Digithin as a starter project

The place for discussion about the RPi add-on RB-TV modulator card developed by G4EWJ and supported by the BATC Shop
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G1LPS Terry
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Re: Digithin as a starter project

Post by G1LPS Terry » Sat Aug 01, 2015 5:14 pm

Hi Brian
I see in an other thred that you mention the 8.912mhz crystal is working for 146.5mhz reception.
Any more information on preformance compared to a standard sup2400.
Thanks
Terry

g8gtz
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Re: Digithin as a starter project

Post by g8gtz » Sat Aug 01, 2015 7:12 pm

I intend to modify one next week (if I get time between trips to the Post Office) and will do some tests.

May have to order some more if they work well at 146 MHz!

Noel

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G1LPS Terry
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Re: Digithin as a starter project

Post by G1LPS Terry » Sat Aug 01, 2015 7:56 pm

Anyone know a source of 8.912mhz crystals? ebay search brought nothing

G4EWJ
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Re: Digithin as a starter project

Post by G4EWJ » Sat Aug 01, 2015 8:46 pm

http://uk.farnell.com/txc/9c-8-912maaj- ... dp/1842350

Farnell seeem to be continuing the free delivery.

I've done nothing further with it. I still need to connect the Si570 module output to the LO input on the DigiThin.

Brian

G8DKC
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Re: Digithin as a starter project

Post by G8DKC » Fri Aug 14, 2015 7:12 am

For anyone following this thread 8.912 Xtal now available Ebay

Peter

g8gtz
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Re: Digithin as a starter project

Post by g8gtz » Fri Aug 14, 2015 7:53 am

Umm - very expensive :-(

I just ordered 25 from Farnell for £5.13, may have a few spare at CAT15....

Noel

BTW - if this works we will have to order some more SUP2400.

BTW 2 - what we really need is someone to do a design of a complete unit or perhaps something to go in front of the modified SUP. Spec could be:
Dual band 2 meters and 70cms up to suit a normal NIm or smilar tuner
Good filtering on both bands generally high pass and bandpass..
Good sensitivity on both bands
Switchable front ends?
Powered by the tuner

G1LWX
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Location: Ashton-in-Makerfield; Lancashire

Re: Digithin as a starter project

Post by G1LWX » Fri Aug 14, 2015 3:36 pm

Farnell are selling them at £0.185 each plus vat with free postage. I ordered 5 last week total cost just over £1.

g8gtz
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Re: 146 MHz rx converter

Post by g8gtz » Sun Aug 23, 2015 6:57 pm

I have just modified the SUP2400 with the 8.912 crystal giving an LO of 2281.6 MHz (I guess that makes it an SUP2281!). Fairly easy to do - I actually broke the big lump of solder on the crystal case off with cutters rather than try to desolder.

The 437 performance at 1844.62 MHz was the same as a normal SUP but the 146 MHz output at 2135.1 MHz was about 10 dB down. More investigations to do to find out where it is rolling off but maybe this can be overcome by 146 MHz pre-amp / filters.

If it can be made to work, it does become a very simple and cheap up converter for 146 MHz.

73

Noel - G8GTZ

G4EWJ
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Location: Wirral

Re: Digithin as a starter project

Post by G4EWJ » Mon Aug 24, 2015 10:23 am

Coincidentally, I was able to test the SUP-2281 at Warrington ARC yesterday.

I used the slightly agricultural ballistic de-soldering method - heat the blob with a big iron and bang it on the table.

Brian
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G8DKC
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Re: Digithin as a starter project

Post by G8DKC » Wed Aug 26, 2015 6:03 pm

Following on from advice from Terry and Posts from Brian & Noel.

I now have a fully working MKII self contained 146.5 Rx with Pye R4002 base station front end, Sup-2400 and sat booster,
plugged into TT-1600 board in my portable Pc, with pre-amp to mount on the Yagi.

Playing with the Xtal swap on another SUP2400 have tested this on the TT-1600 on 21351 all working fine,
also works "very well" on TT-3200, with Baud Rate set to very slow in SR Search Box Expert mode,
as pointed out by Shaun some time ago.

Will catch up with the "USB Tuner" project later...

73

Peter
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