29MHz transmit - Lime problems

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M5TXJ
Posts: 347
Joined: Wed Jul 05, 2017 8:34 pm

Re: 29MHz transmit - Lime problems

Post by M5TXJ » Sun Jun 27, 2021 7:22 pm

Looks good Mike, I may have to add it to the list of future expansion.

73 Dave
...are you sure I can't use a pair of 813's?... :shock:

g0mjw
Posts: 2330
Joined: Sat Sep 20, 2014 9:15 am

Re: 29MHz transmit - Lime problems

Post by g0mjw » Fri Jul 16, 2021 5:28 pm

I have now built two transverters and have successfully sent 333KHz bandwidth 7/8 QPSK DVB-T from a Portsdown 4 Pluto to a Ryde-Knucker on 29.25 MHz. They Ryde doesn't do screenshots so you will just have to believe my webcam that it works. The IF is 149.25 MHz incidentally, its not getting the IF, I checked it really is 29.25 MHz.
WIN_20210716_18_24_56_Pro.jpg
WIN_20210716_18_24_56_Pro.jpg (306.69 KiB) Viewed 1577 times
For academic interest, there are also 16QAM and 64QAM modes. 16 QAM worked, 64 QAM was more difficult but I did get it to lock eventually at 2/3. Academic I expect as we will be needing QPSK and a lot more FEC in reality.

While the TX works on top band, the band pass filter in the RX prevents reception so that's going to need a different filter.

Mike

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M5TXJ
Posts: 347
Joined: Wed Jul 05, 2017 8:34 pm

Re: 29MHz transmit - Lime problems

Post by M5TXJ » Fri Jul 16, 2021 5:33 pm

Great work Mike.

73 Dave
...are you sure I can't use a pair of 813's?... :shock:

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