My Mini SDR Farm v1.1

I recently posted a picture on my twitter account showing my little Raspberry Pi SDR ‘Farm’ and it was one of the most liked pictures I have ever posted(!). I wanted to expand on the info from twitter as there seemed to be a high rate of interest.

Antenna & Coax

My antenna is a diamond D130J Discone, with a ~25m coax run of LMR400 from the roof of my second storey on my suburban townhouse. https://www.diamondantenna.net/d130j.html

LNA

I use a 12v Low Noise Amplifier (LNA) from the roof coax before it gets to the SDRs, I have chosen to do this in the shack in the event I want to repurpose the discone as I only have one other dual band antenna on the roof. This is my LNA https://www.ebay.com.au/itm/LNA-RF-Broadband-Amplifier-Module-Signal-Booster-1-3000MHz-2-4G-20dB-HF-VHF-UHF/303138247368?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Power Divider

To split out the feed from the antenna and LNA, I found this wide band power splitter on eBay. https://www.ebay.com.au/itm/MECA-RF-Power-Divider-0-8-2GHz-SMA/181676778993?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

SDRs

I have been dudded before by fake USB RTLSDRs, so now I only buy from a known source, and this guy is THE business!

https://www.ebay.com.au/itm/RTL-SDR-Blog-V3-RTL2832U-1PPM-TCXO-HF-BiasT-SMA-Software-Defined-Radio/272411458376?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Filter

The only filter in the while system is a 1090Mhz filter on the ADS-B receiver to filter out any other ‘trash’ signals. I have seen a large improvement using this one. http://www.ebay.com.au/itm/1090MHz-ADS-B-Aeronautical-Bandwidth-14MHz-Band-pass-Filter-IL-4dB-SG-/113757709997?hash=item1a7c7ce6ad

Raspberry Pis

The processing power for each of the streams or data sources is the Raspberry Pi 3B+, yes the 4 is out but I still really love the 3b+ for all my work. Again a reputable source is important. In Australia I usually use Core Electronic, however Amazon Australia has been just as fast and cheap when Core is out of stock.

Things they are used for at my place

ADS-B

This is one of my favourite projects at my house at the moment. Frustrated by the censorship shown by Flight Radar 24, filtering out flights at the request of rich business owners while the aircraft is still pinging away transmitting data is crap. If they, and others such as military aircraft, are transmitting, I want the data. So I set up my own downlink station. This is the preferred model for me: https://flightaware.com/adsb/piaware/install

Streaming Aviation Audio

I am currently testing the streaming of AM VHF audio of Canberra Airport Departures using Broadcastify. https://wiki.radioreference.com/index.php/Raspberry_Pi_RTL-SDR_Broadcastify is the instructions I used. And here is the link to the stream https://www.broadcastify.com/listen/feed/31146. It is still very much in the test phase.

VHF WSPR reception

Previously I was using my FT817 and an audio interface to monitor 2m VHF WSPR transmissions from around the region. I co no longer dedicate that radio to the job so looked to the raspberry pi and RTLSDR to pick up the slack. This is the model I used https://github.com/Guenael/rtlsdr-wsprd