GOESRECV crazy high freq(offset) readings

[Captains_Z]

I am bringing up a new system.

I have a circular horn feeding a prime focus dish. 

The horn is connected with two 20 dB amplifiers to a Terratec T stick black with the E4000 chip. They are direct connections without long leads.

The stick is connected to a Dell laptop running Ubuntu 16.4 with about 25 feet of usb cable.

The stick doesn't sync with Goes16 immediately, like my other installation does, but searches around changing the "freq" offset ( as it should do, I guess).  After maybe 5 minutes the stick finally syncs with GOES and the vit values are in the 30s.  A great signal.  Goesproc then starts producing images.  The weird thing is that the "freq" = -133500.  That's correct 133,500??  The gain is 8.5

Once I achieved lock I adjusted the feed-horn position for max signal as well as setting the AZ and El for max signal.

I substituted two other sticks and never achieved lock and didn't wait around for another 5 minutes.

My question is this:  what exactly does the "freq" display mean?  I know it is an offset but from what?  Are the units in Hz or parts/million or what? 

If GOES is 1694.1 MHz, can I change the config file slightly to bring the "freq" offset down to the 2000 range? 

What could be causing the large "freq" offset?

What values should I be seeing for "freq" receiving at 1694.1 MHz? 

My other installation uses a down converter to 140 MHz and works well with an offset dish.  This is maddening!

Thanks.

John

[Pieter Noordhuis]

Hey John,

You're right -- the frequency offset is in Hz. This compensates for the oscillator offset in the SDR dongle. I recall my experiments with the E4000 chip having both problems with frequency drift/offset, as well as temperature (after a while). You could try to hard-code the offset by setting "frequency" in the configuration file to 1694000000, or even lower, but that assumes that the frequency offset of that dongle is constant. Whether or not that's a fair assumption, I don't know.

Folks using dongles with the R820T never encounter these issues, from my experience.

Good luck!

Cheers,

Pieter

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