/Mobile testing with DVB-T - 70cms

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radiogareth
Posts: 679
Joined: Wed Jan 06, 2016 9:46 am

/Mobile testing with DVB-T - 70cms

Post by radiogareth » 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

g8gtz
Posts: 1441
Joined: Wed Apr 07, 2010 6:26 pm

Re: /Mobile testing with DVB-T - 70cms

Post by g8gtz » Sat Apr 10, 2021 5:48 pm

Hi Gareth,

Interesting - exactly the same as my mobile results, clearly more investigation needed.

Re HV - you'll have a job receiving it on 23cms as it transmits on 3.4GHz :-0 Well it should do but it's currently on my workbench having a makeover.

BTW - all you will need is a C band LNB in front of MT to receive it.

Noel

radiogareth
Posts: 679
Joined: Wed Jan 06, 2016 9:46 am

Re: /Mobile testing with DVB-T - 70cms

Post by radiogareth » Sat Apr 10, 2021 6:59 pm

Excellent, I have one here ready.....
Gareth
Last edited by radiogareth on Sun Apr 11, 2021 9:53 am, edited 1 time in total.

G8HKN
Posts: 32
Joined: Mon Jan 21, 2019 4:04 pm

Re: /Mobile testing with DVB-T - 70cms

Post by G8HKN » Sun Apr 11, 2021 8:47 am

AAAAAAAARGH I spent Saturday morning up and down to the loft
adjusting my 2nd C band LNB and got no signal on 3408 from HV.
Now I know why !!
I now have 2 lnb's pointing to JV
Plan B try to send signal on 1248 and view HV streamer
73 Roger.
Last edited by G8HKN on Sun Apr 11, 2021 4:38 pm, edited 1 time in total.

radiogareth
Posts: 679
Joined: Wed Jan 06, 2016 9:46 am

Re: /Mobile testing with DVB-T - 70cms

Post by radiogareth » Sun Apr 11, 2021 3:26 pm

Roger, are/were you getting HV on 3.4 with a BARE LNB IN YOUR LOFT??? I stand little hope here in Hayes, although I can get JV by sticking it out of my shack window.....
Gareth

G8HKN
Posts: 32
Joined: Mon Jan 21, 2019 4:04 pm

Re: /Mobile testing with DVB-T - 70cms

Post by G8HKN » Sun Apr 11, 2021 4:46 pm

Hi Gareth,
I can't answer about HV because Noel has the PA on his bench at the moment.
If I got a hint of a signal I was thinking of a small dish.
JV is no problem bare LNB in loft receiving for 18 months now.
Tomorrow I hope to send some 1248 to HV if streamer is on but only 8 watts so not very hopefull.
Roger.

G8HKN
Posts: 32
Joined: Mon Jan 21, 2019 4:04 pm

Re: /Mobile testing with DVB-T - 70cms

Post by G8HKN » Mon Apr 12, 2021 9:47 am

Tried and as suspected no results
I don't know if I have to do anything with DTMF tones though.
73 Roger

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