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1.3 GHz down converters
Posted: Mon Jun 14, 2010 10:16 am
by G4GUO
Hi,
I am looking for a cheap way to down convert 1.3 GHz to somewhere in the
VHF/UHF TV band. Yes I am still wasting my time with DVB-T and need a way
of translating from 24 cms to somewhere in the range of my consumer TV.
The reason for cheap is so I can give away (I mean loan) some converters
to the locals.
So far all I can find is the Comtech units which have an IF of 479.5 MHz.
The IF does not appear to be brought out to one of the pins so I guess a
mod would be required.
I would appreciate any thoughts anyone has on this
- Charles
Re: 1.3 GHz down converters
Posted: Thu Jun 17, 2010 9:48 pm
by G4EWJ
Some (if not all?) Pace analogue satellite receivers use the same IF. You'd still need to bring the IF out, but they should be very cheap.
Brian
Re: 1.3 GHz down converters
Posted: Mon Jun 21, 2010 7:43 am
by G4GUO
Hi Brian,
Thanks for the suggestion. In the end I bought a couple of Comtech BSU479LXIDS from
someone in Poland for around £10 to play with.
- Charles
Re: 1.3 GHz down converters
Posted: Wed Jul 14, 2010 1:30 pm
by G4GUO
As a follow up.
The Comtech converter was a bit of a disaster, the
phase noise on the PLL was so bad that there is no way
it could be used for Digital TV. Fine for FM ATV.
So it looks as if I am going to have to do it the hard way
(build something).
- Charles
Re: 1.3 GHz down converters
Posted: Mon Jul 19, 2010 1:12 pm
by G4EWJ
AAMOI, just how bad was the phase noise?
Brian
Re: 1.3 GHz down converters
Posted: Mon Jul 19, 2010 2:08 pm
by G4GUO
Hello Brian,
I have no way of measuring accurately but with the analyser set to a 100 KHz span
I could see it jumping about a lot (I know not very scientific but it looked awful).
I think it was about 20 KHz but I would have to go back and check.
At first I thought the PLL was not locked it was so bad but the locked flag was set.
The principal use for the down-converter is for DVB-T which of course is a lot less
forgiving than DVB-S especially the 64 QAM mode.
I am now using an old G8LMW UV02 retuned to 800 MHz and that it is as steady as
a rock, slight frequency drift during warm up but no jumping. The TV has no
problem receiving the (now) 455 MHz signal. The initial capture range of the TV is
100 KHz. I suspect a G4DDK LO could be used in place of the UV02.
I am using a 100 MHz overtone crystal. Someone on eBay is selling 5 for £3.50
so I swapped out the 95 MHz xtal in the UV02. I have 4 of the xtals left.
- Charles