hybridfree/eevblog-posts huggingface dataset:
Antenna Coupling Circuit - Page 1
Forum section: electronics / rf-microwave

author: csheldon
author_rank: Contributor
timestamp: July 25, 2017, 10:13:34 am
content: Hello,I was experimenting with 433 MHz saw based transmitters and found quite a lot of materials about topic, but all they teach you is how to calculate the values of LC tank circuit , and that's fine. But what troubles me is how to calculate the antenna coupling circuit (L2 , C5) in the schematic below. Antenna is a quarter wave monopole , and if I got it right, it's impendance should be around 35 ohms.... L2 and C5 values in this schematic are 470 pF and 120 nH. Can somebody with experience please help me about this? Is it important to know the output impendance of the generator (transistor and surroundig circuit) to calculate this right. This is the link :http://wireless.murata.com/media/products/apnotes/sawbasedtransmitter.pdf

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 25, 2017, 01:20:17 pm
content: Well first of all, what are the reactances?I think you will find C5 is a coupling cap (much lower reactance than the parts around it), and then L2 will be somewhat of a lowpass filter, but also accounting for load capacitance (if the antenna is electrically short, not a properly resonant monopole), or matching to the oscillator (which itself has an oddball impedance, it's hardly a resistive amplifier).Tim

author: IkariShinji
author_rank: Newbie
timestamp: August 04, 2017, 12:07:26 am
content: They are for antenna tunning. Here is another app note from Murata. In the last page, it notes L and C "can be used to tune to an unknown antenna".http://wireless.murata.com/media/products/apnotes/highdataratesaw.pdfThey pick a large inductance value in the reference to avoid loading on the resonator circuit.With a proper monopole antenna, I bet you are better off without L2 at all.
Spacing of two EMC suppression cores - Page 1
Forum section: electronics / rf-microwave

author: Circlotron
author_rank: Super Contributor
timestamp: July 28, 2017, 05:40:51 am
content: So I have this old clunker laptop and the power supply box causes twitter noises on the AM broadcast band. I have several split ferrite cores that I am going to try out. Wurth 742-7113. Leftovers from work. Anyway, I'm am thinking would it make any difference if the cores are separated somewhat or butted right together?

author: cdev
author_rank: Super Contributor
timestamp: July 28, 2017, 08:17:03 pm
content: if either one is big enough for you to loop the power cord through several times that works best.If the noise source is the power brick, you may want to try putting one of them on the AC side if its acting as an antenna for the RFI.If its a real problem you may want to buy some more.

author: Circlotron
author_rank: Super Contributor
timestamp: July 28, 2017, 09:52:17 pm
content: I tried two on the AC side, both with the cord looped through twice and one on the DC side also with two passes. Didn't really help to any noticeable degree. Might just get a better brick.

author: DaJMasta
author_rank: Super Contributor
timestamp: July 29, 2017, 06:48:04 am
content: I don't think spacing matters so much, it's not like the capacitance of the cable in between is going to be that much to make much of a filter outside of just the effect from the number of ferrites and the number of turns you can get through them.I think the difficulty is just that the AM band is pretty low frequency and since just using a ferrite with a couple turns of mains cable isn't a huge amount of extra inductance, the real rolloff point is probably high above the normal AM broadcast band.Is shielding the box or the cable a potential option? May be simpler than just replacing the power supply, though replacing the supply or adding a nice choke on the board would probably be a better solution. Actually, does the power supply have any sort of mains filtering built in? Maybe you could get an IEC connector with built in filter (or something similar) and just splice it onto the mains side. Should do a better job than just a ferrite on the cable.

author: cdev
author_rank: Super Contributor
timestamp: July 29, 2017, 02:27:40 pm
content: (Magnetic) Materials used makes all the difference in RFI suppression for any given frequency.

author: @rt
author_rank: Super Contributor
timestamp: August 02, 2017, 02:49:33 pm
content: If two cores are next to each other, butted together sideways, there’s a magnetic coupling so that a positive going curve produces a negative going curve on any adjacent cores, making it a rather inefficient, but perfectly valid transformer.There are example Amiga computers where separate analogue RGB video signals are sent parallel through RFI suppressors, and they use a piece of heat shrinkon the centre core so that it can’t touch the outer two. They must have found it worthwhile to do for an analogue video signal.
Low frequency RF to HF upconverter with an NE612? What transformer? - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: July 28, 2017, 05:02:26 am
content: Hello,I want to make a simple upconverter thats optimized for the bottom 550 KHz of signals (converting them to something higher.)Ive seen NE612 used in a DCF77 receiver so I am optimistic.I have a large ferrite rod coming on order and so I plan to make an upconverter that allows the balanced input on the Ne612 to be used.With the option to use either the loop or an unbalanced antenna.Does this sound like a good plan?I have an older upconverter which I'm going to reuse in part. I'm a little worried about ESD on the inputs so I want to use a transformer to galvanically isolate the input. Is that enough?I think I am going to use either an Arnold molybendenum iron powder core I have or #2 material. The transformer is the part that I wish that I had a better level of knowledge on.I want a tunable input stage with high selectivity.Does this sound like a good plan?

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: August 01, 2017, 08:19:00 pm
content: Yes, the concept is sound.Here's one I built many years ago. It used an external antenna.http://home.alphalink.com.au/~parkerp/projects/projlfco.htmLater on I built one with a large ferrite rod. This worked fine as a receiving antenna and allowed reception of beacons 100s of km away.
RC Arduino motor controller - Page 1
Forum section: electronics / rf-microwave

author: lolimpol
author_rank: Contributor
timestamp: July 31, 2017, 03:06:17 pm
content: ok, here is the situation, I have an RC boat with a brushed motor, just normal DC. It worked through a servo pressing a switchso every time you pushed the gas it would just fly of. because of that, I wanted to make an Arduino motor controller to take the servo signal through an Arduino/MSP430, through a MOSFET, into the engine. but how do I write the software? I have no idea about the incoming PWM signal, but that's why I'm asking you! so the main question is to help me with the software.

author: Ian.M
author_rank: Super Contributor
timestamp: July 31, 2017, 03:38:07 pm
content: You need to measure the ON time pulse width of the Futaba compatible servo control signal from the RC receiver and use that to control the motor speed by PWM.Seehttps://www.sparkfun.com/tutorials/348

author: lolimpol
author_rank: Contributor
timestamp: July 31, 2017, 04:35:41 pm
content: ok, I'm sorry, the plan has changed. here are some pictureshttps://photos.app.goo.gl/8WtRKasUvBLJvycc2. I am using the Aux input on the controller, for a light instead of the motor. I'm buying an ESC.
TX Power vs Frequency - Same Circuitry - Page 1
Forum section: electronics / rf-microwave

author: gyropilot
author_rank: Contributor
timestamp: July 27, 2017, 05:48:12 pm
content: I've noticed that with some small QRP transceiver kits the transmit power (watts) decreases as the frequency increases. An example is the KN-Q7A and CS-series of SSB transceiver kits sold byCRKits.com. The kit is advertised at 10W on 40M band, 5W on 20M band, and 2W on 15M band. The circuitry is same for all bands but with different band pass filters.Can someone please explain... or at least point me to an article which explains... why this reduction in measured transmit power occurs?I did some web searches and couldn't find anything specific.Thank you and 73,JohnAA7US

author: CJay
author_rank: Super Contributor
timestamp: July 27, 2017, 07:10:17 pm
content: They're using cheap switching MOSFETs, IRF510, they aren't designed for RF and gate capacitance is a problem but they can produce good power up to at least 50MHz so it's got to be down to the design.There's a nice page about using switching FETs here:http://www.m0rzf.co.uk/20W_Amplifier/index.html

author: gyropilot
author_rank: Contributor
timestamp: July 27, 2017, 07:16:19 pm
content: Thank you CJay!Very interesting and helpful information on that link.I appreciate it.JohnAA7US
measurement of probability of intercept for FFT based analyzer - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: August 27, 2017, 05:37:29 am
content: I want to test the probability of intercept on the PlutoSDR.I have a pulse generator and a pulse counter. I was going to hook them together, and hook it up to the SDR, and see how the counter compares to the waterfall totals.Problem is, my counter only has a count mode that goes to 120MHz. The PlutoSDR was hacked to work at 70MHz, however, can I extrapolate that the probability of intercept will be equal in different frequency ranges? Will my results at 100MHz be true at 5.5 GHz?So long I set the LO and bandwidth so that my pulse signal is visible on the waterfall (even if only the edge), is it 'monotonous'? I can't see why not, but I know digital filters can do screwy things sometimes.I want to minimize the possibility of deluding myself (i.e. see if its a good idea to buy a 'commercial' real time SA).Seems ALOT faster then my hp70000 but I want to measure it.I want to measure it because from my reading (based on my previous thread on RTSA), it seems difficult and software implementation specific to determine from just sampling speed.
Help me understand the cost of antennae - Page 1
Forum section: electronics / rf-microwave

author: jeremy
author_rank: Super Contributor
timestamp: July 19, 2017, 01:11:15 pm
content: So it seems like a ballpark price for a 30MHz to >1G bilog antenna used for EMC testing is around $5-10k. Example:http://www.measurement.net.au/p/4410518/aaronia-hyperlog-20300-emi.htmlI'm curious though, does anyone have any idea what fraction of this cost is the calibration? Assuming that you could go get it calibrated at a lab for free, would it be fairly straightforward and cheap for a decent ham radio person to make one of these? Or are there some expensive materials involved?

author: Gribo
author_rank: Frequent Contributor
timestamp: July 19, 2017, 04:25:38 pm
content: As far as I know, there are no special materials involved. Aluminum, Copper, Steel, and plastics. The main contributors to the cost are characterization (pattern and antenna factor at certain frequencies), calibration against a known standard and reaching the required precision for such device (0.1dB tolerance in some cases). Also, it is a very low volume device, so no economies of scale to drive the cost down.

author: D3f1ant
author_rank: Frequent Contributor
timestamp: July 19, 2017, 08:16:21 pm
content: I've wondered the same. With the likes of Rigol/Siglent low cost analysers having EMC filters, I don't get why they don't have a low cost antenna package to go with them. I don't believe too many would be using a 6k antenna on a 2k spectrum analyser. Where are all the china clone antenna?

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 19, 2017, 08:25:13 pm
content: I got an cheaper DVB-T Antenna the work.

author: slurry
author_rank: Regular Contributor
timestamp: July 19, 2017, 08:28:04 pm
content: It's a small market even for someone that clone an ETS Lindgren bicolog, no professional lab would buy a clone anyway.Aaronia makes some antennas in the lower price range that might fit the bill.For the hobbyist or amateur i would say that something like a Create CLP-5130 would do for most part but its a bit large..although i guess you will never get any AF-plot from the manufacturer.Buy two, set up an OATS and make your own plotsAbout USD1500 could get you something useable on ebay if you can wait long enough..

author: jeremy
author_rank: Super Contributor
timestamp: July 20, 2017, 07:03:20 am
content: Thanks for the tip on Aaronia, looks like you can get a 30MHz-1GHz calibrated bilog directly for about 1600 EUR. It's still a lot of money, but certainly less than 10k! I guess its time to start saving my pocket money...

author: dkozel
author_rank: Regular Contributor
timestamp: July 27, 2017, 10:47:27 am
content: These are for different bands than you may be interested in, but if I needed a directional wide band antenna this would be my first stop.http://www.rfspace.com/RFSPACE/Antennas.html
Excellent tutorial videos on RF & Analog design - Page 1
Forum section: electronics / rf-microwave

author: Jose Luis Collado
author_rank: Newbie
timestamp: July 25, 2017, 02:59:38 pm
content: I wanted to recommend a site that I found with many tutotial, repair and troubleshooting videos on RF & Analog circuit design (almost a lost art nowadays). Craig, the author, even found an error in a Jim Williams's book circuit expanation ! Here is the Link:http://www.analogzoo.com

author: GreggD
author_rank: Regular Contributor
timestamp: July 25, 2017, 06:39:55 pm
content: Excellent ! Thanks for sharing.I found things that I never thought about in this video;http://www.analogzoo.com/2015/11/jim-williams-analog-iq-8/Jim Williams would be proud.

author: bozidarms
author_rank: Regular Contributor
timestamp: July 25, 2017, 07:28:41 pm
content: Many tnx - very interesting videosRegards
Variable Attenuator for GSM - Page 1
Forum section: electronics / rf-microwave

author: ChristopherN
author_rank: Unknown
timestamp: July 26, 2017, 11:14:21 am
content: Hi,I need an variable attenuator for GSM signals with the following features:-DC to 3GHz-SMA Connectors-0 to 20dB attenuation settable via knob / poti / setscrew-up to 10WThis does not need to be a precise attenuator, I will use it for some quick tests.Can you recommend a matching product?ThanksChristopher
estimating RF filter power handling capability by size? general ID by temp? - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: July 14, 2017, 06:24:00 am
content: Lots of shit on ebay with no real specifications to be found. old, appears only in catalogs.. new versions cost order of magnitude more.Is there some way to estimate if something is like 1 watt, 10 watt, etc?Is it a safe bet to say if somethings got N connectors on it, its good for 10 watts?Same with isolators: Can you find one of particular size and assume others of similar size have same power handling capability?how about filter pole count estimation?what a fucking messcan you measure temp of these things to determine usability... like run for a minute and see if its physically hot? or is it gonna be internal problems that don't couple well (i don't know whats in these cans).Interested in stuff <1GHZ

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 14, 2017, 11:42:35 am
content: Congratulations, you've discovered why they cost orders of magnitude less.You could do lots of things, time permitting. Buy a couple, blast power at them, see where the one fails, then use the other at some reasonable derating from the failure point. (Or see if the frequency response changes when too hot, or changes permanently, even.)You could desolder / drill / cut / dismantle one and see how hot it gets internally, or inspect its components to get an idea of ratings. In some of these cases, you could still put it back together. Some not.Plenty of money to save, if your labor is heavily discounted.Tim

author: CopperCone
author_rank: Super Contributor
timestamp: July 14, 2017, 01:32:00 pm
content: how about stuff that uses cavities/bolts for tuning? Can you just measure those?

author: CopperCone
author_rank: Super Contributor
timestamp: July 14, 2017, 10:07:23 pm
content: how the hell do you run an isolator w/o a chassis, i thought its a piece of waveguide with magnet

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: July 15, 2017, 07:44:57 pm
content: You can make valid assumptions only within a certain technology, that is compare LC filters to LC filters and cavity filters to cavity filters. Within a technology, body size can give you a better idea of power handling capability than the connectors, as those are mostly chosen for seamless integration into the user's system. The big unknown factor is the number of stages/poles, as those need space as well. Maybe taking the filter's curves, then looking at comparable products will give you a better clue.As for circulators, your notion is correct. It was probably not meant to run them while disassembled.

author: CopperCone
author_rank: Super Contributor
timestamp: July 23, 2017, 04:19:23 am
content: I just bought a bunch of high power isolators on ebay.Assuming I series these up, the reflection from the fried filter should protect my power amplifier right (I got 4x 25w circulators with 20db of attenuation each).The power amplifiers are 10 watts;
Siglent spectrum analyzer does not switch off - Page 1
Forum section: electronics / rf-microwave

author: alexo
author_rank: Contributor
timestamp: August 19, 2017, 10:12:02 pm
content: My SSA3021 was always sluggish to switch off. After installing the TG option it has become practically impossible to switch it off - I need to hold the button depressed for ages and even that does not always work. Is there any fix for this ?

author: alexo
author_rank: Contributor
timestamp: August 19, 2017, 10:17:57 pm
content: Ignore. It is the power button. I wonder how easy is to replace it....

author: DaJMasta
author_rank: Super Contributor
timestamp: August 22, 2017, 07:31:09 am
content: Likely it's a molded rubber piece with a backing pad that makes contact with the PCB directly, and not a replaceable mechanical switch. Replacing the board that it's on is an option, but you'll likely get the results you want cleaning the PCB and under the button plastic, then checking for cracked traces running to and from it. There's a chance something about the latch the soft power button drives or the debounce circuits have some problem or cracked solder joints - it shouldn't be too hard to trace around.If you clean it and don't see damage, you could probe the output of the switch to see where the fault is too. And of course, if it's under warranty.... just send it in. Opening it up at all will void that, so don't attempt a fix if it's going to be covered.
Need low cost Bluetooth Audio module that transmits as AUDIO SOURCE  - Page 1
Forum section: electronics / rf-microwave

author: kjhuebner
author_rank: Newbie
timestamp: July 21, 2017, 11:50:24 am
content: I need a low cost Bluetooth audio module that acts as "Bluetooth AUDIO SOURCE" that transmits audio data TO a Bluetooth speaker.I would like something under $10 -- and ideally, under $5.00. Perhaps a low cost Chinese module.I can find lots of low cost Bluetooth audio modules that work as AUDIO SINK -- which can receive audio data.But no low cost AUDIO SOURCE modules have I found.The Silicon Labs WT32i costs $20, which is too high priced for my product development purposes.Ken HuebnerHardware Engineer

author: CJay
author_rank: Super Contributor
timestamp: July 21, 2017, 02:14:23 pm
content: There are lots of products out there for under $10 which will do just that but they're all consumer items, that does however ean they're available and they're cheap enough for your needs.Maybe buy one or two different versions to rip apart and hopefully find a source?The first that came up in my search:http://www.ebay.co.uk/itm/Wireless-Bluetooth-Transmitter-A2DP-3-5mm-Stereo-Music-Audio-Receiver-TV-DVD-PC-/362044218462?epid=19005746297&hash=item544b845c5e:g:LbMAAOSwAAVZbx-zI also think it's likely that they're the same as the 'receivers' but programmed/configured differently so it may be possible to reconfigure a 'receiver'?
How to connect an antenna wire ... - Page 1
Forum section: electronics / rf-microwave

author: hammy
author_rank: Unknown
timestamp: July 20, 2017, 08:12:38 am
content: Right now I'm designing a new antenna. It is an qrp end-fed antenna for portable use. This means it should be lightweight and small.The toroid is a FT-114-43 and the antenne wire is from dx-wire "UL". The toroid is on a pcb. The pcb is later covered with heatshrink tubing. This means no box, really lightweight.At first I thought I could use a 4mm banana plug to connect the antenna wire to the pcb. But this is too big. But I could use a 2mm plug (http://de.rs-online.com/web/p/2-mm-laborsteckverbinder/1559957/). I don't want to solder the wire to the pcb, it should be removable.Any alternative ideas how to connect the antenna wire detachable?Thank you!hammy

author: ChristofferB
author_rank: Frequent Contributor
timestamp: July 20, 2017, 08:28:53 am
content: A large pad with a large hole on the PCB, a crimp lug on the wire, and bolt the wire on with a short bolt, maybe?Wingnuts for ease of assembly, regular for ultra low profile?That's probably what I'd settle on!

author: hammy
author_rank: Unknown
timestamp: July 20, 2017, 08:47:25 am
content: Quote from: ChristofferB on July 20, 2017, 08:28:53 amI used the "crimp lug and wingnut"-connection in the past. It is the common way, beside a 4mm plug.But is a bolt through a pcb that reliable?How about a "flat male tab" (https://cdn-reichelt.de/bilder/web/artikel_ws/C180/FSP.jpg) ?

author: ChristofferB
author_rank: Frequent Contributor
timestamp: July 21, 2017, 02:09:11 pm
content: A flat tab could work too! I'm a big fan of flush-mounted 4mm banana plugs. you can just remove all plastic insulation and bolts and solder it on flat on the board, I think they make them commercially too.
#127 Yaesu FT-101ZD VFO Repair - Page 1
Forum section: electronics / rf-microwave

author: Radio Tech
author_rank: Frequent Contributor
timestamp: July 17, 2017, 12:29:45 am
content: In this video we take a look at a known problem with the 101ZD VFO

author: voltz
author_rank: Frequent Contributor
timestamp: July 17, 2017, 01:57:26 pm
content: Nice Buddy. One of my favourite radios to work on.Had exactly the same fault on a FT707 recently. These VFO PCBs are likely to have not gone through the flow solder process correctly in the first place. Common problem. And yes, cleaning the VFO buttons and the small relay on the same PCB, usually the first thing on the listThanks for sharing, as always.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: July 19, 2017, 09:37:28 am
content: Thanks. These are fun to work on. Bit of a pita to have to take things apart to fix these common problems but thats the way it goes with these. I was not surprised to see the bad solder connections on this board.I connected the antennas to this rig after the video and had a blast on 20 and 40 meters. Was geting some good contacts then a station from Italy came back.Thanks for watching.

author: voltz
author_rank: Frequent Contributor
timestamp: July 20, 2017, 09:57:31 am
content: Thats good going! Do you ever work the UK? Might hear you on the band on day, although its mainly East coast we get here. 73.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: July 21, 2017, 01:11:36 am
content: Yes I have worked station in the UK quite often. I am on the east coast of North Carolina. 80 miles from the coast. I have better luck working UK than I do west coast of US.Will have to see if we can hook up one day.
Universal Radio Hacker - Bit Interpretation - Page 1
Forum section: electronics / rf-microwave

author: mulu
author_rank: Newbie
timestamp: July 16, 2017, 07:38:24 am
content: I am using Universal Radio Hacker to look at a signal I captured. However, I see some really strange behavior. In the attached image you can see a bit sequence at the bottom, i.e. 01000001... The first 0 URH correctly interprets as the first flat area from the left. Then it sees a 1 where you have 4 high peaks. That look fine as well. Then follows a 0 which again makes sense. However, then URH sees another zero (the forth number in 010000...) which is highlighted in blue (I selected that number so URH highlighted it for me in blue). Clearly this should not be a 0 but a 1. I think this is the source of a bunch of problems I have with URH so if somebody can shed some light on why it considers this a 0 then maybe I can get some good interpretation of the signal.
How does this SMA connector mount to chassis? - Page 1
Forum section: electronics / rf-microwave

author: rcbuck
author_rank: Frequent Contributor
timestamp: June 28, 2017, 11:20:28 pm
content: I was looking at bulkhead mount SMA connectors on ebay and find several listings for this item:http://www.ebay.com/itm/SMA-Female-Center-Nut-Bulkhead-Crimp-RG174-RG316-LMR100-Connector-H5I3-/122490679442?epid=1249448189&hash=item1c85037092:g:0NwAAOSwaEhZJElaHow do you assemble this thing? Looking at the photos, it appears the center receptacle portion screws into the back side of the threaded outer portion. However, the thickness of the panel it is mounted on would affect how far the center female socket is from the front of the housing. They don't specify a maximum panel thickness. It would probably be OK for a .040 aluminum panel but may not work if you are making the panel out of .062 PCB material. This is apparently a Chinese only design as I can't find any U.S. company that makes this type of SMA connector.Has anyone purchased any of these things?Even though this is a one-time use item:http://www.ebay.com/itm/1Pc-Connector-RP-SMA-Female-Plug-Bulkhead-Crimp-RG174-RG316-LMR100-Cable-/272261612717?hash=item3f640e84ad:g:zDsAAOSwwE5WU1RNmaybe it would be better suited for panel mounting?I realize these are cheap Chinese connectors with probably only a micron of brass (hopefully it is brass) plated onto some cheap alloy. But for hobbyist radio projects they should be at least usable.

author: langwadt
author_rank: Super Contributor
timestamp: June 29, 2017, 12:15:57 am
content: Quote from: rcbuck on June 28, 2017, 11:20:28 pmthe outer portion is what goes through the panel, that why there is a nut and washersthat the inner part screws out is just to give access to solder the inner connection, after it is soldered and screwed together is basically like this:https://www.amphenolrf.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/1/3/132422-10.jpgthe limit on panel thickness is how much thread is left after you stick it though the panel and mount the nut and washer

author: rcbuck
author_rank: Frequent Contributor
timestamp: June 29, 2017, 12:36:15 am
content: langwadt,OK, so the panel mounting hardware actually goes on the front of the panel. I should have realized that by looking at the size of the mounting nut.I was looking for something that had the mounting hardware on the back of the panel but this will work OK. It actually has the advantage of having the center coax wire shielded all the way up to the center socket. It essentially mimics what the connector in the second link I posted does and is re-usable.

author: rcbuck
author_rank: Frequent Contributor
timestamp: July 15, 2017, 03:55:42 am
content: Anyone thinking about purchasing these beware of a problem. It will not work with RG174, RG316, or LM100 cable. The barrel that the center conductor passes through is only .046 inch diameter. All three of the cables have .060 inch center conductor insulation so they will not pass through the barrel. It will work with RG178 cable as the center conductor insulation is .033 inch. Luckily I had RG178 in my stock of coax cable.
looking for datasheets/information on Varian klystrons - Page 1
Forum section: electronics / rf-microwave

author: wkb
author_rank: Super Contributor
timestamp: July 13, 2017, 03:44:22 pm
content: I recently acquired 2 Varian klystrons, one is NOS, the other probably used. Am having a hard time finding product data onthese two. So... anyone out here in the possession of an old Varian catalogue or datasheets and willing to help?The images show the part#tia, Wilko

author: cj
author_rank: Contributor
timestamp: July 14, 2017, 11:23:14 am
content: Hello Wilko,All the info I could find on the VA-287 is that it’s adjustable from 10.7GHz to 13.2GHz and is/was intended for ‘studio transmitter communications’, whatever that means.I haven’t got any information on the V-55 but it looks a lot like the X-13. May it has the same pin connection but electrically it’s probably different.The X-13 datasheet can be found onwww.tubecollectors.orgCJ
New Heathkit Product Announced - Precision RF Meter - Page 1
Forum section: electronics / rf-microwave

author: xrunner
author_rank: Super Contributor
timestamp: June 21, 2017, 03:29:48 pm
content: Just received an email announcing this.Precision RF Meter - HM-1002 - pre-order$ 575.00Apparently you can enter certain parameters of your system, and it can do extra calculations such as ERP. It works with two sensors though. It also measures your transmission to +/- 100 Hz. Not very good set of pics either. Check it out.Link -Heathkit HM-1002

author: scdreger
author_rank: Contributor
timestamp: June 29, 2017, 11:35:49 pm
content: The product seems pretty nice, but the price is a little off putting. I wish they had some more affordable kits besides the clockradio (which is itself rather expensive for what it is).

author: German_EE
author_rank: Super Contributor
timestamp: July 02, 2017, 09:53:11 am
content: Here's a better option, and it's a hundred bucks cheaper.http://www.telepostinc.com/lp100.htmlNIST source calibrated as well.

author: N2IXK
author_rank: Frequent Contributor
timestamp: July 02, 2017, 03:13:53 pm
content: Quote from: scdreger on June 29, 2017, 11:35:49 pmThey offer a clock radio? I saw a clock kit, and a radio kit, but not a clock radio kit.Not sure where the new "Heathkit" is getting their product ideas from. $575 for an SWR/Wattmeter is quite steep.They could have come up with a modernized version of their venerable HM-102 (maybe with a cross-needle meter?) for considerably less than this, and they would surely sell a lot more of them.

author: scdreger
author_rank: Contributor
timestamp: July 07, 2017, 12:28:03 am
content: Quote from: N2IXK on July 02, 2017, 03:13:53 pmNot sure why I was calling it a clock radio.Yes, I meant the "reliable clock kit," or whatever it's called.

author: WastelandTek
author_rank: Frequent Contributor
timestamp: July 07, 2017, 12:41:02 am
content: Seems like all the offerings in this Heath reboot have been...a little odd. I'm just not sure who they think their market is.
Open ended coaxial probe inquiry - Page 1
Forum section: electronics / rf-microwave

author: Cacao
author_rank: Contributor
timestamp: July 02, 2017, 11:53:53 am
content: Can you guys help me on where can I find a open ended coaxial probe? or does someone know how to build one? Thanks for the helpSample:https://www.researchgate.net/profile/Juming_Tang/publication/237564911/figure/fig1/AS:349347909783556@1460302440403/Figure-1-Schematic-diagram-of-open-ended-coaxial-probe-all-dimensions-in-mm.pnghttps://www.hindawi.com/journals/ijap/2014/floats/498767/thumbnails/498767.fig.002a_th.jpghttps://www.google.com.ph/imgres?imgurl=https%3A%2F%2Fwww.intechopen.com%2Fsource%2Fhtml%2F40869%2Fmedia%2Fimage9.png&imgrefurl=https%3A%2F%2Fwww.intechopen.com%2Fbooks%2Fmicrowave-materials-characterization%2Frelevance-of-dielectric-properties-in-microwave-assisted-processes&docid=b7Xsaw-GNSK4eM&tbnid=1Fm9nJDGbJKUkM%3A&vet=10ahUKEwiUlPbVw-rUAhUDTrwKHZcOCTIQMwgmKAEwAQ..i&w=980&h=347&bih=676&biw=1366&q=open%20ended%20coaxial%20probe&ved=0ahUKEwiUlPbVw-rUAhUDTrwKHZcOCTIQMwgmKAEwAQ&iact=mrc&uact=8

author: slurry
author_rank: Regular Contributor
timestamp: July 02, 2017, 12:58:18 pm
content: A 7mm PC7 coplanar connector is very close to what you want if you dont fint a probe.https://upload.wikimedia.org/wikipedia/commons/a/ab/Apc7_1.png

author: Cacao
author_rank: Contributor
timestamp: July 02, 2017, 01:42:18 pm
content: Quote from: slurry on July 02, 2017, 12:58:18 pmToo expensive

author: ConKbot
author_rank: Super Contributor
timestamp: July 02, 2017, 03:19:44 pm
content: https://www.digikey.com/product-detail/en/amphenol-sv-microwave/SF2921-61356/SF2921-61356-ND/6050923Looks like it could work

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: July 05, 2017, 12:00:25 am
content: Probe in contact with the egg? Noooo! Remember this post then the mutant chickens overcome us!
Teardown of a Ericsson radio base station, the RBS6000 system - Page 1
Forum section: electronics / rf-microwave

author: madsbarnkob
author_rank: Frequent Contributor
timestamp: July 02, 2017, 05:32:51 am
content: All technical details and high resolution pictures:http://kaizerpowerelectronics.dk/teardown/ericsson-radio-base-station-rbs6000-teardown/The RBS6000 is an indoor Radio Base Station with one to four carriers and one to six sectors at 20/40 Watt RF output power per carrier.
knob for variable capacitor - Page 1
Forum section: electronics / rf-microwave

author: medical-nerd
author_rank: Regular Contributor
timestamp: June 30, 2017, 08:51:47 am
content: HiyaI've just purchased a few variable capacitors - see pic150pF / 210pFThey have a slow motion drive.What type of knob is used for these - it would need an inner and outer mechanism.The other option I am considering is using the outer coarse movement to hold a pointer and use just the inner slow motion as the tuning knob.Suggestions please???Cheers

author: Rerouter
author_rank: Super Contributor
timestamp: June 30, 2017, 09:39:09 am
content: If it works like i am thinking, you put a dial on the outer, and a small knob on the middle, allowing for a very fine tuning range if it suits you.

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: June 30, 2017, 11:40:36 am
content: Yes, I think your last option is best.The gear reduction ratio in these is normally only about 3:1 so it's no impost that you are only turning the thinner shaft.Also, as less torque is required due to the gearing, it will be easier to turn - a great consideration when making fine adjustments eg tuning in a station.

author: cdev
author_rank: Super Contributor
timestamp: July 01, 2017, 09:49:13 pm
content: maybe "vernier" or "vernier drive" like they use to have in old radios.Also, planetary gear (reduction) coupling might be another helpful search term.They attach to the shaft and bring about a substantial reduction in rotation.Very useful for magnetic loop antennas and similar.

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: July 02, 2017, 02:44:25 am
content: Quote from: cdev on July 01, 2017, 09:49:13 pmThis is true but I wouldn't use these on the OP's capacitor which already contains a reduction drive.Add-on reduction drives are normally based on the capacitor they're connected to having 1/2 turn to go from min to max capacitance. 1/2 turn is also 0 to 100 on their dial (if there is a dial)Some drives even have stoppers to prevent them from going more than half a turn (so if you were to use them with a potentiometer which has about 0.8 turns then you need to remove it).If you were to attach the reduction drive to a capacitor that already has an inbuilt drive you will get very fine tuning due to the greater mechanical reduction. This may be useful for something likea magnetic loop or receiver which requires very fine adjustment. But the pointer will go around more than 360 degrees or the 0 - 100 scale will go off the end as there may be 3 instead of 0.5 turns.Not so much a problem if you can determine the frequency another way (eg using a frequency counter in a VFO) but its not ideal if you're just relying on a scale or pointer (unless you can memorise the number of times it's gone around).
Unidentified DBM, any idea of the specs? - Page 1
Forum section: electronics / rf-microwave

author: CJay
author_rank: Super Contributor
timestamp: June 30, 2017, 05:25:08 pm
content: Two devices, apparently DBMs and meant ot be MCL but the logo and part number?MD-1443No hits apart from a couple of obscure mil surplus sites for the part number (which confirm it's a mixer but offer no spec) and the logo doesn't look like MCL so, any ideas what these devices are and what the spec is?

author: AF6WL
author_rank: Newbie
timestamp: June 30, 2017, 07:53:51 pm
content: Anzac

author: slurry
author_rank: Regular Contributor
timestamp: June 30, 2017, 08:22:35 pm
content: It seems to be a double balanced mixer, i would guess level 7.I think MACOM bought Anzac, maybe try sending a mail to MACOM support?

author: CJay
author_rank: Super Contributor
timestamp: June 30, 2017, 08:49:12 pm
content: Quote from: slurry on June 30, 2017, 08:22:35 pmIt looks to be and it was sold to me as but that was the only information I have.I think it's the same pinout as the SBL-1 etc. so I'm going to tack it into a test rig tomorrow and see if I can persuade it to work.
RF detector/demodulator probe questions. - Page 1
Forum section: electronics / rf-microwave

author: xwarp
author_rank: Frequent Contributor
timestamp: March 15, 2016, 10:54:55 pm
content: 1. Why so many different designs.2. Which designs are used for FM. For example, see the following attached images. The "yellow" background images are from Eico. The last is for a Sencore AM/FM signal generator for AM/FM radio alignment.

author: Fank1
author_rank: Regular Contributor
timestamp: March 16, 2016, 09:59:02 pm
content: There is no huge difference in any of them.All you are doing is rectifying the RF and filtering it so you get a dc voltage out.They are not "instruments" just a way to detect RF and get a relative value out.

author: w2aew
author_rank: Super Contributor
timestamp: March 18, 2016, 02:41:21 pm
content: These probes don't care whether the signal is unmodulated or if it is FM - they'll still read the same since FM doesn't change the RF amplitude. Depending on the value of the capacitors used to "hold" the RF amplitude, you may be able to view the baseband on AM signals. I did a video on this:

author: gyropilot
author_rank: Contributor
timestamp: June 29, 2017, 03:07:24 pm
content: Sorry to resurrect such an old thread, but my question dovetails in...Can anyone please explain to me when and why an RF demodulator probe would be appropriate to use with a scope?Now I get why you'd want to use an RF demodulator probe with a DMM, but I'm having trouble understanding the use case for a scope.Thanks!

author: CJay
author_rank: Super Contributor
timestamp: June 29, 2017, 04:07:55 pm
content: They're not that useful now as it's a lot easier to lay your hands on much better spec test gear for cheap (Spec An, multi hundred MHz 'scope etc.) but the demodulating probe is used to check the modulating signal and can show you if there's distortion happening in an RF stage, it won't give you an indication of carrier level with a DMM.Diode peak detectors and demodulating probes are both useful in their own way and can give you very accurate RF measurements if used appropriately

author: PA0PBZ
author_rank: Super Contributor
timestamp: June 29, 2017, 05:20:19 pm
content: Quote from: CJay on June 29, 2017, 04:07:55 pmI agree, but since AM modulation is normally used at lower (HF) frequencies it is equally easy to just feed the signal into the scope directly**Of course properly scaled

author: CJay
author_rank: Super Contributor
timestamp: June 29, 2017, 05:57:38 pm
content: Quote from: PA0PBZ on June 29, 2017, 05:20:19 pmAbsolutely, but back in the day where a 5MHz 'scope was a luxury item that cost many months of salary a demod probe was an exceptionally useful addition to the test gear armoury, these days a 200MHz scope can be had second hand for less than a couple of days wage and has removed a lot of the need for such tools, I'd still contend that the probe can be useful but it's far from essential.
maximum power output from an antenna? - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: July 13, 2017, 07:09:19 am
content: Is this purely a consequence of ohmic heating and arc discharge? (like in waveguide transmission), where you could potentially cool the antenna actively? perhaps fill a horn with freon?Are there any more subtle effects in play here? Some kind of saturation parameters?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 13, 2017, 08:17:16 am
content: The EM field itself is linear until extremely high energy densities, where pair production occurs.Materials are always worse. Vacuum, I think?, is better than an insulatingmaterial, like oil, freon, SF6 or etc. Insulators of course are susceptible to breakdown at some electric field intensity.A dielectric waveguide transitioning into a dielectric antenna will have quite good performance, until either the dielectric melts (so, say we make it mostly out of diamond..?) or it succumbs toself-focusing, which I would think still applies just as well for small objects (fractional wavelength antennas) as large ones (optical lenses and mirrors).Any conductors, if present, are susceptible to field emission at least, as well as good old resistive melting. Or superconductors are susceptible to failure at high magnetic field intensities (critical field), as well as AC losses with enigmatic mechanisms*.(*Type 2 superconductors exhibit flux pinning, which is just hysteresis loss that works all the way down to DC. They're actually not that good at AC, depending on what frequency you're checking at. Obviously, if nothing else, they look black at visible wavelengths, proving they're pretty crappy at some point. Type 1 superconductors are pretty good, with use in LINACs as resonators in the low GHz, achieving Q factors in the 3 x 10^7 range -- better than quartz crystals, but also still not infinite!)Tim

author: David Hess
author_rank: Super Contributor
timestamp: July 13, 2017, 10:49:44 am
content: High voltage breakdown is usually the limiting factor and 25 ohm transmission lines can be used to allow maximum power without physically larger transmission lines. I have however occasionally heard about people melting coaxial cable when it was used at high power while still wound on the spool preventing heat dissipation. I have also heard about flashover in high power waveguide and coaxial transmission lines when the supply of dry air failed allowing excess humidity.This applies to antenna elements as well. Yagi antennas used in high power applications suffer from corona discharge at the end points eroding the antenna elements which led to the development of the quad antenna which has no end points.
Building a 5.8GHz downconverter - Page 1
Forum section: electronics / rf-microwave

author: mdszy
author_rank: Unknown
timestamp: June 26, 2017, 09:10:20 pm
content: I've been pondering the idea of making my own signal strength meter of sorts for RC FPV video.My idea is to make a "module" that has an SMA input for the FPV antenna, and an SMA output that is fed into an RTL-SDR. The RTL-SDR would then be able to display the received signal and how strong it is. It would of course have some form of power supply, which would possibly be from a battery, since it's an RC-centric project, I'd likely be using a Li-Po battery for a power source.However, FPV signals are 5.8GHz, way outside of the range of the RTL-SDR. This is where the "module" would come in, it would downconvert the 5.8GHz signal to something the RTL-SDR can handle.I've been searching around for things and talking about it with a friend and here's what I -- and we've -- sort of come up with.1. In the module, generate a 5GHz LO signal.2. Mix that in with the 5.8GHz3. Feed the resulting 800MHz signal out to the RTL-SDR.Is this basically what would need to be done? The question now is how to choose components to perform #1 and #2, what devices to use to generate the 5GHz LO, the best way to mix them together, etc.I also realize there'll be lots of RF design considerations I'll have to make such as impedance matched traces. I'll certainly be looking heavily into that and what I need to take care of in terms of the PCB design.Finally, is this even achievable? Is this the sort of project that takes years and a team of engineers to accomplish? Or is this within the realm of a hobbyist with a decent chunk of free time?

author: hendorog
author_rank: Super Contributor
timestamp: June 26, 2017, 09:26:37 pm
content: One problem is the bandwidth of the FPV (video) signal would exceed what you can fully capture on the SDR.Aside from that you should be able to do it.There are cheap 'eval' type boards on ebay. e.g.The 5GHz signal could be cheaply generated by doubling the output of one of these cheap boards set to 2.5GHz:http://www.ebay.com/itm/137M-4-4GHz-PLL-Frequency-Signal-Source-Development-Board-SMA-ADF4350-DC5V-/401169578378?epid=879166790&hash=item5d6791f98a:g:xRkAAOSw9NdXraQ0or directly without the doubler:http://www.ebay.com/itm/ADF4355-250MHz-6-8GHz-Sweep-RF-Signal-Generator-VCO-Microwave-Frequency-PLL-/222515462688?hash=item33cef48220:g:aiUAAOSw1WJZHXplMixer:http://www.ebay.com/itm/ADL5801-double-balanced-active-mixer-up-and-down-mixing-module-Barron-coupling-/172351799289?var=&hash=item2820f7bff9:m:mmeTA4MeFEL1DF33kFKjVngDoublers:http://www.qsl.net/va3iul/Frequency_Multipliers/Frequency_Multipliers.pdf

author: mdszy
author_rank: Unknown
timestamp: June 26, 2017, 09:28:35 pm
content: Quote from: hendorog on June 26, 2017, 09:26:37 pmThanks for the links!I'm not really looking to be able to recreate the FPV video with the RTL-SDR, and I've heard from other places that the bandwidth is too wide for the RTL-SDR. I just want to be able to get a signal strength measurement.
yig filter bandwidth control? - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: June 12, 2017, 07:36:47 am
content: is a yig filter a fixed Q or can you control the passband?

author: cj
author_rank: Contributor
timestamp: June 12, 2017, 10:03:25 am
content: I've never seen a yig filter with adjustable bandwidth.AFAIK only frequency is adjustable.CJ

author: CopperCone
author_rank: Super Contributor
timestamp: June 13, 2017, 05:12:54 am
content: this agrees with my observations. and understanding of the device.

author: hendorog
author_rank: Super Contributor
timestamp: June 13, 2017, 10:31:03 pm
content: Google found this patent from 1969 which used varactors to tune the bandwidth:https://www.google.com/patents/US3435385Perhaps they do exist...

author: HarryGT
author_rank: Newbie
timestamp: June 24, 2017, 08:22:26 pm
content: Is this a general question, or are you interested in variable Q YTOs?I would be interested if you happen to come across some. Apart from that post above, I have never seen a YTO with tunable Q.
waveguide to coaxial adapter 'names of subcomponents' - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: June 23, 2017, 12:52:18 am
content: I have a bunch of the little 2.92 connectors that have a little antenna on them and a metal plate with 4 screw holes. They are designed to attach to a special waveguide piece.They are about 1cm squared.What is the section of waveguide that they attach to called?Ready made adapters are expensive. Can you just buy the piece that you screw the actual coaxial bit to.. if so what is it called?Or can you take a regular section of the waveguide and drill holes in it, so long its centered right? The antenna bit on the coaxial connectors I have looks like a little necked/tapered blade/finger.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: June 23, 2017, 06:14:59 am
content: http://www.atmmicrowave.com/flange-size-type/

author: CopperCone
author_rank: Super Contributor
timestamp: June 23, 2017, 04:18:29 pm
content: I don't see flanges there that adapt to a coaxial antenna thingy.