Free to air receiver settings question

Discussion about this major DATV Project. See https://wiki.batc.org.uk/The_Portsdown_Transmitter
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biker_bob
Posts: 36
Joined: Sun Oct 23, 2016 8:02 am

Free to air receiver settings question

Post by biker_bob » Fri Jul 14, 2017 5:09 pm

Hi great hive mind,
I have a portsdown that works OK on 70cm as shown by GB3HV.
I'm now trying to receive it on my free to air satellite receiver so I can do some testing with inputs.
It transmits OK on 23cm as the receiver shows a good signal strength and good 'quality'.
Sadly, no picture. It has even, at some point, picked up my call sign.

I have tried SR's of 2000 and 4000 and found that the RX and TX need to be the same to show a signal strength.
The RX seems to really want to be on 'vertical otherwise I have no signal strength. I just have a bit of wire stuck in the back, no LNB or the like.
I have tried FEC's of 3/4 and 7/8 (the RX tends to say 3/4 so that seemed like a fair idea)
I've tried the pi camera with Mpeg2 and Mpeg4 (both have been proven to work elsewhere for the TX) and all the other inputs.
The receiver works fine, with an LNB, on GB3HV.

Any clues?
Any other settings needed for a satellite receiver? I have no audio so could this be a problem?

Thanks for any suggestions in advance.
Bob G1XIE / M0AJZ

g8vpg
Posts: 387
Joined: Fri Oct 11, 2013 9:35 am

Re: Free to air receiver settings question

Post by g8vpg » Fri Jul 14, 2017 5:36 pm

Bob,
You must set the receiver to the same frequency and symbol rate that you are transmitting. Polarity is irrelevent, all this does is change the lnb voltage output to switch the lnb polarity. The receiver will find the FEC and codec by itself, but once you have saved a channel on a particular codec, the channel is fixed to that codec and you will get a blank screen if send a different one. I have had a couple of occasions tuning in receivers on the bench when they could not see the signal, it was down to excessive signal strength. If your signal and quality meters are over 80 or 90%, try reducing the input signal, this cured my problem.
73 Shaun G8VPG.

G8GKQ
Site Admin
Posts: 2928
Joined: Sun Mar 22, 2009 1:21 pm

Re: Free to air receiver settings question

Post by G8GKQ » Fri Jul 14, 2017 9:43 pm

Hi Bob

Is it an SD or HD Satellite receiver?

If it's not HD, you will need to transmit CAMMPEG2-2 mode to have it show on the receiver. SD (DVB-S) receivers cannot receive H264.

Audio should not make any difference. You'll get the bleeps just like you did on HV.

Dave

biker_bob
Posts: 36
Joined: Sun Oct 23, 2016 8:02 am

Re: Free to air receiver settings question

Post by biker_bob » Sat Jul 15, 2017 8:34 am

Still not too sure what happened but it is now working.
Bob G1XIE / M0AJZ

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