Saturday, 6 October 2012

APRS on 28.800

Today I did a test using APRS on 28.800 MHz FM from the car using a Springer CB antenna (which was actually resonant around 28.800 without cutting anything off).
The background noise in an 8KHz bandwidth (for narrow FM) was around -99dBm all day. This is very high compared to what you would get on VHF.
The FT8900 in the car was set to 20 watts like I usually do on VHF APRS.
Receive antenna was the Antron 99 27MHz vertical on the back of the house.
I drove through Dalton but no APRS data was received from there. At point A, I was receiving my mobile signal at -91dBm over a 7km path (with 70 metres of obstruction) but this was too low to get any data through. At points B (3.5km) and C (2.5km), the signal was around -73dB which is 50uV (the standard S9 signal).
To get the signal readings, I transmitted on the mobile radio whilst watching my PC desktop remotely via Team Viewer.
The APRS tracker device transmits every 110 seconds, but 1 in 6 messages do not contain any location coordinates (it just transmits "Simon, Barrow-In-Furness") so there are some places on the map where there was data received but nothing displayed. One of them is around the Sowerby Woods area on Park Road. I've checked the raw packets and nothing at all was received while I was in Dalton though.