hybridfree/eevblog-posts huggingface dataset:
My active mini whip antenna has gone noisy and insensitive - Page 1
Forum section: electronics / rf-microwave

author: Chris Wilson
author_rank: Super Contributor
timestamp: July 30, 2016, 01:11:04 pm
content: I have a a clone PA0RDT active mini whip antenna atop a wind up mast that used to work well, but has recently become insensitive and very noisy. I will pull it down later and first check the co ax. If I remove its in shack power source the noise stops though, and I have tried it on a battery in case the PSU had gone noisy, but no difference in noise on battery power is seen. The circuit is athttp://dl1dbc.net/SAQ/Mwhip/pa0rdt-Mini-Whip.pdfCan anyone say if the front end FET may have gone faulty, or what to check please? Thanks!

author: Fank1
author_rank: Regular Contributor
timestamp: July 30, 2016, 02:00:17 pm
content: The J310 is probably shot.This design is very susceptible to static from storms etc.You need to add a 100nf cap between the J310 gate and the probe.Then put 2 diodes from the probe to common.One diode anode to common, the other cathode to common.I would use 1N4148 or similar.these will help prevent damage to the J Fet and should not hurt the signals any.

author: AF6LJ
author_rank: Unknown
timestamp: July 30, 2016, 02:59:53 pm
content: Quote from: Fank1 on July 30, 2016, 02:00:17 pmThis is usually what happens with those.
RF output transformers variations. - Page 1
Forum section: electronics / rf-microwave

author: G0FTD
author_rank: Newbie
timestamp: July 03, 2016, 10:55:20 am
content: Greetings all !Attached to this post is a drawing showing to methods of taking out the RF from an output stage.The example I drew represents a FET in this case.I have seen to styles of taking RF out of a device.1 - The combined RF choke and transformer output method. Where of course you can alter the output impedance withturns ratio as normal.2 - Where the device keeps the RF Choke on it's own, and uses a separate RF output transformer, with suitable turns ratioto suit impedance.So why the two methods ?At first glance, you might just say that it means you save on another toroid by having the combined version on example#1, but is that really it ?Is there something that I am missing ?73 de Andy G0FTD

author: uncle_bob
author_rank: Unknown
timestamp: July 03, 2016, 03:35:09 pm
content: HiThe first version puts DC through the core and thus *may* saturate the core. You also see push pull / two device versions that try to reduce this effect.The second version lets you have a high impedance RF choke to B+ that *might* help you keep RF off the supply. You have to get into the details of both the RFC and transformer in each case to really see what the cost impact and matching range really is.Bob

author: G0FTD
author_rank: Newbie
timestamp: July 03, 2016, 07:29:38 pm
content: You're the second person to mention the saturation issue.It's looking like the preference to using the combined RF Choke come impedance transformer is in low signal levelcircuits, whereas large PA stages are best with having a separate RF Choke with a proper and separate rf transformeron the output.Regards,Andy

author: uncle_bob
author_rank: Unknown
timestamp: July 03, 2016, 07:44:40 pm
content: Quote from: G0FTD on July 03, 2016, 07:29:38 pmHiA very common approach in a high power amp is to use a pair of output devices. The RF choke is set up to both transform and have balanced (opposed) DC in the windings to reduce the saturation issue. You have a three winding device, but still only have one core. Wire is cheap ....Bob

author: vk6zgo
author_rank: Super Contributor
timestamp: July 26, 2016, 04:15:21 pm
content: Quote from: G0FTD on July 03, 2016, 10:55:20 amIn Number (1), the primary of the transformer is part of the tuned drain load------not sure what happened to the "C" part of the LC circuit in your drawing,but if it is VHF/UHF,it is possibly made up of stray circuit capacitance.It is a "series fed" circuit,because current from the dc supply flows through the resonant drain load.In Number (2),the RFC is not part of the drain load at all,but is simply a "decoupling" component which has a high impedance at the operating frequency.The LC circuit making up the transformer primary is the drain load.This is known as a "shunt fed" circuit.
microcontroller configurable 5.8GHz transceiver - Page 1
Forum section: electronics / rf-microwave

author: Walloon
author_rank: Newbie
timestamp: July 20, 2016, 08:42:33 pm
content: Hi,I'm interested to begin a 5.8GHz electronics project, but in my web-searches I'm struggling to find any "configurable/hackable" transceiver options suitable for interfacing with a low end micro-controller.My project's goals are broadly similar to a camera video-system such as those used on drones.Of course, there are a bunch of ready-made 5.8GHz RX/TX modules (like say the M5802) serving this market.My problem is that everything I come across is a sealed 'plug and play' system. Nothing I've found seems to come with a detailed datasheet detailing such things as registers accessible through e.g. an SPI interface and allowing access to say, sleep functions etc.By contrast, the 2.4GHz market has modules like say the nRF24L01, readymade for talking to your average Pic, Arduino or whatever...Are there really no options, or am I just searching in the wrong places?any help appreciatedWalloon

author: Kilrah
author_rank: Unknown
timestamp: July 20, 2016, 08:47:01 pm
content: Digital 5.8GHz RF modules aren't common, probably because of "no need".What's the application you see where it would make sense to have 5.8GHz comms?I know of one, need to find the info again...

author: onesixright
author_rank: Frequent Contributor
timestamp: July 20, 2016, 09:17:17 pm
content: Seen this one?http://www.altantechnologies.com/Products/ALT5801.aspxIt has a API, check the datasheet. Not sure if you can access low level functions....

author: hendorog
author_rank: Super Contributor
timestamp: July 21, 2016, 03:30:26 am
content: Richwave based modules like this the M5802 are quite hackable - for the definition of hackable where you get out the soldering iron and remove some resistors to enable the SPI bus, as opposed to the Sparkfun version of hackableI've got some code somewhere if you want it to get it started.The datasheet is available - although it used to be a bit hard to find - parts are RTC-6705/RTC-6715
OCXO is it Vectron International ? - Page 1
Forum section: electronics / rf-microwave

author: marcw
author_rank: Newbie
timestamp: July 18, 2016, 10:05:48 pm
content: Hi,Hamfest find labeled as follows:VI QK O.30.00801EO 0374.803710 Mhz +12V2799 8075291/028On the back01203Device looks like this -Top1 2 3| || || || |4 5Pin 4 is case/ground. As near as I can tell pin 3 is 12V+.Am I correct that this is a Vectron International OCXO?Does anyone have a datasheet? No reply from Vectron and nothing on the web on this device.Thanks,Marc

author: uncle_bob
author_rank: Unknown
timestamp: July 19, 2016, 12:10:15 am
content: HiIt was designed in the old Quartzkeramik plant outside Munich in the 1990's. When that plant shut down, the design and production moved to the old KVG plant (then part of Vectron). Based on the date code (late 1999) it could have come from either plant. KVG is back to being independent again so who knows where the information on that unit might be. After nearly 20 years ... hard to guess.Since it is a standard pinout and you know the supply voltage ... just hook it up and see what happens. If it has an EFC, you can work out the range from the point that it gets to center frequency.Bob

author: marcw
author_rank: Newbie
timestamp: July 19, 2016, 12:50:47 am
content: Bob,Thanks.http://www.kvg-gmbh.de/produkte/quarzoszillatoren/ocxo/Will take me a bit to get the time to try it out, but I'll repost here when I do.Marc

author: marcw
author_rank: Newbie
timestamp: July 20, 2016, 02:16:09 pm
content: From KVG -Hi,please see attached the datasheet of the OCXO.The pin configuration is as follows:1 – RF output2 – Ground3 – Frequency adjustment Vc4 – Reference voltage output (for internal use)5 – Supply voltageBTW: Bob’s comments in the blog you mention are correct. The part was manufactured at Quarzkeramik nearby Munich in 1999 or 2000.EOF

author: marcw
author_rank: Newbie
timestamp: July 20, 2016, 02:19:20 pm
content: Oh and it did work, sounded like dirty square wave on shortwave...scope as time permits.Marc
Agilent ESG-D power search fails - Page 1
Forum section: electronics / rf-microwave

author: tkim
author_rank: Newbie
timestamp: July 15, 2016, 01:39:46 am
content: I got an Agilent E4432B ESG-D unit with options UN8, UND, H99. When I deactivate ACP and do a manual Power Search, it fails with error code -601. I checked the voltages and all the LEDs indicate they are OK. When ACP is active, output power is accurate even with complex modulation active.I/Q calibration also executes a power search and fails, so the whole calibration cannot complete successfully. I suspect the problem must be in the output Module. It is labeled E4400-60155.Has anyone experienced a similar problem? I removed UND and UN8 and continue getting the same error when doing a manual power search.Thanks in AdvanceTony
#64 Collins KWM 1 Repair - Page 1
Forum section: electronics / rf-microwave

author: Radio Tech
author_rank: Frequent Contributor
timestamp: July 30, 2016, 09:40:59 pm
content: #64 Collins KWM 1 RepairIn this video we take a look at a transmit problem with a KWM-1 amateur radio transceiver.

author: AF6LJ
author_rank: Unknown
timestamp: July 31, 2016, 02:03:24 am
content: That was fun..

author: voltz
author_rank: Frequent Contributor
timestamp: July 31, 2016, 12:50:17 pm
content: Yes, enjoyed it.

author: German_EE
author_rank: Super Contributor
timestamp: July 31, 2016, 09:29:41 pm
content: Young Players, please note:1) Before touching an HV chassis Buddy waited until the supply had drained down to a safe level, this is important.2) Buddy did all of his measurements using one hand, that way, if he touched something live, the shock wouldn't pass across his heart. This is also important.3) Buddy has been doing this for a long time and he'll still be around for years, probably because he follows steps 1 & 2As for the final note about the screws, I must have worked for Collins in an earlier life. For as long as I can remember I have been tightening cross head screws until they formed a little 'X' at 45 degree angles then left them alone. Wood screws, machine screws, they all get that little 'X'.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: July 31, 2016, 10:42:07 pm
content: Quote from: AF6LJ on July 31, 2016, 02:03:24 amAgreed. I really love working on these radiosQuote from: voltz on July 31, 2016, 12:50:17 pmSo glad you sis. I also enjoyed doing it. Not every day you get to work on such classics as a Collins.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: July 31, 2016, 10:52:55 pm
content: Quote from: German_EE on July 31, 2016, 09:29:41 pmSeeing a post like this makes me very happyIt does one good to see that folks notice these things that keep us safe. One slip and it's game over.I try to be and show that I am safety conscious. Although I did make a mistake in this video on a particular step I performed. I made another video today to show the correct way and currently editing it now. Will be uploaded soon.Thanks for the notice and pointing out safety here.I agree. you must have been a Collins engineer in a past life.
VE7BPO's 10 mhz trf rx question - Page 1
Forum section: electronics / rf-microwave

author: luckyflyer
author_rank: Contributor
timestamp: July 20, 2016, 05:43:59 pm
content: I'm a new member here on eevplog, it looks like a great site full of useful info. I'm gathering up parts to build ve7bpo's 10 mhz trf wwv receiver. Can anyone that has built this rx tell me what guage of wire is used for L2 & l4?

author: jopie
author_rank: Contributor
timestamp: July 20, 2016, 07:18:06 pm
content: Hi Luckyflyer,wire size is not critical for these coils, their purpose is to decouple DC and AC. 22-26 AWG should be okay.Regards,Joop PG4I

author: luckyflyer
author_rank: Contributor
timestamp: July 20, 2016, 08:02:40 pm
content: Great,thanks jopie!

author: G0HZU
author_rank: Super Contributor
timestamp: July 20, 2016, 08:16:30 pm
content: I think you could get rid of the choke coil L2 and relocate L3 to where L2 was and the performance would be pretty much the same. i.e. I think you could get the same performance in terms of front end preselection and save on having to wind and fit L2. You might also have to increase the value of CV2 to make sure you can tune for 10MHz. To get it even closer you could also reduce the value of the 2k resistor across the L2 location if you want to get the same amount of damping. L2 will be fairly lossy at 10MHz so the 2k resistor would need to be reduced to keep the damping the same. But you would save on having to hand wind and fit L2 if you relocated L3 to where L2 isI'm not sure you 'need' L4 either. If you replaced the 2k resistor here with a 1k resistor and simply removed L4 the circuit would probably work in a similar manner at 10MHz. You'd drop a few volts across this resistor but I'm not sure that would matter much for small signal reception.You could also save/delete the 1meg resistor and 0.001 cap at the input and just connect L1 direct to the gate of the mosfet.

author: luckyflyer
author_rank: Contributor
timestamp: July 21, 2016, 09:25:03 pm
content: I agree that there is certainly room for experimentation with this circuit, hence the desire for the spectrum analyzer.
2.4ghz transciever chip with rssi and i and q out maybe? - Page 1
Forum section: electronics / rf-microwave

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: July 07, 2016, 06:30:38 am
content: I read an old 2007 artical in elektor about a 2.4ghz ism spectrum analyzer. It was very simple using a spi connection to poll the rssi from a cypress wusb6935 break out board from cypress. Theze boards are obselete now and cheap on ebay 10 bucks for 2. I would like to use there idea but with a chip that is obtainable easily to make a handheld version using a psoc5 and 5 inch tft touch. Can anyone recomend a 2.4ghz tranciever or less reciver chip that can get rssi signals and maybe output i and q to an adc. This isnt just for wifi but bt btle and nordic so it cant be locked to wifi. Also a breakoutboard would be awesome!
#61 Yaesu FT101 series Part 2 "Few nuggets and on air listen " - Page 1
Forum section: electronics / rf-microwave

author: Radio Tech
author_rank: Frequent Contributor
timestamp: July 15, 2016, 05:35:26 pm
content: #61 Yaesu FT101 series Part 2 Few nuggets and on air listenIn this video we take a look at a few issues in the 10 dollar 101 before we get into a complete repair. This way we know better where we stand at and can now plan our attack.

author: AF6LJ
author_rank: Unknown
timestamp: July 16, 2016, 04:42:20 pm
content: So far So good...

author: voltz
author_rank: Frequent Contributor
timestamp: July 16, 2016, 05:55:06 pm
content: Watching with interest

author: Radio Tech
author_rank: Frequent Contributor
timestamp: July 17, 2016, 08:57:07 pm
content: Quote from: AF6LJ on July 16, 2016, 04:42:20 pmIt can only get better...right?Thank Sue.Quote from: voltz on July 16, 2016, 05:55:06 pmSo much more to come and so little time.Was going to start on the receiver walk through this week end but had to work Friday plus have stuff in the shop that needs to go for folks. Need to make a payday to buy parts with.I have so much stuff in the shop right now I could make tons of videos.Keep watching my friend.

author: echap
author_rank: Contributor
timestamp: July 18, 2016, 11:49:37 am
content: Keep up the good work. I enjoy your videos.One question, on that shunt resister, it looked like the voltage was creeping up. Is that normal?73,EricK8CCA

author: Radio Tech
author_rank: Frequent Contributor
timestamp: July 18, 2016, 12:37:13 pm
content: Quote from: echap on July 18, 2016, 11:49:37 amThanks.Yes, you were correct. The 101 is plugged into an isolation transformer and variac. There is a foot pedal on the floor that I have to step on to apply voltage to the 101. When voltage is removed you will see a rise as things bleed down.Good eye.

author: echap
author_rank: Contributor
timestamp: July 18, 2016, 01:45:59 pm
content: Oh, sure, that makes sense. Looking forward to part 3, and then the repair of the Fluke. You need to get busy, Buddy. lolzBTW not as good a deal as your 101, but I found a TS-520S over the weekend for a C-note. It's in great shape and seems to work well. Even has a CW filter and the original manual. It looks good sitting next to my 101.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: July 18, 2016, 09:08:38 pm
content: Quote from: echap on July 18, 2016, 01:45:59 pmNot a bad deal for a working rigThe 520 is an excellent rig. Very stable and simple to use.I am getting swamped here with repairs. And emails are out the roof! Cannot believe the amount of mails I am getting daily. If I reply to them all I will not get any work done lol. Most are just "Thank you" type mails. Rest are questions.I still have to get those caps ordered for the Fluke and have not even made a parts list yet. I need a truck load of parts. I did get my parts to finish the HP VTM just need time to get back to it.
RF generator sweep settings for filter test - Page 1
Forum section: electronics / rf-microwave

author: cio74
author_rank: Regular Contributor
timestamp: July 03, 2016, 04:42:46 pm
content: Hello,Until I'll buy a proper SA I am playing with a combo made of an Anritsu MG3633A and a Picoscope 3206MSO.I have made a simple crystal ladder filter with 3 poles, all xtal are 11.0592MHz and then set the generator to output a 0dBm signalstart at 11.00 MHzstop at 11.10 MHzThe first graph has step size 10Hz and dwell time 10msThe second step size 1Hz and dwell time 1msApart from the later taking way longer to complete and a much cleaner plot the measured shape and the amplitude at top are very close.Is there any rule to set dwell time, step size, span for better results?Thanks.

author: cio74
author_rank: Regular Contributor
timestamp: July 03, 2016, 05:18:06 pm
content: Added 3 more crystals, 6 poles now, not exactly flat response

author: Neganur
author_rank: Unknown
timestamp: July 03, 2016, 07:42:33 pm
content: Post a schematic with your tuning and coupling capacitor values, that graph looks like you're not tuned.EDIT: and also, have you measured the xtal frequencies or are you just trusting the values printed onto their enclosure?

author: uncle_bob
author_rank: Unknown
timestamp: July 03, 2016, 11:07:42 pm
content: Quote from: cio74 on July 03, 2016, 04:42:46 pmHiIf you are going for a filter that is 1 KHz wide, a good guess is that 10 ms of dwell per point will work. The approach is to try 100 ms and then back off to 10. If the response does not change, you are ok. If it does then you need to slow down a bit. Bandwidth is not what really determines the number, so it's just a starting point.Bob
VHA components? What are they? - Page 1
Forum section: electronics / rf-microwave

author: tec5c
author_rank: Frequent Contributor
timestamp: July 14, 2016, 12:31:11 pm
content: Whilst looking at current job ads for RF engineers here in Australia, I came across one that has"...experience with RF/radio/VHA/UHF components..."Would someone please care to explain what VHA is?

author: rs20
author_rank: Super Contributor
timestamp: July 14, 2016, 12:34:37 pm
content: VHF

author: tec5c
author_rank: Frequent Contributor
timestamp: July 14, 2016, 12:35:52 pm
content: Yep... I assumed it to be a typo but wanted to make sure.Cheers.
HOWTO: Run Sonnet Lite on OSX under Wine - Page 1
Forum section: electronics / rf-microwave

author: hendorog
author_rank: Super Contributor
timestamp: June 28, 2016, 11:12:52 pm
content: Sonnet Lite is an EM simulator which is useful for analyzing RF microstrip structures. It is frequently mentioned in dispatches here.So when I found it works well under Wine on my Mac I thought it helpful to share that it works well. I also found this post suggesting it also works in Linux:https://www.eevblog.com/forum/chat/how-do-i-get-offa-windows-and-learn-something-else/msg419096/#msg419096Wine has always been a bit hit and miss for me, but Sonnet works flawlessly, no crashes and almost no issues.There is nothing clever in the steps below, just follow your nose.1. Install XQuartz:https://www.xquartz.org/2. Install Wine. I used the Staging Install package from here:https://dl.winehq.org/wine-builds/macosx/download.html3. Download Sonnet Lite4. Run Wine staging from Launchpad, a terminal screen should appear with some instructions on how to install applications.5. Configure wine for Windows 7 (Note: All of the wine commands in the following steps have to be run from the Wine terminal)Code:winecfgIn Applications tab select Default Settings, then Windows 7 then OK6. Install SonnetCode:wine msiexec /i Downloads/setup_sonnetlite1553.msi7. Run SonnetCode:wine ~/.wine/drive_c/Program\ Files\ \(x86\)/Sonnet\ Software/15.53/bin/sonnet.exeI did this a few days ago so hopefully I have captured all of the steps.
Looking for 29MHz(HF) and 433MHz(UHF) RF Transmitter 1W Power. Any Suggestions? - Page 1
Forum section: electronics / rf-microwave

author: meamarp
author_rank: Newbie
timestamp: June 27, 2016, 11:53:47 am
content: Hi Hackers,Currently working on a project which requires RF signal transmitters for freq. mentioned in tittle. Well, Am not a RF guy, almost zero. I am confused about finding better solution.Also, Our application doesn't need to transmit data, just a RF signal.Can you suggest me any solutions?Thanks.Keep Hacking,Keep Innovating!!

author: ebclr
author_rank: Super Contributor
timestamp: June 27, 2016, 11:57:24 am
content: http://pt.aliexpress.com/item/2-PCS-New-2014-Black-BAOFENG-UV-5R-Walkie-Talkie-136-174-400-520MHz-Two-Way/1919320669.html?spm=2114.02010208.3.11.QnZA8G&ws_ab_test=searchweb201556_8,searchweb201602_4_10037_10017_405_404_10032_10040,searchweb201603_10&btsid=19b37009-b6fd-44ae-9c4e-226d1523bc1e
HDSDR hangs on Windows 10 - Page 1
Forum section: electronics / rf-microwave

author: fubar.gr
author_rank: Unknown
timestamp: June 25, 2016, 10:50:24 am
content: My laptop originally came with Windows 8.1 and HDsdr was working fine.But since I upgraded to Windows 10, HDSDR will crash at random intervals. The program won't completely crash, I can still navigate around, but the waterfall stops and there's no sound.I tried uninstalling and reinstalling everything, including the various drivers, but it didn't help.Has anybody encountered something similar? I tried SDR# but it cannot detect the RTL dongle.Is there any other (preferably free) SDR software compatible with Win 10?
ID this QRM/N - Page 1
Forum section: electronics / rf-microwave

author: djacobow
author_rank: Super Contributor
timestamp: June 19, 2016, 08:36:26 pm
content: Can anybody tell me what the source of this signal might be? I see it all over 20m, 61 kHz spacing. It's odd in that there are several tones spread out mostly over 1-1.5 kHz but there does not seem to be any modulation -- signal does no seem to vary except for maybe that third tone.This set of tones is the same for each 61 kHz image. It is not coming from my PSU (which is a Powerworx switcher) or anywhere in my shack; I checked with all power cut except battery.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 20, 2016, 03:02:08 am
content: Fluorescent light or SMPS with a ~kHz subharmonic or control loop oscillation??Tim

author: djacobow
author_rank: Super Contributor
timestamp: June 20, 2016, 02:13:13 pm
content: Thanks. Yeah, there was nothing powered IV the shack except the radio by battery, including lights, so I guess it's from a neighbor. (Shack is detached structure about 50 feet from my house, but closer to some neighbors backyard sheds.)Kind of a bummer.

author: Davegr
author_rank: Newbie
timestamp: June 23, 2016, 08:07:13 am
content: If you have a beam antenna you could get an idea where it's coming from.Dave
Locating sprogs in the shack - Page 1
Forum section: electronics / rf-microwave

author: voltz
author_rank: Frequent Contributor
timestamp: June 20, 2016, 11:20:21 am
content: Hi all,I thought i would share something that could be useful to those wanting to locate unwanted noise / spikes / sprogs in the shack.Its pretty simple and since there's been a few threads asking about it, I thought i would post this.Its basically using your receiver as a signal meter, tuned to the unwanted spike for max signal. This is the signal you want to locate and hopefully reduce. Connect a length of coax, anything will do, 50 ohm like RG58. Make a loop in the end around 1 to 2 inches wide with the inner exposed and shorted to shield to form a basic pickup loop. Now its simply a case of moving around and 'sniffing' for the source of the spike. Watching the S meter and listening to the audio at the same time.This method is quite effective and you should get to within an inch or two of the offending item. If the signal gets too high as you close in, simply use the attenuator. Once found, its a matter of fixing the issue. Usually, by better grounding, shielding or filtering.As an example, i recently had a major problem on 40m. With two big spikes both around S9+10. It sounded like 50hz buzzing so i guessed it was either lighting or computer monitor related. After thinking about it, i came up with the sniffer loop idea. Sniffer loops are not new, but i'd never heard of it being used as a sprog locator before in the shack. Using the receiver as a one point spectrum analyser as it were. Anyway after walking around with the loop, i located the source to a KVM switch which was connected to 3 PCs. All the PCs have ferrite filters in line, so they are good enough but the KVM was going crazy. I located the fault within minutes using the loop and was able to determine the KVM was in fact faulty. I then fixed the KVM by adding a proper ground link internally which connects the earths of the monitors. That fixed it - and the spikes were 100% gone.. Joy, i can hear 40m again.I hope this comes in handy, its cheap and easy to do.

author: ConKbot
author_rank: Super Contributor
timestamp: June 20, 2016, 02:11:11 pm
content: Yep, simple loops are great for sniffing. I had a potted widget fail at work, and with a loop around it going to a spec-an, I was able to see various oscillators working or not working, see which dc-dc converters were operating, and in an hour or so have a pretty confident cause of failure.The bnc to 5-way binding post adapters are pretty handy for making up a quick loop or dipole as needed for stuff like that.
Is this a microwave antenna in the top left corner? - Page 1
Forum section: electronics / rf-microwave

author: hlavac
author_rank: Frequent Contributor
timestamp: June 26, 2016, 03:58:25 pm
content: Check this image of the Skylake Intel CPU die:What do you think the rectangular feature in the upper left corner is?Actual length of the feature is about 3.54mm along the longer side...To me it looks awful lot like some sort of microwave antenna for around 43 GHz...What could it be?

author: Gribo
author_rank: Frequent Contributor
timestamp: June 26, 2016, 10:13:19 pm
content: Either that, or a protection against hacking of its internal fuses.
Listening at 18kHz with WebSDR - Page 1
Forum section: electronics / rf-microwave

author: Circlotron
author_rank: Super Contributor
timestamp: June 12, 2016, 01:00:08 am
content: Was listening to this sitehttp://websdr.ewi.utwente.nl:8901/m.htmlwith WebSDR iPad app and there are signals as low as 18kHz. Are they likely to be real transmitted signals or just spurious receiver artifacts?

author: uncle_bob
author_rank: Unknown
timestamp: June 12, 2016, 02:26:51 am
content: Quote from: Circlotron on June 12, 2016, 01:00:08 amHiThere are indeed real signals down there. Most of what you pick up is EMI from switching regulators and similar stuff.Bob

author: mark03
author_rank: Frequent Contributor
timestamp: June 13, 2016, 05:25:02 pm
content: VLF comms are really interesting. One of the US Navy's big transmitters is not far from me here in Seattle:https://en.wikipedia.org/wiki/Jim_Creek_Naval_Radio_StationWhen you're only dealing with the groundwave you can really push the Shannon limit by going low/slow, because the phase coherence of the channel is much greater than at shortwave frequencies. Here's a fun write-up of an amateur transatlantic communications experiment at 8971 Hz:http://www.w4dex.com/vlf/8971Hz/index.htmFor a test of the web SDR receiver, see if you can pick up the nearest VLF time-standards stations in the UK (MSF, 60 kHz) or Germany (DCF77, 77.5 kHz).
Open hardware near-field probes - Page 1
Forum section: electronics / rf-microwave

author: loxodes
author_rank: Contributor
timestamp: June 12, 2016, 07:55:43 pm
content: I've been lurking around these forums for a few weeks without posting, so I thought I'd share the first-order approximation of near field probes that I built recently:https://github.com/loxodes/em_probes/https://github.com/loxodes/em_probes/tree/master/dochas coupling measurements of the probes above microstrip, They aren't perfect, but seem to work up to about 6 GHz. So far they've been helpful at probing a board that I didn't put enough test points on.. I've never used or seen proper near-field probes before, I welcome any feedback on how to improve the design.If anyone wants to try replicating or modifying these, the layout assumes the OSH Park 4 layer stackup (http://docs.oshpark.com/services/four-layer/); y'all would need to modify the offset stripline for other stackups. The stripline was simulated with the MMTL open source 2.5D EM simulation software (https://sourceforge.net/projects/mmtl/files/tnt/1.2.2/), it could be helpful for tuning this to other board houses.The h-field probe design wasalmost copied frominspired by "Study of Magnetic Probes Used in EMI Measurements" (http://www.apemc2015.org/Proceeding/papers/1570059913.pdf)

author: daqq
author_rank: Super Contributor
timestamp: June 12, 2016, 08:52:54 pm
content: Nice work!
Question about portable scanners - Page 1
Forum section: electronics / rf-microwave

author: mehdi
author_rank: Regular Contributor
timestamp: June 09, 2016, 09:16:17 am
content: HiWhy portable scanners (or wide-range receivers) support frequencies up to 3.0 GHZ?What exists above 600MHZ which can be received with these receivers? (especially with a modulation such as AM/FM)I was thinking that these are useful for receiving amateur/police/emergency radios (HF up to 500MHZ) and can't come up with an explanation for the wide coverage.

author: Jeroen3
author_rank: Super Contributor
timestamp: June 09, 2016, 09:23:51 am
content: Lookup the frequency allocation table from your local telecom regulatory government body.You'll see that there are lot of frequencies occupied. You'll find naval and aviation communications, beacons and navigation, satellite communication, military and other things that you wouldn't have imagined required RF space.It most likely doesn't tell you anything about the details of the signal.

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 09, 2016, 06:32:45 pm
content: QuoteIn US the use the 800Mhz Band for Commercial Radios and 900Mhz Band is open for Radio Amateurs (what i remember).Here in Austria quite nobody use Commercial Radio only for Mass Transportation have there Freq.There are PMR446 Radios for 446 - 446.100

author: shawnb
author_rank: Contributor
timestamp: June 09, 2016, 07:16:07 pm
content: GHz receiving isn't usually practical for casual listening... it typically involves hunting for signals with tuned directional antennas, and the signals are often digitally modulated. But some people enjoy experimenting and trying to decode the digital, or just tracking satellites by receiving the signals or CW beacons.As Jeroen3 said, you can get a general sense for what is up there by looking at a frequency allocation table from your country (or the ITU). You may also be able to find a list of specific frequencies used in your area, since most likely anything you hear on UHF (300 Mhz+) is going to either be a local station or a satellite.The top end of the UHF band is 3 GHz, so a typical wide-band receiver IC is probably designed to operate up to there. If the circuit supports it, there isn't really a reason for a receiver manufacturer to artificially limit the coverage of the receiver. In other words, they aren't adding additional circuitry to receive GHz because there is useful demand for it, it just so happens that the chips used already support it.
Patch antenna on aluminium PCB - 10GHz - Page 1
Forum section: electronics / rf-microwave

author: MortenSkelmose
author_rank: Newbie
timestamp: June 07, 2016, 06:34:06 am
content: Hi everyone,I am planning to do a 10.5GHz patch antenna, but it seems that all cheap PCB manufactures almost only use "FR4" PCBs.As far as I can read, they don't perform well at 10GHz. Then i saw that "pcbway" have "Aluminium boards" .. do anyone have any experience with these for patch antennas?Or better yet - do anyone have any good suggestions as to "where to buy cheap pcb's usable for 10GHz patch antennas"? :-)Cheers!Morten

author: max-bit
author_rank: Frequent Contributor
timestamp: June 07, 2016, 07:48:19 am
content: At the frequency of 10 GHz only laminate teflon or ceramic. (Serch Rogers laminate etc exp. RO4003)Never based on FR4 or Aluma.

author: MortenSkelmose
author_rank: Newbie
timestamp: June 07, 2016, 10:42:08 am
content: Thanks max-bit!Cheers!Morten

author: 1design
author_rank: Regular Contributor
timestamp: June 07, 2016, 12:17:05 pm
content: Try usingTSM-DS3, very good up to 90GHz and much cheaper that 95% of the things Rogers have that compare.BR

author: ovnr
author_rank: Frequent Contributor
timestamp: June 07, 2016, 12:21:02 pm
content: The aluminium boards are MCPCBs, like you would find on "star"-type LEDs. They consist of an aluminium sheet coated in a dielectric, with a layer of copper on top. This obviously means they're not suitable for making an antenna.An alumina substrate is a very different thing.

author: MortenSkelmose
author_rank: Newbie
timestamp: June 09, 2016, 07:24:53 am
content: Thanks everyone for your advice!I am having a hard time finding a cheap prototype manufacturer for these kind of PCB's - do you know any good ones?Cheers!Morten
SDRPlay erroneous tones. SDR Play - Page 1
Forum section: electronics / rf-microwave

author: AG6AV
author_rank: Contributor
timestamp: June 06, 2016, 04:53:59 am
content: Hello,I bought a SDRPlay. It is a Software Defined Radio (SDR). I am using the SDRPlay with HDSDR software. I noticed that the receiver seems to receive many erroneous tones.The SDRPlay is a wide band receiver. Therefore, my first thought was that the receiver may be overloaded. So, I connected the SDR to a Mini-Circuits SMA 50 ohm load. This helped. Then I added some ferrite to the USB cable. This helped a little.I would expect a receiver connected to a high quality dummy load to receive nothing. For example, my HP 8560E reports no tones when terminated into 50 ohms. However, the SDRPlay reports many tones.Has anyone else made this observation? Anyone have a solution?Nathan

author: 9aplus
author_rank: Regular Contributor
timestamp: June 06, 2016, 08:16:38 pm
content: You may start with Al box... keep SMA ground like onlycontact to box and keep your SW gain low and/or attenuators on high.Unit performs great on HF plus 50 & 70 MHz and delay may be useful to hearimportant parts of QSO twice...GL 73

author: djacobow
author_rank: Super Contributor
timestamp: June 07, 2016, 03:06:07 am
content: I have an SDRplay. It works pretty well, but has regularly spaced birdies from DC to daylight. They are very apparent when the gain is set to -45dB or higher, if I remember correctly. I assumed they were from nearby strong overload but never got to the bottom of it. But was able to receive plenty at -50dB or so and they didn't bother me too much.Anyway, I just got my first proper HF rig, and it doesn't have this issue, but I think it's easier to filter for the Ham bands than it is for a wideband device like the SDRplay which had to cover a lot of range with only a few prefilters.You should get on the SDRplay group on Facebook and ask there. People will help, and I believe the designer hangs out there and chimes in.

author: AG6AV
author_rank: Contributor
timestamp: June 07, 2016, 06:36:18 am
content: Yeah,I been doing more research. Many people are observing better performance with shielding. Apparently, the RF front end is not shielded enough, and the USB port is not decoupled enough. I am not sure what the people at SDRPlay were thinking when they utilized plastic shielding. I think its a shame that SDRPlay put a lot of effort into a product, but ruined it by cutting corners. Also, be warned of the many favorable reviews of this product. All the reviews I read did not mention the serious erroneous tones produced. In other words, this receiver is so good that it receives signals that don't exist. Therefore, I put this device in the toy category.
Simple SDR transmitter? - Page 1
Forum section: electronics / rf-microwave

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: June 01, 2016, 01:19:54 am
content: Iv'e been searching the internet for an SDR transmitter project but surprisingly I haven't found one. I was thinking that all you really need to do is use GNU radio to build the modulated signal and then play it out you sound card in to a mixer controlled by a DDS or VCO straight in to an amplifier/antenna. Could it really be this simple. I would assume if it was people would be making and selling little circuits like these everywhere, to pair with an RTL dongle.Kind off topic but how does the pi tx software do its thing without hardware to generate the carrier wave? It says it can transmit up to 700mhz but I know the pi cant flip pins that quick?

author: Earendil
author_rank: Regular Contributor
timestamp: June 01, 2016, 06:47:22 am
content: Yes, theoretically that's it. However I'm not convinced that it's practical to create an add-on for SDRs that's not designed to be used as a transmitter. Usually these are single (or 2) chip solutions. I don't expect that you can reuse many things from the circuit. Probably you'll be developing a complete transmitter.HackRF can transmit btw. I'm pretty sure that some high-end SDRs can transmit too, but I haven't used any of them.

author: Gecko
author_rank: Contributor
timestamp: June 06, 2016, 03:34:16 pm
content: Have you seen the red pitaya SDR apps?The frequency region (0..30MHz or so) you can use it on is very interesting for Ham radio I think. (At least in my opinion).

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: June 06, 2016, 07:45:26 pm
content: ya but that stuff is way to much!!! I mean buy a 10 dollar dongle, buy or make an upconverter/downconverter and you get DC-4ghz range. Then use GNU radio to modulate signal send that out your sound card in to a two dollar mini cirucits ade-1 mixer and mix it with a mini circuits POS 150 VCO and you are able to broadcast in to the whole 2m band along with the airline and commercial FM bands. You could use a DDS with a PLL to get a whole 1-4ghz transmit.Basically it would be like the hack-rf for a ton less money. Adding LNA's and preselecting would probably give you a signal as clean as an airspy. you could build this for under 70 dollars.

author: 1design
author_rank: Regular Contributor
timestamp: June 07, 2016, 01:14:11 am
content: Do it!

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: June 07, 2016, 06:34:32 am
content: Im on top of it! Uts my life right now! There opening a makerspace near me im hoping to meet a like minded partner to help with software.... the ham club near me sucks its a 2m repeater club and no one knows what a toroid is...
Active Loop Antenna Power Feed - Page 1
Forum section: electronics / rf-microwave

author: seriouscoinage
author_rank: Contributor
timestamp: June 19, 2016, 02:38:51 pm
content: I want to build this loop antenna for shortwave SDR listening:http://www.lz1aq.signacor.com/docs/wsml/wideband-active-sm-loop-antenna.htm. As described, it uses two twisted pairs of an Ethernet cable for the output signal and power. I am a bit confused about exactly what is happening with the power and output signal in the circuit. The power supply appears to be floating relative to the output signal, and flows through a current balun, which I believe is there to stop common-mode currents from flowing. What bad things would happen if common-mode current did flow in the power supply leads? Does the power supply need to be floating? The output signal is coupled out of a transformer (L4, L5, L6) resulting in a balanced signal, which goes through another current balun to convert it to an unbalanced signal referenced to ground. Why is this necessary? Couldn't you just attach ground to one end of L6 and the other end to the other twisted pair?When I build this circuit, I would like to use a coaxial cable to bring power to the antenna and take the output signal out, using a DC bias network. Would this result in worse performance than the arrangement shown in the circuit as it is?

author: SeanB
author_rank: Super Contributor
timestamp: June 19, 2016, 03:45:22 pm
content: You can convert it to use coax with power up the coax, and still have reasonable results. Simply use a 100nF capacitor in series with L6 to isolate the DC feed from the output, and connect the 13V supply wire to the centre core instead. You still need the balun on power, but connect the -13V5 side to the shield instead.Bottom end you will need to feed in the power using another balun, basically replicating the input side in reverse, and feeding in your 12-15VDC supply to the new inductor, and connecting the ground lead to the shield. 100nF capacitor to isolate the DC from the antenna input and you are done.
FT-897 CAT Fuse Mod - Page 1
Forum section: electronics / rf-microwave

author: xrunner
author_rank: Super Contributor
timestamp: June 06, 2016, 12:06:38 pm
content: A ham friend of mine wanted me to do a mod for him to his FT-897. Seems that there is a 3.15A SMD fuse that serves 13.8V to the CAT connector. He can't work on SMD devices (too small) and he wanted to be able to replace the fuse again if it blows. So he wanted to install a replaceable fuse. I offered to replace the SMD fuse but he really wanted this mod installed. I agree it seems dumb to have an SMD fuse that's so hard for the average person to replace.This mod has been done before by people, so I simply duplicated it on his radio. The replaceable fuse is simply tacked onto the pads of the SMD fuse. Now he's happy.
Transmit many LVDS clock signals across multiple boards. - Page 1
Forum section: electronics / rf-microwave

author: msngupta
author_rank: Contributor
timestamp: June 03, 2016, 03:25:17 pm
content: Hi,I am designing a system where I need to many transmit LVDS (say C+ and C-) clock signals (around 1GHz) across different boards. The solution I see in many reference circuits is to use 2 SMA coaxial cables (one for each differential signal). I find this rather costly and clumsy (4 SMA connectors and 2 cables for one signal). How can I transmit the LVDS signal using one cable?I was thinking of 2 ways to resolve this1) Converting the differential signal using balun transformers (on both receiver and transmitter ends). Convert differential to single ended and then back to differential.2) One more solution I was thinking (not sure whether this is correct) is to connect C+ to core and C- to the shield of the coaxial cable. Can this be done ?Can someone suggest which solution should I go for? Or any other better cost effective solution where I can properly transmit the signal using a single cable?Thanks,Sainath.

author: tggzzz
author_rank: Super Contributor
timestamp: June 03, 2016, 03:44:15 pm
content: Google for controlled impedance connectors and, if necessary, microstrip/stripline/coplanar waveguide.Differential signalling better than single-ended from the point of view of noise immunity and EMI/EMC.

author: dmills
author_rank: Super Contributor
timestamp: June 03, 2016, 05:28:38 pm
content: I dont know about 1GHz, but sata cables and connectors are one of my favorite things for LVDS between boards.If you want something much less pony, Samtec have what you need for up to way more then 1Ghz.Regards, Dan.
What circa RG-58 size 50 Ohm cable is available in Teflon? - Page 1
Forum section: electronics / rf-microwave

author: Chris Wilson
author_rank: Super Contributor
timestamp: June 05, 2016, 09:51:08 am
content: I have some of the tiny diameter Teflon / PTFE insulated 50 Ohm co-ax, but need some in circa rg-58 diameter, anyone know what's available easily, and its designation please? Thank you.

author: DonRon
author_rank: Regular Contributor
timestamp: June 05, 2016, 05:10:11 pm
content: Hi Chris,have a look at this onehttp://www.kabel-kusch.de/Koaxkabel/PTFE-Koax/RG400/rg-400.htmPrices can be found herehttp://www.kabel-kusch.de/Preisliste/preisliste-kabel.htmCheers,Ronald

author: Chris Wilson
author_rank: Super Contributor
timestamp: June 06, 2016, 07:54:01 am
content: Excellent, many thanks Ronald, much appreciated.
BNC Connectors - Page 1
Forum section: electronics / rf-microwave

author: remoteremote
author_rank: Newbie
timestamp: June 01, 2016, 02:01:22 am
content: The Bayonet-Neil-Concealment, or BNC connector drives its name from the surnames of the type N inventor Paul Neil and type C inventor Carl Concealment-the “bayonet” refers to the style of locking mechanism employed by this series.Developed in the late 1940s, the BNC is basically a scaled down erosion of the Type C, and its compact design, easy quickly connect / disconnect coupling and economical manufacturing cost have all helped to ensure that it is consistently applied I radio equipment and electron tube instrument field and join the coaxial cable of the radio frequency extensively.Series BNC RF coaxial connectors have the bayonet structure coupling mating and developed according to MIL-C-39012/16-24. This series connectors can be interchangeable with the same-type connectors of abroad, engaged and disengaged rapidly, used to connect coaxial cables in radio equipment and instruments.

author: xrunner
author_rank: Super Contributor
timestamp: June 01, 2016, 02:25:25 am
content: I've seen this all before ...

author: remoteremote
author_rank: Newbie
timestamp: June 01, 2016, 02:48:27 am
content: Quote from: xrunner on June 01, 2016, 02:25:25 amThank you. And this kind BNC connectors are the most prevailing kind of all kind RF connectors.

author: Simon
author_rank: Unknown
timestamp: June 01, 2016, 05:50:09 am
content: Quote from: remoteremote on June 01, 2016, 02:01:22 amerosion ? nice chinglish

author: tautech
author_rank: Super Contributor
timestamp: June 01, 2016, 07:26:37 am
content: Thanks for sharing, there will be members that aren't aware of the BNC connectors history.BTWWelcome to the forum.

author: Ice-Tea
author_rank: Super Contributor
timestamp: June 01, 2016, 08:42:26 am
content: Quote from: tautech on June 01, 2016, 07:26:37 amQuick sanity check: you're aware that they only posted that to peddle the link in their signature, right?

author: tautech
author_rank: Super Contributor
timestamp: June 01, 2016, 09:20:12 am
content: Quote from: Ice-Tea on June 01, 2016, 08:42:26 amAnd if they can provide another source of componentry for members, what's wrong with that.I have no affiliation with the OP.

author: rolycat
author_rank: Super Contributor
timestamp: June 01, 2016, 09:21:56 am
content: If you are going to shill for your company with a 'history' of some of the connectors you sell, it would be courteous to at least get the names of the inventors for which they are named correct. They were Paul Neill and Carl Concelman, not "Neil" and "Concealment".

author: Richard Head
author_rank: Frequent Contributor
timestamp: June 01, 2016, 09:24:23 am
content: The Bayonet-Neil-Concealment.How does Concelman get to Concealment?

author: Earendil
author_rank: Regular Contributor
timestamp: June 01, 2016, 11:31:05 am
content: Quote from: Richard Head on June 01, 2016, 09:24:23 amWe won't tell you. It's a trade secret.

author: Simon
author_rank: Unknown
timestamp: June 03, 2016, 05:09:12 pm
content: Quote from: Earendil on June 01, 2016, 11:31:05 amWell they can't as I banned them