hybridfree/eevblog-posts huggingface dataset:
Tektronix 1502 TDR - why this particular physical construction? - Page 1
Forum section: electronics / rf-microwave

author: tggzzz
author_rank: Super Contributor
timestamp: September 19, 2016, 02:59:26 pm
content: The "business end" of the Tek 1502 sampler is rather interesting, but why did Tek choose thisveryelongated layout?https://www.eevblog.com/forum/rf-microwave/tdr-for-measuring-cablesconnectors-what-is-it-worth-to-radio-hams/?action=dlattach;attach=251890;imageWhy not just have the tunnel diode (TD) transmitter and sampling diodes (SD) receiver close together?Reasons I can think of include to minimise crosstalk between the "transmitter" and "receiver", or because fitting the related components into the case required a separation between the TD and SD. neither of those explanations is satisfying; is there a more fundamental benefit from having the long stripline?(FFI on the Tek 1502's performance, seehttps://www.eevblog.com/forum/rf-microwave/tdr-for-measuring-cablesconnectors-what-is-it-worth-to-radio-hams/msg1014762/#msg1014762)

author: David Hess
author_rank: Super Contributor
timestamp: September 19, 2016, 08:55:10 pm
content: One reason not to place them closely together is to prevent the kickout from the sampling strobe from prematurely triggering the tunnel diode as the trigger pulse arrives. When using tunnel diode pulse generators in sampling applications, it is sometimes necessary to add an external delay line to the tunnel diode pulse generator because of this.
Bandpass Filter Design - Page 1
Forum section: electronics / rf-microwave

author: fourierpwn
author_rank: Regular Contributor
timestamp: September 13, 2016, 11:43:06 am
content: Hi all,I am trying to design a bandpass filter for f0 of 9.25 GHz, BW of 500 MHz. I have a somewhat suitable design which was done using a filter design wizard, however there appears to be passbands at all of the multiples of the one intended. So, passband at 9.25 GHz, 18.5 GHz, ~ 27GHZ, ~36 GHz, ~45 GHz etc.If this is undesired, what are some measures I can do to eradicate these extra passband multiples?I hope that is clear enough!

author: Kalvin
author_rank: Super Contributor
timestamp: September 13, 2016, 12:03:25 pm
content: You will get nice hits when you google with the following terms: microwave bandpass filter harmonics

author: KJDS
author_rank: Super Contributor
timestamp: September 15, 2016, 08:27:43 pm
content: It's quite normal to have to add a low pass to a bandpass if you need to reject harmonics.
What are these RF connectors called? - Page 1
Forum section: electronics / rf-microwave

author: ivaylo
author_rank: Frequent Contributor
timestamp: September 15, 2016, 05:45:35 pm
content: Photo attached. They come from a "MINI CIRCUITS 15542 ZFSC-12-1-4 POWER SPLITTER COMBINER". Sorry, I don't have anything for scale on the picture, but they are smaller than SMA and not threaded on the outside. Appreciate your help...

author: mngiggle
author_rank: Contributor
timestamp: September 15, 2016, 05:49:02 pm
content: Looks like SMB to me.

author: PA0PBZ
author_rank: Super Contributor
timestamp: September 15, 2016, 07:31:20 pm
content: Quote from: mngiggle on September 15, 2016, 05:49:02 pm+1(except the one in the middle)

author: ivaylo
author_rank: Frequent Contributor
timestamp: September 15, 2016, 08:37:08 pm
content: Thank you both...

author: blackbird
author_rank: Regular Contributor
timestamp: September 16, 2016, 09:02:22 am
content: Although the center connector looks like a special SMB type ;-)

author: borjam
author_rank: Unknown
timestamp: September 16, 2016, 09:07:43 am
content: Quote from: blackbird on September 16, 2016, 09:02:22 amIt's a D-SMB.D as in Damaged.

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: September 16, 2016, 09:40:37 am
content: Quote from: borjam on September 16, 2016, 09:07:43 amI'd go as far as to say that is an F-SMB
#70  FT-101 Series   parts and surprise gift - Page 1
Forum section: electronics / rf-microwave

author: Radio Tech
author_rank: Frequent Contributor
timestamp: September 15, 2016, 01:57:50 am
content: #70 FT-101 Series parts and surprise giftIn this video we look at the parts for the FT-101 that Mike from Mikes Radio Repair sent in.Also he sent us a very nice gift.
R&S User/Service manuals, CMU200 and CRTU - Page 1
Forum section: electronics / rf-microwave

author: CJay
author_rank: Super Contributor
timestamp: September 09, 2016, 02:43:09 pm
content: As the title says, I'm looking for user manuals for the CMU200 and CRTU R&S devices, if there happens to be a service manual too that'd be handy.Does anyone have a link to them for download or do I need to approach R&S?

author: Brainbox
author_rank: Contributor
timestamp: September 11, 2016, 06:16:09 am
content: When You search for CMU200 there are links on this forum.
32.768KHz tuning fork cut quartz crystal - stability - Page 1
Forum section: electronics / rf-microwave

author: aurmer
author_rank: Regular Contributor
timestamp: November 22, 2016, 10:07:13 pm
content: I am using this 32kihz Crystal, and my requirements need long term accuracy while I don't care about stability between pulses. Can I actually assume that the error caused by instability has a gaussian distribution? Ie, is it realistic to ignore the stability spec when speccing the drift tolerance of the clock?Assume that I correctly calibrated the short term accuracy using a sample of a few minutes worth of counting clock cycles. Each unit is calibrated in production using an inhibition compensation technique.

author: aurmer
author_rank: Regular Contributor
timestamp: November 23, 2016, 02:34:42 am
content: I am duplicating this in meterology; my afterthought is that "Radio" wasn't the place for this question.
Microset R50 Amplifier, obsolete relay  - Page 1
Forum section: electronics / rf-microwave

author: Flump
author_rank: Frequent Contributor
timestamp: September 07, 2016, 09:01:25 pm
content: Hi AllI have a Microset R50 VHF Amplifier with a faulty relaywhich is obsolete, I cant find a datasheet or an equivalent for it.Would anyone have any idea on where to get one or a datasheet from ?This is all the info I have:-femezfh a 0021212v dc9147810.3A 60vdc res0.5A 120vac res1A 24vdc resIt has 8 legs

author: voltz
author_rank: Frequent Contributor
timestamp: September 08, 2016, 11:22:33 am
content: Information here:http://www.cimee.it/gavazzi/15ZFHA00212-1eng.pdfMight help.

author: CJay
author_rank: Super Contributor
timestamp: September 08, 2016, 02:50:17 pm
content: Post a picture, I think I have quite a few of these or equivalent relays, would be a doddle to drop one in the post for you if I'm right.

author: Flump
author_rank: Frequent Contributor
timestamp: September 08, 2016, 06:41:32 pm
content: Quote from: voltz on September 08, 2016, 11:22:33 amThanks very muchQuote from: CJay on September 08, 2016, 02:50:17 pmThats very kind of you CJ, 2 pictures attached below.

author: spudboy488
author_rank: Regular Contributor
timestamp: September 09, 2016, 11:46:27 am
content: http://www.digikey.com/product-search/en?keywords=Z768-ND
OIP3 amplifier measurement question - Page 1
Forum section: electronics / rf-microwave

author: kavea
author_rank: Contributor
timestamp: September 06, 2016, 09:16:06 pm
content: Hello,I'have a question about the OIP3 (output third order interception point) measurement of an amplifier. The question is quite simple, does the OIP3 of an amplifier depends on the impedance of the device connected at it's input ? i.e. if i connect generators which are not 50 ohms to an amplifier which has 50 ohms input impedance, will i measure the same OIP3 as that of the data-sheet ?

author: 1design
author_rank: Regular Contributor
timestamp: September 07, 2016, 02:44:22 pm
content: It should, since OIP3 is the output 3rd order intercept point. Watch not to override it with the IIP3.BR

author: dmills
author_rank: Super Contributor
timestamp: September 07, 2016, 04:06:41 pm
content: Be careful here, some amplifier designs have very poor reverse isolation, thinking of that transformer feedback common base thing with the name I can never remember.In these case source and load do interact, and can cause changes to the gain which can impact this measurement.Just stick a big pad in front of the thing before making your measurements, pads have really nice properties this way.Regards, Dan.

author: kavea
author_rank: Contributor
timestamp: September 08, 2016, 06:29:51 pm
content: Thank you for the answers, i'he done some measurements on MAR6 and indeed, the OIP3 was different in the 50 ohm case and not 50 ohm (capacitive input impedance). However an other amplifier qbit 300 gave the same results, so it should depend on amplifiers and probably on its isolation.
Agilent E8358A - buying used - Page 1
Forum section: electronics / rf-microwave

author: kazam
author_rank: Regular Contributor
timestamp: September 06, 2016, 09:14:05 am
content: Hi,I'm thinking of getting this:eBay auction: #252495829822I have contacted the seller and it seems OK.Does anyone have any issues with this model? I have used a lot of 8753ES, N5230C, etc. etc. but never this model.I need the expanded test set for PA measurements. Time domain is a nice option to have, definitely useful.Thoughts?/K
1.5 volt / 1 transistor pulsing VHF transmitter - Page 1
Forum section: electronics / rf-microwave

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: September 04, 2016, 09:26:20 am
content: It's easier to get reasonable RF power output from a transistor with high collector or drain voltage (within ratings).However there's also novelty value in seeing what can be done with a 1.5 volt battery.This video features a 1 transistor (BC548) VHF transmitter running off a single AA.It's crystal controlled for frequency stability (though there is distinctive chirpy keying) and it only works in daylight.With a makeshift antenna that was not tuned up correctly I got 2km range.More at:

author: Nuno_pt
author_rank: Frequent Contributor
timestamp: September 04, 2016, 10:21:03 am
content: That is good to work some SOTA in WSPR or JT.
#68 Yaesu FT-747 No receive diagnose and repair - Page 1
Forum section: electronics / rf-microwave

author: Radio Tech
author_rank: Frequent Contributor
timestamp: September 03, 2016, 11:47:07 pm
content: #68 Yaesu FT-747 No receive diagnose and repairIn this video we have a look at why a FT-747 has no receive on any band.After the repair we find that SSB has distorted sound and then we inspect for the cause.
#67 Eico 315 SG repair and alignment  - Page 1
Forum section: electronics / rf-microwave

author: Radio Tech
author_rank: Frequent Contributor
timestamp: August 22, 2016, 01:55:26 pm
content: In this video I have a look at multiple problems with the Eico 315 signal generator. Then replace capacitors, resistors and do an alignment.

author: voltz
author_rank: Frequent Contributor
timestamp: August 23, 2016, 12:25:10 pm
content: Another fine repair.Was that red wire actually loose when you moved it or was it just shifting frequency as you went near it? Working on a harmonic i can imagine it was critical, but it looked like a dry joint in the video.Thanks!

author: Radio Tech
author_rank: Frequent Contributor
timestamp: August 23, 2016, 12:43:48 pm
content: Quote from: voltz on August 23, 2016, 12:25:10 pmAlthough I did remove the old solder and re-solder the connection, I saw no problem with it.The problem was the wire was just too close to the other coils and trimmers.This is why it is always best to try and keep stuff routed per the assembly manual.Thanks for watching.

author: German_EE
author_rank: Super Contributor
timestamp: August 28, 2016, 10:10:15 am
content: I like that copper plated chassisA rather large soldering iron would be needed to make a connection but it looks much nicer than steel or aluminum. What amazes me though is that something works at RF with all those long wires, I was always taught that connections at RF should be as short as possible.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: August 31, 2016, 09:22:33 am
content: Quote from: German_EE on August 28, 2016, 10:10:15 amYep, takes a big iron to heat that chassis.Agreed on the long wires. Amazing what they could design and make work back then.
600MHz to 2GigaHz, 25DB - Page 1
Forum section: electronics / rf-microwave

author: cantel
author_rank: Newbie
timestamp: August 22, 2016, 03:46:46 pm
content: I am a newbie, My question is for "RF 600Mhz-2GigaHz, 25DB", what does 25DB means ?To build a Anechoic chambers, what is the attentuation required ?thanks

author: donmr
author_rank: Regular Contributor
timestamp: August 22, 2016, 05:38:16 pm
content: It looks like the attenuation is 25 DB.DB (usually lower case) stands for decibels (ie 1/10th of a Bell but the unit Bell is hardly ever used by itself just decibels).In general this is a ratio of power levels, exactly how you would specify attenuation.Google for a lot more info.

author: max-bit
author_rank: Frequent Contributor
timestamp: August 30, 2016, 06:10:05 am
content: dB - no DB
RF RANGING PERFORMANCE REDUCED FROM 90M TO 40M - NEEDED HELP - Page 1
Forum section: electronics / rf-microwave

author: Anirudh_THABJUL_SB
author_rank: Contributor
timestamp: August 29, 2016, 09:37:16 am
content: Hello Everyone,I am Anirudh THABJUL, an Electronic engineer working for a company called "SECOND BRIDGE", We are based on Paris.In our applications, We are measuring distance between two 10 layer PCB's. To achieve this, We are using mainly1. IMX6 Processor (Main processor)2. SAM4E (Secondary processor)3. RF215 + Antennas for RF ranging sectionOur issue is when we just measured distance between two PCB by putting the IMX6 in ideal state we are able to range upto 90M (Refer the attachment1) but when we activate the iMX6 for running other applications, ranging is reducing to 40M(50 % performance reduction).Can any explain this RF phenomenon? If possible please suggest us the possible ways to solve this problem like some reference sites or some reference documents?Thank you.Regards,Anirudh THABJUL

author: Simon
author_rank: Unknown
timestamp: August 29, 2016, 09:45:28 am
content: Topic locked due to duplicate post. Please don't post twice the same topic. It's very annoying.
Will this work for the basic function i require? - Page 1
Forum section: electronics / rf-microwave

author: sandman1976
author_rank: Newbie
timestamp: September 10, 2016, 10:16:17 am
content: Hi all, Ok before i start sorry if the diagram does make any sense whatsoever. I am currently on long term sickness and a lot of prescription drugs that are screwing me up a bit.Its very basic, the diagram is my car headlight wiring.The spotlights on my roof are wired via a relay to the high beam and work properly.I want to be able to switch on the sidelights and the spotlights glow at low power at the same time if that makes sense?The idea is two diodes across both lives going to the spots to stop feedback from each other and some sort of resistance on the sidelight output for the dimming?Would resistance alone do it?I have some sort of fuzz in my head talking to me about voltage drop diodes in series for this kind of thing but i just cant focus enough to make sense of it at the moment.If anyone can help me out here i would appreciate it,Best wishes from Halifax United Kingdom!Adrian.

author: helius
author_rank: Super Contributor
timestamp: September 10, 2016, 11:36:39 am
content: Before getting into the wiring, have you considered whether your modifications are road legal?Driving lamps are very distracting to other drivers, even if they were at half brightness. The reason they connect to the high beams is so they can be turned off when you approach other vehicles.

author: sandman1976
author_rank: Newbie
timestamp: September 10, 2016, 02:58:49 pm
content: It is road legal, the spots are intended to low glow when the sidelights are on not be on full, Its just like adding DRL's apart from i intend using the spots that are there rather than additional lighting.

author: sandman1976
author_rank: Newbie
timestamp: September 10, 2016, 04:32:00 pm
content: I have just realised i posted this in the wrong section, can anyone move it for me please or will i need to delete and repost?Thank You.
How to to change Gain on RFID-RC522 ??? - Page 1
Forum section: electronics / rf-microwave

author: rantwhy
author_rank: Contributor
timestamp: August 26, 2016, 04:53:32 am
content: so I just got my RFID-RC522 to work with my arduino But the range is absolute shit. its less then the thickness of a sticky note stack.I have read other forums on how to change it but no one gives a clear answer as to were to change the values rather it be in the library or the sketch itself. here is a link to the pdf on the unithttp://www.nxp.com/documents/data_sheet/MFRC522.pdfMy interests are page 59 Table 98. were do I put the max value witch is 111? do I put it in the sketch or library? and how should it be formatted so I don't throw any errors?Thanks a bunch!!!!

author: jmsigler
author_rank: Regular Contributor
timestamp: August 26, 2016, 05:58:47 am
content: What library are you using?If you're using miguelbalboa's it looks like you should be able to do something like below in your sketch:X.PCD_SetAntennaGain(0xFF);Where X is your MFRC522 object var name

author: rantwhy
author_rank: Contributor
timestamp: August 26, 2016, 08:37:54 am
content: Im using the one from Addicorehttps://www.addicore.com/RFID-AddiKit-p/126.htmThe library was in the pdf as a linkhttps://www.addicore.com/v/vspfiles/downloadables/Product%20Downloadables/RFID_RC522/AddicoreRFID.zipI will try the miguelbalboa it seems like it comes with more bits Thanks! Ill let you know what I come up with

author: rantwhy
author_rank: Contributor
timestamp: August 27, 2016, 11:24:18 pm
content: so I looked around and that line of code you showed me is only in the library were should I put this 0xFF value I tryed putting it everywhere and it just gives me errors can you post a mode descriptive example?

author: jmsigler
author_rank: Regular Contributor
timestamp: August 27, 2016, 11:51:50 pm
content: Keep the library the same. put that line of code in your sketch.
How does this Amazon flat TV antenna (a Moho Leaf Clone?) work? - Page 1
Forum section: electronics / rf-microwave

author: valley_nomad
author_rank: Contributor
timestamp: August 25, 2016, 10:10:16 pm
content: Hello, I just disassembled my Basics Ultra Thin Indoor TV Antennahttp://goo.gl/DAioLgand found that the cable is not connected with the antenna wire/loop directly. There are a few components between the cable and antenna terminals. Without connecting with antenna wire the resistance is infinite between cable signal lead and two terminals to the antenna wire/loop. the resistance between the cable shield and two terminals are 7.2 ohm and 19.3 ohm respectively. The resistance between terminals on antenna itself is 15.7 ohm. This is a non-powered antenna. My knowledge on RF is very limited. I am wondering how it could possibly work

author: Ian.M
author_rank: Super Contributor
timestamp: August 25, 2016, 10:44:38 pm
content: The mess of unpopulated pads to the right of the second image would be for the amplified version.S2 is probably a balun. The signal then gets coupled via C16, the bypass track round the amlifier section and C14 to the center conductor of the coax.As to how it works as an antennae, I'd bet the answer is poorly. Its allegedlyQuoteand the faint lines on image 1 look like a modified bow-tie dipole, but antennaes that aren't intentionally directional are highly vulnerable to multi-path distortion due to signal reflections off metal objects (including many parts of buildings) so unless you are in a high signal strength suburban area with a line of sight to the transmitting tower going through a minimum of walls and buildings, your experience is likely to be less than satisfactory.
(Australian?) Coaxial connector confusion: F-type, F-59, F-81, F56... - Page 1
Forum section: electronics / rf-microwave

author: rs20
author_rank: Super Contributor
timestamp: August 23, 2016, 07:10:47 am
content: Hello, I'm trying to do some mischief with Belling-Lee connectors (the standard TV antenna connector in Australia and New Zealand), but since no-one ever decided on a consistent name for that connector (75 ohm TV? "PAL connector"?) and I can only find few adapters for it, I'm opting to adapt it to the hopefully slightly better-supported F connector. However, when in-store at Jaycar, I found all sorts of weird names I hadn't seen before: F59, F81, etc. It looked to me like F59 mates with F81, and there's one random source I found on the internet that says that F59 is code for "female F connector", whereas F81 is code for "male F connector"; although I can't find even the remotest bit of "official" confirmation of this.What's going on here? Can anyone offer any clarification on what F-type, F59, and F81 actually mean?

author: helius
author_rank: Super Contributor
timestamp: August 23, 2016, 08:14:16 am
content: the 59 almost certainly means RG-59. Coaxial connectors need to be matched dimensionally to the type of cable used. All F connectors (and most coaxial connectors generally) are only male on the cable end. Female connectors are jacks mounted to panels or PCBs.F81 is used all over the web for female-to-female couplers for F connectors (the type you would use when joining two cables together).I don't know which manufacturer first used it to mean that.Most F connectors are made for RG-6 or RG-59 only, and have no physical pin. Instead, the center conductor protrudes through the barrel into the female socket. This makes them very easily bent and tarnished. A few types of F connectors do have a pin, but these are more expensive (Huber+Suhner makes some, and I'm sure Times Microwave does).

author: ConKbot
author_rank: Super Contributor
timestamp: August 23, 2016, 04:23:18 pm
content: +1 to F59 sounding like an F-connector for RG-59. Get a connector which fits your coax, RG-59, RG-6, or RG-6Quad shield, (RG-6 is recommended for short runs or where you need the flexibility, RG-6Q for long runs) and mate them with the appropriate F coupler. Don't worry too much about the center conductor being used as a pin though, all the stated cable types will be copper plated steel center conductors so not as flimsy as you may expect. Just be really, really sure that you don't nick the center conductor stripping it, as you'd force the RF current to flow though the steel instead of staying in the copper. (Skin depth at 50 MHz in copper is 9.22 um)If you want to spend the money on a compression tool, compression connectors are the best(can be had in a weatherproof version, I'd still recommend heat-shrink on a cable-cable splice) followed by crimp on and twist-on connectors.
HEMT Wafer Probe Card Layout - Page 1
Forum section: electronics / rf-microwave

author: tec5c
author_rank: Frequent Contributor
timestamp: August 27, 2016, 05:10:15 am
content: I have some spare panel room on a design I'm getting fabricated and I want to utilise this space. I would like to create a test jig for the HEMT I am using which I can measure its parameters using wafer probes at my University.Things I know:3 probe setup - G S GDimensions of probes for probe pads; width, spacing etcRF measuring layout pattern; given in datasheet.What I am unsure of is how to combine the dimensions into a layout.I found this in a Cascade Microtech app. note, I believe this is what I need to do?This is my attempt, as you can see it didn't work out.The probe pads (G S G) are 100 micron squares, with a spacing of of 200 microns from edge to edge. The HEMT device has pin sizes of ~740 microns wide, which I why the tapered lines were included. However, the wafer probe pads are spaced at 200 microns (edge to edge) apart. This results in the tapered line from Gate/Drain pins overlapping with the ground strips for the two Source pins. (my apologies for the crude drawing)Any advice on where I am going wrong?EDIT: I just noticed that the dimensions for the spacing between the Drain and Gate probe pads is incorrectly labelled in my diagram (I said it was crude!). It should be 2.06mm/2060 microns
CATV signal levels and how do you measure them? - Page 1
Forum section: electronics / rf-microwave

author: peterdb
author_rank: Contributor
timestamp: August 19, 2016, 05:44:01 pm
content: Wat are the recommended cable television signal levels for DVB-C and analog signal distribution and how do you measure them with a spectrum analyser?I know they are described in the IEC 60728-1 international standard, but I don't have access to this document, and its not for free.Can someone fill me in with the basic principals?What’s the norm?How much may the signals deviate from the norm?Thanks in advance,Peter

author: Nermash
author_rank: Frequent Contributor
timestamp: August 19, 2016, 06:40:35 pm
content: Of the top of my head, signal level of 60-70 dBuV, with SNR 35-40 dB. Installers use CATV analyzers/level meters for setup, most of them have simplified spectrum analyzer.Not sure with how much lower level and SNR you can get away with, I think that 50-55 dBuV with 30 dB SNR should work.You can choose a channel and measure it on any SA, providing you use impedance adapter 50 to 75 ohms. SNR is measured on the 8 MHz wide channel.

author: Bicurico
author_rank: Super Contributor
timestamp: August 20, 2016, 07:28:47 am
content: Hi,If you are looking for recommended measurement values for DVB-C, please look at this link:http://www.roverinstruments.com/upload/UserFiles/Articoli_Tecnici/SUGGESTED_MEASUREMENT_VALUES__AUTOMATIC_QUALITY_MEASUREMENT_ENG.pdfRover Instruments is a leading manufacturer of professional TV field meter.In CATV you distinguish analog from digital transponders.Analog transponders: you measure the signal LEVEL, Noise Margin and A/V-ratio.Digital transponders: you measure the signal POWER. Also, looking at the constellation diagram provides important feedback regarding modulation problems. MER (Mean Error Ratio) and BER (Bit Error Rate) are important measurements, too.Finally, on both you can and should measure TILT to adjust amplifiers in such a way that the whole CATV band provides an evenly amplified signal.Regards

author: peterdb
author_rank: Contributor
timestamp: August 21, 2016, 08:22:23 am
content: Thanks all,looks like the numbers work out for me!
Connect rtl-sdr to 1V p-p sine wave source - Page 1
Forum section: electronics / rf-microwave

author: freebil
author_rank: Regular Contributor
timestamp: August 13, 2016, 09:10:44 am
content: Hello. Is it possible to connect to rtl-sdr voltage signals? I read in another thread that it is possible with attenuator? Thanks.

author: whalphen
author_rank: Regular Contributor
timestamp: August 13, 2016, 01:59:57 pm
content: Yes, you can feed your signal through an attenuator to reduce it to the level that's safe for the SDR. The amount of attenuation depends on the maximum level specified for the SDR. You can use the formula, dB = 20 log(Vin / Vout), to calculate the needed attenuation. Alternatively you can feed the signal into a resistor and then place the SDR antenna in the vicinity of the resistor to pick up the radiated signal. This approach is less consistent or repeatable, but I use it frequently to look at spectral shapes.

author: freebil
author_rank: Regular Contributor
timestamp: August 13, 2016, 04:23:56 pm
content: Thank you very much for the answer, but I cant find the maximum level for the sdr. I have this sdrhttp://www.rtl-sdr.com/new-products-rtl-sdr-with-1ppm-tcxo-sma-f-connector-r820t2-bias-tee-improved-tolerances-direct-sampling-break-out-pads-now-available-in-our-store/.I will send an email to manufacter of this but what to ask? What is the maximum level of voltage that this sdr can handle as input?

author: jpanhalt
author_rank: Super Contributor
timestamp: August 13, 2016, 04:51:53 pm
content: I simply made a small loop of solid copper wire and terminated it with 50 ohm. Connected that to my frequency generator. Thar was more than enough signal to calibrate my RTL-SDR.I then tuned up a few known stations of high accuracy (NIST stations).Such free-air testing is frowned upon, but given the very low signal level and the short time I used it, I figured it was OK.John

author: Ammar
author_rank: Regular Contributor
timestamp: August 19, 2016, 07:57:05 am
content: I fed about 100mW of RF power into and rtl-sdr without an attenuator thinking it would damage the device. It got a little warm, but worked fine,
Battery powered LNA after 20v power injector and down converter  - Page 1
Forum section: electronics / rf-microwave

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: August 17, 2016, 04:12:26 am
content: Ok so right out of my SDR stick I use an LNA for all or a self made LNA with the same mini circuits ps-4blah mmic. These work awesome because there noise floor is so much lower than the RTL stick you barely have to use any of the sticks gain, I usually just power with a 9 volt or something. Now if im running a decent feed line and trying to pick up anything over 1ghz I use a cheaper e-bay LNA at the antenna to make up for the coax loss, these dont even have an option for bias tee. So I recently modified a few DirectTV down Converters to get to 4ghz, but they require a power injector from 12 to 20v, which I have a 20v around. My question is if I run antenna -> self powered LNA -> 20v injector with down converter ->feedline -> LNA4ALL -> RTL-SDR am I going to blow up the LNA right behind the antenna? Even if it didnt blow up wouldn't I be pumping a bunch of DC noise through the mmic?Im hoping I can run my lines this way but if not, I could use two female sma connectors back to back with a DC blocking cap between them how would I size that cap and what kind of cap should I use, also is it ok to use a through whole cap with the lead practically cut off or should I really be using an smt cap? How would I calculate the loss, just calculate the capacitive reactance and thats the resistance but how do I turn that from R/Z to DB?The other option would be to put the LNA before the down converter/injector but then i am incurring the insertion loss from the combo, and im only amplfying the down converted signal, not the acuall signal im trying to recive, so im guessing this is kind of a bad solution?
Swan WMM-200 SWR / Power meter - Page 1
Forum section: electronics / rf-microwave

author: marcw
author_rank: Newbie
timestamp: July 22, 2016, 01:16:39 am
content: Hi,I have a Swan WMM-200, but no manual and nothing on the net. The one at the .de site is something else.Might anyone have a manual?Thanks,Marc

author: AF6LJ
author_rank: Unknown
timestamp: July 31, 2016, 02:05:32 pm
content: I don't have a manual, however they are not hard to reverse engineer.

author: LA7SJA
author_rank: Regular Contributor
timestamp: July 31, 2016, 05:46:23 pm
content: Quote from: marcw on July 22, 2016, 01:16:39 amAre you sure the type is WMM-200 and do you have a picture?And are you looking for the (l)user manual or the service manual?If you have a picture of the front almost all ham radio opperater should be able to make a short user manual.Anything like thishttps://www.google.no/search?q=Swan+swr+meter+picture?Johan-Fredrik

author: marcw
author_rank: Newbie
timestamp: August 08, 2016, 07:56:44 pm
content: it has the meter on the left and an external coupler. I googled for 'Swan WMM-200 SWR / Power meter'https://www.google.com/search?q=Swan+WMM-200+SWR+/+Power+meter&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjAib7nzLLOAhXK4yYKHSD-BAwQ_AUICSgC&biw=1024&bih=507#imgrc=_Thanks,Marc

author: LA7SJA
author_rank: Regular Contributor
timestamp: August 14, 2016, 09:23:22 am
content: I don't give up:QuoteIf you need to learn how to use a SWR meter you should find some of this videos useful:https://www.google.no/search?q=how+to+use+a+swr+meter+youtube&sourceid=ie7&rls=com.microsoft:nb-NO:IE-SearchBox&ie=&oe=&gfe_rd=cr&ei=ZDewV_nWCY-r8wfMm4GABgJohan-Fredrik
Icom IC-736 Power Supply Problem - Page 1
Forum section: electronics / rf-microwave

author: njvprodux
author_rank: Newbie
timestamp: August 07, 2016, 10:51:54 pm
content: Hi, My IC-736 came to me with an intermittent power problem, sometimes it wouldn't switch on, sometimes it would.I found a hairline fracture on one terminal of a main smoothing capacitor - the big ones. I also found some wetness and discolouration near other electrolytic caps so I replaced them all - only a few bucks but make sure you use 105C types from a reputable (not Chinese) manufacturers such as Rubycon, Chemicon etc.The IC-736 is a great radio! I love mine.73s GK3NJV
CC1125 half carrier harmonic - Page 1
Forum section: electronics / rf-microwave

author: veryevil
author_rank: Unknown
timestamp: July 23, 2016, 08:37:12 am
content: Hi, have a CC1125 on a project I'm working on in the 868MHz ISM band but when I fired it up I get a really large peak at 430ish MHz it's at about -17dBm and carrier is about 14dBm. Its way over limits for out of band power and I'm not sure where is best to look.Any ideas? Thanks.

author: jmsigler
author_rank: Regular Contributor
timestamp: July 23, 2016, 08:39:51 am
content: Are you using the reference design with the saw filter?

author: veryevil
author_rank: Unknown
timestamp: July 23, 2016, 08:43:37 am
content: Yeah its really close to the Cat1 reference design

author: veryevil
author_rank: Unknown
timestamp: July 25, 2016, 07:52:26 am
content: I've got a screen shots of it now.Hope this might help get a clearer idea of whats going on

author: jmsigler
author_rank: Regular Contributor
timestamp: July 26, 2016, 12:05:01 am
content: What saw are you using?

author: veryevil
author_rank: Unknown
timestamp: July 26, 2016, 07:10:04 am
content: Hi, I'm using the Epcos TDK B39871B3744H110 SAW filterHad an idea?

author: jmsigler
author_rank: Regular Contributor
timestamp: July 27, 2016, 01:22:33 am
content: Well I'm wondering how your measurement is possible since the saw datasheet lists 55dB attenuation in that band... I understand that there are various factors that can degrade this figure, but It looks like the saw isn't even there.Are you sure everything on the board is soldered right?

author: veryevil
author_rank: Unknown
timestamp: July 27, 2016, 06:04:06 am
content: The SAW is in the receive path not the transmit path.

author: Gribo
author_rank: Frequent Contributor
timestamp: August 05, 2016, 06:28:59 pm
content: What is the difference between your design and the reference design? Are you sure the RX path is properly decoupled from the TX path?

author: veryevil
author_rank: Unknown
timestamp: August 05, 2016, 06:34:14 pm
content: Hi, funny you should mention that. After some work with an rf engineer the track between the tx rx switch pin to the rx tx shunt cap was too long making a large inductor.It made the output very load dependent and we had an extra filter on the output which it didn't like either.Need another respin to be sure but think we have it.Thanks
RC522 PCB Antenna Problem - Page 1
Forum section: electronics / rf-microwave

author: efel
author_rank: Newbie
timestamp: August 05, 2016, 12:08:52 am
content: Hello everybody, how are you doing?I'm developing a custom Arduino UNO board that includes a MIFARE RC522 chip. The communications between the ATMEGA328 and the RC522 seems to be working since the serial console is showing this:Looking for MFRC522.Found chip RC522 Firmware version: 0x92But I'm not able to read any tag. I have a RC522 shield for testing and with it I can read all my tags.I made some mistakes in the design of the PCB antenna. At the beginning I was having a gain of 230mV and 13.56 MHz, so my first impressions were that the strength of the signal was the problem, I made some cuts to the board and now the oscilloscope shows about 10.7V and 13.56 MHz (Wave.jpg). I don't have the expertise to know what is wrong with my design. I attached the eagle project. It's a little frustrating because my first attempt was using a PIC16@3.3v (white board of the Boards.jpg) and the board works but now with Arduino@5V with a shifter I have communication with the chip but I'm not able to read anything.This is the sample code and tutorial I'm usinghttps://brainy-bits.com/tutorials/card-reader-with-an-arduino-rfid-using-the-rc522-module/Any suggestion is appreciatedThanks and best regards.
#65 Shop Talk Sniffing RF signals safely  - Page 1
Forum section: electronics / rf-microwave

author: Radio Tech
author_rank: Frequent Contributor
timestamp: August 01, 2016, 12:23:22 am
content: #65 Shop Talk Sniffing RF signals safelyIn this video we show a simple way to sniff out RF signal safely.

author: nowlan
author_rank: Frequent Contributor
timestamp: August 01, 2016, 02:44:48 am
content: Audio is very soft or just me?Think it is me.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: August 01, 2016, 09:25:13 am
content: Quote from: nowlan on August 01, 2016, 02:44:48 amLevels looks ok here.Quote from: GEuser on August 01, 2016, 06:30:39 amNice probe. I will look those up. Thanks

author: voltz
author_rank: Frequent Contributor
timestamp: August 01, 2016, 09:33:32 am
content: Thats great. I'm sure someone getting into RF will find this invaluable information. Keeping it safe - defo

author: Radio Tech
author_rank: Frequent Contributor
timestamp: August 02, 2016, 12:52:18 pm
content: Quote from: voltz on August 01, 2016, 09:33:32 amThanks. And for this type of test these homemade ones are much cheaper than near field probes.
eBay PE4302 Attenuator modules - Page 1
Forum section: electronics / rf-microwave

author: CJay
author_rank: Super Contributor
timestamp: August 01, 2016, 08:53:47 pm
content: Has anyone tested the PE4302 (or similar PE*) modules that are available on eBay?http://www.ebay.co.uk/itm/PE4302-Digital-RF-Attenuator-Module-High-Linearity-0-5dB-Step-1MHz-4GHz-50-DSA-/141738265401?hash=item2100424b39:g:T~AAAOSwiYFXKyEt
LNA Question - Page 1
Forum section: electronics / rf-microwave

author: jmsigler
author_rank: Regular Contributor
timestamp: July 30, 2016, 06:47:50 pm
content: Hello,What performance trade off does a LNA make to achieve its low noise factor compared to a regular amplifier? Why would it be a bad idea to use a LNA other places in the signal chain besides right after or close to the input? Is it mainly a cost thing?

author: German_EE
author_rank: Super Contributor
timestamp: July 30, 2016, 07:01:29 pm
content: These folks can explain it all far better than I can:http://www.digikey.com/en/articles/techzone/2013/oct/understanding-the-basics-of-low-noise-and-power-amplifiers-in-wireless-designs

author: jmsigler
author_rank: Regular Contributor
timestamp: July 30, 2016, 07:17:26 pm
content: Good point, I probably should have used google first. Thanks for the response!

author: whollender
author_rank: Regular Contributor
timestamp: July 30, 2016, 08:00:39 pm
content: The big tradeoff for LNAs is usually performance at higher power levels. So LNAs will usually start distorting at lower power levels than other amplifiers. They also tend to be more expensive than simple gain block type amplifiers, so it usually only makes sense to put the LNA at the beginning of the receiver chain where the low noise figure really makes a difference.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: July 30, 2016, 10:03:37 pm
content: In order to push the noise figure very low, LNA designs tend to be narrow band. They might still have gain outside their specified bandwidth, but other properties like saturation power (P1dB) and linearity (IP3) suffer outside the specified bandwidth.Amplifier design: you have noise figure, power output and bandwidth. Pick two.

author: rfbroadband
author_rank: Unknown
timestamp: July 30, 2016, 11:17:47 pm
content: trade offs are:1) input impedance match2) bandwidth3) large signal performance (P1dB, IP3, IP2)1) the optimum NF is achieved at impedances other than 50 or 75 Ohm...-> google for noise matching2) matching for lowest possible noise will (in many cases) be narrow band3) in order to operate the device for best noise performance requires a bias point that is non optimal for large signal behavior of your amp.I provided a very basic, simplified explanation. The trade offs depend on the type of device (MOSFET, BJT) and the type of circuits you choose (common gate, common source etc).You could study a few text books that derive the equations for each case to get a deeper understanding.
These eBay attenuators any good? - Page 1
Forum section: electronics / rf-microwave

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: July 22, 2016, 11:54:44 pm
content: http://www.ebay.com/itm/1dB-3dB-5dB-6dB-10dB-15dB-20dB-30dB-6GHz-2W-SMA-RF-Attenuator-/262176080490?hash=item3d0ae9826a:g:-zkAAOSwnipWYmWZThere should be a "marketplace" section to discuss various experiences with sellers and their products...

author: AF6LJ
author_rank: Unknown
timestamp: July 24, 2016, 09:04:09 pm
content: An SMA attenuator is hard to mess up in that frequency range.Bot do take note the VSWR is okay but not great.

author: uncle_bob
author_rank: Unknown
timestamp: July 25, 2016, 12:03:58 am
content: HiI think that for the price, I'd want to see a little more data. Is the attenuation +/- 1 db over the range? Is the VSWR 1.2 at 6 GHz and 1.05 below 3 GHz? Lots of things you might want to know.Bob

author: ConKbot
author_rank: Super Contributor
timestamp: July 25, 2016, 02:29:51 am
content: I doubt they are really good for 2w, they look like they are a bit smaller than minicircuits 1w attenuators. And +1 to a vswr vs freq and attenuation vs freq plot would be reassuring. Since they make them, maybe they can provide them if you ask.

author: AF6LJ
author_rank: Unknown
timestamp: July 25, 2016, 03:02:28 am
content: What for $9.00?They are dirt cheap....Would I buy them to be used as test equipment?Nope...For a beginner and for use in a piece of gear I was building they are fine.

author: cncjerry
author_rank: Unknown
timestamp: July 26, 2016, 04:27:39 am
content: find one of the attenuators taken out of an HP SA for less than $50 and you can go from 10 - 70db with a battery and a few switches. There are also attenuators in 1dB that are pulled from analyzers as well.

author: uncle_bob
author_rank: Unknown
timestamp: July 26, 2016, 10:48:30 pm
content: Quote from: cncjerry on July 26, 2016, 04:27:39 amHiAt least around here, surplus attenuators are a "sub $2" sort of thing when you find them for sale.Bob

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: July 30, 2016, 04:28:06 pm
content: Thanks all, but I'm such a hoarder I just found a box full of Huber Suhner SMA attenuators!

author: David Hess
author_rank: Super Contributor
timestamp: July 30, 2016, 05:56:12 pm
content: Quote from: uncle_bob on July 26, 2016, 10:48:30 pmThe last time I visited the HAM swap meet around St. Louis which is hardly a hotbed of surplus electronics these days, I was happy to pick up an assortment of NOS Minicircuit SMA attenuators for $5 each.I have a whole collection of used Tektronix BNC calibration attenuators from Ebay and they all tested good.As far as these Chinese ones, $8 seems reasonable if you have a way to roughly verify their performance since the seller is not going to want bad feedback but I have found name brand NOS SMA attenuators on Ebay for less than that before.
#63 A look at a mint Collins KWM 2A in for repair  - Page 1
Forum section: electronics / rf-microwave

author: Radio Tech
author_rank: Frequent Contributor
timestamp: July 25, 2016, 09:39:03 am
content: I had the opportunity to work on a Collins KWM-2A this week end. Did not have4 time to do the repair on camera due to getting the radio back to the owner. Rig came in with a broken power port. While testing the unit I found several bad solder joints and repaired those as well.#63 A look at a mint Collins KWM 2A in for repairIn this video we look at a viewers Collins KWM-2A. I have to install a new power port and repair a few solder joints then align the radio off camera.

author: German_EE
author_rank: Super Contributor
timestamp: July 25, 2016, 03:57:54 pm
content: Given their age the cosmetic appearance of Collins gear always amazes me. There was some for sale at Friedrichshafen and it looked like it was fresh from the factory.When owners kick up a fuss about fitting the wrong replacement part in their radios you sometimes have the option of fitting the new part INSIDE the old one. I've sometimes done this with can capacitors where the new part has a higher voltage rating and yet is half the size.

author: AF6LJ
author_rank: Unknown
timestamp: July 26, 2016, 01:06:25 pm
content: Good Video.Never worked on one of those...I'd love to have a KWM-1...I have worked on a 75-A4, and used one for a few weeks back decades ago.A friend, and member of our 75 meter rag chew group has a 75-A4 that he replaced all the mica caps along with all the electrolydics and black beauties. He recently had one of the ceramic disc caps fail, but it is a sixty year old receiver that gets use on a weekly basis.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: July 29, 2016, 07:48:34 pm
content: Quote from: German_EE on July 25, 2016, 03:57:54 pmIt is amazing how well they hold up after so many years. Amazing what the price of these radios are also.Yep, Have stuff a many caps over the years. Specially guitar amps.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: July 29, 2016, 07:56:07 pm
content: Quote from: AF6LJ on July 26, 2016, 01:06:25 pmThanks Sue.The -2A was not too bad. Just time consuming. But he is very happy with it. Worked on many of them.Now the KWM-1 is a different story. He bought it non working. receives very well. But no output. At the moment I am missing the 260 VDC. These are a pain to work on. All wiring is in a loom and no underside illustration showing what each part is. Using the SA it a "sniffer" on the end of a piece of coax I see I have drive signal on selected frequency. That is a good thing.Part that gets me is someone did a recap job. Looks decent. But in the back of my mind I have to wonder is this when the failure occurred. Before, during, or after....I have never worked on a 75-4A. Maybe one day. Seen caps in RF stage fail often. Specially in the FT-101.
alternatives for mesh network? (solar powered) - Page 1
Forum section: electronics / rf-microwave

author: otrab
author_rank: Newbie
timestamp: July 29, 2016, 12:37:21 am
content: Hi!I want to make a protoype with 4 nodes for sensing vibration on a bridge. Also this thing need a gateway with 3G capability and solar powered.The max length bridge it's about 3km with 36 nodes aprox. Only send data if vibration it's outside of an umbral.Some year back I made a wsn proyect with zigbee it's there another better alternative (protocol - hardware)?Have any sense work with mesh network with the bridge topology?max 40 nodesmax distance between nodes 150 metersonly transmit if data it's out of umbral3G Gatewaybytes!

author: LabSpokane
author_rank: Super Contributor
timestamp: July 29, 2016, 12:51:13 am
content: Forget the gateway. Throw sims in everything. Cellular radios and data plans are stupid cheap now.Look at aeris.com. They have an extremely affordable plan for data usage similar to the few bytes per month you'll need to xmit.

author: batteksystem
author_rank: Regular Contributor
timestamp: July 29, 2016, 01:30:46 am
content: Quote from: otrab on July 29, 2016, 12:37:21 amWhat is your problem with mesh network?

author: otrab
author_rank: Newbie
timestamp: July 29, 2016, 03:42:27 pm
content: LabSpokane sounds interesting to use 3G, I worry about having to manage a sim plan for each node that you develop.batteksystem, I think that being a bridge would not take advantage of the mesh network. All nodes are aligned in a row.thanks