hybridfree/eevblog-posts huggingface dataset:
"SDR" LNA for DVB-T2 Reception? - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 22, 2018, 03:50:21 pm
content: Sry for the Stupid Question can I use an ordinary SDR LNA to get better DVB-T2 Signal on an "oridinary" Ebay DVB-T2 Dongle who have no LNA Build in?

author: dkozel
author_rank: Regular Contributor
timestamp: March 22, 2018, 05:37:52 pm
content: Almost certainly yes since LNAs aren't on their own specific to SDRs or any other receiver. So you're using a DVB receiver as a DVB receiver?Things to be careful of are that many require power to be supplied using a bias-t into the RF Out connector. Your DVB-T2 dongle won't have a bias-t so you'll need an LNA which has external power options or a bias-t to put between the DVB-T2 dongle and the LNA.Also the LNA and DVB-T2 receiver are both broadband devices so any noise around you will be amplified as well. This can actually make your reception worse. Consider adding a filter either before or after the LNA which will remove the signals which are not in the DVB frequencies. You'd have to find out what the frequencies of the channels you want to receive are.

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 22, 2018, 05:46:00 pm
content: I could not find any pic of then online but mine have an normal usb port for power.Sadly I could not find any Filter who is for the DVB-T2 and is usable Mobile.

author: dkozel
author_rank: Regular Contributor
timestamp: March 22, 2018, 07:43:15 pm
content: What frequencies are the DVB channels you want to receive? There are a wide variety of band-pass, high-pass, and low-pass filters available.

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 22, 2018, 08:01:25 pm
content: What I know just: 470000000 - 694000000
Having dielectric constant and loss tangent measured - Page 1
Forum section: electronics / rf-microwave

author: Koen
author_rank: Frequent Contributor
timestamp: March 22, 2018, 03:32:45 am
content: Hello,would you know where I could have dielectric constant and loss tangent of some cured epoxy resin measured ? Ideally around 0.868 and 1.6GHz.Are there some common laboratories who could do this ? In the same way dentists or veterinarians are sometimes said to be a good solution for the x-ray imaging of ball grid arrays solder joints.I only found this so far :-http://www.keycom.co.jp/es/sdps.htmlin JapanAlong with a lot of literature on how to do it but I would like to ship a sample and receive the results back. Anywhere in Europe would be great, it's easier for shipping.Thank you,Koen

author: hagster
author_rank: Frequent Contributor
timestamp: March 22, 2018, 08:57:11 am
content: These guys do it. No idea on price.http://compasstech.com/
Can you use to SDR's on the samecomputer at the same time? - Page 1
Forum section: electronics / rf-microwave

author: Beamin
author_rank: Super Contributor
timestamp: March 11, 2018, 09:13:54 am
content: I got a SDRPlay and an SDR dongle recently. I like to use the decoder tools (morse and digital) but I find they are hard to find the stations Vs HDSDR or SDRUno software. So I will find a station using SDRUno then shut the program open the decoder which has a crappy waterfall. This works but its more of a pain then worth listening. Decoding is trial and error as you get used to the sounds. I don't know of any program that finds or figures out the stations.So could you plug in two SDRs and use one to listen and one to decode? Ideal would be two SDRPlays because it's the best at HF which is all I use besides the ADSB airplane tracking.Can you use two of the same SDR with same software?Can you use the same antenna for both? That won't mess up impedance since I'm not TXing?I know setting up the com port was a pain in the ass and I ruined my other computer by disabling the track pad on one of those little tablet with a magnetic keyboard computers. Can not figure out how to fix it since you don't get CD's to set up the computers anymore. Sucks because that was the best computer for traveling since I carry a computer with me 24/7 to sell bitcoins and not get board. It was like a netbook but lasted six hours.I was debating a down converter for the dongle if I can't run two SDRPlays. I have to figure this out first since I can't risk messing up this computer.

author: hagster
author_rank: Frequent Contributor
timestamp: March 11, 2018, 10:12:37 pm
content: Not 100% sure about the SDRplay, but you can definately use 2 or more HackRfs and RTLdongles and USRP or any combination of them. Each has its own serial number. You normally need to seleft the device number via a config extension. Eg in GNUradio it would be Hackrf=0 or Hackrf=1. or hackrf=ab1234fda for instance. Again not sure about the SDRplay, but it probably similar.

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 19, 2018, 06:21:04 pm
content: You can edit the Serial No. at many SDR. The main Problem not every Software can Handle the Serial No.Man Application dont have an option to see even the Serial.
Source for small SMA bandpass filters - Page 1
Forum section: electronics / rf-microwave

author: MattSR
author_rank: Regular Contributor
timestamp: March 12, 2018, 10:19:18 am
content: Does anyone have a good source of RF bandpass filters, of various frequencies and bandwidths from 50MHz to 6GHz?I need them as front end filters on an SDR receiver that is wide open.Thanks!

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 12, 2018, 11:43:29 am
content: ebay...https://www.ebay.com.my/sch/i.html?_odkw=bandpass+ghz&_osacat=0&_from=R40&_trksid=m570.l1313&_nkw=bandpass+filter&_sacat=0if you have simulation software you can make your own such as this...https://www.ebay.com.my/itm/NEW-2-4GHZ-microstrip-bandpass-filter/131329136711?hash=item1e93d39847:g:5gsAAOSwajVUSIS-

author: daqq
author_rank: Super Contributor
timestamp: March 12, 2018, 12:00:14 pm
content: Try searching minicircuits - they've got all things RF.

author: ThomasDK
author_rank: Regular Contributor
timestamp: March 12, 2018, 02:08:34 pm
content: Crystek has a range of filters as well. Mouser carries them.Thomas

author: medical-nerd
author_rank: Regular Contributor
timestamp: March 12, 2018, 02:43:37 pm
content: HiyaDon't know how to include the reference in this, but in the thread ' Breadboarding at RF ' the member whalpen posted details of his filter pcb's:Quote from: whalphen on January 27, 2018, 07:14:54 pmDunno what frequency they go up to but they look interesting. I'm waiting for some to arrive.Also there are these:https://oshpark.com/shared_projects/RwCKDBgkCheers

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 19, 2018, 06:29:14 pm
content: https://www.ebay.de/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=AOR+Airband&_sacat=0https://www.ebay.de/sch/iseeabluewhale/m.html?_nkw=&_armrs=1&_ipg=&_from=
L-Network Question - Page 1
Forum section: electronics / rf-microwave

author: rcbuck
author_rank: Frequent Contributor
timestamp: March 15, 2018, 11:40:52 pm
content: I have been playing with L-Network matching circuits. Is there a formula that can be used to absorb the load series capacitor into the L-network?For instance, in the attached schematic, assume the load is a crystal filter with an impedance of 210 ohms. The source impedance is 50 ohms as indicated. The design frequency is 9.0 MHz. I want to absorb the 88 pF cap into the L-network as that is one less component to deal with. The values shown for the L-network assume the load is 210 ohms including the 88 pF series capacitor.Edit: Forgot to add schematic jpeg

author: Neganur
author_rank: Unknown
timestamp: March 16, 2018, 10:24:21 am
content: Is C2 Part of the crystal?Do you happen to have the part number of the crystal?

author: rcbuck
author_rank: Frequent Contributor
timestamp: March 16, 2018, 02:50:31 pm
content: No, C2 is not part of the crystal. It is the series resonating cap that changes the frequency of the first crystal in the filter. The part number of the crystal doesn't matter.

author: yl3akb
author_rank: Regular Contributor
timestamp: March 16, 2018, 04:08:32 pm
content: Quote from: rcbuck on March 15, 2018, 11:40:52 pmI like graphical approach better, when it comes to matching these circuits. Of course, You can absorb C2. L1,C1 and C2 transforms 50 ohms to Z = 209-j199 ohms. The same impedance can be obtained with L1=2.34uH and C1=160pF. See Smith chart graphs how it is obtained.

author: rcbuck
author_rank: Frequent Contributor
timestamp: March 16, 2018, 05:36:51 pm
content: yl3akb, thanks for that reference. I knew it could be done with Smith chart. I was hoping there was a formula (or formulas) that would work.I tried using SimSmith to perform the task. But I kept coming up with numbers that I knew were wrong. I guess I need to learn how to use Smith chart. I know W2AEW has few youtube tutorials on how to use it.

author: KJDS
author_rank: Super Contributor
timestamp: March 17, 2018, 06:04:17 pm
content: The formulae are given in Rhea's Yin and Yang of Smith chart matching.
Modular incrementally improved SSB receiver - thoughts - Page 1
Forum section: electronics / rf-microwave

author: ChristofferB
author_rank: Frequent Contributor
timestamp: March 17, 2018, 10:39:30 pm
content: Hi! I've spent a year or so building and improving upon this ssb receiver design, and i was forced to upgrade my homemade IF stage after it died completely. Here's the design so far (see attached). I'm using ebay modules for all MMIC amps and mixers, and those little MuRata ceramic IF filter modules as filters.I used to get fairly good reception of stations in the 4-6 MHz range, but after the update to a new BFO and product detector (before it was just a diode mixer), I get very high-passed audio, and much fainter modulation is heard. I can hear the carriers whistle by, and also some CW and RTTY stations, but everything is very high-passed, screechy in the audio.I've added larger AC coupling caps for my 2nd AD831, about 200 nf, since it outputs AF.Any hints on what's causing this? Any ideas for future improvements?Thanks!

author: ChristofferB
author_rank: Frequent Contributor
timestamp: March 18, 2018, 01:57:37 am
content: Turns out the AD831's has around 10dB of gain each; moving the 30dB IF amp to the RF input helped immensely on modulation strenght! CW now goes trough VERY clear, and other signals are more noticeable too. SSB stations are still kinda hard to make out though.A feature I'd like to add is an RF switch switching IF between the product detector/BFO and an AM demodulator.
Can you help me identify type of RF PCB Coax Connectors From 1970's - Page 1
Forum section: electronics / rf-microwave

author: K1JOS
author_rank: Regular Contributor
timestamp: March 12, 2018, 07:41:05 pm
content: I am working on a late 1970's Collins tranceiver and all of the inter-PCB board coax are of the type shown in the 2 attached pictures. The male is just a trimmed coax with an exposed 3/8" center conductor while shield is folded back and crimped with some circular metal housing. The PCB female appears to be some kind of spring/tension hood with female center conductor hole. Are these still available and if not any recommendation how to repair or reconfigure? The holes in the PCB are not matching more modern SMA or SMB PCB connectors.Jerry NY2KW

author: dave_k
author_rank: Frequent Contributor
timestamp: March 12, 2018, 08:19:01 pm
content: Looks very similar to a Peltola connector from Tektronix.

author: Flump
author_rank: Frequent Contributor
timestamp: March 13, 2018, 12:12:03 am
content: Could it be one of these ?https://www.ebay.co.uk/itm/Taiko-Denki-TMP-K01X-A1-RF-Coaxial-Plug-TMP-Connector-Plug/122113894996?hash=item1c6e8e2a54:g:TBgAAOSwezVWt73V

author: K1JOS
author_rank: Regular Contributor
timestamp: March 13, 2018, 12:27:59 am
content: Yes, the Tektronix Peltola is very similar in concept. The Peltola coax shield part makes a real nice contact with its PCB mate. The Rockwell-Collins design looks older and the shield part crimp looks like it wouldn't make a very good shield to shield contact but apparently it holds up well except it probably withstands far fewer remove/insert cycles than the Peltola.I am surprised since there must have been a lot of Rockwell Collins military gear that used this connection but I have not been able to find anything with GoogleJerry NY2KW
Keysight Genesys PCB Layout Ground Plane - Page 1
Forum section: electronics / rf-microwave

author: SparkFly
author_rank: Regular Contributor
timestamp: March 10, 2018, 05:30:42 pm
content: Hi all,I've recently managed to gain access to Keysight's Genesys software, and I'm excited to use it. I've just finished a simple low pass filter design which I'd like to lay out and simulate. However, I am having some real problems understanding how Genesys likes to work. I've attached a screenshot representing the problem I've having. I am unsure exactly how Genesys likes to represent ground. It seems to me Ground itself is a 'component' and not a net as in software like Eagle or Altium, and it is represented by the blue circles which I think is copper on the bottom. When I try to do a ground fill polygon, it actively avoids the ground pads of components (see C2) unless the ground component is connected (as C1 is through a via). This doesn't seem very sensible to me. Am I doing something stupid? Is there a better, more elegant way to connect nets? Or is there a reason behind this layout method? I presume if I want a ground 'pad' on the top layer, I'd need to create my own footprint for it, as I cannot see any top copper ground footprints...I've tried watching the tutorial videos, and have scoured the manuals etc for advice, but can't find anything. It seems this is very specialised software.Any other advice/tips/tricks would be greatly appreciated.Regards,SF

author: eb4fbz
author_rank: Regular Contributor
timestamp: March 11, 2018, 10:28:44 am
content: Check stackup properties, bottom layer is probably defined as GND, but hidden. However you are running a linear simulation, so layout doesnt matter. Its only taken into account for EM simulation (EMPower, Momenmum...)
Variable Capacitor Sealed In Oil - Page 1
Forum section: electronics / rf-microwave

author: Yavin101
author_rank: Newbie
timestamp: December 18, 2017, 11:13:43 pm
content: I came across this variable cap at a junk sale, and was wondering if anyone had any info about it. I put a meter on it and got a reading of (30pf -> 800pf) @ 1kHz) I cannot find anything about it on Internet searches (except for a eBay listing with no information,) just looking for any type of datasheet or information about its original uses. Thank you

author: xwarp
author_rank: Frequent Contributor
timestamp: December 19, 2017, 12:41:24 am
content: Looks military grade. Post about this here and I'll bet you get an answer:http://www.antiqueradios.com/forums/viewforum.php?f=5&sid=6cc28cf95602f7737ca73d2cf8a67881

author: TheSteve
author_rank: Unknown
timestamp: December 20, 2017, 01:56:53 am
content: I have no info to share but do think it's very very cool. I wonder what the break down voltage is with the oil.

author: Yavin101
author_rank: Newbie
timestamp: December 20, 2017, 03:31:24 am
content: The info I received from antiqueradios.com/forums is that its WWII surplus equipment.http://antiqueradios.com/forums/viewtopic.php?f=19&t=332790&p=2786256#p2786256

author: Cyberdragon
author_rank: Super Contributor
timestamp: December 29, 2017, 01:57:02 am
content: It's probably a transmitter tuning capacitor. It's used in the output section of a high power amplifier to either tune the output or the antenna. I've never seen a clear one like that though.

author: Yavin101
author_rank: Newbie
timestamp: March 09, 2018, 07:36:12 pm
content: I used it to tune a homebrew long wire antenna. the wire is 256' with a coil. it works well on 80 and 40 meters. SWR of 1.1 at 7.189 MHz and 1.3 on 3.968 MHz. I still plan on building a magnetic loop antenna for 40 and 20 meters.
help with amplifier connection to FM transmitter IC - Page 1
Forum section: electronics / rf-microwave

author: lostengineer
author_rank: Newbie
timestamp: March 07, 2018, 03:56:05 pm
content: Alright guys,I'm designing a little FM transmitter using the silicon labs Si4713 transmitter chip. This chip is intended to be connected directly to a wire antenna. I've got the chip working on a custom PCB and I have functional test code.The chip is very low power, so I've tried to add a 12dB RF amplifier (a TI TRF37A73 12dB gain block IC that works from 1MHz to 6GHz). Unfortunately I have no idea how to connect the amplifier, and I now believe I did it wrong in the first place. Please no lectures about FM amplifiers - my application is in a controlled environment and will be kept 100% legal.The problem is that I have NO IDEA what the output impedance of the si4713 is. Everything in the datasheet is specified in dBuV. Supposedly the si4713 can output 115dBuV max, which for a 50 ohm system is 8dBm. Thus, connecting the 12dB gain block, I should get 20dBm, or 100mW of RF output from the entire system. Unfortunately, I don't believe I'm anywhere close to 50 ohms at the output of the si4713. The output seems to be a tank circuit that the si4713 attempts to resonate - which to me means infinite impedance at this output?!?!Please see attached pics and help me figure out how to properly connect these two chips. My RF knowledge here is seriously lacking. Thanks!From Si4713 datasheet:"The TXO output has over 10 dB of output level control,programmable in approximately 1 dB steps. This largeoutput range enables a variety of antennas to be usedfor transmit, such as a monopole stub antenna or a loopantenna. The 1 dB step size provides fine adjustment ofthe output voltage.The TXO output requires only one external 120 nHinductor. The inductor is used to resonate the antennaand is automatically calibrated within the integratedcircuit to provide the optimum output level andfrequency response for supported transmit frequencies.Users are responsible for adjusting their system’sradiated power levels to comply with local regulationson RF transmission (FCC, ETSI, ARIB, etc.)."
Coaxial Cable Selection Help - High power, High Shielding - Page 1
Forum section: electronics / rf-microwave

author: astro10
author_rank: Newbie
timestamp: March 20, 2018, 02:08:22 am
content: Hello,Is there a good reference for which coaxial cable to use for a given power, frequency, and shielding desired?I am looking at something to use with ~1kW at ~1.5MHz. Currently just a regular RG58 is used, which leaks RF noise everywhere into the lab, and gets quite warm. Visiting Pasternack's website, for example, I can a whole host of options that have >90dB of shielding and will handle the 1kW power, with prices varying over an order of magnitude, with no clear difference between options. Currently RG142 looks like a decent option, but maybe there is something else way cheaper that would work equally well.Thanks!

author: vk6zgo
author_rank: Super Contributor
timestamp: March 20, 2018, 02:57:51 am
content: Quote from: astro10 on March 20, 2018, 02:08:22 am1kW at 1.5MHz is equivalent to many lower powered AM broadcast Transmitters.Broadcast practice is to go for "overkill", using cables rated well in excess of actual requirements.You might be battling to get rid of the RF in the lab, no matter what you do, as some may leak from your source & load.

author: edpalmer42
author_rank: Super Contributor
timestamp: March 20, 2018, 04:04:30 am
content: Wouldn't RG8 do the job and be a lot cheaper than RG142? Look for one that has a foil/braid shield to get the best shielding.Ededit: e.g. Belden 9913 - foil/braid - power 4KW @ 5 MHz - Mouser ~$200 for 100 ft. - 4 in stock - other lengths in stock

author: bb37
author_rank: Newbie
timestamp: March 20, 2018, 04:32:36 pm
content: RG8 is the standard for amateur radio stations running 1500 watts at 1.8 to 30 MHz. RG8 should be able to handle up to 4 kW.RG213 is a step up with a little better shielding and about the same power handling capacity.RG214 has even better shielding.Belden 9913 and Times Microwave LMR400 have even better shielding.All of these are fairly large cables, approximately 0.405 inches in diameter, with varying degrees of flexibility. I would stay away from small diameter cable like RG58 or RG142 if I was running 1 kW. They might have the rating for that, but they are kinda on the ragged edge especially if you have an impedance match problem.

author: astro10
author_rank: Newbie
timestamp: March 20, 2018, 05:36:17 pm
content: Thanks for the recommendations!The L Com CA-195R looks like a good candidate.>90 dB of shielding2.5KW peakAnd its quite cheap

author: kj7e
author_rank: Frequent Contributor
timestamp: March 22, 2018, 02:17:21 pm
content: If you can use RG8 size cable then LMR400 is hard to beat. A thinner alternative is LMR230, has the same 100% foil + heavy braid as LMR400 but its RG8X size and will handle 1.5KW at 30MHz. They make a more flexible version as well, only difference is a stranded center conductor which adds a slight amount of attenuation. Personally, I would not run 1KW though anything smaller than LMR240 (RG8X size).
Electrokinetic sonic amplitude measurements  - Page 1
Forum section: electronics / rf-microwave

author: stcoso
author_rank: Regular Contributor
timestamp: March 06, 2018, 09:17:01 pm
content: Hi, I'm a chemist and I'm interested in electronics... So, in nanomaterials science a technique called "Electrokinetic sonic amplitude" is sometimes used to measure the mobility of suspended nanoparticles in solution.I've attached a scheme of the basic measurement cell for this technique.I'm wondering how the generation of the sine wave works...The solution between the electrodes can basically be described as a resistor (ranging from 1MOhm to 100Ohm)In series with a capacitor (in the order of magnitude of 100pF)

author: rhb
author_rank: Super Contributor
timestamp: March 07, 2018, 01:19:02 am
content: Buy a JDS-6600 AWG good to 25 MHz, place the electrodes 2 mm apart. Set the AWG to 20 Vpp. Actual mileage may vary, but it will get you started. Very likely you will want to add an external amplifier to boost the output voltage a bit so you can use a wider cell.That's a large frequency span, so the impedance is varying quite a lot. As a consequence you will need to build an automatic tuner to adjust the impedance matching. I suggest reading my posts to the "Roller inductor... and other craziness" thread. The OP is trying to build a mass spectrometer.At about age 13 I was morally corrupted by Clair Stong's volume of Amateur Scientist columns from Scientific American. "For less than the price of an average set of golf clubs, you too can smash atoms in your backyard." The column goes on to describe a linear particle accelerator built by a faculty member at Brooklyn Polytechnic IIRC.Above 1-2 MHz life starts getting complicated. At 20 MHz you're just at the edge of a real adventure.Take a look at the amateur radio literature describing power amplifiers and antenna tuners for HF from 160 m to 15 m. It appears to me you've got a doozy of an impedance matching problem. So you're looking at a more complex version of what I described in the mass spec project thread. You'll have to tune the system by sampling the voltage potential across the electrodes. Not hard, just more moving parts. The paper by the Stanford folks referenced in that thread is rather poorly done, but the concept is very similar to what you need.Have Fun!Reg
FM Modulator Design - Page 1
Forum section: electronics / rf-microwave

author: iman_os
author_rank: Newbie
timestamp: March 04, 2018, 08:20:38 am
content: hi guysI want to design High-quality FM modulator with carrier frequency about 455KHZ without using any modulator or oscillator IC.I have two questions:1. At first, Is it better to Modulate signal in one step from baseband to this frequency (455Khz_ considering the output low frequency) or Modulating with a lower carrier frequency and then Upconverting the modulated signal using a mixer?2.secondly, is it good to use BJT class AB amplifier for output, the last stage before antenna? if not, what should I do?

author: 4CX35000
author_rank: Regular Contributor
timestamp: March 04, 2018, 12:44:25 pm
content: Firstly. You would normally modulate on a fixed frequency such as 455 KHz or 10.7 Mhz and then mx the output to the desired frequency. This simplifies the modulator and synthesiser design.Second your using FM which has a fixed amplitude, therefore it is common practice to use Class C. Class AB is more power hungry and therefore there is no benefit in running class AB on a RF circuit on FM. If you wish to run SSB or AM then you would need to run Class AB.
R820T2 discontinued. - Page 1
Forum section: electronics / rf-microwave

author: medical-nerd
author_rank: Regular Contributor
timestamp: March 06, 2018, 11:59:11 am
content: HiyaThere seems to be some devastating news that will impact on the rtl-sdr dongles and all devices using the R820T2.I have quoted the text below from the airspy groups and reddit.https://airspy.groups.io/g/main/message/28134I have some bad news. Rafael Micro officially discontinued the R820T2 since a few months. This is the tuner we use in the Airspy R2 and Airspy Mini.We tried to secure an extra batch from Rafael (even at a higher price) but the quality of the silicon of the samples we received wasn't very good and most units didn't pass our automated QA tests. Sacrificing the performance is out of question. The alternatives proposed by Rafael are not pin compatible and require both a significant hardware redesign and new tuner control code - and this is a large investment with very little guarantees on the final result.I can say this has been one of the longest running designs that resisted the new silicon tuner SDR's popping in and out while setting a standard for performance and price.For now, our distributors are running out of R2/Mini's very quickly and, until a final solution is found or a new replacement is designed, there won't be any new batches out.

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 06, 2018, 05:19:29 pm
content: That mean buy as fast as possible the last remaing sdr on the market?

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 07, 2018, 01:55:42 am
content: What chip are they using on new RTLSDRs?

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: March 07, 2018, 02:13:26 am
content: Good thing I just bought my replacement SDR with the T2 last week. I'm sure the price will either be jacked up or they will dump them.

author: 1Ghz
author_rank: Unknown
timestamp: March 07, 2018, 11:10:11 am
content: R820T2 Chip Discontinued: Low Cost R820T2 RTL-SDRs will Continue, Airspy Will Redesignhttps://www.rtl-sdr.com/r820t2-chip-discontinued-low-cost-r820t2-rtl-sdrs-will-continue-airspy-will-redesign/Quote
amp hour Podcast #381 Amateur radio – An Interview with Derek Kozel   - Page 1
Forum section: electronics / rf-microwave

author: jonovid
author_rank: Super Contributor
timestamp: February 28, 2018, 09:33:28 pm
content: amp hour Podcast #381 – An Interview with Derek Kozelhttps://theamphour.com/381-interview-with-derek-kozel/this is not place for amp hour, But this Podcast is about Amateur radio & SDR!if you're interested.

author: hagster
author_rank: Frequent Contributor
timestamp: February 28, 2018, 11:01:37 pm
content: Just in time for a long drive tomorrow. Thanks for the heads up.
crazy charger - Page 1
Forum section: electronics / rf-microwave

author: djacobow
author_rank: Super Contributor
timestamp: February 24, 2018, 08:42:38 pm
content: I just bought a Radioddity GD-77 as a low-cost way to experiment with DMR.It came with this insane charger:https://photos.app.goo.gl/XDFDxstTv0dCKgcC3https://photos.app.goo.gl/t92jNSjaUnk3hvOu1https://photos.app.goo.gl/Gv3MvTk8BPlSblyk2I mean, I appreciate wanting to save some cost, but this is a phone killer.

author: denverpilot
author_rank: Regular Contributor
timestamp: February 24, 2018, 08:53:42 pm
content: I believe you meant to say, “Stupid person’s phone killer.”LOL.

author: djacobow
author_rank: Super Contributor
timestamp: February 24, 2018, 08:59:12 pm
content: Quote from: denverpilot on February 24, 2018, 08:53:42 pmSo, in my house, I have drawer full of generic USB chargers. I could probably trust myself to keep this object out of that drawer, but several other people live in my house, so.... I'll probably epoxy the cord into the charger!

author: denverpilot
author_rank: Regular Contributor
timestamp: February 24, 2018, 09:02:03 pm
content: Probably be simpler just to label it (bigger than it’s already labeled, in non-electronics dumber words) with a label maker...... this is assuming anyone who might use it to charge something can read.Ahh the joys of no kids and a ham shack in its own room where the wife never bothers to go...

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 24, 2018, 09:49:27 pm
content: Have you tested it to see if it actually outputs 12V by default? Qualcomm Quick Charge and Asus TF101 chargers can also output 12V, but only if they receive the correct signal from the powered device.

author: djacobow
author_rank: Super Contributor
timestamp: February 24, 2018, 10:04:49 pm
content: Quote from: NiHaoMike on February 24, 2018, 09:49:27 pmIt does. It's just a dumb 12V PSU.I mean, it's fine. It works well for its purpose and a ham probably won't get confused.

author: Cyberdragon
author_rank: Super Contributor
timestamp: February 24, 2018, 10:42:23 pm
content: Why the hell would they use a USB connector instead of just a standard barrel jack?
How are wifi sight surveys done? - Page 1
Forum section: electronics / rf-microwave

author: nowlan
author_rank: Frequent Contributor
timestamp: February 22, 2018, 10:27:50 am
content: Just curious if anyone here can shed light.I think in the past you would walk around with a laptop and use netstumbler and record signal strength on a floor plan etc.Now a days, you have wifi controllers that will control access points power, so they dont clobber each other. I understand the 3 usable channels, and overlapping hexagonal type pattern.But wondering if anyone would use a spec.analyser etc, to see interference from devices, such as microwave oven.(my $50 target special knocks out wifi when running). Not why im asking, but just using as a suggestion.

author: Rerouter
author_rank: Super Contributor
timestamp: February 22, 2018, 11:31:02 am
content: I cannot say how they are done other than walking around, but at a guess they are less required these days, mimo wireless has led to beam steering, which means you can get a lot furthur away and still be able to connect.I would caution that rf propegation through 3d space is hard, almost every case i have seen had the measuring setup changing the results when rotated. The gradients still exist, but at certain locations reflections catch up, signals that where delayed by different densities in concrete interfere, etcUsing a spectrum anaylyser however would help find all the competing noise sources much easier.

author: eeviking
author_rank: Regular Contributor
timestamp: February 23, 2018, 03:08:45 pm
content: Ekahau HeatMapper etc.:https://www.ekahau.comThey also have a spectrum analyser.

author: Kalvin
author_rank: Super Contributor
timestamp: February 23, 2018, 04:08:42 pm
content: In addition to the Ekahau HeatMapper, Ekahau has also Ekahau Sidekick spectrum and network analyzer for the 2.4 GHz and 5 GHz Wifi bands. The device can provide 20 frequency sweeps per second on 2.4 GHz and 5 GHz Wifi bands simultaneously with >70 dB dynamic range, which can be very useful when hunting down any intermittent interference sources.https://www.ekahau.com/products/sidekick/overview/https://www.ekahau.com/products/ekahau-site-survey/overview/Unfortunately I haven't used the device so I have no further detailed info or experience to share.

author: SL4P
author_rank: Super Contributor
timestamp: February 23, 2018, 11:22:43 pm
content: An 'oldie but a goodie' for simple walk-around SITE surveys isINSSIDERrunning on a laptop.
Matching 50 Ohm sig gen to 75 ohm tuner input - Page 1
Forum section: electronics / rf-microwave

author: Simon Spiers
author_rank: Regular Contributor
timestamp: March 24, 2018, 01:23:44 pm
content: I have just finished repairing a Pioneer f91 tuner that had cracked joints in the FM input module. I realised after I had performed a front and alignment that i was connected to a 50 ohm output of the Marconi signal generator.I have two questions that maybe someone could clear up for me.1 With the mismatch stated, will the effect be negligible, or should I re align the set with it connected to a 75 ohm antenna and just connect a wire to the generators output?2 Are simple resistive pads good enough or shall I make an "L" pad?Simon

author: slurry
author_rank: Regular Contributor
timestamp: March 24, 2018, 04:38:45 pm
content: What you are looking for is a MLP, Minimum Loss Pad.Turns 50 ohm to 75 ohm and vice versa, with a minimum loss of about 6dB, which you just add to signal generators output.look here for a DIY MLP:http://ham-radio.com/k6sti/match.htm

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: March 25, 2018, 09:07:45 am
content: For all but the most critical applications the effects of such a mismatch would not be noticed.

author: w2aew
author_rank: Super Contributor
timestamp: March 25, 2018, 12:33:21 pm
content: Quote from: vk3yedotcom on March 25, 2018, 09:07:45 amThis.As Peter says, don’t worry about it. The mismatch is only VSWR of 1.5:1, which is not bad at all. Return loss is about 14dB. The power reflected is only 4%.

author: Simon Spiers
author_rank: Regular Contributor
timestamp: March 28, 2018, 07:29:47 am
content: Thanks Guys that's a big help. I was wondering if the mismatch would make any significant difference , but I built the matching pad in the end.Cheers. Simon
Australian Magazine AM transmitter kit may spark interest in New Amateurs - Page 1
Forum section: electronics / rf-microwave

author: jonovid
author_rank: Super Contributor
timestamp: February 19, 2018, 07:05:47 am
content: March 2018 Silicon Chip Magazine has an AM micro power 535-1605 kHz transmitter kit.Amateur radio is always looking for ways to spark interest in the hobby.this may help kids get in the hobby?with just two AM 535-1605 kHz mw silicon chip transmitter kitsand two AM broadcast receivershas kids playing with radio over a range of just 10 meters. and...no license needed.Do you have a posted copy of March 2018 SC Magazine. if any missing pagescontact editor@siliconchip.com.au

author: BradC
author_rank: Super Contributor
timestamp: February 19, 2018, 07:16:39 am
content: Quote from: jonovid on February 19, 2018, 07:05:47 amI can't see why not. One of my first projects with my shiny new Tandy 200-in-1 kit was an AM transmitter. I remember very well the awe in speaking into the crystal earpiece and hearing it loud and clear on the Stereo. Probably 35 years ago now. Stuff like that sticks with you forever.I guess the difference with that was poking wires into springs while following a diagram, vs the Silicon Chip one requiring soldering and construction and therefore some Adult supervision / assistance. The beauty of the old 200-in-1 was I didn't need to seek any parental help to do whatever I liked with itNone the less, kits are getting less and less theoretical and more "just plug the blocks together", so anything that goes back to basics like that can't be bad.

author: hamster_nz
author_rank: Super Contributor
timestamp: February 19, 2018, 07:32:31 am
content: I wonder at if it has appeal, given that most kids can now talk over 100s of kilometers..It isn't like back in the day, when a shortwave allowed you to listen to the word, and it seemed only the state or large companies could TX.

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: February 23, 2018, 08:24:57 pm
content: Could be a fun project. Uses a MC1496 RF mixer chip - beloved of Theremin builders.But AM is becoming increasingly rare on radios - whereas FM is more common.It is also difficult for a beginner to build and adjust an efficient antenna for ~1 MHz.On a range achieved per component basis, I think there's a lot to be said for FM bugs.Good audio, efficient antennas, more people have radios that can tune it and better range (>200 metres).http://www.talkingelectronics.com/projects/FM-BugsIntro/FM-BugsIntro.htmlis a good introduction.
why Phase detector IC input pin reading is always the same? - Page 1
Forum section: electronics / rf-microwave

author: fikadu
author_rank: Newbie
timestamp: February 14, 2018, 01:12:34 am
content: I am software guy, don't have much idea about RF design.These days, I am trying to experiment on phase detector IC(AD8302). As attached figure, while trying to measure an input values at pin INPA and INPB, it always reads 4.85V. This reading is the same whether there is RF power or not. Actually, the output reading is correct as compare to phase shift on Oscilloscope. An input limitation(maximum) at those two pins is –13dbV(0.22V) as it is described on the datasheet. Even that was why I added the voltage divider on the input side as shown in the figure. My doubt here is that, why the reading is always 4.85V and would it be safe? can input at pin INPA and INPB exceeds –13dbV(0.22V) ?Datasheet:http://www.analog.com/media/en/technical-documentation/data-sheets/AD8302.pdfThank you all

author: Rerouter
author_rank: Super Contributor
timestamp: February 14, 2018, 09:47:55 am
content: The voltage is due to the architecture of the device, it not being there would be more concerning, now what frequencynare you feeding in, the stockncircuit expects about 100KHz and up, needing the capacitor values tweaked for lower frequencies at the cost of responsiveness

author: fikadu
author_rank: Newbie
timestamp: February 18, 2018, 06:16:43 am
content: Thank you a lot.I am using 13.56MHz RF power.
OOK Modulation compatibility - Page 1
Forum section: electronics / rf-microwave

author: stern0m1
author_rank: Contributor
timestamp: February 16, 2018, 06:28:29 pm
content: Hi,For a system that I know uses OOK modulation are there fine details that I need to know, in order to be able to design a transmitter that would work?I mean on the RF level.I'm a beginner and I may be over simplifying things.Thanks

author: ogden
author_rank: Super Contributor
timestamp: February 16, 2018, 08:42:31 pm
content: Quote from: stern0m1 on February 16, 2018, 06:28:29 pmYou shall tell whatrough detailsyou already know. Mention your RF experience as well. You shall know what's frequency band, TX frequency, symbol rate, transmission duty cycle. Then you start studying standards/regulations for area your transmitter is designated for - because fine details for US differs from Japan and so on. Regulations/standards specify how transmitter shall operate at given frequency in quite details.It could be so that you transmit signal which is fine for receiver, but does not meet regulations, for instance radiates excessive out-of band signal.How to achieve RF performance to meet particular standard - this most likely is whole another discussion.
Video: Using SimSmith to design L matching network - Page 1
Forum section: electronics / rf-microwave

author: w2aew
author_rank: Super Contributor
timestamp: February 12, 2018, 11:05:29 pm
content: This video shows how to use the SimSmith software program to design L matching networks for the same complex load shown in video #276. Here are links to download SimSmith, as well as to Larry W0QE's excellent YouTube site with SimSmith tutorials.W0QE SimSmith Tutorials and more:https://www.youtube.com/channel/UCKSyLSu4fm_1RHoO3Jvk4YQAE6TY SimSmith site:http://www.ae6ty.com/Smith_Charts.html*Poor Audio Quality - yes, I know the SNR of the audio in this video is not great. This was my first video using a screen capture utility instead of my video camera. My PC mic isn't very good, and recorded very low volume. I had to boost the audio using Handbrake, and that boosted the noise too. Sorry about that. Will try to improved upon this for future videos using screen capture.
Adding Amp to Transmit Mag Loop... - Page 1
Forum section: electronics / rf-microwave

author: ronsch
author_rank: Newbie
timestamp: February 12, 2018, 05:30:19 pm
content: Just curious, has anyone tried to add a receive amp to a transmit loop? I wonder if this could be done using some form of PTT circuit. This would provide high gain receive along with transmit capabilities.RonK2RAS
Taxi Radio Basestation teardown – UHF/VHF Storno radio - Page 1
Forum section: electronics / rf-microwave

author: madsbarnkob
author_rank: Frequent Contributor
timestamp: February 12, 2018, 09:54:32 am
content: This is a teardown of a complete Taxi computer and radio base station system. The Taxi car computer and connection box is used for location tracking, taxation, passenger detection and correct price calculation. All done in order to make sure that correct taxes are paid to the government but also to ensure that fair prices are billed to the customers.The radio base station backbone of the systems are rather old and works in the 150 MHz range for both transmitting and receiving.The two amplifiers are a Storno CQF612 and a Storno CQF9112, there is plenty of historic data to find on these using google if it is of further interest to the reader.
with this method, can i measure 60Hz radiation noise ? - Page 1
Forum section: electronics / rf-microwave

author: ammjy
author_rank: Regular Contributor
timestamp: March 10, 2018, 12:11:03 am
content: Hello Guys ! always thanks you for reply !i want measure intensity of radiation noise 60Hz from stand light. (it's not LED bulb)i already know measurement of frequency be change by the antenna length.but, i want know with this antena, can i measure enough result.ill measure with scope FFT funtion.please, let me know !

author: Karlo_Moharic
author_rank: Regular Contributor
timestamp: March 10, 2018, 10:40:37 am
content: Why don't you just try it out?

author: CopperCone
author_rank: Super Contributor
timestamp: March 10, 2018, 11:21:11 pm
content: You can pick up 60hz radiation noise with anything really, its just a question of how much gain the antenna will have at that frequency.If you are interested in more, specific, ways to measure 60Hz, i.e. with performance similar to antenna performance that we are used to in higher bands, check out this website for some ideas on measurement.http://www.vlf.it/This one is rather specific towards your goal ,but you can learn alot about lower frequency measurement from that website.http://www.vlf.it/feletti/around50hz.htmlThis link is specifically oriented towards man made 60 hz fields.Remember around powerlines everything will be in the near field region unless your really far away, so its better to think about it in terms of inductive coupling.I calculated that you are operating in the5,000,000 meter band, or the wavelength is 5000 km.People also tend to use large ferrites for this job with alot of windings. With 60Hz simply connecting a floating oscilloscope probe with the grabber attachment on high scope gain will show it up well...Can you be more specific to your goals?
Software fro scanning an TV Transponder? - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: December 21, 2017, 09:45:08 am
content: HiI found some German Speaking Webpage who explain which Software is good to scan an Sat Transponder for Transmissions. There are some older Sat get used for TV Station to Transmit some Live contend from a remote Area.I will buy an new TV Card and the should compatible with.Does anyone know which Software can do that? I rember there was 3 of them. Sadly my Pc died this Summer and all my Stuff are gone.

author: Lord of nothing
author_rank: Super Contributor
timestamp: February 11, 2018, 10:59:39 pm
content: I dont want ask again but does anyone know with Software can make an Blind scan from an Transponder?

author: Bicurico
author_rank: Super Contributor
timestamp: February 11, 2018, 11:47:15 pm
content: You are certainly talking about CrazyScan (https://sourceforge.net/projects/crazyscan/).If you want to use this for satellite reception, use EBSPro (http://ebspro.net/). Again, as this uses the CrazyScan streamreader.dll, but has a nicer GUI and more DX related functionality.You need compatible TV cards.Hope this helps.Regards,Vitor
Blast from the past link about "Wok-Fi" antennas - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: February 08, 2018, 01:53:30 am
content: I hadn't seen this web page in years, its long gone but it turns out that it was archived at archive.org.Worth looking at because of its innovative use of cheap USB wifi dongles.https://web.archive.org/web/20140817040813/http://www.usbwifi.orconhosting.net.nz/Am I just imagining it or did 802.11b have more distance-spanning oomph than g+n?
Looking for a BFO Xtal for Yaesu 101 3178.5Khz - Page 1
Forum section: electronics / rf-microwave

author: tkamiya
author_rank: Super Contributor
timestamp: February 04, 2018, 02:03:14 pm
content: Hi....I am refurbishing FR101 and found that one of the BFO Xtal is totally dead. 3178.5Khz. FT101 series uses exactly the same Xtal in modulator board. Anyone have a part unit and willing to sell just this piece? It's in HC-6 housing. Thank you.

author: tkamiya
author_rank: Super Contributor
timestamp: February 04, 2018, 09:38:50 pm
content: Someone just listed for-parts-only FR101S on eBay and I just grabbed it. Luckily, pictures showed the part/board I need is still in there.
SSA3021X Peak Marker to CF Bug? - Page 1
Forum section: electronics / rf-microwave

author: kr5j
author_rank: Contributor
timestamp: February 04, 2018, 04:35:07 am
content: I pressed PEAK to put a marker on a signal. I then pressed Next Right to measure another peak to the right of the first peak. Then I pressed Peak to CF and the SA moved the first peak to the center not the currently selected peak. Is this a bug? FW isSW1 1.2.8.3SW2 20170512-1SW3 000000D1HW 07.03.00Thanks for reading
Mini VNA analyser fix intermittent readings - Page 1
Forum section: electronics / rf-microwave

author: cleanworkbench
author_rank: Regular Contributor
timestamp: February 03, 2018, 09:37:07 am
content: I have the early mini vna from mini radio solutions, the rectangle shaped one.It worked very well then ! the swr impedance display went intermittent , like straight line traces not the ususl curves on the graphic chart.Then it came back then went.Checked the coax for continuity , wiggled the coax , tapped the vna box gently , rebooted the laptop , still nothing.Changed the coax to the DET port and it worked , changed back to DUT port and a fat NOTHING ! Hmmm Nearly 300 quids worth of tricks is history i thought , but what if the unthinkable ?.So off came the lid of the VNA , a look at the DUT port pcb connector with a magnifying glass revealed a BNC centre pin with no solder on it and looking pretty grey and dull . Gently pushing this little PCB connection C shaped pin that curves around the BNC centre pin revealed not only a loose connection but also a small air gap , unbelievable !!! Looks like it was never soldered at all.Fired up the soldering iron and gave it a nice soldering job.Result , Job done , Fixed and works perfect.