VHF/UHF capabilities added to Super Stations #1 & #3

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KA1GJU
Posts: 263
Joined: Tue Aug 11, 2020 2:16 pm

VHF/UHF capabilities added to Super Stations #1 & #3

#1

Unread post by KA1GJU »

Today I tried to add VHF/UHF capabilities to Super Station #4, but the Stridesburg HF Multicoupler that feeds all four SDR's from one antenna feedline doesn't pass VHF/UHF signals without a +28dB loss. The plan was to place a diplexer in front of the multicoupler to allow both the HF antenna and the newly installed 2m/70cm vertical feed the 4 SDRs. A quick test proved the losses are too excessive, so the diplexer was placed in my house where Super Stations #1 and #3 reside. A simple PL-259/SO-239 Tee is used to share the antenna, so there is a 3.5dB (~1/2 S-unit) on VHF/UHF, but it is what it is. If I didn't tell you, you probably wouldn't know it! Station #1 HF antenna is shared in the same way between the two SDR's, and I haven't fielded any complaints yet.

So... if you are in the need for VHF/UHF listening in SE NH (FN42mw), in order of best server to an OK server:

Super Station #4 Airspy HF+ (dual port) and Airspy R1 on an X-200 up ~65' AGL on tower on a 243' MSL hill, so antenna is at ~308'MSL.

Super Station #3 Airspy HF+ (dual port) via a diplexer on a Diamond X-200 in attic of house at ~ 250'MSL
Super Station #1 Airspy Discovery on same diplexer and antenna above

Attached images show the difference in signals (and QRM) via the Airspy HF 2 port on the two different antennas/locations, while monitoring 132.050MHz, Pease Tradeport ATIS at 13.5miles to the NNE. The clear winner is Super Station #4 due to it's height on a tower, almost line of sight if it wasn't for the tall pine trees 500' north of me.

I have a suspicion that the ADSB server running in attic on a Raspberry Pi via Ethernet connection is causing the QRM on Station #1 & #3 VHF since the antenna is ~25 feet away. You can clearly see how weak the ATIS is and the numerous vertical QRM lines.


73 Kriss KA1GJU
Home of the ever expanding Super Stations in NH, USA
Attachments
KPSM_ATIS_Station#4.png
KPSM_ATIS_Station#3.png
73 Kriss KA1GJU Home of the KA1GJU Super Station SDRC Servers in NH, USA (FN42mw & FN43na)

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N6ATC
Posts: 50
Joined: Sat Aug 08, 2020 6:25 pm

Re: VHF/UHF capabilities added to Super Stations #1 & #3

#2

Unread post by N6ATC »

Kriss:

Thanks for the update. Nice VHF signals on Super Station #4. I agree, there is a lot more QRM in the attic. I would lose sleep at night wondering how to choke off that noise. But, that's just my inherent air traffic controller personality CDO kicking in. (CDO is the same thing as OCD, except that the letters are now in the correct order.) :=)

You've got a very nice setup there. Your servers are in my web-SDR speed dial list!

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