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  • Although, connecting PE directly to DC- might make things also worse, since there might be noise on PE. I have the DC input now filtered like this, which seems to be blocking any PSU noise. https://forum.kiwisdr.com/uploads/278/OX1Z37O77HGG.png
  • I did more tests with the Apple 20W supply. In the end I figured out how to get rid of the 100 kHz noise, but I don't know why that works. Maybe someone can give me a hint. The antenna is a DC isolated inverted-L, with about 1000m worth of ground ra…
  • Ok that's interesting. It happens on all 3 of my kiwis, but they run debian 10.13. The "good" count even drops to zero from time to time. https://forum.kiwisdr.com/uploads/749/D8B1HQYOBXLS.png
  • I had a few QSOs with the Olivia mode. It's been a while since, but there was regular activity between 14100 and 14150 kHz.
  • I haven't connected the Apple charger to the kiwi yet. But I charged my phone with it, in the same room where the kiwis are and it is generating a bit noise in the spectrum from 100 to 200 kHz. I guess this is from the AC side. The DC side is too sh…
  • Linear PSUs are not expensive, but electricity is ;) My current linear PSU has an efficiency of 37%, the Apple PSU has 85%.
  • Thank you for sharing your experience Peter, I'll give the Apple PSU a try.
  • I have also tried several (about 10?) SMPS and one problem was always conducted noise on the primary side (230V). It would be interesting to know if the Apple power supplies do also have sufficient filtering on that side. I feel confident to build f…
  • Well it is read once, so, you would have to define it every time before you read the variable. Or you could do: get_attenuation() { jq -r '.init.rf_attn' kiwi.json } attenuation=$(get_attenuation) One query requires 33 ms CPU time on my BBG, So yo…
  • Where do you need that variable? In bash you could do something like attenuation=`jq '.init.rf_attn' kiwi.json` # echo $attenuation 4.5
  • Alternatively, you could use the S-Meter/RSSI readings from kiwirecorder   --S-meter=S_METER, --s-meter=S_METER             Report S-meter (RSSI) value after S_METER number of             averages. S_METER=0 does no averaging and reports each      …
  • @IK8SUT jks wrote earlier, that the plan was to sell the Kiwi2 bundled with a BBB. But I do have also a spare BBB waiting for a Kiwi board :D
    in KiwiSDR 2 Comment by HB9TMC October 15
  • Thank you for sharing the measurements. Maybe it would be also interesting if you could do comparisons of the sensitivity across the frequencies. For example feeding a -120 dBm signal to the antenna input and measuring the audio SNR.
  • Ok thanks
  • Works, thank you!
  • Does the kiwi boot if the GPSDO is connected but with its clock output disabled? It could be RFI to the BBG. You could try to reduce the signal level from the GPSDO. Or add a 50(?) Ohm load across J5 on the kiwi.
  • @studentkra Yes there is harmonics from the SMPS radiated on VHF. They only start to show up above about 40 MHz. I think it is radiated from the kiwis antenna cable. I do receive them too on my 6m antenna very weak, which is about 10 meters away. I…
  • If I understand studentkra's issue corretly, the problem is radiated interference from the kiwi to a different receiver? I can measure the SMPS harmonic at 65 MHz from the kiwi with a H-field probe about 5-6 meter along the antenna coax. But that s…
  • It's probably a lot of work, but you could try to debug, using strace -p to see what kiwid does when you access the web interface.
  • Glad you could fit it there, thanks. I wonder if it would be useful to add a choke in series to the static drain resistors. Just to make sure there is really minimal common mode current. But 100k is probably enough.
    in KiwiSDR 2 Comment by HB9TMC August 17
  • I got the resistor arrays replaced and everything is now as it should be. Also the noise floor without antenna connected, which was too low with the dysfunctional D3/D4.
  • Yes, field strengths are high on VLF/LF, but most broadband antennas are either severely mismatched or have low gain in this frequency range. For example the noise floor on my 50m endfed wire antenna is just -150 dBm/Hz at 50 Ohm on the 136 kHz ham …
    in KiwiSDR 2 Comment by HB9TMC August 15
  • I use every tenth of a dB in that frequency range, that's why I mention it. But agreed, CM rejection isn't as good, particularly on the higher frequencies. Here's a rough measurement of my FTB-6-1 https://forum.kiwisdr.com/uploads/886/76S2I9NPUX8U.p…
    in KiwiSDR 2 Comment by HB9TMC August 15
  • ADT-1-6 has 0.08 dB at 50 kHz. I think it is better suited for the kiwi than the ADT-1-1 and it has the same footprint. I think there was ambiguity whether they are galvanically isolated, but mine are. (And from the datasheet they are as well)
    in KiwiSDR 2 Comment by HB9TMC August 15
  • https://forum.kiwisdr.com/index.php?p=/discussion/comment/14238#Comment_14238 "I don't know about the ADT1-1+ but I do know that the T1-6T+, spec'd to go lower in frequency is NOT a good idea. Rather than being a simple flux coupled transformer…
  • Does anybody have insertion loss measurements for the ADT1-1+ at VLF/LF range (10-150 kHz), the specs in the datasheet are only for above 150 kHz and it seems to be increasing towards the lower end.
    in KiwiSDR 2 Comment by HB9TMC August 14
  • Good to hear! Which input transformer do you use? According to the data sheet, the PE4312 has a lower frequency limit of 1 MHz. What are the implications for frequencies below 1 MHz? Maybe I read it over, but I can't find anything about it in the da…
    in KiwiSDR 2 Comment by HB9TMC August 14
  • Maybe the logs give a clue why kiwid crashed /var/log/messages and the "dmesg" command.
  • In that case, the coax shield was positive. If the bias-T's power supply has negative connected to mains earth, there could have been current running through the kiwis GND. I would check the voltages too. (Also since the AI-64 might draw more power …
  • It's the resistor array. The resistors for D3/D4 are open. I don't know how i missed that before. And I don't know how that could happen. Considering the circumstrances, the FPGA input might be damaged as well. Its input resistance is not suspicious…