Usually a 1/4 wave open stub, or a half wave shorted stub...

I used to use 1/4 wave stubs to attenuate strong local TV signals from a
masthead amp that was primarily used for weaker signals. The frequency
of the wanted vs interferring signal were a nice 2:1 relationship so I
was kind of lucky. I used 75r coax and just chopped it to about .82VF
and it actually worked first time.

I'd suspect though that the problem is more likely to be fundamental
overload. Of course it cant hurt to try.

Both a 1/4 wave open and 1/2 wave short stub present a low Z to the
tuned frequency, or if you like "shorts it out", If however the wanted
pass freqency is an odd multiple (1/4 wave) or an even multiple (1/2
wave) then you end up attentuating that as well.

Cheers Bob VK2YQA

ml wrote:
after my building changed to a new tv antenna and master amp
seems i am giving alot of tvi on strangly enough 2m