What are you trying to do?
I believe I have an old BlonderTongue (BT) ch 12 modulator floating around.
I grew up midway between the baltimore and DC market, we had strong signals on Ch 2, 4, and 5 -
but since 11 & 13 were both quite a few miles away in Baltimore,
Chan 12 was great for injecting a AV source like a VCR into a local MATV system ...
(Master Antenna TV system) so you would not get local interference ...
- I used to do that sort of stuff 25-30 years back ...