* skipp025 <[EMAIL PROTECTED]> [2007 Jul 26 11:49 -0500]:
> Depending on how often the problem comes back I would first check
> for possible mixing, receiver blocking, receiver & preamp 3rd order
> problems. You've said the mix numbers were already figured with
> some type of computer program... but that's not a 100% tell all.
We found the TX frequencies of the site and everything with a few miles
(this is a rural site with no other towers nearby) Using the FCC
database and ran those numbers into a program found online. I won't
vouch for the program.
We've only been involved for about two weeks so we're still in the
information gathering stage for the most part.
> Taking a first shot in the dark with cavities... I'd probably try
> to insert a notch or suck out cavity on the other repeater/base
> station tx frequency... in your/my repeater/receiver antenna line/
> path.
I agree. But, we don't have one handy.
> Relative to the grand scheme of things... tis probably better to
> suck than to bandpass (in this case). You'd probably get more bang
> for your buck... (result for your effort).
This is simply an idea to try and will help us work toward the next
step which will surely involve some $$$.
One aspect of this is the poor construction of the site. The site is
owned by the county and located on county land. The local (to that
county) 2-way shop maintains the site. To be fair, I'm not sure if the
county doesn't wish to spend any money or if the 2-way shop is simply
incompetent as I've not seen any of their other sites.
In short the site is a disaster with not even the basics of proper
grounding or installation adhered to. The feedlines from the tower
hang through the wall and dangle to the floor, if they reach that far,
or just hang by their own weight (the weight of one was being held by
the RG-8 jumper between it and the radio). No lighting protection or
ground kits. One ground rod on the opposite side of the hut from the
AC service entrance and the two grounds aren't tied together. There
does appear to be a ground rod for the tower, but the ground wire
spirals up the leg, wrapped around it, no less, to its attachment
point. As I mentioned in my first post, I tightened several coax
connectors that weren't even finger tight, which gives an idea of the
sloppy work at the site.
The reputation I'm hearing of the 2-way shop is that a service call to
fix one problem usually leads to more problems and additional billable
follow up service calls. Sadly, they contract for our county as well
as they are the only shop within an hour of here.
It is in this poor environment that their repeater lives.
Accessability is an issue as the site is not accessable after 4:30 PM
and I've noticed the interference most during the evening hours.
For the record, I work for a transportation company and our land mobile
radio system is part of my job. Our sites are independent and we have
no other services co-located with or even near us. So, I've not had to
address a case of interference like this yet (call me lucky!).
Lost in all of this, though, is whether the coax length between the
receiver port of the duplexer and the Celwave cavity I will loan them
is critical. I don't think it is.
BTW, we checked the Celwave cavity with 50 ohm pads inline and there
was no change in the tuning. I don't have access to the duplexer at
the moment.
73, de Nate >>
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