The question is this another dirty pager (data)transmitter actually transmitting a third harmonic OR is your receiver being overloaded by this other wise clean "pager" transmitter?
If the problem is a dirty transmitter nothing can be done at your receiver to alleviate the problem as the pager is actually transmitting a "carrier" on your frequency. Another bad thing is the pager transmitters are usually significantly high power. Used to have a lot of problems in the Dallas area with dirty VHF pager transmitters. It seems the operators did not care if other receivers were interfered with as long as the pagers on their system worked. Since most went to 900 or cellular the problem has pretty well gone away. If the offending transmitter is clean, notching out the 152 MHz carrier may be a solution. You are right to not expect a duplexer to notch this out. In my experience a quarter wave stub would create about a 20 to 30 db notch. Commercially made cans may be available with higher notching specs. Perhaps some of the wizards on the group can provide more and better help. 73 and Good Luck Bernie Parker K5BP --- In [email protected], Tony KT9AC <kt...@...> wrote: > > Hey everyone, > Working on a MSF5000 repeater with a 457 receiver getting overload from > a nearby 152 data transmitter (almost exact 3rd harmonic). The two > towers are about 10 miles apart and of course line-of-sight. > > I seem to recall that UHF duplexers only have a useful range of 300-600 > Mhz so that might explain why the 152 signal comes through so strong > (monitoring on the receive port of the Moto T4084 duplexer). The 457 > "harmonic" signal is also very splattery so I'm not entirely convinced > its just a mathematical problem, but I'll address that later... > > What would be the best course to eliminate this signal? I can't notch > out the harmonic since it falls almost exactly across our receiver, so > going after the 152 signal makes sense. Can I add a stub tuned 1/4 wave > with a T between the duplexer and receiver? Do I need something stronger > as a notch filer, or some sort of band-pass? > > Thanks in advance for any help. > > Tony >
