Tim Shephard wrote:
> I service a public safety repeater. It's a master II.
>
> About 6-8 months ago I rebuilt the PA, replacing the two output transistors,
> caps, etc... I even added a couple of fans and it's been working great at
> around 40 watts.
>
> Lately we have been having some trouble which has been nicely termed the
> whale noise. After dispatch would transmit via a wire line, very
> infrequently we would have a noise come through or cover their
> transmissions.
>
> Yesterday I checked everything and found I was getting some desense, around
> 8db.
>
> I looked at the duplexer and it looks like it has not been touched in around
> 25 years. The shafts are rusty, cables look very fragile.
>
> So, I decided not to try and retune it because I feel something inside may
> snap and I'd be worse off then I am now. So I adjusted the transmit power
> down to 25 watts and no desense.
>
> We are planning to replace the radio system in the next year, so I don't'
> really want to invest in a new duplexer.
>
> What do you guys think?
>
> -Tim
>
I think you did the right thing. If it works ok at 25W, leave it alone
and hope it lasts until you get the new box.
Replacing the cables between the duplexer and station is easy enough,
since length isn't important, if you suspect they may be a problem. The
cables between cans in the duplexer are a different matter-length is
critical, and unless one goes completely, I wouldn't mess with it, again
since it's all gonna get replaced soon.
--
Jim Barbour
WD8CHL
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