Dear "Lex--Lutor" (no call sign):

1. In North America, the frequency spacing between FM broadcast
transmitters in the same area is usually 800 kHz. 105.3 MHz - 104.7 MHz =
600 kHz. Are you sure about the two FM broadcast frequencies?

2. IM is produced from a nonlinear response in something. The odds are
strong that the 145.1 MHz signal is being produced in one or more of the
three transmitters - most likely one or both of the FM broadcast
transmitters. Adding filtering in your system will have no effect if the IM
is produced outside.

3. It is a good idea to perform a classical IM analysis (up to at least
seventh order) that involves all seven of the broadcast frequencies and to
use the analysis to select a repeater pair that does not involve an IM
frequency.

4. Theoretically, you could place a filter or isolator in the broadcast
transmission lines.

73, Mac N8TT

cross posting has been changed
--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Lex-Lutor" wrote in message
...
Any idea how to slove intermod problems at repeater location, very close (
150 meters) to VHF repeater antenna is located FM-TV tower with 7 strong
FM
channels, nominal power is from 5-10KW + antenna system gain. Bad thing is
that combination of 104.7 MHz + 145.7 MHz (repeater tx) - 105.3 MHz =
145.1
MHz ( same frequency for repeater input ) !



There is 3 +3 cavity duplexer pass/reject type and professional type of
vertical dipole with 0 dB, I`m sure if notch cavity can change this
problem
or installing high quality FM Trap filter to existing setup.



Tnx for any help !