In message , Dave
Oldridge writes
ml wrote in :

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

also some tvi from 10m too never did before

my antenna is physically pretty close to the antenna (thou it also
was previsiously )

for an experiment i was thinking about just making a coaxial stub
for 2m to see if that would 'notch ' out the interference

and using a T connector putting it just before the master amp (which
i think is just amplifing my 2m signal and mixing w/the tv channels
and or overloading the tv's)


should the stub be 1/4w on 2m or would say 1/2w be 'better'?

i'd cut it for the center of 2m

Try an open quarter-wave stub. Remember to take the velocity factor for
the stub line into account when you cut it. Alternately a shorted half
wave stub would be OK.

If you have no test equipment, simply cut the stub when listening to
preferably strong signals on a 2m receiver, and transfer it to the input
of you TV amplifier.

As stated in another post, a single stub is fairly broad. The notch will
be typically 25dB deep on 145MHz, but it will still cause considerable
attenuation of any TV signals around 175MHz. However, it is quick to
make, and it should tell you if you are on the right track for
eliminating the TVI. If necessary, you can improve it.

Two stubs, separated by an electrical quarterwave, are much sharper and
deeper than a single stub.

As has also been mentioned, a 145MHz stub will also remove signals on
odd harmonic frequencies (ie 435 and 725MHz). Any TV around 725MHz?
--
Ian