SDRPlay feedpoint receiver project for 2m/70cm

After removing all equipment from the remote site and re-assembling what could be accommodated at home, it became evident that I had some spare items which could form the basis of a new project.

Recent discussions with Bri, G0MJI, regarding UHF operating generated interest in developing an antenna project using a receiver as close to the feed point as possible to minimise feed losses, something that could be useful at 70cm and above.

The USB extension cable from an SDR could take the place of a coax run, which would also be cost beneficial as low loss coax has become increasingly expensive. If successful, the concept could be applied in future to the 23 cm band where it could yield greater benefits.

The equipment comprised of the following, most of which I already had available:

 

Assembling parts
Testing SDR fit inside the enclosure
Completed, ready for installation
Installed in temporary position
The USB cable was connected to a remote computer, and SDR Server (V3) was used to send data over the network to be viewed by SDR Console V3.
Tests were conducted with satellite downlink signals and terrestrial FT8 on the 70cm band:
CW Ident of VZLUSAT1 (QB50 CZ02)
 NBFM voice on SAUDISAT-1c (SO50)

 

G0MJI (IO83NI) transmitting FT8 (Distance: 47 km)
The project concluded successfully, with qualifications. The SDRPlay RSP1 does not have a TCXO, so there will be challenges in the UHF range. This could be mitigated by replacing the RSP1 with the RSP1A which has a 0.5 ppm TCXO.  The satellite signals were weak but usable – both passes were of low elevation – a good preamp would probably improve things markedly.
Overall, the ability to independently tune around the 2m/70cm bands with an SDR is a very useful additional capability installed at next to no cost.

 

Remote site issues and 2m FT8

The recent inclement weather in the UK caused a number of issues at the remote site which hosts the KiwiSDRs and other receivers.

I had originally listed here a number of issues which had to be overcome, such as the breaking of the 6m/4m mast in the wind, but recent events have made these points redundant.

I have taken down and dismantled the remote site antenna and all receivers due to the termination of the operating agreement by the site owner. The search for a new site will begin shortly.

The 2m antenna has been relocated to the home location (IO83LS).  The breaking of the mast was fortuitous as I was not happy with the performance of the antenna at the remote site and having retreived it safely I now had an opportunity to test it in a different environment. It was mounted on a pole about 3m above the ground, just below the 6/4m duoband Yagi.

Temporary VHF setup, 2m 4 Element Quad, 4/4 Element 6/4m Yagi

After reading the good results that G3XBM was getting on his blog, I tuned to 144.174 MHz,  FT8 mode, using WSJT-X 1.9 rc2.

F1DRN received QRB 1253 Km on 2m FT8

Given the modest antenna – a 4 Element Quad at 3m AGL, no receive preamp or power amp, and an IC7100 transceiver there is a surprising amount to be heard. I’m pleased I gave it a chance.

Aircraft scatter is common, and sometimes helpful:

GM4JJJ on 2m FT8, with Aircraft Scatter