> Is the 400 really
> not that suitable for duplex operation even at 6 meters? What
> would be a good alternate choice ?
Foil and braid cables have a long running history of causing duplex noise
problems. God knows I've pulled enough of it out of service of the years.
More often than not, though, problems don't happen immediately after putting
it in service, so the fact that you have a new run and it's already that
noisy leads me to think that you may have other problems.
The first thing that jumps out at me is that you said your antenna is only
35 feet off the ground. While you didn't say how far away your repeater
was, my first thought is that at such a low elevation that the radiated RF
(from the antenna) is getting back into your equipment directly, overloading
the receiver. Terminating your feedline (at the antenna location) with a
known-good dummy load may help determine if this is the cause.
Again, related to the antenna height, I'd be looking for anything else in
the quasi-near-field (maybe within a hundred feet or so) of the antenna that
could be the cause of noise. With the repeater keyed up and a weak signal
injected into the receiver, wiggle/bang/shake anything you can see that
could be the cause to see if you get a sudden change in noise/desense.
I don't know enough about the Diamond's construction to have any comment on
its suitability for duplexing.
Hope this helps.
--- Jeff WN3A
