR111 navy VLF radio - Page 1
Forum section: electronics / rf-microwave

author: Beamin
author_rank: Super Contributor
timestamp: August 26, 2018, 12:57:43 pm
content: This is the coolest thing ever. Where can you buy stuff like this? I have only seen people say they bought these at ham swaps which I don't have the ability to go to on a regular basis and wait for this to show up.He paid $40 for this or $0.57 /lbs.My father worked on one of these for the navy submarines recently. But he only does digital so I'm not sure which part he did. I know at home one day he kept complaining he was losing packets during testing on the computer, don't think he could take the stuff from work. He needed a security clearance to work on it and he wasn't allowed to see some parts of it even with clearance. Too bad he's a prick I would love to see that stuff first hand or learn how it works. That's where you tax dollars go and my father makes extra care not to let any of the wealth trickle down to other people. He once argued with verizon for an hour over 2 cents or 1/1,000,000,000 of his total wealth. But I have done the same.There must be all kinds of stuff now declassified that the public can own. Time to replace the caps for sure!https://youtu.be/MBN8EjnJC9I

author: Lord of nothing
author_rank: Super Contributor
timestamp: August 26, 2018, 11:36:33 pm
content: QuoteI dont kow does the Navi have some Contractor for Recyling?Ebay?!

author: Beamin
author_rank: Super Contributor
timestamp: August 28, 2018, 02:54:51 pm
content: Quote from: Lord of nothing on August 26, 2018, 11:36:33 pmFixed your post the last one was way to informative.But I think you have to spend years stalking ebay and craigslist like a crazy ex boyfriend. "Just give me another chance I'll quit drinking and go to anger management I promise! I love you If another man is with you I'll kill him... I mean you don't need him you need me!! I can't live without you. Just drop the restraining order please" Do that for surplus equipment and you would be surprised wat you can find!

author: chris_leyson
author_rank: Super Contributor
timestamp: August 28, 2018, 04:02:39 pm
content: Your could try Toronto Surplus and Scientific, the do a lot of Harris Comms gear.
LORAN/low RF frequency dervied clock jitter - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: August 27, 2018, 08:41:02 pm
content: Am I correct in thinking that atomic clock transmission signals carried by low frequency RF, like in the KHz, will have very high jitter compared to signals derived from fast clocks, because there is a greater period where noise can effect the markers? Then something with GPS in the GHz? I am thinking about it in terms of zero crossing noiseAnd like, how is the quality of the clock derived from the different WW(or other) stations different as their transmitter frequency goes up (I think the slowest are like 10KHz and it goes up to 30MHz or so)
Wideband Signal on <30Mhz Possible? - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: August 26, 2018, 10:46:33 pm
content: HiDoes it is possible to transmit a Wideband Signal on <30Mhz?Likehttps://de.wikipedia.org/wiki/Olivia_MFSKAre there any commercial "Wide Band" Mode in use? The only I know is DRM (?!) Radio who get broadcast von Radio Romania and from Saudi Arabia.

author: David Hess
author_rank: Super Contributor
timestamp: August 26, 2018, 11:06:43 pm
content: Sure, why not? There are practical difficulties with a channel bandwidth which is a large part of the carrier frequency but it is not impossible.Olivia MFSK however is still a narrowband transmission mode as it is required to stay within the bandwidth of an SSB voice channel or smaller and is typically 1000 Hz.

author: Lord of nothing
author_rank: Super Contributor
timestamp: August 26, 2018, 11:20:38 pm
content: Do you know a (Commercial Used) Mode who is Wideband on <30mhz?

author: David Hess
author_rank: Super Contributor
timestamp: August 26, 2018, 11:57:36 pm
content: The best real example that I know of off hand was the old VHF television channel 1 which was between 44 and 50 MHz. It was removed in 1948 making VHF television channel 2 the lowest channel.An internet search show that the military is looking into something and has done tests with a 24 kHz bandwidth in the HF band but that is hardly wideband.It would not surprise me if some nations use wideband HF direct sequence spread spectrum for some secret communications systems with a bandwidth of at least 100s of kHz. The limitation with small installations is antenna tuning.

author: Lord of nothing
author_rank: Super Contributor
timestamp: August 27, 2018, 01:06:57 am
content: Here the lowest who currently (by law) could be TV Transmitt is 47,0 - 68,0 MHz

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 27, 2018, 01:58:09 am
content: https://en.wikipedia.org/wiki/Duga_radarThere are a number of similar systems in operation around the world, don't know if their frequencies are published though. Likely they're all frequency agile or hopping, these days, so you don't get incessant interference on any given channel/band.Tim

author: xaxaxa
author_rank: Regular Contributor
timestamp: August 27, 2018, 05:37:35 am
content: You probably want to use OFDM since it is unlikely the antenna/channel characteristics will be constant across a wide fractional bandwidth; OFDM plus a suitable error correction scheme can deal with frequency-selective fading and the bad frequency response of your antenna.
pulse width extender - Page 1
Forum section: electronics / rf-microwave

author: fateme mrbs
author_rank: Newbie
timestamp: August 25, 2018, 11:35:56 am
content: It says in the paper that it's a pulse width extender. but how does it work (and give tht result)? What is that dc current source for? It doesn't extend the input pulse width based on my simulation.

author: Rerouter
author_rank: Super Contributor
timestamp: August 25, 2018, 12:13:45 pm
content: It leaves out many of the assumptions, And personally playing with it, It appears pretty horrible,For this application, 2 Open Collector Not Gates make more sense, pulling down an RC network, However My personal favorite is linked below, I use it in a modified form to shape automotive frequency input signals.Falstads Circuit Simulator

author: eb4fbz
author_rank: Regular Contributor
timestamp: August 25, 2018, 04:54:16 pm
content: http://jcoppens.com/radio/prop/stretcher/index.en.php

author: coppercone2
author_rank: Super Contributor
timestamp: August 25, 2018, 05:46:50 pm
content: LTC timerblox have this function too for signals maybe up to 3MHz IIRC

author: fateme mrbs
author_rank: Newbie
timestamp: August 26, 2018, 01:09:53 pm
content: Quote from: Rerouter on August 25, 2018, 12:13:45 pmWhy does it look horrible?Actually it worked for an input like the first picture. But not for an input like the second picture. and I am trying to demodulate the second picture. Why is that so?
Looking for some Splitter - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: August 26, 2018, 11:43:52 pm
content: I got some from Ebay the are still ok for my crappy Setup. Now I will make a much more professional setup.I got a small Server Rack and other stuff to mount my Radio properly. Sadly I need for me SDR some Splitter.for example I have an VHF Antenna where I need to splitt the Signal into an Amateur Band, DAB+ Band, Air Band,... I got some Filter I need to use. For example for DAB+ I want receive 2 different Station so I need "just" 2 Ports where I can hug my SDR in. Can I plug between the Filter some LNA in?How to calculate the loss?Thanks!
How Receiver is tuning to the Transmitter frequency in FHSS? - Page 1
Forum section: electronics / rf-microwave

author: sangar
author_rank: Regular Contributor
timestamp: August 21, 2018, 07:04:42 am
content: Hello All,I am working on Frequency hopping based system. I know that the next hopping frequency is determined by some code or numbers. Assume, Once transmitter is moved to next hopping frequency, how it is letting know Receiver which is sitting on the different frequency. Because, in this case, though transmitters sends some codes or numbers which tells Receiver to move to transmitter frequency, Receiver can't receive because of transmitter and receiver is locked to different carrier frequency. Please let me know how it happens....Thanks,Muthu

author: Gribo
author_rank: Frequent Contributor
timestamp: August 22, 2018, 04:39:11 pm
content: In FHSS, they have to either agree in advance, or follow some rule for hopping. That is, the receiver has a channel list, it listens to a specific channel for a certain time period n, to cover all the hops in the list. Once it receives a packet on that channel, it knows where to hop next. The 'Where to hop next' can be transmitted in the current packet, agreed upon previously, or calculated according to a specific algorithm, which is up to the system designer.Obviously, that is only one part of a bigger state machine.
RF Engineer's Keychain Tool - Page 1
Forum section: electronics / rf-microwave

author: soerenbnoergaard
author_rank: Contributor
timestamp: August 21, 2018, 03:45:26 pm
content: Hi all,I just wanted to share a few keychain tool I have modified.The modification turns the bottle opener into an 8 mm wrench for loosening an SMA connector when you forgot the torque wrench at your benchThe first tool is a Nite Ize Doohickey.The second tool is a Gerber Shard. This has more screwdrivers than the the Nite Ize, which I like.This has gotten me out of trouble many times, so I thought it might be useful to others as wellBest regards,Søren

author: D3f1ant
author_rank: Frequent Contributor
timestamp: August 21, 2018, 10:42:18 pm
content: That's pretty cool...but do they still open bottles?

author: AF6LJ
author_rank: Unknown
timestamp: August 22, 2018, 01:34:00 am
content: That will get the job done.

author: soerenbnoergaard
author_rank: Contributor
timestamp: August 22, 2018, 05:25:50 am
content: The Nite Ize still opens bottles. Haven't checked the other one yet -- I made it yesterday -- but I'm sure it will.If you are desperate enough, the bottle will be opened

author: Berni
author_rank: Super Contributor
timestamp: August 22, 2018, 05:30:11 am
content: Oh its simple you just use a screwdriver to open bottles. With enough determination pretty much any tool can be used to open one, even a chainsaw(Actually works surprisingly well, google it if you haven't seen it)

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: August 22, 2018, 06:41:10 am
content: I've opened bottles with lighters, keys, screwdrivers, knives, other bottles, beer crates, rocks. I've even known people who can do it with their teeth, though that just sounds like a stupid idea if you ask me.

author: Gribo
author_rank: Frequent Contributor
timestamp: August 22, 2018, 04:31:51 pm
content: Also, door latch holes.
APRS Decoder Question / Advice - Page 1
Forum section: electronics / rf-microwave

author: curiousmuch
author_rank: Newbie
timestamp: August 19, 2018, 04:17:23 pm
content: Hello,I'm writing an APRS packet decoder / AFSK demodulator in Python3 as an algorithm test bed. I have little digital signal processing training so I figured it would be best to simulate everything before porting the methodology to my intended embedded platform in C. I've generated test packets via the Direwolf utility gen_packets, but I'm seeing some strange artifacts after demodulation.The demodulator is quick basic. I'm using the Goertzel algorithm (basically 1 bin FFT) to calculate the energy at each frequency for Bell 202 sample by sample. The difference of the energies is then taken and low pass filtered. The result is then fed through a comparator / sampled appropriately to finish the demodulation.The test signal sent in TNC2 format looks as follows: WB2OSZ-15>TEST:,The quick brown fox jumps over the lazy dog!The AX.25 frame starts with a flag 0x7E and then sents the destination callsign. In this case it would be "TEST".I'm decoding AX.25 and TEST just fine, but there is a mystery bit in the test signal right after the 0x7E flag. Please see below. I'm not sure if these kinds of mistakes are common for APRS TNCs or it's only in the gen_packet utility for Direwolf? I know APRS is kind of the wild west. Does anyone on the forum have any information on this? Do you believe it's an issue with my implementation? Is this somehow bit-stuffing? I though this should occur after every 5 bits not after any 5 bits?

author: Dwaine
author_rank: Frequent Contributor
timestamp: August 19, 2018, 05:03:13 pm
content: Did you post your question to the direwolf forum? People there are very helpful and the main person that writes the code is responsive.I have actually push some code changes to fix some of the buffer over/under runs and it was done in a day or two. Also, what branch of code are you running in your test. Most recent changes are from the dev branch.

author: curiousmuch
author_rank: Newbie
timestamp: August 20, 2018, 04:05:44 pm
content: I didn't know there was a forum. I saw there was a quite a few un-closed issues on github so I figured they'd be difficult to contact. I'll try that now.Thank you!!!
RFID aperture detection - Page 1
Forum section: electronics / rf-microwave

author: Lomax
author_rank: Frequent Contributor
timestamp: August 19, 2018, 01:38:05 pm
content: Hi all,I'm hoping to come up with a method to detect the passage of an object through one or other aperture using RFID. Would it be possible to make an RFID antenna "loop" around an opening such that tags passing through are read, while any passing on the outside are not? I've looked briefly at (expensive)"travelling wave" antennas, which seem to be designed for this purpose, but at $300 a pop they're way outside my budget (this is a hobby/diy project!). I'm new to RFID tech, so please excuse me if this is a silly question

author: Lomax
author_rank: Frequent Contributor
timestamp: August 19, 2018, 09:05:33 pm
content: Could it be that I will need an additional detection method (e.g IR, ultrasonic), to detect thatsomethingis passing through, and trigger an RFID read to find out what tag it has? I hope not, as this would complicate the design quite a lot...
AD9361 wideband SDR questions - Page 1
Forum section: electronics / rf-microwave

author: sangar
author_rank: Regular Contributor
timestamp: August 21, 2018, 10:45:37 am
content: Hello All,I want to use AD9361 for one of my applications. This application is going to be Frequency hopping based, says 1000 hops/sec.The confusing thing is, there are two transceiver mode FDD and TDD, I don't know which one I have to select for my requirements (1000 hops/sec). If anyone have worked with AD9371, please share your knowledge.Thanks,Sangar
TX Line opinions - Page 1
Forum section: electronics / rf-microwave

author: mayor
author_rank: Regular Contributor
timestamp: August 17, 2018, 07:23:04 pm
content: Hi,I'm working on a breakout board for TI's CC1352, and before sending to fabrication, I figure it might be good to get some feedback.The top transmission line in the attached image is 868-915MHz, bottom is 2.4GHz. Top is about 4mm long, bottom adds up to 6mm (1/20th wavelength or so). I still need to tweak line width a little to get to just above 50 ohm (TI states that impedance is lowered by solder mask). One thing I find annoying is the 0402 component pad sizes; I tried to make the tx line width the same as the pads (0.6mm) with this toolhttp://wcalc.sourceforge.net/cgi-bin/coplanar.cgi, but the PCB stackup makes it almost impossible to get 50 ohm with this CPWG layout. Ground plane on first inner layer is 0.18mm below top, and this is FR4.I figure none of it is a major issue at these lengths, but would absolutely welcome feedback from experienced RF folks here!TIA

author: ThomasDK
author_rank: Regular Contributor
timestamp: August 18, 2018, 11:20:37 pm
content: Quote from: mayor on August 17, 2018, 07:23:04 pmIt will be fine at those lengths.Anyway, one trick is to remove the GND plane below the traces and use the next layer down as the RF ground.Thomas
70 MHz Monolithic Filter Source - Page 1
Forum section: electronics / rf-microwave

author: rcbuck
author_rank: Frequent Contributor
timestamp: August 14, 2018, 06:59:14 pm
content: Does anyone know of a U.S. distributor that stocks 70 MHz Monolithic Filters? I need a couple for a project but Mouser and DigiKey do not stock anything over 45 MHz.I want to use a 4 Pole filter to obtain a more narrow bandwidth than a 2 Pole would have. I can use either a through hole or SMD part.

author: kony
author_rank: Regular Contributor
timestamp: August 14, 2018, 08:45:39 pm
content: http://www.krystaly.cz/en/Products/FiltersNot US distributor, but Czech mfg. However they will gladly make even customised values of crystals and filters.

author: rcbuck
author_rank: Frequent Contributor
timestamp: August 15, 2018, 04:11:32 pm
content: Kony, thanks for the suggestion. Unfortunately, shipping to the U.S. would probably cost more than the parts. Maybe something will turn up on Ebay.

author: rhb
author_rank: Super Contributor
timestamp: August 17, 2018, 10:48:37 pm
content: If you find a distributor for such things please post it. There are a lot of really neat filters (e.g. SAW) but no one stocks them.Not exactly what you asked for, but you might look at what else they have on offer.https://www.rf-microwave.com/en/cepe-filtre/stf-1005-2/72-mhz-band-pass-filter/f-72m-k9/

author: BrianHG
author_rank: Super Contributor
timestamp: August 17, 2018, 11:17:20 pm
content: Found you 8 of them:https://www.onlinecomponents.comPart numbers:70M20Band70M15BData sheet:datasheet

author: rcbuck
author_rank: Frequent Contributor
timestamp: August 18, 2018, 01:52:36 am
content: Thanks Brian, I will contact them.
frequency measurement circuit - Page 1
Forum section: electronics / rf-microwave

author: yalect
author_rank: Regular Contributor
timestamp: January 13, 2016, 07:29:51 pm
content: Hello,I would like to ask you about simple cheap microcontroller frequency counter circuit, I found some projects but I am looking for one can's measure from Hz up to 200Mhz or more 7-segment LED display maybe with prescaler.Thank you

author: Wolfgang
author_rank: Super Contributor
timestamp: August 15, 2018, 10:05:09 pm
content: If it is to be simple there the famous PIC16F84 counters with a prescaler and either LED or LCD output. I built some and they work.
pa0rdt-Mini-Whip antenna. - Page 1
Forum section: electronics / rf-microwave

author: hamster_nz
author_rank: Super Contributor
timestamp: February 21, 2017, 10:15:50 am
content: I've had a long term project which never made it to the top of the list to spend the time building- a pa0rdt-Mini-Whip LF/MW antenna, for use with a direct conversion SDR rig.Interesting because of the small physical size - it is capacitively coupled to the e-field. This also gives it a wide flat frequency response.The transistor footprint was flipped, but tombstoning three 0 ohm resistors and flipping the transistor fixed that.I'm yet to get it connected to the SDR (need connector), but had it on a USB scope's FFT as a poor man's spectrum analyser. The local MW stations stood out like the proverbial dogs bollocks vs that of a random length of wire, even without a decent ground reference.Original design details are athttp://dl1dbc.net/SAQ/Mwhip/Article_pa0rdt-Mini-Whip_English.pdf,but built with SMD and some of the parts were substituted (esp the JFETs for the front end).Oh, I must buy some flux cleaner....

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: February 21, 2017, 01:06:16 pm
content: Interesting project.Here's my experiences when I built one a few years back.

author: awallin
author_rank: Frequent Contributor
timestamp: February 22, 2017, 03:58:46 pm
content: Quote from: hamster_nz on February 21, 2017, 10:15:50 amThere is an updated cricuit by PA0NHC that uses BF998 for the first FET:http://www.pa0nhc.nl/Miniwhip/indexE.htmand also a version by RA0SMS, for sale on e-bay. also seems to use BF998.http://www.ra0sms.ru/p/the-active-antenna-mini-whip-10-khz-30.htmlI just tested the original PA0RDT design against a long-wire (around 35m IIRC), looking at some LF time-code signals. The long-wire has a tuning coil for resonance at 136 kHz - so the comparison isn't entirely apples to apples...Anyway the mini-whip seems to perform quite well and is significantly easier to find space for than the 35-40m wire!For the TDF signal at 162 kHz the tuned long-wire provides almost the same signal as the amplified mini-whip.I also made a ferrite-sleeve-loop, and a ~1m diameter coax-loop, but haven't had time to test them properly. For LF it seems SNR is key and it isn't obvious that a bigger antenna or more gain will help...The time-code transmitters pretty large installations:Anthorn,https://goo.gl/maps/nVymTZ7zi8L2Mainflingen,https://goo.gl/maps/mKD297oE1rqAllouis,https://goo.gl/maps/K71JtKVVGAz

author: Wolfgang
author_rank: Super Contributor
timestamp: August 15, 2018, 09:38:31 pm
content: Hi, dont worry, these antennas are quite tolerant to sloppy construction.I made some of them in different sizes, all work OK:https://electronicprojectsforfun.wordpress.com/antennas/active-antennas/
Adding notch/reject filters in series - Page 1
Forum section: electronics / rf-microwave

author: jujun
author_rank: Regular Contributor
timestamp: June 20, 2018, 11:11:07 pm
content: Hello,When adding notch/reject filter by putting them in series, will it work?Is it as easy as the losses are added and nothing more complicated? It sound a little too easy...And what about the length of cable between the filters ?Basicaly, I want to block two annoying signals, that are one each side of my band of interest. Is it good to make a notch/reject filter for each ?Because if I make a band pass, on UHF, the loss are too big. But the added losses of two reject filters are not a very big. 0.5db + 0.5db it's quite goodBy the way, why it's so different ?Thank you for any advicesJulien

author: ejeffrey
author_rank: Super Contributor
timestamp: June 21, 2018, 01:57:16 pm
content: As long as the notches don't overlap it should work fine. If they overlap there will be a standing wave between the filters and rejection may decrease at some frequencies relative to a single filter.

author: jujun
author_rank: Regular Contributor
timestamp: June 21, 2018, 02:43:45 pm
content: Quote from: ejeffrey on June 21, 2018, 01:57:16 pmThank you!So it's wonderful, and it's a lot better than making a band pass!I will try to make very broad band block filter to see if it's possible to have low losses.

author: CopperCone
author_rank: Super Contributor
timestamp: June 21, 2018, 02:54:41 pm
content: You can put an isolator between reject filters of the same notch i think

author: jujun
author_rank: Regular Contributor
timestamp: June 21, 2018, 05:00:25 pm
content: Quote from: CopperCone on June 21, 2018, 02:54:41 pmWhat is it ?

author: Wolfgang
author_rank: Super Contributor
timestamp: August 15, 2018, 08:40:36 pm
content: Tip: You could simulate the circuityou have in mind using SPICE you have in mind so you can predict the effects.I notoriously do this, results are OK:https://electronicprojectsforfun.wordpress.com/rf-module-gallery/the-rf-filter-gallery/
Unfamilar coaxial connector - Page 1
Forum section: electronics / rf-microwave

author: SpencerTC
author_rank: Contributor
timestamp: August 14, 2018, 05:31:50 am
content: Hello all,I was cleaning up the lab at work today and ran across some coax connectors that are unfamiliar to me. They have a relatively small outside diameter of 5mm and an odd collar that looks like you pull back on (reminds me of a compressed air quick disconnect) to release 2 barbs that seem like they would lock it in place with the female version. Can anyone tell me the name of these connectors? Their primary uses? Assuming they are used for RF/MW what frequencies could one expect out of them reliably?I'm mostly just curious, as I don't have anything to use with them, it would be nice to know in case I ever run into a case where they may be required though.Thanks in advance,Trent Spencer

author: helius
author_rank: Super Contributor
timestamp: August 14, 2018, 06:05:00 am
content: Looks like a push-pull connector from Lemo, Fischer, or Redel, or a knockoff from the far east. These types are not very commonly used.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: August 14, 2018, 07:05:11 am
content: LEMO .00 connector, used by the bucket in NIM.https://ndt.nu/index.php?item=lemo-00-equ_-------lemo-1-equ_--cable_s_&action=article&aid=91&lang=enhttps://en.wikipedia.org/wiki/Nuclear_Instrumentation_Module

author: SpencerTC
author_rank: Contributor
timestamp: August 15, 2018, 05:18:52 am
content: Wow, that is even more unusual than I was expecting.I'll keep it in my kit in case I ever run across a need for it, but I don't expect that to happen.Thank you for your response, I doubt I would have ran across that information myself.
"Omnidirectional" indoor TV antennas - Page 1
Forum section: electronics / rf-microwave

author: Peabody
author_rank: Super Contributor
timestamp: August 15, 2018, 01:51:47 am
content: It looks like I'll be needing to cut the cord, and I'm trying to figure out the OTA TV situation. I see indoor antennas which claim to be omnidirectional, but they are flat, and hang on the wall. I don't understand how they could not be directional. Also, wouldn't a truly omnidirectional antenna have considerably less gain than a directional antenna?There are six channels that I would watch, 15 to 19 miles away. Five are at azimuth 100 or 101 degrees, and the other one (channel 10) is 110 degrees. However, my TV is on the West side of the house, so the signals have to go through interior walls, and I have topographic issues. I have three VHF channels (real channels 8, 10 and 11) and three UHF (real 22, 42 and 45).I have an RCA model ANT112R, and it doesn't do so well, particularly with channel 45, and it is highly directional.https://www.walmart.com/ip/RCA-UHF-VHF-Digital-Indoor-Antenna/20976672I don't know if that means no indoor antenna will work, or just that I need a better one.Any insights would be appreciated.

author: helius
author_rank: Super Contributor
timestamp: August 15, 2018, 04:11:48 am
content: Quote from: Peabody on August 15, 2018, 01:51:47 amThose wall hanging antennas are called dipoles."A dipole is omnidirectional in the plane perpendicular to the wire axis, with the radiation falling to zero on the axis"It can receive signals equally in the plane parallel to the ground, which makes it omnidirectional. It cannot receive signals from directly above or below, but this isn't usually an issue.QuoteGain is entirely a measurement of how directional an antenna is. The smaller the "field of view" of the antenna, the higher the gain. TANSTAAFL.Some antennas are powered and have internal LNA (low noise amplifiers), which could improve reception considerably for weak signals.

author: MarkF
author_rank: Super Contributor
timestamp: August 15, 2018, 04:53:50 am
content: You might take a look at this little antenna that I bought.https://www.eevblog.com/forum/projects/questions-about-digital-tv-antennas/msg1610263/#msg1610263

author: Peabody
author_rank: Super Contributor
timestamp: August 15, 2018, 04:01:28 pm
content: Quote from: helius on August 15, 2018, 04:11:48 amThe little antenna I have now has a simple rounded-off rectangle sticking straight up for UHF. I think that's functionally similar to the flat ones you hang on the wall. Mine is highly directional, which suggests it doesn't receive signals equally in the horizontal plane, but must be pointed toward the transmitter. Why would that be?The VHF rabbit ears portion also appears to be directional, although not as much.Well, I obviously need to read up on antennas.
Chip antenna - Page 1
Forum section: electronics / rf-microwave

author: madhu.wesly01
author_rank: Regular Contributor
timestamp: August 11, 2018, 07:13:25 am
content: Hi,I am planning to include GPS chip antenna in my design , regarding the placement it says we have to follow some considerations like1. They mentioned some keepout Area 5X5mm surrounding that antenna .As I've size constrain I'm placing 5mm keepout area on one layer of the board and the other layer I'll keep 3mm keepout area .How much it will impact on the GPS signal reception ? and It will be greatful if anyone suggest me to overcome that issue ?Thanks in advance .

author: ThomasDK
author_rank: Regular Contributor
timestamp: August 11, 2018, 11:06:09 am
content: Hard to say, if you do not follow the guide lines you are on your own. All antenna specifications are out of the window, as the gap itself is part of the antenna.

author: D3f1ant
author_rank: Frequent Contributor
timestamp: August 11, 2018, 09:11:43 pm
content: I'm doing something similar at the moment. I started by using a chip antenna that had design examples that at least closely resembled how I needed to use it. Some GPS chip antenna data was hopeless , it made wonder how they manage to sell anything with such inadequate datasheets, no application examples or other app notes.I added a provision for a basic 3 element pi matching network, following that up with a SAW and LNA. In my experience small GPS chip antenna performance is terribly compared to ceramic patch antennas.
What are the best books on how analog Radio/TV circuits work - Page 1
Forum section: electronics / rf-microwave

author: lordvader88
author_rank: Frequent Contributor
timestamp: August 26, 2018, 09:42:17 am
content: I love looking at radio/TV schematics, and still don't get 1/2 of it or more. And of the tons of utube videos, they never get into the detail I want.What are some great books on that, especially from the tube days and early solid state days before all the digital chips (I'll leave that for later)

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: August 26, 2018, 12:12:53 pm
content: If there's a hamfest in your area go to one and buy an armful of old books for a few dollars.One to look out for (for radio) are the ARRL handbook.There's also a lot of old tube era books that have been pdf'd and can be downloaded.http://www.talkingelectronics.com/has a lot of simple transistor circuit fundamentals.Ron Bertrand's book is also goodA lot of simple radio circuits can be broken down into block diagrams eg:

author: rhb
author_rank: Super Contributor
timestamp: August 26, 2018, 01:42:12 pm
content: I recommend these:Electronic Principles by Malvino 1st, 2nd edElectronic Communication by Schrader 4th edApplications of Electronics by Grob and Kiver 2nd edAll of these are very well written trade school texts. Dr. Malvino took great pride in building and testing all the circuits in the book. It's all semiconductors. Schrader is mixed tubes and transistors. A 70's ed of the ARRL handbook is also a must. Grob & Kiver is mostly tubes with a intro to transistors.The big transition was mid 60's to early 80's, so textbooks from that era will provide what you want. I've listed the editions of these that I have. These are real standouts. I have a 5000+ volume technical library, so I have many others. I worked my way through Malvino and Schrader. Grob and Kiver was a more recent acquisition.