hybridfree/eevblog-posts huggingface dataset:
Is a loading coil antenna better than a whip for HF reception - Page 1
Forum section: electronics / rf-microwave

author: prabhatkarpe4
author_rank: Contributor
timestamp: September 10, 2024, 10:14:42 am
content: I would like to know whether a loading coil antenna can be used for receiving HF signals, especially for the SW broadcast?Usually, any HF resonant antenna would be too long but can a shorter whip antenna with a loading coil be used for HF reception and will it work better than a resonant whip antenna?I want to connect that loading coil antenna with the whip antenna of the radio using an alligator clip.

author: A.Z.
author_rank: Super Contributor
timestamp: September 10, 2024, 10:41:46 am
content: avoid multiposting, you already asked the same question and got replies, do not repost the same question againthanks

author: Simon
author_rank: Unknown
timestamp: September 10, 2024, 07:18:08 pm
content: double posting is a banning offence!
How good is this cable from TEMU ? - Page 1
Forum section: electronics / rf-microwave

author: donnyDA
author_rank: Newbie
timestamp: September 15, 2024, 07:54:08 am
content: Has anyone made use of this cable from TEMU ?RG316 from Temu.The URL is long winded so a search on temu will display it.It's just cut to different length and 3mm Diameter.I'm just doing bench work, nothing outdoors as yet.

author: tooki
author_rank: Super Contributor
timestamp: September 15, 2024, 08:55:15 am
content: The diameter of RG316 is 0.098” ±0.004” (2.49mm ±0.1mm) according to the standard.I don’t know why you’d buy it on temu, given the sundry reasons one shouldn’t buy from them. Even AliExpress is preferable IMHO. I’m also sure there must be some Australian dealers that sell it at reasonable cost.Of course with no-name stuff, who knows how good it is. In my experience, cheaper coax cables tend to be stiffer and harder to strip than top brands, even if they meet the nominal specs.P.S. You know you can just copy and paste a URL, you don’t need to type it by hand. You should not expect others to do a search for you, especially since even Temu has multiple listings of any given item, so you need to link people the listing you have in mind.
Detuning an UHF RFID tag on purpose - Page 1
Forum section: electronics / rf-microwave

author: engarlanded_boa
author_rank: Newbie
timestamp: September 02, 2024, 12:20:34 pm
content: As the title suggests, I'm looking to modify a couple of tags so that I can control their backscattering behavior(ON/OFF) using a logic input signal. I don't know much about RF. Any ideas? Thanks!

author: engarlanded_boa
author_rank: Newbie
timestamp: September 09, 2024, 09:16:58 pm
content: Something like the button version found herehttps://cs.uwaterloo.ca/news/smart-hacks-turn-tagging-devices-internet-things-sensors, but electronically switchable? I've tried with an RF SPST that is rated for 900MHz, but it didn't work as expected.
Beginner question about alignment. - Page 1
Forum section: electronics / rf-microwave

author: Yamin
author_rank: Frequent Contributor
timestamp: September 08, 2024, 02:56:24 pm
content: Hi guys,I am pretty noob when it comes to RF stuff and superhetrodyne but very keen on learning. So basically I want to try an follow online videos about modifying small fm pocket radios to pickup vhf. The basic idea (at least from what I understand is) change the inductance value of the LC tank's coil in order to get up into the vhf band, please correct me if I'm wrong.I have done this sometime back and was able to receive ATC chatter. Now what I would like to do is actually measure it on scope what I'm doing and be able to exactly dial into say the ATC frequency which is known, and also afterwards change it back to the original spec of the radio.My problem is I'm not really sure where to measure and what to measure and I was hoping that someone could direct me on what measurements to take perhaps on a typical pocket radio schematic. I'm happy to go and do the research but was hoping that I could get some starting pointers.Thanks for the help.

author: wasedadoc
author_rank: Super Contributor
timestamp: September 08, 2024, 05:50:53 pm
content: Not a complete showstopper but do you realise that aircraft band uses AM, not FM?Also the IF bandwidth of a broadcast FM band receiver is hundreds of kHz compared to the few kHz for AM so selectivity will be very poor.

author: Yamin
author_rank: Frequent Contributor
timestamp: September 09, 2024, 02:52:22 am
content: Quote from: wasedadoc on September 08, 2024, 05:50:53 pmWoops

author: szoftveres
author_rank: Regular Contributor
timestamp: September 09, 2024, 04:15:11 am
content: Quote from: wasedadoc on September 08, 2024, 05:50:53 pmThose 2 minute how-to Youtube videos also give instructions about how to de-tune the ratio detector so that the small pocket transistor radio becomes much more sensitive to AM. Aligning the radio back properly is a different story and requires some instruments and expertise; cannot be done "by ear".

author: LM21
author_rank: Regular Contributor
timestamp: September 09, 2024, 05:53:02 am
content: Small radios use ICs I think, I wonder how easy it is to modify them. Some kits may be better?The reason I write is my late (Danish) FM tuner. It was an anything goes model. It used dual gate fets in VHF parts and they were probably a bit soft. I could hear weather forecasts from local airfield, taxis and other VHF traffic. Broadcast sensitivity was good and bonus sensitivity was poor, but the bonus was there.Then there is SDR kits, not so exciting or fun, but easy to get working and does not cost much.
New to the site and curious about this SPY board????    - Page 1
Forum section: electronics / rf-microwave

author: peeceebored
author_rank: Newbie
timestamp: September 07, 2024, 11:10:42 am
content: This is a board that has ended up in my scrap stash and I cannot for the life of me figure out what and where it came from. Any input would be greatly appreciated.

author: radiolistener
author_rank: Super Contributor
timestamp: September 07, 2024, 01:16:21 pm
content: Looks like PCB from Chinese Christmas lights.

author: coromonadalix
author_rank: Super Contributor
timestamp: September 07, 2024, 01:21:05 pm
content: can you zoom out a bit and see the whole thing both sides

author: Bud
author_rank: Super Contributor
timestamp: September 07, 2024, 02:18:20 pm
content: The silk screen has printing for Vol and Mic, and a Hi Mid Low switch. Could be some type of audio gear with RGB LED shit.

author: radiolistener
author_rank: Super Contributor
timestamp: September 07, 2024, 08:02:28 pm
content: Probably some kind of Chinese USB microphone with LED's
Driving dual coil latching microwave relay - Page 1
Forum section: electronics / rf-microwave

author: dobsonr741
author_rank: Frequent Contributor
timestamp: September 02, 2024, 03:06:57 pm
content: I picked up a microwave relay at ham swap to build an antenna switch.The label reads:DYNATECH SCM 50667MOD D1-418D58The coil config is rather interesting:- 3 wire driver connection, with common and 1 and 2- The DC resistance across any pins shows open- When applying 24V to comm and 1 or 2 it clicks and latches- Polarity matters: Com is +, terminal 1 or 2 needs to be - to switchWhat is the standard driver circuit for this kind of relay, current and timing wise?

author: joeqsmith
author_rank: Super Contributor
timestamp: September 02, 2024, 04:29:34 pm
content: Maybe just a SPDT momentary contact toggle:https://www.digikey.com/en/products/detail/te-connectivity-alcoswitch-switches/MTA106G/724912

author: Andy Chee
author_rank: Super Contributor
timestamp: September 02, 2024, 05:24:33 pm
content: How about an SCR dumping a fully charged capacitor into the coil (say 2200uF), should give enough of a pulse to flip the relay without burning out the coil from continuous current.

author: EggertEnjoyer123
author_rank: Frequent Contributor
timestamp: September 05, 2024, 06:03:41 am
content: Connect +24V to the +COM, and use a BJT to connect pin 1 or pin 2 to ground. A microcontroller or something could be used to send the signal to switch.As long as you have the flyback diode a crappy transistor like the 2N2222 should work. Current is usually < 200mA.

author: Randy222
author_rank: Frequent Contributor
timestamp: September 05, 2024, 10:55:28 pm
content: Quote from: EggertEnjoyer123 on September 05, 2024, 06:03:41 am+1Odd that it only works with +V on the comm terminal. Perhaps they put inline diodes to each half of the coil?Instead of BJT an nFET (2x) could be better. comm +V and then 1 (2) to drain of nFET with fet source to gnd. Many FETs are avalanche rated, but you can still drop a diode(s) from 1 to comm and 2 to comm, but in blocking direction.
HP 8497K attenuator maintenance  - Page 1
Forum section: electronics / rf-microwave

author: Michael-VK2BEA
author_rank: Regular Contributor
timestamp: September 03, 2024, 01:25:26 pm
content: I need to do an o-ring replacement of an 8497K attenuator with N connectors and a Viking control cable.I have done this on an attenuator with SMA connectors and an IDC ribbon socket. Disassembly on that was fairly straight forward.The SMA socket had nuts that when removed allows the cover plate to come off revealing the bolts to disassemble the attenuator bank but still retaining the SMA sockets.With this one, it seems, I have to remove both N connectors before I can get to the cover plate. Is that right? Can someone with experience confirm this? Between the N socket and plate I can see what looks like a nun around an SMA connector so the N f/m may be an adapter.I also presume that the Viking connector is removed by taking off the circlip and pushing it through the side plate; is this correct?The last one I did had three sections (12 o-rings) and that was a cow ... this one has four section (16 o-rings)!
WANTED: antennaX mailing list archive - Page 1
Forum section: electronics / rf-microwave

author: niconiconi
author_rank: Frequent Contributor
timestamp: August 31, 2024, 05:13:30 pm
content: In the early 2000s, there was a popular online magazine called antennaX for RF/antenna designs and amateur radio, and it also had a mailing list with many interesting discussions. Around 2017 , one day it suddenly disappeared, and 20 years of mailing list archive completely vaporized... I noticed it when I've read an article that cited a thread on its mailing list, and I found all links to the mailing list are now a 404...Almost nothing about the mailing list was saved by archive.org because the site had anti-bot and login restrictions. The only page saved was the list's landing page , the list archive itself was not saved due to restrictions (e.g. see ). Does anyone have personal copies of the historical mailing list threads? Also, interestingly, the website mentioned they had CD-ROM archives for the magazine? Does anyone have any of these CD-ROMs? Does the CD-ROM contain mailing list posts too?All "artifacts" would be greatly appreciated.https://groups.google.com/g/rec.radio.amateur.antenna/c/eE8AkLWI3YI/m/GeES_XMWBQAJ?pli=1https://web.archive.org/web/20160314014428/http://antennex.com/help/subscribe.htmhttps://web.archive.org/web/20120915012310/http://antennex.com/listlogin/index.htmlhttps://web.archive.org/web/20080826030335/http://www.antennex.com/listarch/archives.html

author: A.Z.
author_rank: Super Contributor
timestamp: September 01, 2024, 01:58:06 pm
content: did you already try this ?https://web.archive.org/web/20040101181243/http://www.antennex.com/

author: niconiconi
author_rank: Frequent Contributor
timestamp: September 02, 2024, 08:10:56 am
content: Quote from: A.Z. on September 01, 2024, 01:58:06 pmReread the first sentence in my second paragraph, and review the third attached image.
Why do pocket radios have small antennas - Page 1
Forum section: electronics / rf-microwave

author: prabhatkarpe4
author_rank: Contributor
timestamp: August 15, 2024, 09:54:16 am
content: I need to know why do most pocket AM radios come with a small whip antenna of about 20 cm because that would work only with 80 cm bands. How it will receive SW from 2 MHz to 22 MHz with a 20 cm whip antenna?

author: Phil1977
author_rank: Frequent Contributor
timestamp: August 15, 2024, 10:36:22 am
content: A physically short antenna can be electronically prolonged e.g. by inductors. And even a non-matched antenna is not an ideal antenna, but it´s receiving anyhow - it´s just much less efficient.For a receiver a bad antenna efficiency can partially be compensated by amplification. That´s why well matched antennas are most important for transmitters.For much longer wavelengths like LW and MW you can also receive the magnetic part of the transmission e.g. with a ferrite rod antenna. Again that´s only pragmatic for receiving, not for transmission.

author: tszaboo
author_rank: Super Contributor
timestamp: August 15, 2024, 11:25:20 am
content: To state the obvious, they have small antennas because otherwise they wouldn't fit in your pocket, and then they wouldn't be pocket radios.

author: radiolistener
author_rank: Super Contributor
timestamp: August 18, 2024, 12:33:11 pm
content: Quote from: prabhatkarpe4 on August 15, 2024, 09:54:16 amShort antenna has worse efficiency. But it also has smaller Rayleigh near field region, which helps to reduce near field coupling when you use receiver near buildings or other objects that can have noise sources. Smaller efficiency can be compensated with low noise amplifier, so the main issue of antenna is noise floor which is very sensitive to near field coupling and smaller antenna size also helps to compensate its low efficiency for a little by reducing near field coupling.And since portable radios are unable to use large antenna and usually are used near buildings, it's short antenna is a compromise which works not so bad.

author: Infraviolet
author_rank: Super Contributor
timestamp: August 30, 2024, 07:13:18 pm
content: Does antenna size have some general relation to power levels (atleast for transmission) too? For anything pocket portable they'd design to keep the power requirements as low as they could, both to prolong battery life and make it weak enough not to be likely to interfere with other users of the same slice of spectrum.

author: radiolistener
author_rank: Super Contributor
timestamp: August 31, 2024, 11:15:47 am
content: Quote from: Infraviolet on August 30, 2024, 07:13:18 pmAlmost no. But if you want to increase antenna efficiency, it needs to increase antenna size. And if you building high power transmitter, there is a sense to make it very efficient in order to pay less for electricity and as result it needs to be large. Small antenna can radiate the same power, but it will have more losses for heating due to higher voltage/current required to radiate the same power.
G0HZU ECal standard long term drift  - Page 1
Forum section: electronics / rf-microwave

author: joeqsmith
author_rank: Super Contributor
timestamp: August 30, 2024, 08:30:12 pm
content: Found your post from 2015:https://community.keysight.com/s/question/0D52L00005Idp7oSAB/ecal-module-calibration-intervalI am guessing you tracked the drift over this time. Can you provide any details?

author: G0HZU
author_rank: Super Contributor
timestamp: August 30, 2024, 09:27:51 pm
content: I can't really add much info since I wrote that stuff. I had only owned the VNA a day or two when I wrote that back in 2015. I had just collected it (and the ecal module) from the auction company.What I have done since was to cal the VNA directly at the VNA port (no cable used) using the Ecal. I did this for all four ecal ports.I then measured the short and open parts from a healthy 85033E mechanical cal kit on the VNA and then post processed the results by applying the C0-C3 and L0-L3 coefficients from the 85033E cal kit to see if it delivered a flat line for phase and a flat reflection coefficient for all four ports for both open and short.I've only done this a couple of times (maybe 5 years ago and about 1 year ago) and I had remarkably good results each time out to 8.5GHz. Not quite perfect, but easily good enough to justify not sending the ecal out for calibration. I've had that ecal module for 9 years now!Below about 300MHz, nothing beats a decent mechanical cal kit for s11 in my opinion. The ecal always does really well here but it can't quite compete when doing critical measurements. Above 300MHz the consistency of the ecal calibration is probably enough to give it the edge, especially for full 2 port calibrations.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 30, 2024, 11:07:43 pm
content: I was going to send mine off but it seems Keysight no longer services them. I saw a message from I think 2016 saying they would no longer calibrate them.My plan is use the 85033E to setup various user characterizations. My VNA is limited to 20001 data points or 450kHz step size. So I plan to create a separate user sets for < 500MHz and for < 9GHz. They state the compression level is 9dBm. I plan to create another set at lower levels to see if there is any improvement. You can use unlimited data points as long as you don't plan to save the data to the ECal.Once all of this work is done, I plan to go back and calculate new coefficients for my poor mans mechanical standards.You can run a confidence check on them but in my case, someone swapped the connectors and overwrote the factory data. I was surprised that the fingers on the 3.5mm female had not been damaged. Mechanically it appears in excellent condition.
10MHz Wireless Power Plasma Candle - Page 1
Forum section: electronics / rf-microwave

author: jonovid
author_rank: Super Contributor
timestamp: August 30, 2024, 10:44:33 am
content: an interesting 10MHz radio frequency candle project video I found on YT. if interestedas for the safety of running a 10MHz radio transmitter of this specification?

author: ftg
author_rank: Frequent Contributor
timestamp: August 30, 2024, 10:59:47 am
content: It's a very short vertical, so it should radiate badly on 10MHz, the power wiring will likely be radiating more than the plasma flame.The harmonics from it might radiate better.It does look like a simple power oscillator, might make for a fun weekend project.
Edwin Armstrong, history - Page 1
Forum section: electronics / rf-microwave

author: joeqsmith
author_rank: Super Contributor
timestamp: August 24, 2024, 05:07:42 pm
content: https://njpalisades.org/majorArmstrongsTower.htmlArticle about the tower being used after 9/11Quotehttps://www.fybush.com/wtc-recovery/
CPI CMA382400AUP  up-converter hook up question - Page 1
Forum section: electronics / rf-microwave

author: mr ed
author_rank: Regular Contributor
timestamp: August 22, 2024, 03:32:15 pm
content: I have a CMA382400AUP which is a 13GHz to 40GHz tripler and I see conflicting power supply voltages for it.The seller indicates 5, 8, -5 volts but other paperwork says 12volts which I guess is for 8v line. Maybe.The power out is low at 8v and varies when the 8 volt line is dropped. It looks like the 8v line is meant to be good to 12v which might give the 20dBm I expect. Obviously, I don't want to apply 12v and destroy it. Searches have failed me.Does anybody know for sure what the voltages should be?

author: mr ed
author_rank: Regular Contributor
timestamp: August 23, 2024, 02:06:40 am
content: The -5V line is a bias of some sort, you need to tune the output RF gain by reducing this voltage down from -5v as it's not fixed at -5V as shown in the spec sheet. It needs to be variable.Dropping from -5v to -3v adds more than 20dB of output power at 38GHz.The +8 volt line also varies power out but it's less sensitive. Leave at +8 for normal ops.So, pinouts follow and are from the WR28 port going up on the body ...Common black+5 400mA main power grey0 to +8v V control red (adj for power desired)-2v to -5v bias green (adj to peak RF for each unit)(Follow the colors to get the connectors pinout).
Best way to pass impedance controlled signal out of a shielded can - Page 1
Forum section: electronics / rf-microwave

author: m98
author_rank: Frequent Contributor
timestamp: August 21, 2024, 06:11:15 pm
content: I have an RF section that outputs a broadband signal above 4 GHz via a coplanar waveguide. I want to shield the whole section with an off-the-shelf smd shielded can like the Laird BMI-S-203-C. This leads to the question, how can I pass the signal from inside to outside without some heavy impedance discontinuities, and ideally without mechanically modifying each shield?

author: tggzzz
author_rank: Super Contributor
timestamp: August 21, 2024, 07:22:23 pm
content: Quote from: m98 on August 21, 2024, 06:11:15 pmStart with a 50ohm coplanar waveguide?Use a (?minicircuits?) transformer?More.helpful answers would be available if you told us more about the problem, and what you have considered and rejected.

author: selcuk
author_rank: Frequent Contributor
timestamp: August 21, 2024, 09:10:32 pm
content: I think you are going to use something like BMI-S-203-F on the PCB side to put BMI-S-203-C on top of it. It has 3mm spaces between its pads. Those are the places I usually route signals while using such shields. Do you need more than that for your signal?
Current Limiting in High Speed RF circuits - Page 1
Forum section: electronics / rf-microwave

author: Arsh ahmad
author_rank: Regular Contributor
timestamp: August 19, 2024, 07:16:11 am
content: Hi,I am working on Photo diode circuit that use both RF and DC for Biasing.I am using a bias Tee made using Mini Circuits TCCH-80+ RF choke for DC and 100pF cap for DC, The issue is since I am using RF PA(PHA-202+) for making RF 6V peak to peak the current capability is also increasing.In order to limit the current I had put a 330K ohm resistor in series with my photo diode and Bias tee output. The Problem with this is that Current limiting resistor along with the parasitic capacitance of the diode is forming a low pass filter for the RF and Diode is not seeing any RF at its end.But I cannot remove the current limiting since max Photo diode current is 450uA.I need a method to provide a current limit without losing my high speed signal

author: Sorama
author_rank: Frequent Contributor
timestamp: August 19, 2024, 07:58:25 am
content: I use an RXE (020) in series just after an RS485 driver @345kbaud.It's a PTC reset fuse, they come in different values, although I think 100mA is the lowest.https://eu.mouser.com/ProductDetail/Littelfuse/RXEF020?qs=hv6pn79dJPS5HLx1%252BdAJDg%3D%3D&utm_id=9882662061&gad_source=1&gbraid=0AAAAADn_wf2CVdHCRh4bXlvlyofhGB57c&gclid=Cj0KCQjw2ou2BhCCARIsANAwM2G_p9j8fdnOwLVC8jRogNkz1WffROKrg-uUo9Zb6g2IQMQ78-pqPy8aAjezEALw_wcB

author: Arsh ahmad
author_rank: Regular Contributor
timestamp: August 19, 2024, 12:18:45 pm
content: Quote from: Sorama on August 19, 2024, 07:58:25 amI got minimum PTC of 30mA but my diode's absolute maximum current is 450uA only.

author: LM21
author_rank: Regular Contributor
timestamp: August 20, 2024, 08:33:05 pm
content: How about simple two transistor current limiterhttps://electronics.stackexchange.com/questions/39430/help-needed-optimising-simple-current-limiting-circuit

author: fourfathom
author_rank: Super Contributor
timestamp: August 20, 2024, 10:01:52 pm
content: Quote from: Arsh ahmad on August 19, 2024, 07:16:11 amCan you provide a schematic for the circuit?It sounds like you have the current-limiting resistor in series with the signal path. If so, just put a bypass capacitor in parallel with the resistor. The value of the cap will depend on the frequency range of the optical signal. Probably a 0.1uF chip cap will be fine, or if these are leaded caps use a 0.1uF and a 100pF in parallel.
How to build a load for dummies rather than a dummy load... - Page 1
Forum section: electronics / rf-microwave

author: Co6aka
author_rank: Unknown
timestamp: July 09, 2024, 03:31:52 am
content: And be sure to solder the tabs FIRST before mounting the resistors.

author: joeqsmith
author_rank: Super Contributor
timestamp: July 09, 2024, 03:48:53 pm
content: No spreader. Can't drill a simple hole. Best part was claiming 400W.I had watched a couple of their very early videos when they started out, and pointed out some obvious mistakes he made about some of the components he was attempting to identify. Their fix, pull my offensive post.I really haven't watched any of later videos, but it appears in this case he pulled the whole video.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 14, 2024, 12:03:31 am
content: Seeing a trend with their channel!https://www.eevblog.com/forum/testgear/amazon-do-multimeters-now/msg3017388/#msg3017388

author: radiolistener
author_rank: Super Contributor
timestamp: August 14, 2024, 07:59:37 am
content: It shows "This video is private"...What was there?

author: joeqsmith
author_rank: Super Contributor
timestamp: August 14, 2024, 02:04:09 pm
content: Just a review. I assume he wants to be perceived as some sort of expert. Pointing out that he doesn't know basics, his way of dealing with it is to pull the video. If I did that, I would need to pull 100% of my content.

author: tszaboo
author_rank: Super Contributor
timestamp: August 14, 2024, 02:12:51 pm
content: Quote from: joeqsmith on July 09, 2024, 03:48:53 pmWhich Youtube channel was this posted on?

author: joeqsmith
author_rank: Super Contributor
timestamp: August 14, 2024, 05:26:58 pm
content: I don't have a link for his channel and with so many channels now, both Google and YT search didn't locate it. Even when searching for the couple of DMMs I knew they reviewed. I thought it was "learnelectronics". Doing a search, seems that channel closed. Its that guy that was calling Dave a snob then couldn't figure out the difference between a diode and resistor. Decent sized channel, > 100k last I knew.If he comes up again on a suggested video, I will tag him.***Yes, that was him as I remember their icon. Looks like they shut the channel down.https://socialblade.com/youtube/c/learnelectronics
How to use this antenna? - Page 1
Forum section: electronics / rf-microwave

author: daisizhou
author_rank: Super Contributor
timestamp: August 10, 2024, 04:08:00 am
content: I got an antenna that was phased out by a carrier，It looks like it is from the 2G or 3G era.I don't know how to use it,In other words, can I connect it to the SMA port of a wireless router?I am a beginner in radio or antenna and I don't know how to choose an antennaIf you know how to use it please let me know, thanks

author: uer166
author_rank: Super Contributor
timestamp: August 10, 2024, 04:11:59 am
content: This vaguely looks like a GSM band antenna. WiFi (your router) is 2.4GHz and 5GHz. For the former band it will most likely somewhat work, but what's the point? This antenna looks relatively directional and not optimized for WiFi bands.

author: PA0PBZ
author_rank: Super Contributor
timestamp: August 10, 2024, 10:43:00 am
content: This is a 4G (LTE) gsm antenna, not much use for anything else, for WiFi you mostly want an omnidirectional antenna, this one has 2 beams (+45 and -45)

author: wasedadoc
author_rank: Super Contributor
timestamp: August 10, 2024, 01:24:30 pm
content: The two bands of frequencies are clearly shown on the label in the first photo.

author: ftg
author_rank: Frequent Contributor
timestamp: August 12, 2024, 12:10:05 pm
content: Their design of the 1710 - 2635 MHz side of things looks wideband, so it could work fine as a directional antenna on the 2.4GHz wifi band.I would not expect it to work on 5.8GHz, but who knows if there is some 3/4 wave resonance in there for it as well.But that would require measuring it with a VNA.
Balanced/Unbalanced Attenuator Conundrum - Page 1
Forum section: electronics / rf-microwave

author: Guille
author_rank: Regular Contributor
timestamp: August 09, 2024, 09:50:36 am
content: Hi everyone!I understand the topic doesn't strictly adhere to RF but I've asked everywhere and figured RF people are the ones who'd know more about attenuators.I've been testing an HP 4436A 600Ω balanced attenuator but there's something about the balanced connection that I just can't get right.The setup described in the manual is simple: A signal generator is configured to 600Ω output and hooked to the attenuator HIGH and LOW input, the GROUND input goes to cable shield. The HIGH and LOW outputs are then connected to a multimeter to check how much voltage is being dropped, lastly 2 * 300Ω shunts are placed to match the high impedance of the voltmeter to the 600Ω output impedance of the attenuator.The problem is I reproduced this setup but my readings are off. The attenuation is adjustable and will work allrightish from 0dB down to around -80dB but from -80dB to -120dB the voltage doesn't drop at all. This is my implementation of the setup (I swapped the DMM for a lockin amplifier with floating differential inputs because of the very high attenuations). The signal generator is putting out 1Vrms sine wave at 1 kHz, the attenuator is rated from DC to 1 MHz and the lockin is rated from 1 mHz to 102.4 kHz, it's input impedance is 10 MΩ.Initially I suspected a hardware error but the attenuator is fine, no resistor has drifted out of tolerance, all switches make clean connections, everything is up to spec. To drive the point home the manual (attached) specifies the attenuator can be set up with an unbalanced connection so I checked and sure enough when configured as the image below it works flawlessly down to -120dBHooking the generator output to attenuator LOW (instead of HIGH like in the picture) will also work equally well so both T-pad attenuators forming the H-pad are working perfectly independently. This has me thinking it's got to be user error, there has to be something about the balanced setup that I'm misunderstanding.Thank's for reading this far.

author: wasedadoc
author_rank: Super Contributor
timestamp: August 09, 2024, 02:27:12 pm
content: You already asked the same and were replied to in another section of the forum.https://www.eevblog.com/forum/beginners/balanced-attenuator-confusion/Duplicate posts are strongly frowned on.

author: Simon
author_rank: Unknown
timestamp: August 09, 2024, 03:46:48 pm
content: You can't just duplicate your post. It totally pisses people off as they feel you are wasting their time as others may have already helped in the other topic you created.
Best Complete free RFIC course - Page 1
Forum section: electronics / rf-microwave

author: DejanC
author_rank: Regular Contributor
timestamp: August 08, 2024, 03:54:36 pm
content: Can someone please provide the best possible free RFIC courses available online? I know it is a very vast subject matter but whatever you can suggest would be greatly appreciated.

author: EggertEnjoyer123
author_rank: Frequent Contributor
timestamp: August 08, 2024, 06:25:03 pm
content: https://www.youtube.com/playlist?list=PLc7Gz02Znph-c2-ssFpRrzYwbzplXfXUThttps://www.youtube.com/playlist?list=PLyYrySVqmyVPzvVlPW-TTzHhNWg1J_0LU

author: RomDump
author_rank: Regular Contributor
timestamp: August 08, 2024, 06:29:11 pm
content: Quote from: DejanC on August 08, 2024, 03:54:36 pmRadio System Design CourseAdditional Content
WSJT software for shortwave listening - Page 1
Forum section: electronics / rf-microwave

author: jonovid
author_rank: Super Contributor
timestamp: August 04, 2024, 09:12:53 pm
content: it is obvious WSJT software is for communication between amateur radio operators.but what if you just wanted to only receive WSJT weak-signal radio communication on a shortwave receiver &a laptop computer. but the software is written for radio operators not shortwave radio listeners.my experience with open source WSJT software for listening only was disappointing.some improvement in thesoftware for radio listenerswould help a lot. like adding text to speech.& or automatic scrolling text logging screen while tuning the radio receiver up & down the radio bands.

author: mag_therm
author_rank: Frequent Contributor
timestamp: August 04, 2024, 10:21:19 pm
content: WSJTdoeswork well in SWL only mode. It is necessary to set in Settings > Radio > Rig:NoneIf you want to participate as SWL auto uploading to pskreporter and wsprnet, give yourself a SWL name, and then enable the Upload boxes in > SettingsPut your SWL name and Maidenhead in > Settings > General ( read more about latest SWL only on pskreporter and wsprnet)You can use an SDR. I even have an (extensively modified) old tube HF rx which works very well via the sound card audio jack.Happy DX !KE8UZFAdd: Recent 24Hr log on wsprhttps://app.box.com/s/5efgjxlsst12uld53h66yb9308zdykyd
Adalm-Pluto SDR or Pluto+ JTAG programming HELP - Page 1
Forum section: electronics / rf-microwave

author: jemp
author_rank: Contributor
timestamp: July 29, 2024, 03:21:28 pm
content: Hello, AllAs many of the Pluto User i have seen, there are many that obtained a bricked version after changing the firmware..AD describes how to JTAG this bricked Pluto Plus, which will not come into DFU mode and NOT recognized by Windows anymoreSo I bougt a Xilinx USB Platform II Cable and installed XilinxSDK 2017.4I downloaded the Jtag firmware v0.29, to be found on the Github, with 4 files in it run.tcl, ps7_init.tcl, system_top.bit, u-boot.elf and installed these in ...sdk/scripts/xmd folder of Xilinx SDKMy pluto is seen by the SDK and when I enter run.tcl I get this result.. ( see picture )The ps7_init.tcl is not found.. strange because I put them beside the run.tcl file..Can anyone explain this.. or where should this file be then ?Tnx for any help
Controlling Special Chinese Module MAX2870 TFT Unit DDS Generator - Page 1
Forum section: electronics / rf-microwave

author: jemp
author_rank: Contributor
timestamp: July 08, 2024, 11:15:38 am
content: HEllo AllI've obtained a small TFT Cotrolled MAX2870 from AliXpress ( see picture ) but the seller did not provide any instructions or PC software.Does anybody has this PC controlled software ?Does anybody know how to calibrate this module , since the main clock is about 575 Hz off and so any frequency generated has a substantial difference !!On the back side is a jumper with calibration marked on it..Any Manual or others ?Tnx for any HELP, ON7MA

author: EggertEnjoyer123
author_rank: Frequent Contributor
timestamp: July 18, 2024, 06:40:26 pm
content: You'd probably have to desolder the crystal oscillator on the board, and attach your own clock signal to "calibrate" it.All the chip does is generate multiples of the input clock frequency, and it shouldn't need any calibration since the output frequency is locked to the input frequency.

author: shabaz
author_rank: Frequent Contributor
timestamp: July 18, 2024, 08:01:02 pm
content: I'm not sure it's worth it. It's a very basic freq synth with steps of 10 kHz and 20 kHz depending on the desired frequency. It is not a DDS, despite some adverts mentioning that.I was not able to get online software to function with it. It's possible to disassemble the firmware if there was a real desire to investigate computer control. The firmware binary content is easy to read out using any SWD tool. I placed theMAX2870 board firmware binary file hereif anyone is interested. But, personally I think it's not of value, since one may as well make a custom freq synth board with that chip, with their desired microcontroller of choice (or use the microcontroller already on the board, but will probably be easier to just start from scratch with a custom PCB), and using (say) SCPI or some other normal protocol.

author: Kees Hofwegen
author_rank: Newbie
timestamp: July 27, 2024, 02:33:06 pm
content: Hi,I have a small max2870 board (not this one) that I can control through an micro controller.In my case an arduino nano.Using both Integer-N and Fractional-N modes I can control the frequency quite accurately ( < 10Khz).having said that, this board probably uses Integer-N only since that is quite simple to calculate.Control of tha MAX on that board is done with 5 registers so an analyser on the LE, DATA, Clk lines will showwhat is sent to the MAX.The rest of the code is only control for the menu's, switches and LCD.As said by others, better to start from scratch or live with the 10Khz resolution.Greetings Kees
Series through impedance measurement with Bode 100 | Working principle - Page 1
Forum section: electronics / rf-microwave

author: nico98
author_rank: Newbie
timestamp: July 17, 2024, 09:18:15 am
content: Hi all,currently i am working with the Bode 100 VNA to analyze impedance spectra. Since my DUT is far above 10 kOhm impedance, the user manual suggests to use the Series through measuring set up. On the internet i could find a lot of research on the port setup but it was never explained on how this setup work in detail. Why does the series through setup allow to measure high impedances whereas the oneport method doesn't? Is it because the DUT is put in parallel with a short connection which lowers the overall impedance or has it something to do with the internal reference resistors?Cheers, Nico

author: mtwieg
author_rank: Frequent Contributor
timestamp: July 17, 2024, 12:03:04 pm
content: Here's a document explaining in detail why certain measurement methods suit different DUT impedances:https://www.mwrf.com/technologies/test-measurement/article/21849791/copper-mountain-technologies-make-accurate-impedance-measurements-using-a-vnaBasically with a shunt method, as the DUT impedance approaches infinity, incremental changes in impedance have no effect on the measured S11 or S21, even though the measured signals are still large. With a series connection, as the DUT impedance approaches infinity, incremental changes in impedance will still cause significant changes in S21, even though the measured signal at port 2 may be tiny. If you carry out the math, the latter case gives better accuracy in the final impedance measurement.

author: nico98
author_rank: Newbie
timestamp: July 17, 2024, 12:30:17 pm
content: okay thanks, that helps a lot. So as far as I understand is the impedance not "too high to measure" in a oneport set up, but the variance goes up to infinity at high impedances whereas the variance for the series thru set up goes down with higher impedances. I thought the reason is a technical one but this makes sense.

author: mtwieg
author_rank: Frequent Contributor
timestamp: July 17, 2024, 01:21:06 pm
content: As impedance goes towards infinity, the series method accuracy will also degrade (because your S21 measurement will hit the instrument's noise floor), but the overall occuracy will still be better than the shunt method.
CC1101 multiple frequencies - Page 1
Forum section: electronics / rf-microwave

author: DocRaptor
author_rank: Contributor
timestamp: July 15, 2024, 03:10:32 pm
content: Hello,I have a question with the CC1101. I want to use it with multiple frequencies. I want to switch the antennas with filters with two BGS13SN8E6327XTSA1 hf-switches controlled from the MCU. Has somebody experience with this? Can it work or will the CC1101 "hate" me?

author: Gribo
author_rank: Frequent Contributor
timestamp: July 23, 2024, 07:36:27 pm
content: Are the frequencies within the same ISM band? (433? 868? 905?) Or do you want to switch between bands? The former is easy, the latter is extremely difficult.
FM frequency modulated waveform  - Page 1
Forum section: electronics / rf-microwave

author: sneily
author_rank: Contributor
timestamp: July 19, 2024, 11:08:18 pm
content: Can I view a frequency modulated waveform on an oscilloscope?I have a Fluke 6060b for modulated signal generation, and a 200Mhz digital scope. I want to view any modulated waveform in the range of 88Mhz to 108Mhz.I can view an AM modulated waveform, no problem.But the FM modulated waveform just looks like a normal 88Mhz sine wave.How can I see the modulation effect on the scope??Thanks,Sneily

author: sneily
author_rank: Contributor
timestamp: July 20, 2024, 02:45:13 am
content: Thanks. If I set the carrier frequency low enough, and the FM Deviation high enough, I am now able to view a modulated waveform on my O'scope.Cheers

author: radiolistener
author_rank: Super Contributor
timestamp: July 20, 2024, 08:57:39 am
content: It's hard to see details of 100 MHz carrier on oscilloscope. It requires to use oscilloscope with much higher bandwidth.You can use mixer to do frequency down conversion, to get FM carrier at lower frequency, for example 500 kHz, then it can be more easy to see details.

author: tggzzz
author_rank: Super Contributor
timestamp: July 20, 2024, 09:19:44 am
content: Quote from: sneily on July 19, 2024, 11:08:18 pmAn oscilloscope displays V-vs-t.A spectrum analyser displays V-vs-f.You want a tool that displays the third variant: f-vs-t. The Hp-Agilent 53301A is such a "modulation domain analyser".Alternatively, an SDR or "real time spectrum analyser" could display the f-vs-t in the form of a waterfall display. The span will depend on sampling rate.

author: MarkT
author_rank: Frequent Contributor
timestamp: July 20, 2024, 12:05:04 pm
content: With a digital scope you can set triggering way to the left of the screen to multiply the visibility of the frequency variation - set the time base to say 10us, move the trigger cursor to the left edge, then zoom in on the time base till you can see the waveform and its wriggling (perhaps 20ns/div)... A 100MHz broadcast with 75kHz deviation ought to be easy to visualize this way, deviation is 0.075%, assuming the modulation frequency and amplitude is high enough.You will need a decent sample memory in your scope to zoom in that far, and good trigger circuit at those frequencies.

author: LM21
author_rank: Regular Contributor
timestamp: July 20, 2024, 01:46:06 pm
content: At 100Mhz the frequency change with "normal" FM modulation is so small you can not really see it. If you have a digital scope the sampling frequency matters. It must be much higher than the bandwidth,and you still can't see modulation of broadcast FM.Edit: you cannot see 100MHz broad cast FM with +-75kHz deviation=frequency change with a scope
Bandpass filters out of metal tubes? (Bird electronics) - Page 1
Forum section: electronics / rf-microwave

author: Phil1977
author_rank: Frequent Contributor
timestamp: July 15, 2024, 08:29:44 pm
content: Hi,I was wondering how the bandpass filters shown in this video are working:I have no need to know it, I´m just curious. I can roughly imagine how a waveguide works, but just have no idea how a set of tubes creates a well defined and mostly flat frequency response.

author: madires
author_rank: Super Contributor
timestamp: July 15, 2024, 10:17:28 pm
content: They are called stub filters. When the stub is lambda/4 long and reflects the wave you'll get a lambda/2 delay (180° phase shift).

author: Phil1977
author_rank: Frequent Contributor
timestamp: July 16, 2024, 04:45:07 am
content: Thank you madires, that wording leads to the right explanations!
2SC2078 Matching Circuit - Page 1
Forum section: electronics / rf-microwave

author: jamfletch
author_rank: Contributor
timestamp: July 13, 2024, 10:16:49 am
content: Hi again all,I'm trying to build a 2SC2078 amplifier, I thought I'd start with the application circuit given in the datasheet (https://www.futurlec.com/Transistors/2SC2078.shtml). I've attached a screenshot of the test circuit. Just wondering if anyone knows what is meant by "90 4T" for the inductors? I initially thought maybe this meant "4 turns on a Type 90 ferrite core", but doesn't look like Type 90 is actually a thing.Any suggestions?

author: OZ1LQB
author_rank: Regular Contributor
timestamp: July 13, 2024, 10:33:43 am
content: hiit is not 90 but 9Ø which means 9mm diameter..have fun

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: July 13, 2024, 04:41:10 pm
content: Those are just coils without any cores. "air core" Since this is a 27MHz amp you may wish to look at some of the common CB Radios for insight. Get a schematic of a simple cheap CB. I think that 2078 was used in CBs before MOSFETs were common and less expensive.With prices these days, maybe think about a IRF 520 MOSFET based amp. 520s are really cheap.I think that the 2078 is usually provided with a DC Bias on the gate also. Through a higher value "choke"

author: jamfletch
author_rank: Contributor
timestamp: July 14, 2024, 09:59:09 am
content: Managed to built the circuit, I've tried driving the Base of the transistor with a 27MHz source. I've got about a 2V pk-pk sine wave drive at the base, which I thought would've been enough for driving the transistor on (Measure Vbe to be about 0.6V) . Don't suppose anyone has any ideas? Collector is biased to 12V, but I'm getting no current draw from my 12V supply.

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 14, 2024, 10:15:20 am
content: Quote from: jamfletch on July 14, 2024, 09:59:09 amIf you look at the 3rd graph under the schematics in the datasheet the transistor is just 'waking up' with a Vbe of 0.6V. I think you have to drive it a little harder!

author: OZ1LQB
author_rank: Regular Contributor
timestamp: July 14, 2024, 11:36:24 am
content: You have to remember that the vast majority of 2sc2078 on ebay and ali are fake transistors, so you should probably try to find an old CB and pick from there, believe me I have pulled out a lot of my sparse hair because of fake transistors from ebay/ali

author: jamfletch
author_rank: Contributor
timestamp: July 14, 2024, 12:26:58 pm
content: Yeah tbh I can't even remember where I bought these from.I've just tried driving it with an IRF510 amp I made, so about 23/24dBm output into 50 ohm. Obvious some loss due to poor return loss to the 2SC2078.Gain wasn't great though, maybe only a few dB. Max output of barely a Watt. Datasheet says it can deliver 4W, but maybe my output match is just extremely poor.So maybe they are just poor counterfeit transistors, or I have a crap input/output matching network
Small Signal S-Parameter simulation component: Microstrip Open - When to use it? - Page 1
Forum section: electronics / rf-microwave

author: hilper
author_rank: Contributor
timestamp: July 09, 2024, 03:25:31 pm
content: Small Signal S-Parameter simulation component: Microstrip Open - When to use it ?Shal it always be uses, even if the microstrip line is loaded by a lumped component ?Or shall it only be used for resonators, open stubs etc ?BR hilper