> > Are you using a preamp? If so, what do you have ahead of it
> for filtering,
> > and/or have you tested without the preamp?
>
> Yes I use a preamp.
> DB4062 duplexer and two DB4002B 11" pass cavities, pass cavity loops
> set for 1 dB insertion loss each cavity. I tried tightening it up to
> 3 dB per cavity, no help there.
> The problem is still there without the preamp.
Have you tried putting one or more pass cavities on the transmitter? It's
more of a longshot, but if there's something strong coming back down your
feedline it could be getting to your PA resulting in intermod. The problem
would come and go with the strong signal obviously, and only when your Tx
was keyed.
> Preforms, right. I was wondering about the integrity of RF contact
> between the preform and the EHS wire since the preforms are coated
> with whatever that stuff is on the inside.
Yeah, they're coated with that semi-clear plasticy stuff usually. I
wouldn't consider that to be a "high risk" factor, but hard to say. How
close is the nearest guy wire attachment point on the tower to your antenna?
Is your antenna currently side-mounted or top-mounted? If side-mounted, at
what height?
What kind of mounting brackets/clamps for the antenna?
What else is on the tower?
How are the feedlines attached to the tower?
Does the noise get any better or worse when it's raining out?
How are the guy wires attached to the tower (looped around a leg, with or
without thimbles, torque triangle/arms, etc.)?
I'm guessing not, but is the tower lit?
When you changed out antennas and heliax, I presume you replaced any topside
jumpers as well?
Where is your equipment with respect to the tower (i.e. how close to the
base)? And how well-shielded is the equipment (enclosed metal cabinet
hopefully), and are you taking the usual precautions as far as cabling into,
and within, the cabinet to keep RF out?
--- Jeff
