Kudos and many thanks to you Jeff, got the filter in yesterday and installed it today and seems to have solved the problems. Muchos Gratis and see you here in Dayton. Randy
--- In [email protected], "Jeff DePolo" <[EMAIL PROTECTED]> wrote: > > > Randy, > > > > There could be 2 problems why you get desense. 1.overload by > > the other repeater tx, but more likely 2. his wide band tx > > noise, down maybe 85 db, is getting into your receiver...the > > wide band noise is actually on your rcvr freq. > > I thought about that issue (Tx noise from the repeater) when I wrote my > original reply but didn't bother to comment on it. The offending > transmitter is a repeater, transmitting low (444.6) and receiving high > (449.6). Its duplexer, assuming it's pass/reject, and I can't imagine it > wouldn't be if it's at a commercial site, should provide a fair amount of > noise supression at the vicitim's receive frequencies in the 446.7ish range, > though not the full 90 dB or thereabouts that it provides on the repeater's > receive channel at 449.6. Maybe it's affording 40 dB or so of attenuation > at 446.7 as a WAG. When combined with the spatial isolation between > antennas (20 or 30 dB as another WAG), there should be a decent amount of > noise attenuation already. > > In contrast, the victim receivers have no protection from the high- level > signal from the repeater transmitter, hence I would expect the lack of > carrier supression to be the first evil to combat. But, Tx noise supression > via additional filtering on the repeater Tx may ultimately need to be added > later if protecting the receivers from overload doesn't cure the problem. > Again, without having measurement data to work with, it's hard to say for > sure, but starting with filtering on the link Rx's seems like a logical > first step. > > --- Jeff WN3A >
