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Re: Digithin as a starter project
Posted: Mon Jul 20, 2015 1:20 pm
by G1LPS Terry
I had planned to feed a dish with a cut down one for that purpose Brian.
But until theres more activity from the ISS datv tx than the ocasional black screen its not worth the investment and time.
Re: Digithin as a starter project
Posted: Mon Jul 20, 2015 1:51 pm
by G4EWJ
Nice idea, but agreed on the lack of activity.
It's a shame they didn't go for a non-commercial amateur design. They could have used an MK808-DigiLite and had a carousel of test transmissions on an SD card. It would probably have needed some silicone around it to survive the launch though.
Brian
Re: Digithin as a starter project
Posted: Tue Jul 21, 2015 9:02 am
by g8gtz
Brian,
Had a very good evening last night - at the last minute I went along to the local radio "what's on your bench" evening and took the RpiDATV and Minituner. I showed it and then proposed it could be a club project as kits and full documentation will be available so everyone should be able to get it working and work someone across town. To my surprise several people came up to me afterwards and said they were very interested and could I give them more details - this really has potential so try and talk to your local club about it....
Re SUP2400 - that's really interesting, will try later and do some measurements such as LO leakage on a standard one and then performance on shifted oscillator. We probably ought to go for a standard crystal such as 8 MHz.
Re: Digithin as a starter project
Posted: Tue Jul 21, 2015 11:20 pm
by G4EWJ
That's a good level of interest. Were they newcomers to ATV?
I assumed that the 2400 problem was direct pickup of the SUP-2400 LO by the antenna, because of proximity. It seems to work for Terry.
I kept the modified SUP LO above 2150 to keep it out of the receive band. It has a 2150MHz filter. Maybe that's its purpose.
Brian
Re: Digithin as a starter project
Posted: Wed Jul 22, 2015 3:18 pm
by G1LPS Terry
Changed crystal to 8hmz no joy
Terry
Re: Digithin as a starter project
Posted: Wed Jul 22, 2015 5:43 pm
by G4EWJ
>>Changed crystal to 8hmz no joy
In what way? It didn't oscillate or produce an LO?
Brian
Re: Digithin as a starter project
Posted: Thu Jul 23, 2015 3:10 am
by G1LPS Terry
No Lo Brian.
Terry
Re: Digithin as a starter project
Posted: Fri Jul 24, 2015 5:41 pm
by G4EWJ
I had an 8.192MHz crystal installed at one point that I thought was working, but I had a strange fault on the receiver so I didn't try for long. It's probably best to keep the LO above the top of the signal band at 2150 or it might cause some blocking if it gets amplified.
Brian
Re: Digithin as a starter project
Posted: Mon Jul 27, 2015 6:45 pm
by M0DTS
I did a sweep this evening of the VCO/lock range of the SUP 2400, see screen shot below. Mine is 9.375MHz reference crystal as standard.
Freq range as-is can be 2300-2560, you could modify the vco components to shift it lower.....
That gives 9-10MHz crystals as a possibility.
73
Rob
Re: Digithin as a starter project
Posted: Mon Jul 27, 2015 7:59 pm
by G4EWJ
I must have been wrong about the 8.192MHz crystal working and the 8.912MHz crystal was just scraping in.
Brian