OT: CH4 Trap.

Get another TV, tune it to 4, extract the signal before it gets to the IF, invert it, add it to the input of the TV you want to watch. Adjust signal strength as needed to match.

More fun than just buying one...

Mark L. Fergerson

In Thunderbird double, clicking just opens an email and puts that message ID in the TO: line. Mikek

I built some for Ch 3, almost 40 years ago. It took nine tuned circuits to cleanly remove the existing Ch3, to allow the insertion of another signal. I could do it with less, but it caused losses at several higher channels. They weren't cheap to build. I ended up with glass piston trimmer caps, silver mica caps, Adjustable ceramic coil forms and coils hand wound on Amidon T50-6 torroids. I also had to put matching transformers at each end of the filters to match the assembly to 75 ohms. I had about four double sided sheets of calculations before I found a way to build it with real world parts. It was a series of series and parallel tuned traps. Unfortunately, all my design notes and the BOM are long gone. I may have one damaged prototype, lurking somewhere my badly damaged shop building.

You're not supposed to use an E-mail client as a newsreader ;-) ...Jim Thompson

Yowsers. I bet it was expensive to tune up, too.

I couldn't get it to work, either. clicking does NOTHING. But then again, everybody knows why

I didn't have a sweep generator or a network analyzer back then, so I tuned it with a Sadelco TV FSM, and fed by the local CATV system. Since all nine adjustments were interactive, it took over an hour for each. They were built for MATV systems at the local schools, to remove the scrambled HBO, and insert the output of their reel to reel VTRs. The design also included a combiner at the output, to insert the new signal. The 'Q' was so high that I read a little over 300 volts of RF on some of the series tuned traps. Of course, the highest was the one that was used to remove the HBO jamming signal.