"Pilots", when should they be turned on or off please?

[Basil]

Could someone far more technically savvy than I kindly explain how to decide whether "Pilots" should be turned on or off when transmitting please?

Thanks. Chris, 2E0ILY

[G3GJA]

DVB-S2 includes pilots to help acquisition of the signal in broadcast environments.

It seems to have no benefit for Amateur reduced bandwidth DATV, so it is normally left disabled.

Clive

[Basil]

Thanks Clive, I asked because in the "Chat" someone was having trouble decoding another person's marginal signal and asked them to turn Pilots on, after which they claimed to be decoding them fine... I have always left them off as I didn't really understand what they do.

[G4EWJ]

Perhaps that was me asking for pilots late last night.

I was trying some tweaks in LongMynd to make it work at 35kS. Reception was OK without pilots at 8PSK, but not at 16APSK. The signal locked, but packets were being dropped, presumably due to CRC errors. With pilots turned on, reception was OK at 16APSK and also at 32APSK.

Pilots are blocks of 36 zero symbols inserted every 1440 symbols, just before the symbols are pseudo-scrambled. I assume that they make it easier for the receiver to detect and correct a slip in synchronisation, particularly with the higher modulation modes. It certainly worked for me, but I'm sure that my tweaks are rather less optimum than MiniTioune. I can't find the notes of other tweaks that I did some time ago.

Turning pilots on only consumes about 2.5% of the bandwidth (36 / 1440), so I would leave them on all the time. They may even be a help for software based decoders.

Brian

[Basil]

Thanks for the explanation and suggestion Brian. I will turn on Pilots for a while and see if anything changes, reports wise. So much to learn with all of this, fascinating stuff. All the best for Christmas and the New Year.