/Mobile testing with DVB-T - 70cms
Posted: Sat Apr 10, 2021 4:41 pm
In eager anticipation of trying out the multi-path-'proofness' of DVB-T I took my gear /M today. Transmitting a 'Test signal' from my home station, I drove around locally looking at the received signals. It would be great if the bouncing bubbles 'CQ' could be available again in PD4- much easier to know if its live video or not. I got reasonable coverage, home station running about 1 watt to my triband colinear and a 70cms mag-mount co-linear on the car roof, Knucker and PD4 on the seat next to me. Having tried RX, this afternoon I headed over to Martin G4FKK. En-route I stopped off at my local highspot (Shirley Hills, Croydon) and by a fortuitous combination of finger trouble got into GB3HV on less than 1 watt of DVB-S. Despite it being a high spot, no phone coverage at all? Onward to Martins QTH at which point I realised that I had been transmitting DVB-S for the last three miles anyway. Having established lock outside his house on DVB-T, I proceeded to drive around the locality. We found that lock was lost if I was moving, but quickly established once stationary, even with 20dB+ S/N. I tried running 1/8 guard band, no noticeable difference - lock still lost when moving. Travelling back home, we maintained a video link every time I stopped and parked, out to about 2 miles (built up area). Spurred on by getting into HV, I parked in a slightly different car park on Shirley hills and found I had good strong 4G. I transmitted again to HV using DVB-S and checked the stream output via my phone. Great, I was getting in. Then I remembered I still had the aerial down (car park barrier). Put it back up and still getting into HV. My power supply was 3-cell Lithium ion packs and they were beginning to wilt (10.3V). But colour and sound at 40+miles on less than a watt - very pleased
I must take my 3 over 3 bi-quad for 23cm back there and see if I can receive the output. Suspect I'll need a preamp to help the MT, but that's just waiting to be built.
Onward
Gareth G4XAT

Onward

Gareth G4XAT