Repeater with Comtech boards
Posted: Sat Jun 05, 2010 6:06 am
Hi all,
Need some help in making a repeater with modules like Comtech.
I've managed to get very good results with a single tx - rx link but when I use two links (on different bands and not harmonically related, so the problem is not RF feedback etc.) I have small problems.
All I am doing is connecting the video out from link A to the video in on link B.
One of the problems I see are that white areas of the picture, especially at the top of the screen are distorted.
I see that the sync pulses on those lines are reduced in amplitude.
I have got round this by making a limiter that keeps the white areas at 1v or less, but there is probably a better way.
I also see that when I use a testcard there is kinking of some of the vertical lines where a horizontal line crosses - same can be seen on a crosshatch pattern.
I don't know where to look for the problem - TX or RX, pre emphasis, de emphasis or DC restoration etc! I've tried many different ways but can't get it right.
If anyone is able to offer advice I can email pictures off the receiving
Thanks
Dave ZS6BNT /G3ZGZ
Need some help in making a repeater with modules like Comtech.
I've managed to get very good results with a single tx - rx link but when I use two links (on different bands and not harmonically related, so the problem is not RF feedback etc.) I have small problems.
All I am doing is connecting the video out from link A to the video in on link B.
One of the problems I see are that white areas of the picture, especially at the top of the screen are distorted.
I see that the sync pulses on those lines are reduced in amplitude.
I have got round this by making a limiter that keeps the white areas at 1v or less, but there is probably a better way.
I also see that when I use a testcard there is kinking of some of the vertical lines where a horizontal line crosses - same can be seen on a crosshatch pattern.
I don't know where to look for the problem - TX or RX, pre emphasis, de emphasis or DC restoration etc! I've tried many different ways but can't get it right.
If anyone is able to offer advice I can email pictures off the receiving
Thanks
Dave ZS6BNT /G3ZGZ