RadioBanter - View Single Post - HB VHF low-pass filter

April 21st 06, 02:00 PM posted to rec.radio.amateur.homebrew

wrote:

I've notched out a a local pager just using a coax T and a ~12-13"
open stub section of LMR400 (1/4wl @ pager frequency).

Allison

I'd try that first. I work in cable tv and one of our older methods of
"scrambling" was to use an interfering carrier ~2 MHz above the video.
It was fairly easy to use a little stub of coax and completely remove
the jamming...ie 40db of rejection with only a few db hit on the video
carrier 2 MHz away. In your case 7 MHz away it (insertion loss) will be
a non-issue.
You'll find the stub length to be critical to about 5mm so its a true
cut-n-try technique. Use some old scrap television cable for the stub
so you don't waste the good stuff.

GL,
Bill