Testing a new 1:9 Unun I plan to use for a permanent non-resonant multiband vertical

1/2)
A fellow #hamradio operator and electronics enthusiast brought me a vintage X-Band power sensor, thanks OZ1ETE

It has a super sensitive NTC Thermistor, a tiny spherical bead, encapsulated inside a small glass tube. It’s by far the most sensitive Thermistor I’ve ever seen, just holding your hand in front of the waveguide flange, not actually covering it, will make it change slightly.
#rfengineer #rfengineering #electronics #testandmeasurement #sensorsunday

Always wanted a portable directional to spot emitters at higher frequencies - decided to try this one.

My test ceiling is 4GHz, but at least that far, it seems OK I doubt it’ll go all the way to 10GHz as advertised because of the (FR4?) PCB Material.

It always amuses me, how violently antennas like this collapse at the lower frequencies - suddenly the size no longer accommodates the input wavelength and they simply stop being an antenna

For some reason, these logperiodic (LPDA) antennas always come with a SMA connector at the tip - that’s completely wrong: you need to solder a semirigid coax all the way down the centerline and feed it from there. The PCB was even prepared for it - go figure

Anyway, now fixed, tested, and ready to go signal hunting

I’ve been looking for an antenna for a permanent #meshtastic node in my attic and I found this one, along with 5m RF200 low-loss cable.

I know that this setup will most likely render me ‘excommunicado’ in the #meshtasticcommunity: “thou shalt always install thy node right below the antenna!”, but here’s the thing: I want to experiment with different hardware, I want to do some interference measurements at night (ever heard about the ‘Mammotion’ lawnmower which illegally jams 868MHz?) , AND I have a powerful 2m/70cm transmitter close to it, and I don’t want EMI issues on a sensitive 5V line.

Besides, the antenna has 3dBi gain and I measured the cable loss to 1.4dB at 868MHz, so given its better location, the numbers still come out positive

See that dip near 145MHz btw.? Need to do a test to see how much signal it’ll pick up from my VHF rig - don’t want to damage my LoRa module

#lorawan #electronicsengineering #rfengineering #rfengineer #hamradio hamr #testandmeasurement

Hackaday Links: March 31, 2024 - Battlelines are being drawn in Canada over the lowly Flipper Zero, a device seen b... - https://hackaday.com/2024/03/31/hackaday-links-march-31-2024/ #reverseengineering #hackadaycolumns #stencilprinting #specialeffects #hackadaylinks #rfengineering #flipperzero #rollingcode #solderpaste #steadicam #antenna #slider #canada #cloud #movie #radio #solar #theft #car #iot #sfx #smd

It’s #signalsaturday and I’m continuing the #CuteGen test series by looking a bit at the harmonics How clean is it?

Starting at 1kHz I’m using my #Siglent #oscilloscopes powerful FFT functionality and with harmonics >60dB down, this little thing really is a decent audio function generator.

I then moved to the spectrum analyzer and did some tests at (much) higher frequencies. Only included 10 and 30MHz here, but pattern is clear: harmonics are generally nicely attenuated, more than 60dB, although at the high end, it’s not quite that much, more like 50dB and a sub-carrier spur appeared as well. Makes me wonder how well the 60MHz version performs

#testandmeasurement #rfengineering #rfengineer #electronics #electronicsengineering #uni-t #hamradio #hamr

It’s #signalsaturday and here’s a mystery SW signal I picked up at my friends place

5-15s bursts, centered at about 1.5MHz, total bandwidth 2MHz. Starts with carriers 4kHz apart, then spreads out to a noise field, which then goes back to single carriers.

Mostly present weekdays, signal is ‘local’ ie not observed on SDRs further away. No apparent timing of the bursts, occurrence seems ‘random’.

Either it’s 1) alien (joke) or 2) Some communications channel or 3) some kind of VFD
#hamradio #rfengineering #rfengineer #thetruthisoutthere