hybridfree/eevblog-posts huggingface dataset:
weird wr42 waveguide wtf  - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: June 29, 2017, 05:24:22 pm
content: I have a antenna that claims to be wr42 but the flange hole on it is kinda pill shaped, and it measures like 6.6 mm wide (with rounded edges like this (____) while my wr42 adapter is |_____| and is 4.3 mm wide.The holes between my wr42 adapter and the antenna line up. However, the dimensions of the antenna suggest its wr51, however the frequency of the antenna suggests its wr42 (bandwidth of the antenna is outside of the bandwidth of wr51 waveguide).hole spacing wr42 - ~0.5 incheshole spacing wr51 ~ < 0.6 inchesWTF is going on? Can I just use the wr42 adapter there, despite the 'discontinuity"? the adapter is from HP and it looks nice. the antenna is brand new old stock.so i can make the two peices.. the antenna is narrowband between 23-26ghz. does it just have special 'pill shaped' waveguide for this reason?i think its a flexible wr42. do you need an adapter between flexible wr42 and nonflexible wr42 with a taper?

author: slurry
author_rank: Regular Contributor
timestamp: June 30, 2017, 10:07:56 pm
content: The pillshape is for a flexible WG, there is tapered adapters/transitions from elliptical to standard rectangular WG'sI have no good source for K-band stuff, unfortunately.edit,example:http://www.rfcell.com/wg-connectors

author: CopperCone
author_rank: Super Contributor
timestamp: July 01, 2017, 12:22:43 am
content: how well do they line up.. without an adapter? how much loss am I looking at?

author: slurry
author_rank: Regular Contributor
timestamp: July 01, 2017, 07:32:10 am
content: Not only loss, you will have a lot of reflections that may be a bigger problem than the loss.

author: hendorog
author_rank: Super Contributor
timestamp: July 01, 2017, 10:00:12 am
content: When you post a question like that, pictures are not optional.Just sayin...
Today is Field Day for hams here in the US, so good chance to hear QRP stations - Page 1
Forum section: electronics / rf-microwave

author: TheSteve
author_rank: Unknown
timestamp: June 24, 2017, 07:01:31 pm
content: The generator is running out back so I can still run my 100 watts.I keep hoping ISS will be on the air but haven't heard anything.

author: The Doktor
author_rank: Regular Contributor
timestamp: June 25, 2017, 09:41:57 pm
content: If the QRP stations wanted to be heard, they'd buy themselves amps

author: TheSteve
author_rank: Unknown
timestamp: June 25, 2017, 09:44:07 pm
content: Quote from: The Doktor on June 25, 2017, 09:41:57 pmI do love my solid state kilowatt!

author: piranha32
author_rank: Unknown
timestamp: June 29, 2017, 05:01:47 am
content: Quote from: cdev on June 24, 2017, 05:42:37 pmWhat a nice and clean spectrum. 40m was plastered with overlapping signals.
network analyzer as a reciever - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: June 19, 2017, 06:14:30 am
content: Is there a downside to doing this? My network analyzer is pretty sensitive and fast. (300MHz span).Plugging it into the IF output. Is there anything I should be aware of?

author: chris_leyson
author_rank: Super Contributor
timestamp: June 19, 2017, 07:42:20 am
content: In principle I don't see any reson why you can't use a network analyzer as a receiver. You might need to add extra input protection just to be safe, the phase noise performance and dynamic range will probably not be as good as a receiver and your IF downconverter will need AGC.
noise source (seems to be confusion) - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: July 23, 2017, 04:15:50 am
content: I see noise sources, noise power meters and fully integrated units.I am looking for someone that (preferably has N or SMA/2.9mm connectors, that I can plug to my device under test, turn the thing on, and see a nice curve of whats my deice under test doing. I understand a swept sworce) like one I have, will probably have a slightly difference response.I understand my swept noise source will probably require its own power source, but I would like to own one.Does anyone have any tips for such a setup (the 1MHz sweep (ddue to the DAC ) in my sweeper is annoying me and I would like a truly analog noise source.Thanks,

author: Muxr
author_rank: Super Contributor
timestamp: July 23, 2017, 05:51:11 am
content: Not sure if I understand your question, but if you're looking for an inexpensive wide band noise source, you can check out one of these:http://www.ebay.com/itm/2016-verison-Noise-Source-Simple-Spectrum-External-Generator-Tracking-Source-SMA-/172241109978
Ham Radio and Radio Repair Videos - Page 1
Forum section: electronics / rf-microwave

author: BootstrapWorkbench
author_rank: Newbie
timestamp: June 18, 2017, 04:13:40 pm
content: I've started a YouTube channel, and I am starting to build up some content related to repairing old test equipment, repairing and checking out radio equipment and some tips and tricks for Icom radios. Please stop by and check it out. I add more video every few days, as I have days off and can get away from my studies.https://www.youtube.com/channel/UCAynV-VPTboDpfZLMFFZFkQ73,Bootstrap Workbench
2 Good 2b True Jee Stream Dig TV Antenna? - Page 1
Forum section: electronics / rf-microwave

author: Paul Price
author_rank: Super Contributor
timestamp: June 16, 2017, 11:48:26 am
content: http://smartertech365.com/lps/thrv/responsive/saferweb/en/tv_fox_3/index.php?tsid=TBL&offerid=1804&trkcity=&mycmpid=%7Bcmpid%7D&tbl_click_id=CiAwNDUxNUE1MEZBNjI2NDI4MjcyODUwRjNGQjg2NjUzRRITYWRzMnBhcGVyLXR2ZnJvZy1zYw&campaign_id=619857&utm_medium=msn-msn-home&uss=%7Buss%7D&adid=A2&channelid=msn-msn-home&sxid=7y16ovp619yiIt's a passive antenna, claiming to give optimal reception at 30-miles.Sound too good 2 me!Anyone take one apart?
ultra high POI reciever for low frequencies (using SA as front end) - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: June 15, 2017, 03:29:05 pm
content: I am interested in using a spectrum analyzer as a front end for a SDR. I want high POI.What radio fits the bill? I just found out the signal hound is 15uS.. artificially limited. No way I'm buying it now, if they treat foreign countries before Americans because of export restrictions.Is there a SDR radio meant for low frequencies that has a blazing fast FFT? I intend to use the LO on a SA to receive my signal.

author: CopperCone
author_rank: Super Contributor
timestamp: June 15, 2017, 03:34:14 pm
content: 'lets fuck with buisnesses and scientific research (mind you it exists for fast signals, anyone who thinks otherwise is delusional.. (communications engineer lol)) because they might intercept our spy devices and outdated communications systems'
SML VLF Q vs active amplification - Page 1
Forum section: electronics / rf-microwave

author: electrolust
author_rank: Unknown
timestamp: June 14, 2017, 07:00:28 pm
content: I'm novice wrt electronics in general, and pretty much clueless wrt RF. So excuse me if this is just dumb or if I ask obvious followup questions.I'm building a 5.5kHz receiver using what I guess is referred to as SML. Probably not too different than a DCF77 receiver.If I optimize for packaging, which is important for my final product, I would choose small SMD inductors which have low Q factors at the resonant frequency. I will (obviously?) need to amplify the signal. Since I can just actively filter for desired bandwidth at each gain stage, do I need to worry too much about the Q factor of the antenna LC circuit? My understanding is that the resonant signal peak needs to be above atmospheric and thermal noise floor (important at VLF), so to the extent Q affects the peak amplitude it matters, but beyond that I'm hoping I can pick the best inductor within my packaging constraints and not necessarily optimize for Q.

author: CopperCone
author_rank: Super Contributor
timestamp: June 14, 2017, 11:53:31 pm
content: I'm no RF expert either, but basically the benefit of a prefilter is of course its harder to bring devices to saturation on a rail and cause errors.It increases robustness to nasties. and being passive, its lower noise. so your op-amp noise has less effect.
performance of cross plate antenna vs bicone/desicone - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: June 14, 2017, 05:48:15 am
content: It is easy to build a cross plate antenna. I have seen one somewhere, it was made by cross linking two 20'x20' copper plates and mounting them over another copper plate of the same dimensions, kind of like a desicone construction but with a plus sign rather then a cone. I have also seen a variant of it that has a "swastica" shape, which should not be more difficult to fabricate with a bending apparatus.What are the performance benefits of such an antenna? I'm not sure if I want to order the copper for one, since I have a large bicone already (described in another thread)... though I remember bandwidth of the cross-plate antenna being narrower. My effort to gas weld it out of thin aluminum was impossible due to my lack of bracing materials. Perhaps I will try aluminum solder, but it warps so much... i would need to make a sophisticated clamping apparatus to do it with what I have, perhaps with angle irons, if I ground off all the failed aluminum beads on it.Does anyone know about these things? Is it worth my effort? I like wide bandwidth things. I'm not sure if I will get different performance then my large bicone.
what is the impedance of my biconical antennas? - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: June 14, 2017, 05:43:02 am
content: I made one (not following instructions well), that is made of two 16 inch tall cones, that are 16 inches wide, separated by like 2mm with a BNC connector soldered into the bottom of one of the cones.The other one is different, each cone is 3 inches wide and 5 inches tall. It is separated by about 1mm and has a piece of 0.86mm hardline soldered into it. Does anyone know enough about these things to estimate their input impedance?The formula scared me.
near field probe bandwidth / size  - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: June 14, 2017, 05:22:08 am
content: So I see that you can make near-field probes out of coaxial cable thats looped.Is there an upper limit on bandwidth that can be had with this method? I.e. can you take very thin hardline (0.086 and less) to make probes that are capable of sniffing emissions that are very fast? I see 10GHz near field probes available, but for 10,000$ each... however you can also buy a rf probe sniffer kit on ebay for 400$ and people seem pretty confident in making them for <5$ out of old hardline pulled out of test equipment.
most affordable high performance flexible RF (ku band +) cable? - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: June 14, 2017, 01:47:05 am
content: What is the most affordable vendor for this stuff? I can get lengths on ebay for some stuff.. but if I wanted 25 feet of something low loss and flexible (it seems all the 'lab grade' flexible ones have better performance or similar that to rg-seamless copper hardline)Are there any 'gems' that give everyone a run for their money and stand out?Stuff like florida rf labs lab-flex 200 (most impressive that I found) , pasternacks VNA cable, multiflex 141... who would have something similar and cheap for 25-50 feet? What is the bottom dollar price for performance stuff like that (outside of rare ebay deals?)
stripping / cutting hardline less then 1/8th of an inch? - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: June 14, 2017, 01:40:22 am
content: How is this done? I see pipecutters for sale for hardline thats <1/8th of an inch.. for 12$ but how about smaller ? (0.083 etc)I have done it by nibbling away at it with carbide cutters, (which I am selling in the WTS section) but it can't be good for RF reasons.Are there affordable tools for this not part of a 1000$ kit?
do the chinese counterfit rf cable on ebay? - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: June 12, 2017, 10:22:42 pm
content: high end stuff

author: Johncanfield
author_rank: Regular Contributor
timestamp: June 13, 2017, 10:02:58 pm
content: Really? They will fake anything if there's a profit involved. They consider it "borrowing", normal Chinese business behavior.
rf antenna coatings? (biconical) and effect of wood  - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: June 11, 2017, 04:59:42 pm
content: I have made two biconical antennas, made of two equal cones, that have height=width. I'm not sure about the impedance, I think I messed it up (they come out to ~60 degree cone angles, one is about 1.5 feet tall, the other one is about 8 inches tall)... it seems that the small one has very similar performance to the big one above like.. 500MHz.. but they both seem to receive fairly high frequencies when tested (though the 3db point of the big one is low).. cone spacing is like 1.5mm for the small one and 4mm or so for the large one. The large one uses a BNC connector soldered into the bottom of the cone, the smaller one uses a hardline soldered to the bottom of the cone. The big one has two plexiglass disks separated by fiberglass rods giving it support (the cones are glued to the plastic disks using goop, and the rods are attached using plastic epoxy, while the small one just has kabob skewers superglued to it acting as supports (for now).I don't think the impedance is near 50(I messed up following other peoples plans, they meant for a 50antenna it should be the same height and width as a finished antenna, not per cone).But anyway, I figured I can put them on the roof, or in the attic.They are made of copper sheet that has been soldered together and hand formed into cone shapes using template cutouts. What kind of (cheap) coating can I use on these antennas? I figured the smaller one will be more sensitive to the coating used.How much loss in signal would I get from the wooden roof covered in aslphalt tiles for different frequency ranges? I thought a good solution would be to put the big one in the attic hanging off the center beam (as the frequency is not that high), while the small one should be mounted outside, elevated over the house (since it can pickup fairly high frequencies (i tested it to the big one to GHz, like 12.. the BNC cable might be to blame, and the small one could do 18 (my max)). Not 3db points of course I would expect the big one to take a beating from the wind.. so I think it will have to stay in doors. The small one if mounted properly and protected can survive.
Eddystone Shortwave Manual #4 from 1938 - Page 1
Forum section: electronics / rf-microwave

author: EdEditz
author_rank: Contributor
timestamp: June 10, 2017, 08:49:18 am
content: I found this PDF file of magazine number #4 of the 1938 Eddystone Shortwave Manual.It is full of DIY build projects like tube transmitters, receivers, power supplies etc.It's a real little goldmine for those that love vintage RF electronics.Here is the link to download the PDF straight from Mediafire (free of course):http://www.mediafire.com/file/aiw7wvg7qaszqla/Eddystone+Shortwave+Manual+No4+1938.pdf

author: xrunner
author_rank: Super Contributor
timestamp: June 10, 2017, 12:03:17 pm
content: Quote from: EdEditz on June 10, 2017, 08:49:18 amIntersting find. Even has an oscilloscope project. Alas those days are long gone. The vast majority of the young crowd doesn't care about building those types of projects (even using modern tech). They don't even know what ham radio is - or what shortwave radio is. In know I have neighbors in their 30's that don't.

author: EdEditz
author_rank: Contributor
timestamp: June 10, 2017, 02:46:49 pm
content: Yes you are so right. What a shame really isn't it. When I started my electronics hobby in the early 80's (I was born in 1968) I loved to build transmitters with vacuum tubes. I found it fascinating to watch them glow and if you drew current they'd glow blue! Amazing. These days, if it hasn't got a color display, they won't give it a second glance.
Series of 5 ham radio howto articles by ham/fashion designer Diana Eng - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: June 08, 2017, 01:56:16 am
content: This is all really useful information.http://makezine.com/2015/11/06/5-ham-radio-projects-with-diana-eng/The log periodic antenna might lend itself well to a roll-up fabric treatment.So what do people think about the newer woven coated antenna wire she mentions? Has anybody worked with it?
Microwave Oscillator Expertise Desired - Page 1
Forum section: electronics / rf-microwave

author: Engineer Tom
author_rank: Newbie
timestamp: June 07, 2017, 01:58:48 am
content: I have a friend who is interested in using a commercially available inexpensive oscillator in the 850 to 1020 MHz range. The unit has a square wave output. He wants to convert the square wave output to a clean sine wave output. His efforts so far have been (expectedly) met with challenges related to stray inductance and capacitance when building an outboard amplifier and resonant circuit to achieve this goal. Breadboarding in this frequency range is different than at audio frequencies.I believe the solution can best be crafted by someone with experience in this area. He was frustrated by not having the mathematical background, however I do believe practice will trump (let's not go there!) theory in this case.Does anyone here have such experience, able to assist or know someone who is able to assist him? I have no involvement in this project other than posting this message. I will pass along any preferred contact information so he can directly pursue the matter with the individual.

author: AF6WL
author_rank: Newbie
timestamp: June 07, 2017, 04:07:42 am
content: Easy place to start is with an off the shelf filterhttps://www.minicircuits.com/pdfs/LFCN-1000+.pdfSame company has lots of other building block components e.g. simple to use MMIC amps if you need more output.
grease on microwave connectors? - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: June 17, 2017, 11:23:32 pm
content: dielectric type... for increased mating cycles?

author: Krytron
author_rank: Contributor
timestamp: June 18, 2017, 12:13:07 pm
content: usually used to displace water that will condensate in the connector over time.

author: CopperCone
author_rank: Super Contributor
timestamp: June 18, 2017, 04:33:31 pm
content: i mean, will it decrease thread ware? and is it ok to use for like ku band stuff?

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: June 18, 2017, 04:47:25 pm
content: Haven't heard of anyone doing this - I'd imagine it would change the impedance of the line due to the grease filling up any air voids. Having said that, connectors used at Ku band (SMA, N, TNC) don't have air voids so this may not be an issue. Someone with access to a VNA and expendable cables/connectors could try it out?Also, the limits placed on mating cycles are due mostly to spring tension on the leaves of female connectors. They will give a low resistance connection after the cycle limit, but there's no guarantee on decent VSWR.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: June 18, 2017, 06:03:42 pm
content: I remember having read a recommendations both to use pure vaseline and (prevailing) not to do this at all.Did not apply specifically to any frequency band, though.Of course, anything with more various ingredients will be worse. Some measurements might be a good idea.

author: CopperCone
author_rank: Super Contributor
timestamp: June 18, 2017, 06:04:13 pm
content: oh I see. It's just that they make this horrible feel tightening... by my standards anyway. I wanted it silky smooth.
How are wideband 90 degree hybrids constructed? Possible to DIY cheaply?  - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: May 30, 2017, 07:03:29 pm
content: Some of the most interesting antennas for ultra high frequencies require 90 degree phase transitions. What goes into a 90 degree hybrid, especially a broadband one and is it possible to construct one oneself without fancy equipment?

author: rfeecs
author_rank: Frequent Contributor
timestamp: May 30, 2017, 07:16:42 pm
content: Depends what you mean by ultra high frequency and fancy equipment.For microwave frequencies, branchline couplers are easy to fabricate but typically narrow band.Coupled lines give broadband 90 degree phase performance but can be harder to fabricate.Have a look at this:http://www.markimicrowave.com/blog/2015/04/top-7-ways-to-create-a-quadrature-90-phase-shift/
Looking for some waveguide expertise here - Page 1
Forum section: electronics / rf-microwave

author: wkb
author_rank: Super Contributor
timestamp: May 11, 2017, 09:51:43 am
content: Picked this up at a local ham fest. Not being a microwave nut by any stretch of imagination I wonder what this stuff does? OK, horn antennes butthere is more to it. Maybe something with polarisation ?? No clue..Hope the images are enough clue to the initiated...

author: wkb
author_rank: Super Contributor
timestamp: May 11, 2017, 09:52:52 am
content: more pics

author: kazam
author_rank: Regular Contributor
timestamp: May 18, 2017, 09:51:24 pm
content: 45 degree polarizationSeptum could be cross-polarization suppression. CP polarizer if made of metal but doesn't look like it.Dielectric around edges I'm not sure but could be far-field sidelobe suppression. Or cross-pol. Or both!Radome is most likely just for protection or to keep pressurized air inside. This prevents dust from entering the waveguide.Looks like radar stuff for X-band. 10GHz.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: May 19, 2017, 06:17:34 am
content: That's a double ridge waveguide. The ridge increases the bandwidth that the waveguide can transmit without multiple modes (ie, without dispersion). Same goes with the ridges inside the horn flare - these extend the bandwidth of the horn. They work just like aVivaldi antenna. You don't often see double ridge waveguide in radar, so this could be X-band satcom equipment, or EW or radar warning receiver antennas. Very cool find!Edit: septum polarizers are not normally flared, they usually have a 'stair-step' appearance. They're used to create circular polarization. You'll often find them inside satellite TV LNBs.

author: cj
author_rank: Contributor
timestamp: May 29, 2017, 08:54:12 am
content: Looks like the parts you have are from this type of feedhorn.CJ

author: wkb
author_rank: Super Contributor
timestamp: May 29, 2017, 07:31:02 pm
content: The Heelweg picture shows a very similar but a lot bigger horn.Wilko
Precision RF Meter from Heathkit - Page 1
Forum section: electronics / rf-microwave

author: CharlieWorton
author_rank: Regular Contributor
timestamp: June 22, 2017, 06:08:42 am
content: Hi, all - I've built my share of Heathkits over time; a few of them I still have, and they still work. Sometime in the 1990's they got out of kits entirely, and focused on education. But they couldn't make that work either, and went out of business shortly thereafter.A few years ago, they announced that they were back. Their first kit was a very simple AM radio; their second was 'the worlds most reliable clock'. Not the worlds most accurate; just the most reliable.The retail price for these goods was perhaps 5 to 10 times what a similar product would cost at a local store, so I chose not to participate. I already own a clock and a radio.But they now have another offering, which may be of interest to the Hams in the group; it's called an HM-1002 precision RF meter. I'm not a ham, so I don't understand the meaning and usefulness of the gear. And I'm certainly not endorsing it. But Heathkit is very proud of it, and they speak glowingly of it.And given how important a role Heathkit has played in ham radio over the last century, I felt it might be of interest to the people here.Here's a link:https://shop.heathkit.com/shop/product/precision-rf-meter-hm-1002-pre-order-33Anyway, that's it. I have now fulfilled my entire purpose in life; to breathlessly bring the news of the existence of a product that I have no clue in the universe about. Ahem. I shall now scurry back to the beginners page, where I belong.Hope this is of interest - Charlie
[Video] Radio technology display and demonstration - Page 1
Forum section: electronics / rf-microwave

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: May 25, 2017, 05:16:12 am
content: Last weekend the Wireless Institute of Australia held its annual convention at Hahndorf, just outside Adelaide.A major event on the Sunday was the 'Come and Try Radio Day' at the local football oval.This was a cooperative event organised by Adelaide's amateur radio clubs.Numerous radio activities were on show including a near-space balloon launch (and tracking), microwave (gigahertz) communication, amateur television, home construction, antennas and more.If radio and electronic geekery appeals, you might enjoy this video.
Pll loop filter - Page 1
Forum section: electronics / rf-microwave

author: stcoso
author_rank: Regular Contributor
timestamp: June 05, 2017, 10:49:33 am
content: Hi, i'm trying to design a loop filter for pll.I'm using an ne564 with a divide by 4 flip flop. The frequency of the VCO is around 55 MHz and the reference frequency is 13.56MHz . It works in the range between 13.66MHz and 12.11MHz ( which is fine for me) but when i set ( with an externel signal generator) a frequency near 12.56 MHz i loose locking. If i move just above or below that freq everything is fineRight now i'm using the Values showed in the attached picture.EDIT: forgot to mention that there's a 1.3k resistor in series with the filter inside the IC

author: w2aew
author_rank: Super Contributor
timestamp: June 05, 2017, 01:30:36 pm
content: Loosing lock at one frequency, and picking back up again on either side of that frequency, is likely not a problem with the loop filter, but maybe with the connection to your external siggen. Are you terminating it? Have you verified the signal amplitude at the chip? Have you looked at what the VCO and phase detector voltage are doing when locked and unlocked?Lots of good design information and performance curves in the datasheet:http://pdf.datasheetcatalog.com/datasheet/philips/NE564.pdf

author: stcoso
author_rank: Regular Contributor
timestamp: June 05, 2017, 02:30:52 pm
content: The signal is terminated. At the ic input I see no difference at that particular frequency. The VCO get simply crazy, producing frequency all over the range.PS: I've been following your YT channel for a while... Great job.. Learned a lot.

author: w2aew
author_rank: Super Contributor
timestamp: June 05, 2017, 04:01:53 pm
content: Make sure you check the basics - proper power supply decoupling, etc. If you alter (slightly) the VCO related components, does the problem frequency move?

author: stcoso
author_rank: Regular Contributor
timestamp: June 05, 2017, 04:25:27 pm
content: Well.. Seems like I've got some problem with the Schmidt trigger of the flip flop. It doesn't get triggered at the right time...
Best strain relief compound for HF (say USB 3) - Page 1
Forum section: electronics / rf-microwave

author: alanambrose
author_rank: Frequent Contributor
timestamp: May 23, 2017, 02:59:34 pm
content: Hi,Can anyone recommend a hot snot / potting epoxy kind of compound to protect USB 3-speed connections from vibration. This is a non-critical application for some exhibition equipment which has just come back for repair due to some shipping-induced damage (probably a big drop) ... I've done all the physical strain relief I can but I would really like to embed some USB C-speed connections in something like epoxy / hot snot etc to provide further protection against vibration / shipping container impact ... but without screwing the HF characteristics of course.Alan

author: Lord of nothing
author_rank: Super Contributor
timestamp: May 23, 2017, 05:07:36 pm
content: How about Rugged USB Connector?The Industry build such for an good Price.I know some USB Card have USB Connector who could screwed in:http://www.delock.de/produkte/F_319_USB-3-0_89325/merkmale.html?setLanguage=enMaybe someone here know how does it called?!

author: alanambrose
author_rank: Frequent Contributor
timestamp: May 23, 2017, 07:03:03 pm
content: The physical and electronic design is not up for grabs (this is a repair). IthinkI'm asking (I'm no RF guy) are there readily available glues / compounds which have a low dielectric strength at 10GHz? The connector is this one FYI - not that it makes any difference to the question:http://www.cliffuk.co.uk/products/usb/dualusbinxlr.htm(the dual USB 3 one at the 2/3rds down the page).This page:http://www.engineeringtoolbox.com/relative-permittivity-d_1660.htmlsuggests Araldite has a dielectric constant of about the same as glass. If only I could remember what that meantAlan

author: DaJMasta
author_rank: Super Contributor
timestamp: May 23, 2017, 07:19:25 pm
content: What part of it, exactly, are you trying to pot? If you can keep the potting material away from the signal lines (or outside the shielding), it can be basically whatever you want, because then your dielectric is either the stuff already in the connector or it's air. I don't see why you'd need to get potting compound either in the connector housings or on the header contacts, so I'm not sure the choice of materials would need to be too elaborate.I think mentioning other connectors as options isn't a bad notion, since a repair could just swap them out, but it may be difficult to find very different ones in that form factor. If the mounting of the XLR plate is solid, then maybe the best way to relieve physical stress on the connectors is actually securing the wires externally - like bundling with other cables or holding down to tie points or something.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 23, 2017, 07:49:44 pm
content: What does RF have to do with it? If you're glopping the goo all over the connections, you're doing it wrong... it's a shielded connector.Tim
SDR that was able to display signals coming from diff directiondifferent colors? - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: May 23, 2017, 10:49:39 pm
content: I vaguely remember seeing this a few years ago. Somebody had made a build of some SDR software that they modified to work with a multi-input receiver or specialized antenna array? Multiple receivers?anyway it was a demonstrated working system that could in realtime not just determine the direction the signal was coming from but also display it in different colors in the waterfall, the waterfall was colored with the directions of different signals- visualized in color, in realtime.I am sure I bookmarked and saved it but now cant find it. Does anybody know what I am talking about, or where it can be found? Seems like a cool project.

author: hendorog
author_rank: Super Contributor
timestamp: May 23, 2017, 10:57:41 pm
content: Not sure if this is it, but I remember seeing this a while back which sounds similar:http://www.rtl-sdr.com/building-a-passive-radar-system-with-an-rtl-sdr/

author: cdev
author_rank: Super Contributor
timestamp: May 23, 2017, 11:32:08 pm
content: No, that's not the thing I was referring to,(Still that experimenters underlying technique of running multiple dongles off a single crystal oscillator is a great idea)

author: piranha32
author_rank: Unknown
timestamp: May 24, 2017, 02:57:06 am
content: Maybe this one?http://df6nm.de/ColourDF/ColourDF.htm

author: cdev
author_rank: Super Contributor
timestamp: May 25, 2017, 04:33:09 am
content: Thats it, thank you! Isn't the idea pretty neat!

author: jpanhalt
author_rank: Super Contributor
timestamp: May 25, 2017, 04:49:23 am
content: That method of using the phase relation of an E-field antenna to resolve the 180° ambiguity inherent in crossed loop H-field antennas has been used in ADF for many years (https://en.wikipedia.org/wiki/Radio_direction_finder#Automatic_direction_finder_.28ADF.29).Neat to see it applied to SDR receivers.John
Separation of toroid chokes - Page 1
Forum section: electronics / rf-microwave

author: piranha32
author_rank: Unknown
timestamp: May 22, 2017, 08:31:38 pm
content: Hello,I'm building a low pass filter for a switching mode USB power supply. The filter has T layout, with two toroid chokes and a capacitor to ground between them. A crude prototype proved to give sufficient attenuation of the switching noise, and now I want to build the final board. Initially I planned to mount the chokes perpendicular to each other, but unfortunately I don't have enough space in the case for such layout. My only options are to mount them side by side parallel to each, ~5mm apart, or to experiment with 3D layout. Because lifting one of the chokes off the board will create a lot of problems with mechanical design and possible pickup of the stray magnetic field from the converter, I would prefer to mount them side by side. However, I don't know how it will affect the performance of the filter. In theory all the magnetic field should be contained within the core, but in reality there will be some leaks outside.The question I have is how should I proceed with the filter? Will the leakage be so insignificant that I should not worry about it, or should I install a piece if steel screen between the chokes? Or maybe give up on mounting them together and try to find another arrangement?
SAW/BAW filter identification  - Page 1
Forum section: electronics / rf-microwave

author: kazam
author_rank: Regular Contributor
timestamp: May 18, 2017, 02:20:28 pm
content: Hi,I need to identify an unknown filter. It's in a typical SAW filter capsule. Marking isT6E2Bw 50MhzFc 1086MhzIL 0.7 dBThanks!/K

author: edensrock
author_rank: Contributor
timestamp: May 19, 2017, 03:25:05 pm
content: Have you checked Tai-Saw filters? The markings remind me of their filters. How did you get the BW, Fc and IL values? IL seems to be too good to be true.

author: kazam
author_rank: Regular Contributor
timestamp: May 19, 2017, 06:12:07 pm
content: Found it. It's a Sawnics SA1090HPI measured the IL with a calibrated VNA in a small test fixture. Yes, it's very low indeed. Notice that rejection is really not that great though.
Made Colpitts and Hartley oscillators, what does the radio pickup ? - Page 1
Forum section: electronics / rf-microwave

author: lordvader88
author_rank: Frequent Contributor
timestamp: May 18, 2017, 09:23:13 pm
content: I solder'ed up a Colpitts and Hartley oscillators, about 980kHz and 720kHz. I have a transistor radio here, tuned to some random dead space, and it locks in on my circuit, and the AVC circuit sometimes thinks this is a proper signal.Sometimes this thing squeals in the audio range, and I can influce that modulation by tocuhing the inductor

author: lordvader88
author_rank: Frequent Contributor
timestamp: May 18, 2017, 09:33:08 pm
content: The radio is powered by the same 12V DC output wall transformer, as the oscillator circuitI am using a Byrmen 869, which does not have very consist frequency measurements at any range it seems, I can read freq. from a few dail settings with this thing, and they often don't match, because some will read zerofor instance on AC+freq, I read 1.5257V and 0.000Hz yet if i switch to mV(AC)+Hz I get 748.0kHz(it changes a lot)thats about what it should be by the equationsthis little 1/4W inductor gets warmSo I guess its the changing conductance of the transistor, thats changing at is also modulated, and sometimes drops into AF and I hear it

author: lordvader88
author_rank: Frequent Contributor
timestamp: May 18, 2017, 11:38:17 pm
content: well I believe A capacitor exploded, and I don't know whywow something really blew up and i don't think it was on the radio, Colpitt's oscillator circuit, it sounded like it was the 12V 0.75A wall supply

author: w2aew
author_rank: Super Contributor
timestamp: May 19, 2017, 12:32:13 pm
content: Quote from: lordvader88 on May 18, 2017, 11:38:17 pmSomething is certainly "off" with the design if an inductor is getting warm! Inductors would normally not dissipate power because their resistance should be quite low - sounds like you had a LOT of DC current flowing through the inductor - not something you'd usually have in an oscillator design.

author: lordvader88
author_rank: Frequent Contributor
timestamp: May 19, 2017, 02:47:25 pm
content: No just a standard common emitter circuit, using about 25mASo with an AM radio tuned to something random I think, its dial is taken off, it might be near the circuits frequency or not, IDK, and I don't have a working oscilloscope right nowwhat part of the circuits pick this up ?
I need an Spectrum analizer for my hobby - Page 1
Forum section: electronics / rf-microwave

author: Free_WiFi
author_rank: Regular Contributor
timestamp: May 18, 2017, 11:38:58 pm
content: I drawing wifi antennas (2,4 Ghz) and from not long time ago, i also started an project from this thread here : Diy metcal power supplyhttps://tinyurl.com/z6be7c7Arrived at this point i can't proceed anymore in my hobby without an spectrum analizer .I dont need something of very expensive ,i just need something that can cover my basic needs for wifi antennas (2,4Ghz) and give me a help on projects like the DIY METCAL POWER SUPPLY (13,56 Mhz)I need your help to take 1 spectrum analizer ,pls help me in this "adventure" also because i would be a newbie to this stuff .Thanks you soo much .

author: tautech
author_rank: Super Contributor
timestamp: May 18, 2017, 11:49:30 pm
content: Other than second hand units that could be cheaper than these but you won't know if they are working to spec or have been damaged by misuse.These are pretty popular on the forum for those getting into SA's, the 2.1 GHz units can be improved to operate up to 3.2 GHz.https://www.eevblog.com/forum/testgear/hack-of-sigllent-spectrum-analyzer-ssa3021x/

author: dmills
author_rank: Super Contributor
timestamp: May 19, 2017, 11:58:26 am
content: Get thee to a Ham rally, what you want is a "Radio comms test set", even something like an Anritsu 8801B would do, and I got one of those for £60 (Screen is poor, a common failing on that model, but replacements are allegedly available).They usually (these days) come designed for mobile phone testing, but a few button pushes will usually get you to a useful spectrum analyser, power meter, and often a signal generator. Because they do not usually say "Spectrum analyser" on the box they go for little money considering that the original price was usually 5 figures.I would suggest however that what you really need for antenna work is more likely to be a VNA, somewhat rarer at a reasonable price point.73 Dan.

author: brucehoult
author_rank: Super Contributor
timestamp: May 19, 2017, 12:10:55 pm
content: I have one of these and find it useful.http://j3.rf-explorer.com/40-rfe/article/80-getting-started-with-rf-explorerThere are models covering a single ISM band (e.g. 433 MHz or 915 MHz) for $99, plus you can add on an extra module such as the 2.4 GHz one for $45.If you only want 2.4 GHz and nothing else then there is a model for $119https://www.seeedstudio.com/RF-Explorer-model-2.4G-p-924.htmlOr you might want the "WIFI combo" modelhttp://j3.rf-explorer.com/60-rfe/specifications/131-rf-explorer-wifi-combo-specificationfor $270https://www.seeedstudio.com/RF-Explorer-WiFi-Combo-p-2321.html
Calculate antenna PCB attenuation - Page 1
Forum section: electronics / rf-microwave

author: DavidDLC
author_rank: Frequent Contributor
timestamp: May 16, 2017, 07:24:14 pm
content: I'm not an RF engineer or have too much RF experience.But is there a way to calculate a PCB antenna attenuation ?Or how do you measure it ?David DLC

author: Pratik_Panda
author_rank: Newbie
timestamp: May 18, 2017, 12:59:24 pm
content: Simulators like Microwave Studio are the best way to get a proper set of measurements for antenna designs.I'm not entirely sure about the term "antenna attenuation" here, are you referring to its power loss?

author: DavidDLC
author_rank: Frequent Contributor
timestamp: May 18, 2017, 09:31:24 pm
content: Thanks for you answer, and when I refer to attenuation I was referring to antenna power gain or loss.David DLC
eBay sig gen - Page 1
Forum section: electronics / rf-microwave

author: CJay
author_rank: Super Contributor
timestamp: May 28, 2017, 10:21:26 am
content: Not sure if this belongs in here or in the test gear section but as it's RF and my interest is for Ham Radio...Has anyone laid hands on one of these units?http://www.ebay.co.uk/itm/0-5Mhz-470Mhz-RF-Signal-Generator-Meter-Tester-For-FM-Radio-walkie-talkie-debug-/332167042350?hash=item4d56b2d52e:g:IPMAAOSwmgJY2kJgIt doesn't look like the usual AD PLL/VCO units as the ranges are wrong and it appears to have some sort of attenuator built in as well as offering FM modulation.Would be very interested in opinions of anyone who has got or used one of these and if possible some idea of the internals of the unit?

author: W2NAP
author_rank: Unknown
timestamp: May 29, 2017, 01:39:20 am
content: personally I would not touch it. I avoid made in china as much as possible. i got a fluke sig gen from ebay last year for a bit over 150 shipped
Gadget for high frequency guy - Page 1
Forum section: electronics / rf-microwave

author: oe7dbh
author_rank: Newbie
timestamp: May 15, 2017, 05:04:14 am
content: 23cm band, power amplifier for different use..... tested by OE7DBHhttps://www.oe7forum.at/viewtopic.php?f=7&t=284&start=150#p2048and slightly different version with 2 gain values :https://www.oe7forum.at/viewtopic.php?f=7&t=284&start=165#p2123and All mode UP converter with Output on 13cm band :https://www.oe7forum.at/viewtopic.php?f=7&t=410&start=375#p2050.
Thread on Relatively Inexpensive "Power Meters" in Test Equipment Forum - Page 1
Forum section: electronics / rf-microwave

author: Electro Fan
author_rank: Super Contributor
timestamp: May 12, 2017, 11:42:24 pm
content: In case any RF, Microwave, Ham Forumers might find this interesting....https://www.eevblog.com/forum/testgear/26-chinese-powermeter/msg1207285/#msg1207285(this is just to point any interested folks over there, might be best to keep the comments together in one thread)
Musings on mixers, tri-filar wire and crystal filters. - Page 1
Forum section: electronics / rf-microwave

author: CJay
author_rank: Super Contributor
timestamp: May 12, 2017, 06:30:22 am
content: So I've built a couple of double balanced mixers using FT37-43 cores, home wound Tri-filar wire and various diodes (1N4148, 1N6263 and now I'm attempting to find some HSMS-2829 diodes) and they certainly seem to work but...How much influence on performance does the wire have?I can find all sorts of information about how long the wires should be to get a number of turns on the core, how many twists per centimetre, what percentage of the core should be covered etc. but so far I've not really found anything 'simple' about how wire diameter affects performance, maybe because it can't be made simple?Of course the thicker the wire (within practical limits) the easier it is to handle, but am I doing my amateur DBMs a disservice and not giving them the best opportunity to perform for me if I choose a wire that's too thin or too thick, is there a sweet spot or a way to calculate the optimum by rule of thumb or rigid equation?Maybe I'm thinking too much into it?I've also recently got my hands on half a dozen NATO marked crystal filters, centred around 43MHz and using, I think*, 8 crystals. They seem like they may be ideal for use in a homebrew receiver (HF bands) but I'd find it quite useful to have some data on them, does anyone know of a way to find data from a NATO part number or even just what they were intended for use with?I could (and will) attempt to characterise them for myself but my CMU200 doesn't want to play nicely with GPIB and FRERES as yet and I'm not confident how I would work out input/output impedances and match them to prevent skewing results anyway.* I think 8 crystals because my over enthusiastic disassembly efforts may have scattered a crystal or two around the garden but in my defence it is a massively overengineered device that required a *LOT* of heat to take apart.

author: German_EE
author_rank: Super Contributor
timestamp: May 12, 2017, 06:05:22 pm
content: I can't remember the formulas for this but the wire diameter, the insulation thickness and the number of twists per inch affect the impedance of the overall circuit. Just think of networking cable, the twist is designed to make a 100 ohm transmission line. I have one design for a mixer in my files where one transformer must be made using 100 ohm twisted pair and the other must be made with 50 ohm twisted, not easy.The only source of information for your filters that I can think of is a guy called Ben Knock G4BXD. He's been collecting military radios for decades and can be reached at military1944ataol.com
Storing Data Fast - Page 1
Forum section: electronics / rf-microwave

author: jpanhalt
author_rank: Super Contributor
timestamp: May 11, 2017, 11:08:36 am
content: I have decided to try using a 3 MSPS ADC (16-bit, e.g., a ADS7885 or similar ADC) to allow digital filtering of a relatively low frequency (center at 500 kHz, bandwidth < 1 MHz) signal. Ideally, I would like to record for 1 second, but recording for 300 millisecond would be OK. Presumably, some sort of DMA controller and memory (FRAM?) is needed, but the number of offerings are staggering.How does one get from the raw ADC output to a memory that can be accessed at relative leisure? Any specific suggestions?Regards, John

author: w2aew
author_rank: Super Contributor
timestamp: May 11, 2017, 04:45:25 pm
content: While I don't have any specific recommendations (I'm really more of an analog guy), the common way to do this as ADC speeds ramp up is to immediately DMUX the data samples into several parallel paths that are written to memory at a more leisurely writing rate.

author: David Hess
author_rank: Super Contributor
timestamp: May 11, 2017, 06:09:30 pm
content: 3 MS/sec with 16-bit words is pretty slow on the scale of things. Ancient digitizers handled faster data rates with just TTL logic.A 333 nanosecond cycle time is so slow that it could be divided into 2 phases leaving 150 nanoseconds to update the address counter and 150 nanoseconds to write the data to RAM. A discrete logic DMA controller for this is trivial but most designers would use a small CPLD or FPGA. The logic only has to deal with the address and control lines and not the 16 data lines.1 second at 3 MS/sec is 3 million words. 3 million 16 bit words is 48 Mbits. That is larger than available SRAM parts but two 2Mx8 SRAMs (16Mbit and about $10 each) would be good for 2/3rds of a second.A design using a single 8 bit wide DRAM and more complex logic would be less expensive and have a much longer recording time.