hybridfree/eevblog-posts huggingface dataset:
What are you Realy hearing when youtuneyou SDR lower then it's bandwidth? - Page 1
Forum section: electronics / rf-microwave

author: Beamin
author_rank: Super Contributor
timestamp: August 11, 2018, 12:38:29 pm
content: On HDSdr and other programs you an tune down to DC but not really. My SDR Play goes really low but the TV tuner SDRs don't but you still hear things, even signals, where there shouldn't be. So first why are there mirror signals down below DC is this just software or is there actually something to this? What are you hearing below 50mhzon the TV tuners; artifacts inside the radio itself? I thought at first that the hardware really went this low but the specs say no. Another thing I couldn't figure out was on the SDRPlay I would hear the BBC down in shortwave. At first I thought it was a station but there are none and it would disappear but other long distance stations should disappear too but they didn't . Also it wasn't a ghost image like AM or FM broadcast because we don't have any in this area. I thought maybe it was the IF of another radio but that was a higher frequency and almost all radios are the same. Since we are on impossible questions what do the numbers stations say?(the smiley is for the readers with Asperger's who will think that's a real question) I'm also 99% convinced radio Havana plays number stations on the same mast/antenna as their civilian one from the exact same sound/strength of the two signals. Isn't the tower owned by the government making this easy to do covertly? I would think a spy with a SW radio would be more obvious then one getting instructions over the internet or phone. Any chance of ever seeing the one time pad found in the bar of soap of that British spy?
Homebrew waveguide isolator? - Page 1
Forum section: electronics / rf-microwave

author: Mrt12
author_rank: Regular Contributor
timestamp: August 09, 2018, 01:38:29 pm
content: I am making a waveguide harmonic mixer for my HP 8568B 'boat anchor' spectrum analyzer. First experiments show that it 'sort of' works properly, at least I could measure a signal at 25 GHz... what I am thinking about now is to include an isolator into the mixer to improve the matching of the waveguide input.However, there is only little literature available on the subject; all I could figure out is that some sort of ferrite material is used, together with permanent magnets.Has anybody ever thought about making such an isolator?I do have a working isolator, but I don't want to take it apart to see its internal construction.Any ideas?
Shortwave voice transmitter circuit ( not cw) - Page 1
Forum section: electronics / rf-microwave

author: Dom13c
author_rank: Regular Contributor
timestamp: August 01, 2018, 11:23:28 am
content: Transmitting voice over shortwave is quite fascinating to me. But whenever I google for shortwave AM phone, the results turn out as cw transmitters.Well, I've already made and played with them. So my next goal is to transmit voice over shortwave. Well ,don't recommend the SSB stuffs. They are just too hard to be bulit. Output power may stay within one or two watt as I'm planning to drive a class B linear amplifier with it.( If possible suggest a circuit that is based on crystal oscillator) And I'm not talking about AM radio( 550-1500khz in India) transmitter , I'm talking about shortwave transmitter(3-30 mhz) with amplitude modulation

author: PA0PBZ
author_rank: Super Contributor
timestamp: August 01, 2018, 11:30:37 am
content: https://www.google.com/search?q=short+wave+am+transmitter&tbm=ischSome are CW but there's a lot AM too.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: August 01, 2018, 11:53:15 am
content: Try it with a NE602:http://www.elektronikbasteln.pl7.de/am-modulation-mit-einem-sa612-oder-sa602-ne612-ne602.htmlwith the trimmer you adjust the carrier suppression (if wished for SSB), otherwise it outputs an AM signal

author: tkamiya
author_rank: Super Contributor
timestamp: August 08, 2018, 11:31:14 pm
content: You might be better off googling "AM modulation circuit".AM is nothing more than CW transmitter that is keyed down and power to the final section modulated. There are much fancier way to do it but that's the basics of it.

author: kg4arn
author_rank: Unknown
timestamp: August 09, 2018, 01:29:36 am
content: http://www.phonestack.com/farhan/bitx.htmlCheck out how this ham did it. Very popular simple design.

author: vk4ffab
author_rank: Frequent Contributor
timestamp: August 09, 2018, 07:22:42 am
content: What you want to do is google DSB Double Sideband, double sideband suppressed carrier. Its the easiest method of generating vioce RF. Peter Parkers Beach 40, the MDT by ozqrp etc are rigs that use direct conversion of audio to RF.
Impedance match cpwg with a complex impedance? - Page 1
Forum section: electronics / rf-microwave

author: mik4el
author_rank: Contributor
timestamp: August 13, 2018, 07:49:21 am
content: I'm working on improving a PCB using the CC1350 dual band MCU for 868 MHz and BLE. I got the chip working but the RF part is performing very bad. It is usable for testing but has very bad performance which requires a redesign. A big reason (I hope the main reason) for the bad performance is that I've used excessively long transmission lines that weren't properly impedance matched.The RF part on the PCB from the CC1350 consists of first a differential pair (common for sub-GHz and BLE) that goes into an DC bias circuit, then there is an RF switch to switch between sub-GHz and BLE for the antenna path that first goes into a balun and then 50 ohm into the antenna. I think I have the part from the RF switch and forward figured out now with regards to impedance matching and baluns. However from the CC1350 into the DC bias circuit the differential pair is stated by TI in the datasheet (http://www.ti.com/lit/ds/symlink/cc1350.pdf,p51) "On the Texas Instruments CC1350_7XD-Dual Band reference design, the optimal differential impedanceseen from the RF pins into the balun and filter and antenna is 44 + j15."Therefore my question is: How do I impendace match the transmission line from the CC1350 from RF pins and into the baluns to 44 + j15? Do I need to if I keep the traces really short? All the impedance calculators I find only state the characteristic impedance Z0. I've attached my previous calculations for the 50 ohm transmission lines.20180814: Changed to DC bias circuit

author: the_janitor
author_rank: Newbie
timestamp: August 13, 2018, 08:01:48 am
content: You can either use websites such as these:https://home.sandiego.edu/~ekim/e194rfs01/jwmatcher/matcher2.html(most common configurations) or you can impedance match using a software like SimSmith, which is really a handy tool and it's freeware! You can download it athttp://www.ae6ty.com/smith_charts.htmlYou can find tutorials about SimSmith at:https://www.youtube.com/user/ae6tyhttps://www.youtube.com/channel/UCKSyLSu4fm_1RHoO3Jvk4YQ

author: mik4el
author_rank: Contributor
timestamp: August 13, 2018, 08:54:46 am
content: Thanks for your comment. I guess I could use an impedance matching circuit as you suggest but I was more after what my transmission line for the 44+15j impedance should look like as a cpwg etc?

author: mik4el
author_rank: Contributor
timestamp: August 14, 2018, 09:53:09 am
content: Found the answer myself athttps://e2e.ti.com/support/wireless_connectivity/proprietary_sub_1_ghz_simpliciti/f/156/t/717102?jktype=e2ebut posting it here for anyone interested.The traces in question are so short that they don't need to be considered transmission lines and one should instead pick the pcb trace width from the width of the 0402 components.
Stupid and strange answer from Analog Devices IC HMC862  - Page 1
Forum section: electronics / rf-microwave

author: max-bit
author_rank: Frequent Contributor
timestamp: August 07, 2018, 07:44:19 pm
content: I got a very strange and stupid response from Analog Devices (Hittitle).I wanted to get a sample of the HMC862 IC (divider up to 24GHz), the IC is not easily accessible, so I asked if they are able to deliver to the IC prototype.And what did I get to answer? That the IC is no longer produced?WTF?How's the new IC?http://www.analog.com/en/products/rf-microwave/frequency-dividers-multipliers-detectors/frequency-dividers-prescalers-counters/HMC862A.html#product-overview

author: TassiloH
author_rank: Regular Contributor
timestamp: August 08, 2018, 01:33:47 pm
content: Did you ask for the HMC862 or the HMC862A? The former seems to be out of production, and the latter is in production and available from arrow.com for 16 EUR.

author: max-bit
author_rank: Frequent Contributor
timestamp: August 08, 2018, 01:49:46 pm
content: of course 862A (I am not asking for not available only available)

author: iMo
author_rank: Super Contributor
timestamp: August 08, 2018, 03:29:10 pm
content: Does AD send samples to CEE??
Raspberry pi DMR demodulation  - Page 1
Forum section: electronics / rf-microwave

author: Charlie86
author_rank: Regular Contributor
timestamp: August 06, 2018, 08:07:42 pm
content: Hi,Now I use windows machine with SDRsharp and dsd plus to demonstrate DMR digital signals.Is it possible to create same setup on raspberry pi B +?Dsd only works in windows so I am looking for some similar program that can run on raspberry pi.Thank you

author: tsman
author_rank: Frequent Contributor
timestamp: August 06, 2018, 09:14:47 pm
content: https://forums.radioreference.com/voice-control-channel-decoding-software/254829-dsd-raspberry-pi-3.html#post2693430You're going to want the fastest RPi board you can get your hands on. If you've got a 3B+ then you can give it a go. An old B+ however isn't going to work as it is just too old + slow. Buying one of the faster but more expensive Odroid boards might be a good idea TBH.

author: HoracioDos
author_rank: Frequent Contributor
timestamp: August 07, 2018, 12:10:00 pm
content: Hello.DSD plus is a windows fork of this projecthttps://github.com/szechyjs/dsdhttps://github.com/szechyjs/dsd/issues/67It should compile on a raspberry pi.https://github.com/szechyjs/dsd/wiki/InstallationPS: gqrx is also available for raspberry pi. B+ should work. Try it first.
high power mixer? - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: July 09, 2018, 04:21:25 am
content: Can you mix high power signals? Like if you had two high power signals you want to efficiently mix without amplification afterwords.

author: helius
author_rank: Super Contributor
timestamp: July 09, 2018, 05:16:08 am
content: It is possible for microwaves.https://en.wikipedia.org/wiki/Magic_teehttps://en.wikipedia.org/wiki/Wilkinson_power_divider

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 09, 2018, 07:34:42 am
content: Nonlinear mix, not linear superposition (audio mixing).Here's an example at power:http://davidberning.com/technologyOnly used as a DC transformer, but that's one possible application of a mixer: synchronous modulating and demodulating at a driven clock frequency.I don't know of any general method for high frequencies. At low frequencies, it's just ordinary power electronics.Tim

author: Wolfgang
author_rank: Super Contributor
timestamp: August 08, 2018, 12:02:13 am
content: Do you want a "transmit" mixer ?What frequency range should it have ?What are the power levels ?Is efficiency an issue ?
2x RTL SDR one antenna - Page 1
Forum section: electronics / rf-microwave

author: Charlie86
author_rank: Regular Contributor
timestamp: August 05, 2018, 03:08:01 pm
content: Hi,I want to listen trunked signals (DMR) with two SDR USB keys. Can I use one antenna for both of them?If yes, what splitter should I buy?I found this one at home and have no idea from where it is an if it capable of splitting antenna signal to two SDR key?https://ibb.co/fxvake

author: wolferl1210
author_rank: Contributor
timestamp: August 07, 2018, 11:50:33 am
content: The device you show in the picture is a TV attenuator. Has one in and and one out with -0.8db and one out with -12.5db (!)it is using F-connectors and who knows, for what frequency range it will work.http://www.dxing.info/equipment/rolling_your_own_bryant.dxhttp://www.hdtvprimer.com/antennas/merging.htmlare examples - how to.I am using a Mini-Circuits PSC-2-1 for my secondary antenna input on a Kenwood transceiver.Any splitter will degrade your signals by -3db. Sometimes simply connecting both SDR on oneantenna with an Y-BNC connector will do it without any problems (and loss). Just try it!73's
Trying to understand how this RC receiver works - Page 1
Forum section: electronics / rf-microwave

author: atmfjstc
author_rank: Regular Contributor
timestamp: August 04, 2018, 11:39:32 pm
content: I've taken apart a cheap RC car and I'm trying to understand exactly how the receiver/demodulator works. I know that the incoming signal is 27MHz with binary amplitude modulation, i.e. pulses on/off, and the receiver is supposed to essentially isolate the 27MHz from the antenna and extract the binary envelope which is then fed as-is to an IC. What puzzles me is the very first stage of the receiver, whose schematic I've attached here (the other stages seem to do filtering mostly).The topology confuses me and I'm not sure where to begin analyzing it. What is the transistor doing? Is it filtering? Oscillating? If it's an amplifier/filter, what topology is it? The input seems to be going into the collector and the base serves as an output, which doesn't make sense.P.S. Note that the tank circuit formed by C2 and L1 matches the desired frequency.

author: Circlotron
author_rank: Super Contributor
timestamp: August 04, 2018, 11:47:33 pm
content: Superregenerative receiver?https://www.google.com.au/search?q=superregenerative+receiver&rlz=1C9BKJA_enAU745AU745&hl=en-GB&prmd=isvn&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiX1PmkytTcAhUOAogKHS5sDXEQ_AUIESgB&biw=1024&bih=653#imgrc=XUQrb3HammucmM:

author: atmfjstc
author_rank: Regular Contributor
timestamp: August 05, 2018, 02:48:39 pm
content: Interesting. The circuits do look similar. Looks like I have quite a lot to unpack, I never imagined the receiver in a toy car would employ such sophisticated principles.

author: iMo
author_rank: Super Contributor
timestamp: August 05, 2018, 04:27:44 pm
content: There is nothing sophisticated in that kind of receiver. They are used for last80100 years at least.It is a combination of a "regenerative receiver" and a relaxation oscillator (called therefore "superregenerative receiver").The relaxation oscillation (10-50kHz) are set by the R1C4 (and isolated from the regenerative part by L2), relaxation sawtooth wobble the regenerative part L1C2-C3 such it passes from pre- to post-regeneration periodically, and that creates an enormous amplification (~millions). With "averaging" this events by the low pass filter R4C6-R6C23 it "demodulates" the RF signal envelope (AM or FM). The relaxation frequency is set such it is above audible spectrum when used for transmitting voice.It works, but it is not recommended to use this receiver type today as it radiates a lot of EMI crap. Do not use it in Europe..
ECG1198 / uPD858C Frequency Divider - Page 1
Forum section: electronics / rf-microwave

author: dentaku
author_rank: Frequent Contributor
timestamp: August 04, 2018, 03:19:03 pm
content: I found a new old stock Sylvania ECG1198 Frequency Divider and Phase Detector still sealed in it's plastic bag in my bins of stuff I got from an old man and can only find simple two page datasheets for it.I see that's it's the same as the uPD858C and there are pages describing how to modify radios that use this chip (even Defpom has written stuff about this online) so that's useful information about how to use it.https://www.radiomods.co.nz/integratedcircuits/upd858c.htmlAre there any more detailed datasheets for the 1198/858C that I'm missing? Does it maybe go under another name?I've messed with the 4046 PLL before, mostly because it has a VCO in it and I'm more interested in synthesizers than radio and I've played with simple phase detectors on breadboards and in simulations in the past just for fun as a learning exercise.QUESTION:I'm simply curious about the Divide-by-N Counter part of the chip and if it can bemis-usedby itself for other purposes than radio.Can it be used as a sort of digitally control oscillator "DCO" through the Fin and PD Out pins sort of in the way a 4046 can be used as just a VCO for generating different frequencies and ignore all the other PLL / Phase Dectetor-ish functions this chip provides.Or is that not what that section of the chip is for and it relies on all the other parts plus crystal oscillators for it to be of any use?
#176 Alinco DR 570 UHF Receiver Failure  - Page 1
Forum section: electronics / rf-microwave

author: Radio Tech
author_rank: Frequent Contributor
timestamp: August 06, 2018, 01:39:41 pm
content: We take a look at the Alinco DR-570 that has no UHF receive.This is a common problem with these radios due to there is no front end protection.Strong signals causes front end overload and destroys the first RF amp.We will look at an old circuit to prevent this failure.For more troubleshooting on this particular radio have a look at TRXBench video on this radio where he has a similar issue with the VHF.
future of Amateur radio maybe Delay-Tolerant Networks - Page 1
Forum section: electronics / rf-microwave

author: jonovid
author_rank: Super Contributor
timestamp: August 03, 2018, 08:36:03 pm
content: https://www.eevblog.com/forum/amphour/401-an-interview-with-brent-and-bryce-salmi/delay-tolerant networks the amphourhttps://faradayrf.com/delay-tolerant-networks-killer-app/Internet connectivity over amateur radio bands digital voicewill this be a type of twitter for amateurs with type of message queue or data bankpriority would go to small data files like QSO contacts 140 charactersmid-size data files like voicemail - artificial intelligence for amateur radiothe delay-tolerant-networkthis is not just anther D-STAR but an open source software Internet type connectivity over amateur radio bandsusers can study, change re-design do experiments in data connectivity,one more videoDelay / Disruption Tolerant Networking
NB-IoT Modules Power - Page 1
Forum section: electronics / rf-microwave

author: Ronan Keets
author_rank: Newbie
timestamp: August 02, 2018, 09:17:41 am
content: Hi Forum,I am working on a NB-IoT related project for use in Norway. I am looking to identify a module that is low power and yet is available easily. For the power comparison I googled and came across thishttp://www.ensembletech.in/nb-iot-modules-power-consumption-comparison/I think going by this post I will go with Digi Xbee module as I already have XBee boards so working will be easier.Any one here has any experience with these modules here?

author: mjs
author_rank: Regular Contributor
timestamp: August 03, 2018, 12:51:20 pm
content: I evaluated some Cat-M1 modules when they first came out. My advice is that do some measurements of the energy consumption with your operating profile instead of looking up current consumption from the datasheets. And also check what is the voltage used when specifying the current consumption..I wish the firmware and network are more mature for you than they were for the M1 project a year ago. It was a pain, but that was to be expected.Also, first measurements were much much better than with the firmware that finally passed the operator testing and were done in realistic field environment. Fortunately we took a good PPT-factor for the design.
Vertically symmetric "microstrip" - Page 1
Forum section: electronics / rf-microwave

author: Odysseus
author_rank: Regular Contributor
timestamp: August 02, 2018, 05:30:40 am
content: I'm trying to find geometry equations for a microstrip-like transmission line which is vertically symmetric where both the "signal" and "ground" lines are of equal width, but my google-fu is too weak. I imagine such a geometry has already been characterized, but I can't seem to find any info on it.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: August 02, 2018, 05:51:25 am
content: I think you are referring to a broadside stripline? Usually these are used for differential signals though, and surrounded by ground planes. I haven't seen them used much outside of couplers and feedlines for antennas. I believe they are not great for many applications because any connection to a planar passive on the top requires asymmetry of some extent between the two conductors.

author: Odysseus
author_rank: Regular Contributor
timestamp: August 02, 2018, 07:23:53 am
content: Your description is close, but the structure I'm thinking of consists of only two layers, with no surrounding ground planes. My motivation for this question is more academic than practical. There's a glut of references/calculators for the more common planar transmission lines, but I haven't seen any material covering this type. The term "broadside" is helping with my search.This page (https://www.polarinstruments.com/support/cits/AP147.html) seems indicate that this broadside-coupled differential pair can be treated like a pair of conventional mircostrip lines, back-to-back. I'll agree that the electric field might be identical in both cases, but I don't yet agree that the magnetic field would also behave the same, and then neither the resulting impedance.

author: xaxaxa
author_rank: Regular Contributor
timestamp: August 02, 2018, 08:10:23 am
content: use the mirror image theorem (or whatever it's called) and you can see that it's simply two microstrips back to back, each with half the height
What is harmonic conditioning? - Page 1
Forum section: electronics / rf-microwave

author: fonograph
author_rank: Frequent Contributor
timestamp: July 29, 2018, 02:06:07 am
content: I was looking at Tektronix website,reading about the TTR500 usb VNA when I stumbled upon unfamiliar term "harmonic conditioning".What is it? What it does? How does it do it? Why its in VNA?

author: fonograph
author_rank: Frequent Contributor
timestamp: July 31, 2018, 07:13:45 am
content: Eh,no one?

author: xaxaxa
author_rank: Regular Contributor
timestamp: July 31, 2018, 01:48:42 pm
content: it's just a bank of lowpass filters to get rid of the harmonics from the signal generator

author: fonograph
author_rank: Frequent Contributor
timestamp: July 31, 2018, 03:44:36 pm
content: Thank you xaxaxa

author: Bud
author_rank: Super Contributor
timestamp: July 31, 2018, 04:08:38 pm
content: We do not know the architecture of this particular device model. Harmonic conditioning may have different meaning for different device arcitecture. Say, if the device employs harmonic mixing to extend the frequency range, conditioning may mean the opposite what the other poster said, such as selecting specific harmonics and amplify them for mixing (condition them for the needed function)

author: DaJMasta
author_rank: Super Contributor
timestamp: July 31, 2018, 05:30:37 pm
content: Yeah, it's not a standard term but it vaguely suggests to me that rather than just eliminating harmonics around the tone, it may be using some sort of multiplier and the eliminating the frequencies it doesn't want. I don't think there's anything particularly spectacular about it, but basically ever bit of RF test gear is going to have a pretty extensive set of filters to get the sort of spectral purity they need to meet spec.
11.600Mhz 15:40 UTC -> who is the Insane Guy?! - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 27, 2018, 03:43:48 pm
content: I think the title say everything.Who is the insane US Voice Sound Guy?!The sound like someone who was on a run from a mad house and broke into an Radio Station and transmitt some weird stuff.http://www.shortwaveschedule.com/index.php?freq=11600-> nada.

author: mark03
author_rank: Frequent Contributor
timestamp: July 27, 2018, 05:24:21 pm
content: You need to give us some more detail. No way to comment intelligently based on what you've said.That being said... Was the voice reading numbers, by any chance?

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 27, 2018, 08:23:40 pm
content: Nope it was no number Station the was sayed something about God and other strange thinks.Normally that people who speak such a weird crap are Hospitalised and become the right treatment.If he can hear the Voice of God he must be a very sick man.

author: PhilipPeake
author_rank: Regular Contributor
timestamp: July 27, 2018, 09:07:49 pm
content: America has always been somewhat famous for its proliferation of SW religious radio stations. No idea why they proliferate in the US, they just do. To any normal Christian they sound a bit unhinged.

author: GrahamC
author_rank: Contributor
timestamp: July 27, 2018, 09:27:40 pm
content: Sounds like "Brother Stair".Transmissions are usually quite strong and usually just below or above the usual shortwave broadcast bands. I just check 2018-07-27 21:20 UTC but did not hear what you were hearing.here a thread on a different online forum that will give you some idea on this character but a quick search using your favourite search tool will provide much more interesting reading.Do note, I am not saying that what you heard was in fact "Brother Stair" but by your limited description it may well just be. In any case, there is no shortage of such characters on the air.cheers, Graham

author: Karlo_Moharic
author_rank: Regular Contributor
timestamp: July 31, 2018, 07:25:16 am
content: +Lord of NothingWhat you heard was God itselfe, because as we all know God is an American and has a radioamateur licence
A really dumb really cheap RF/EMI shielding solution - Page 1
Forum section: electronics / rf-microwave

author: ChristofferB
author_rank: Frequent Contributor
timestamp: July 29, 2018, 01:03:43 pm
content: ...I just have to share this with someone, it actually works rather well! cutting an A3 piece of aluminum foil, folding it in half and laminating it.The edges are then cut off, and the two layers split apart, giving two sheets of 'aluminized' plastic that's conductive on one side. it can be folded, cut, have holes punched in for bolts and ground lugs.I don't think shielding gets cheaper. It could get a lot better though. Maybe someone will find this useful. Would be even better with thin copper foil, which could be soldered to.

author: drew23
author_rank: Contributor
timestamp: July 29, 2018, 09:10:08 pm
content: I use copper shim for shielding and making large copper parts using PVC pipe as a base. Aluminium shim, used to keep white ants out, can be used as well. Drew VK4ZXI

author: james_s
author_rank: Super Contributor
timestamp: July 29, 2018, 11:11:46 pm
content: Hmm I'll keep that one in mind.Has anyone compared the effectiveness of copper vs aluminum? Aluminum foil is certainly much cheaper and easier to get than copper foil.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 30, 2018, 12:22:29 am
content: Aluminum foil is thinner than 1oz copper foil (PCB stock, say), and higher resistivity besides, so it will only be effective down to higher frequencies. This doesn't matter much for, say, VHF+.I wish McMaster had tin plated steel, I'd get a 24x24 sheet of that. Otherwise, there's just the little craft squares at the hardware store, overpriced. It's easy to solder, easy to form, strong for its thickness, and somewhat effective magnetic shielding down to DC, as well as to lower AC frequency than a comparable piece of aluminum (because skin effect).Tim
WiCard WiFi module with ESP8266 - Page 1
Forum section: electronics / rf-microwave

author: mvtdesign
author_rank: Newbie
timestamp: July 28, 2018, 04:47:47 am
content: Hi,I have made a WiFi module (its name is WiCard) with an ESP8266EX and an ATMega8A, This video shows how it works (Please enable the subtitle):https://youtu.be/EwaLmF114rII programmed my WiFi module GPIO only in a few minutes, while if I wanted to make this program only just with an ESP8266 module, it took a long time to be completed.If you'd like to know how to make it, please take a look at these two articles on my website:How to make a WiCard WiFi module:https://wicard.net/wicard13-pcb-schematic/How to make a WiCard WiFi module on a breadboard:https://wicard.net/make-breadboard-wicard-esp8266/More videos:https://youtu.be/UP3T7rz2yUEhttps://youtu.be/wIqEkXeTji0https://youtu.be/VreEjaUTIJ0By the way, I'd love to hear your suggestions and ideas about WiCard. Thank you so much
Is there a way to send HDMI signals wirelessly a short distance? - Page 1
Forum section: electronics / rf-microwave

author: Beamin
author_rank: Super Contributor
timestamp: July 23, 2018, 02:15:37 am
content: I want to able to plug a "dongle" into my computer or RPi and then plug the other end into a monitor. This way you could use your raspberrypi like you do with the wireless USB mouse and key board. Or you could use your lap top to the monitor on the living room wall and watch movies. The keyboard/track pad could be the remote control.How much band width does HDMI use? How much if any of the signal can be lost before you notice?Or is there a way to broadcast the signal and have it come up on channel three, or higher to make a small antenna, using DTV type modulation? Are there chips for this that can be bought commercially?Don't steal my product ideas unless you want my marketing/business/sales skills and experience (I'm good at being the link/interpreter between the smart engineer with Asperger's like peoples skills, to the dumb/average customer)...

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 23, 2018, 02:31:06 am
content: I have town down a LG wireless HDMI kit that does just that.https://www.eevblog.com/forum/reviews/teardown-$10-wireless-hdmi-kit/

author: Beamin
author_rank: Super Contributor
timestamp: July 23, 2018, 02:34:09 am
content: Quote from: NiHaoMike on July 23, 2018, 02:31:06 amDid you break the link on purpose? Why do people do that on this site?

author: tsman
author_rank: Frequent Contributor
timestamp: July 23, 2018, 02:45:10 am
content: Quote from: Beamin on July 23, 2018, 02:34:09 amThe regex the forum software uses to recognise a URL doesn't think a $ is a valid character so it truncates it there.

author: Beamin
author_rank: Super Contributor
timestamp: July 23, 2018, 02:53:53 am
content: Quote from: tsman on July 23, 2018, 02:45:10 amSo no www.$.com ?

author: a59d1
author_rank: Regular Contributor
timestamp: July 23, 2018, 05:58:31 am
content: Quote from: NiHaoMike on July 23, 2018, 02:31:06 amJust move the /url tag to the end and fix the url="" tag.
gain/phase error from not having reflection/transmission kit - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: July 24, 2018, 06:12:11 am
content: So I have a VNA that has the capability to measure reflection/transmission but it does not have a build in directional coupler or whatever the 87512A is. The manual says to simply use a power splitter. I tracked down that there is a option to use a 87512A with it.I guess taking reflection measurements only using a power splitter to supply the reference channel does not make sense... but how much error does the reflection cause for a typical gain/phase measurement? The VNA is a E5100A and it goes to 300MHz.I mean the reflection goes into the reference port through the external power splitter. It seems really bootleg. the 87512A has 40dB directivity. How can it make any meaningful measurements if it gets that reflection?Is there something I am missing in my understanding of how this works? Are reflections just really small typically? I don't really know what % of the signal power is lost in a reflection.
Can I embed these antennas in epoxy? - Page 1
Forum section: electronics / rf-microwave

author: DTJ
author_rank: Super Contributor
timestamp: July 20, 2018, 05:15:21 am
content: I'm looking at an application where small patch or dome antennas are mounted in public locations exposed to potential vandalism.One thought was to pot these in some grey epoxy so they blend in with the galvanised steel housing they are mounted to so as to not attract attention.The cabling is all concealed its just the dome we want to protect.The patch / dome antennas (4G, GPS etc) will be different depending on the location and could be anything from 400MHz through to 2100MHz.I guess its a broad question but how much will a generic potting epoxy degrade the signal?An alternative might be to see what protective covers are available. I've not been able to find any.I've seen some fitted on power infrastructure so they do exist.Any and all ideas welcome!

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 20, 2018, 05:50:29 am
content: you put anything near antenna it will change characteristic hence performance, let alone penetration strength. so you need a tool to be sure.

author: DTJ
author_rank: Super Contributor
timestamp: July 20, 2018, 06:37:35 am
content: Ok, thanks for the replies.I'm a plug'n play as far as RF goes so playing around with antenna tuning is not going to happen!I guess I'll need to either just try it or try to find off the shelf covers.Are there particular plastics that are used for radomes that have a minimal effect on the signal?

author: hagster
author_rank: Frequent Contributor
timestamp: July 20, 2018, 10:11:27 pm
content: From a quick search Epoxy has a permitivity of about 3.6. That will definatly make a difference if very close to most antenna.

author: DTJ
author_rank: Super Contributor
timestamp: July 21, 2018, 02:34:15 pm
content: Thanks Hagster. I did a quick check on a polyurethane compound, it had a permittivity of 4 so I guess that is not good either.Am I correct in assuming these values are relative permittivites in relation to the permittivity of free space?So the closer the value to 1, the less effect it would have on the antenna?

author: mjs
author_rank: Regular Contributor
timestamp: July 22, 2018, 05:39:59 pm
content: Right, 1 is vacuum/air. PE foam is much closer to 1 and can be used to reduce close-field losses and antenna detuning. But even then you probably need to tune the antenna.

author: Beamin
author_rank: Super Contributor
timestamp: July 22, 2018, 06:32:15 pm
content: Quote from: mjs on July 22, 2018, 05:39:59 pmThat was my suggestion then paint over it minding the type of paint. While foam is not vandal proof if it looks like what ever it is blending into people will have no reason to try and mess with it. Out of sight out of mind.Where I live people will steal anything metal even if it's bolted to the ground they will steal the nuts too!
How to use BNC tees properly? - Page 1
Forum section: electronics / rf-microwave

author: technix
author_rank: Super Contributor
timestamp: July 22, 2018, 06:34:35 pm
content: I bought a few BNC tees so I can tap off the output of my function generator directly, along with a few 30 centimeter BNC patch cables. How should I use it?* Mode 1: attach the bottom of the tee to the output jack of the function generator, and attach the output connectors (BNC or alligator clips) and the patch cable leading to oscilloscope input to the arms.* Mode 2: attach the bottom of the tee to the input jack on the oscilloscope, the patch cable from the function generator comes in on one arm, and the output lead goes to the other arm.Also is this an approximate of a network analyzer?

author: HB9EVI
author_rank: Frequent Contributor
timestamp: July 22, 2018, 06:42:44 pm
content: it depends. if you work in 50 ohm impedance system, both sides of the cable have to be properly terminated.I would set it up like the cable without tee on the signal source, the tee on the scope, one end in direction of the signal generator, the other end with the lead to dut.

author: bigsky
author_rank: Regular Contributor
timestamp: July 22, 2018, 08:04:03 pm
content: Quote from: HB9EVI on July 22, 2018, 06:42:44 pmIf you split a signal with a T piece and terminate both sides with 50 ohms, the source drives into a 25 ohm load, which is probably not what you want!

author: David Hess
author_rank: Super Contributor
timestamp: July 22, 2018, 08:11:57 pm
content: Quote from: technix on July 22, 2018, 06:34:35 pmThis works fine at lower frequencies.QuoteThis way also works at high frequencies where a 50 ohm termination is used at the output end and the high impedance input of the oscilloscope is attached in the middle using the BNC-T.QuoteIt can be used that way but it is better to apply the function generator output to the DUT (device under test), and use two oscilloscope probes to sample the input and output. The function generator's trigger output can be attached to the oscilloscope's external trigger.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: July 22, 2018, 09:00:59 pm
content: Quote from: bigsky on July 22, 2018, 08:04:03 pmthis is not what I meant. When I say both sides, I mean - source and load.
esp 01 firmware update - Page 1
Forum section: electronics / rf-microwave

author: abdulsamaddabu
author_rank: Contributor
timestamp: July 21, 2018, 07:16:55 pm
content: i just bought new esp 01(black one). it was working fine on first day but now it is not working, when i open the serial monitor it just gives me strange characters. so i decided to reflash the chip but i couldnt do it either. i am using the software xtcom to upload firmware but when i try to connect it it gives me the error of failed to connect with target

author: D3f1ant
author_rank: Frequent Contributor
timestamp: July 22, 2018, 02:43:33 am
content: Wrong serial baud rate?

author: sleemanj
author_rank: Super Contributor
timestamp: July 22, 2018, 06:29:24 am
content: Standard baud rate is 9600 I believe, try that.
RF Basics - Page 1
Forum section: electronics / rf-microwave

author: papamoscas
author_rank: Newbie
timestamp: July 19, 2018, 08:14:45 am
content: Hi,I'm a beginner in the world of the PCB's and of RF. I need your help and your knowledge.I want to make a PCB with the Quectel MC60E with the two SMA connectors, one for GSM signal, other for the GPS/GLONASS. For the BLE I want to put one antenna on the board like A5839 Antenova (http://www.antenova-m2m.com/wp-content/uploads/2016/01/Rufa-A5837-A5887-PS-1-2.pdf).I already did my research but I'm a bit confused, I think I only need to take care of the 50 Ohm pad from the MC60E to SMA connector.My questions are :- I only need to take care of the impedance matching? What is the best procedure to do that?-What are the most important things to have a PCB without EMI problems? The PCB will have more components like sensors for example...Thanks in advance
Tiny micro transmitters - Page 1
Forum section: electronics / rf-microwave

author: Howardlong
author_rank: Super Contributor
timestamp: July 11, 2018, 07:41:59 am
content: I came across this article in Nature a few days ago where they have tied tiny VHF transmitters to hornets for tracking purposes.https://www.nature.com/articles/s42003-018-0092-9The article claims a range of "up to 800m". These micro transmitters used a 100mm antenna.http://www.biotrack.co.uk/pdf/pip_picopip.pdfhttp://www.biotrack.co.uk/pdf/pip.19.pdfThey're using tiny 1.5v silver oxide coin cells. One uses the "AG337" appears to be the same as SR416SW, 8.3mAh in 4.8mm dia by 1.6mm thick. There is another device Pip.19 (12mm x 5mm x 2mm,http://www.biotrack.co.uk/pdf/pip.19.pdf) that uses an "AG190" cell, but I haven't been able to find any specifications on that one.The AG337 lifespan is quoted as 12 days days, with a 0.7Hz RF pulse, 20ms pulse width, so a duty cycle of 1.4%. With 8mAh, that suggests about 27uA average current, or at most 2mA when the pulse is active. So output power is ITRO 1mW.I'm not clear if the pulse is modulated for identification, let's assume not.So how would you generate 1mW at a reasonably stable frequency at ~150MHz given a 1.5V cell source?

author: philpem
author_rank: Frequent Contributor
timestamp: July 11, 2018, 11:59:07 am
content: Given the size and power constraints? Probably a transistor oscillator ringing a tuned circuit?

author: NivagSwerdna
author_rank: Super Contributor
timestamp: July 11, 2018, 12:56:29 pm
content: Quote

author: iMo
author_rank: Super Contributor
timestamp: July 12, 2018, 11:16:44 pm
content: QuoteA complete PLL tuned transmitter (ie. 6.25/12.5kHz channel spacing @140-170MHz) could be placed on a 1x1mm WCSP chip (9pins) easily (except the crystal). When using the 01005 smd R,L,C it may fit on a 2x3mm board.. I wonder what crystal size they used..

author: Howardlong
author_rank: Super Contributor
timestamp: July 13, 2018, 04:04:24 pm
content: Quote from: imo on July 12, 2018, 11:16:44 pmI don't doubt the size is eminently achievable, I'm more interested in how to achieve this given the power constraints (voltage and current). A PLL is going to be quite power hungry in my view.It is possible to find miniature crystals with fundamentals up to 300MHz (2mm x 1.6mm).https://www.golledge.com/products/gsx-228-ultra-miniature-high-frequency-fundamental-crystal-with-inverted-mesa-technology/c-26/p-155

author: hagster
author_rank: Frequent Contributor
timestamp: July 15, 2018, 08:53:03 pm
content: The old school way to do this was with a single diode and a very short antenna. When lit up with a radar the non-linear diode creates 3rd order harmonics that can be detected.
Radar sensor failure - Page 1
Forum section: electronics / rf-microwave

author: dpavid
author_rank: Newbie
timestamp: July 19, 2018, 11:03:36 pm
content: What might be some reasons why an radar antennae or sensor fails to give out true infomation?not things that can go wrong with hardware but what aspects of the outside world can interfere with normal operation?We're building a rover that can use a sensor to pickup its surroundings but want to be sure that it can work in all places.Thankyou!

author: johnnygoode1
author_rank: Newbie
timestamp: July 19, 2018, 11:46:51 pm
content: I just posted a similar question here a few days ago about failure modes of a radar sensor. We had already looked at RF noise, ghost targets, and obscurants on the sensor but I'm sure other modes exist. What about an antenna that sort of radiates in a pattern that can't be reflected by the environment?

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: July 20, 2018, 04:49:32 am
content: Antenna grating lobes can be an interesting thing.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: July 20, 2018, 05:11:14 am
content: Multipath (also called three-body scatter) - the beam undergoes specular reflection off one target, illuminates a second, then the energy makes the return trip. Causes additional targets to appear at further range from a strong one.Sidelobe illumination - you pick up a strong target that's not where your antenna's pointed because it falls in the sidelobe of the antenna's patternAttenuation - absorption of transmitted energy by the medium or by the object being detectedAnomalous propagation - caused by refractive index changes in the atmosphere causing the beam to bend towards the ground (probably not an issue for small radar systems)What sensor are you using? That has a huge impact on the kinds of imperfections you can expect.

author: wmcdonald1
author_rank: Newbie
timestamp: July 20, 2018, 11:16:47 pm
content: If the installation angle of the radar is imperfect you could get bad readings but I think the doppler effect would take care of that.

author: johnnygoode1
author_rank: Newbie
timestamp: July 20, 2018, 11:47:28 pm
content: If it's anything like the one I was looking at it's a small automotive radar sensor with a range of about 200 meters.
Xmicrowave - RF breadboarding - Page 1
Forum section: electronics / rf-microwave

author: RoGeorge
author_rank: Super Contributor
timestamp: July 09, 2018, 08:43:04 am
content: This looks very promising (at 21:15)Anybody know more about pricing, please?

author: CopperCone
author_rank: Super Contributor
timestamp: July 10, 2018, 01:27:34 am
content: There is a thread about it some where on this forum. I think AD sells some parts equipped to work with this technology, they are not cheap.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: July 10, 2018, 05:00:17 am
content: They are not cheap for home design, but they are very affordable for prototyping in a professional environment. Just designing and manufacturing a PCB at somewhat high frequencies is going to cost you more than the starter kit for Xmicrowave stuff.
Looking for RFID resources - Page 1
Forum section: electronics / rf-microwave

author: katzohki
author_rank: Frequent Contributor
timestamp: July 09, 2018, 06:02:12 pm
content: I've been asked to design somewhat of a tool identification system. So far I've been looking at the HTRC110 from NXP for the reader IC and Atmel for the tags. I got the ATARFID-EK1-ND dev kit from Digikey, but it didn't really teach me much other than how to fiddle with the tags and reprogram them. So I guess that means I've been looking at a 125kHz system.I'd like to find some tags that are smaller, something along the lines of a sticker that can be placed on the tool, but I've had a hard time matching up the tags that I see with the actual data IC and with what reader IC would be compatible. As for the reader antenna, I'm not really sure where to start. Our tool acceptor can be around 0.5" give or take (pretty variable at the moment) and the tool would fit inside. The flex circuit style looks like it would work well for us. Any help is appreciated, thanks.

author: D3f1ant
author_rank: Frequent Contributor
timestamp: July 10, 2018, 12:17:42 am
content: I would look at Ti TRF7970 13.56Mhz. it was fairly easy to build a reader/writer and the chipset reads all the common protocols. They have reference design board to evaluate and experiment with. You can get standard sticker tags in various sizes for dirt cheap from China.
crystal radio earth problems - Page 1
Forum section: electronics / rf-microwave

author: RobertMWillis
author_rank: Newbie
timestamp: July 09, 2018, 07:38:55 am
content: lately i have built a crystal radio and i tested it using a cold water pipe at our school and worked perfectly but when i tested it at my house and would not work, but if i touch the lead that is attached to the earpiece and diode i get a constant buzz sound.this buzz sound would change volume depending where i test it around my house leading me two two conclusions1 the gnd is not good enough2 the underground mains wire is interfering (our suburb has its power underground)so the question i have is could there be anything else interfering with the radio and how do i mitigate it and how would i go about getting/making a better ground

author: tkamiya
author_rank: Super Contributor
timestamp: July 09, 2018, 09:52:29 pm
content: The buzzzzz sound you hear is your mains power (house AC) being picked up by your body. As you get closer or further from appliances or wires inside wall, volume will change.The reason your pipe ground doesn't work is probably because you have PVC pipe. Obviously, it is not conductive, so it won't perform as a ground.You could, perhaps, get a better result if you improve your antenna (longer and higher) and find another suitable ground. Relatively large metal structure, such as your window frame can act as ground, even if it not connected to ground. OR, you could hunt down where your ground rod is, and hook it up to that. By the way, too long of ground wire will end up acting like another antenna.In my young days, I used to have a long wire for antenna, and used my own body as ground. Not the smartest of things to do but worked. Danger involved in this would be, if my antenna are to touch another voltage source or get hit by lightening, I'll be fried.