> As
> soon as the 33
> subscriber unkeys the interfering signal on 165 goes away.
I'd bet a box of isolators that the problems at the 165 site, NOT at the 33
site.
> Is it valid to add 600 kHz to the intermod calculator? I get
> an interesting
> fifth order when I do.
Just add the mobile frequencies to the mix and you'll get the hits.
> As I said before, the owner may have added a preamp to
> 147.165 a day or two
> ago.
Sure sounds like this is the problem. Without knowing anything else, my bet
is that the 165 repeater doesn't have enough Tx to Rx isolation resulting in
the preamp being driven into nonlinearity, thereby producing the mix you're
seeing. Adding pads to the input of the preamp would be the easy way to
confirm this is the case (while keeping all other variables, including the
signal strength of the 33 user, constant).
> It looks to me like the cure is to notch 147.930 at the
> 147.756 receiver.
That would be ideal, but you're talking about a 165 kHz difference there.
That's not to say that it can't be done, but it's getting kinda tight.
Before trying to notch out 147.93, I think the other repeater owner needs to
take a closer look at their isolation. Any idea what kind of preamp it is?
For kicks and giggles, have someone within a mile or two of the 165 site
transmit on 147.600 while both repeaters' transmitters (147.33 and 147.165)
are up. That would produce the same IM product (147.600 + 147.330 - 147.165
= 147.765) If you can get the 765 receiver to open up with this trick,
that's one more finger pointing toward the 147.765 receiver/preamp as being
the culprit.
--- Jeff
