VHF Groundstation setup report (further optimizations)

SatNOGS Hardware
1

Hi!

During the weekend i successfully optimized my VHF Groundstation. I want to share some of the steps i went through.

I use a Raspberry PI3B+ using the Ethernet connection. SDR is a NooElec NeSDR at highest gain. In front 15 meters Ultracell-7 cable and a NooElec Bandstopfilter.

  1. Antenna: Wimo Turnstile TA-1 @ 11m above ground.

After installing this antenna last week i thought, lay back and enjoy the results. I did several mistakes.

a) The wiring inside the antenna is that the cable shield and the centre wire are connected. (I asked Wimo and they confirmed that).
So for instance if you made a mistake during soldering the connector it is hard to find the error. I double checked this an went to another connector, where i was sure, everything is fine.

b) The manual says: "Stay away at least 2-Meters from metallic stuff.

Snapseed

This was my first installation resulting in poor results.

I removed everything below the TA-1 and the results got much better.

  1. Heatmap / rtl_power

The breakthrough at least was using rtl_power.

I followed the instructions here:

Do i need a filter? / Heatmap / rt_power

I followed option one and did all on the RPi.

So this resulted in the following pictures:

a) Before:

scan1

and

b) After

scan4

At the end the culprit was the power supply at the RPi.

Changing to wifi, switching HDMI off, did not show noticeable changes.

Good luck and 73 Oliver

DL6KBG (VHF)

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by the way. There’s still some sort of switching noise (dashes on the right picture half) left. I guess it is from the power supply of the pasture fence in the neighbourhood.

So that needs further investigation. I get almost clear decodes from all sorts of telemetry but you can see the noise in the observations waterfalls.

73 Oliver DL6KBG

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I think i am happy for now.

You may also try use a shielded or a non-shield cat/ethernet cable.

My remaining noise is from the fence nearby, i am sure. In a few weeks the horses will have gone. So i have to check that later.

68 frames of on FOX1-D pass is not so bad :slight_smile:

FOX1-D

Good luck and 73 Oliver

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Nice observation and station! Glad you are part of this community!

This noise hunting has been proved the most difficult part of setting up a station. Thanks for the analysis on your issues, it could be very helpful for others with similar ones. :slight_smile:

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Tnx dr @fredy. I have to wait until the horses move to the next ground :grinning:

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I have posted several times in the past about the noise created by Cheap and nasty switched mode power-supplies, noise generated by Raspberry Pis and USB cables. I had S9 noise on VHF as heard/seen by my FT-817. Now the noise is all gone.

I made an analog 5V power-supply using a 3 terminal 5A regulator. A 12V computer fan running on 5V is silent and keeps the regulator, the RPis and the RTL-SDRs cool. The SDRs used to get quite warm running 24/7.
All my RPis are in aluminum earthed cases. The RTL-SDRs are grounded to the RPi cases (some RTL-SDRs cases are not grounded properly)
No USB cables
I switched off my 1Watt WSPR beacon because it is not clean despite 2 low pass filters on 10MHz.
See for yourself station ID-568 & 724. The third RPi collects transponder data from aircraft on 1090MHz

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