> > .. I'd like to add a filter in front of it.
>
> Do you need it?
Not sure yet. I'll know when I get up there with the SA, so I can
see what's coming down the pipe.
I'm just gaming out my options.
> You know the old saying... "if it works don't mess
> with it"..?
Yes, and it's about to get messed with in EVERY degree.
Of the equipment at the site, I plan to keep the feedline and the VHF
cans, and the cabinet (because I don't have another one) The
existing system's power amp is from "DAIWA", and has an SSB/FM
switch, if that's any indication of quality. :) Old maggiore TX and
RX in bud boxes.
It was in sad shape when we got it, and after a rushed overhaul it's
a poor performer.. (better than a total non-performer which is what
it was before) We've been dealing with coordination issues and
scouting for sites over the last year, so I didn't want to put a lot
of time and effort into improving it at that site if we were going to
move.
> If you really don't need the bp filter,
> don't bother.
Sure, I'm aware of those issues.
> The extra loss and potential for problems
> from coax - connector joints, junctions and extra
> hardware just might shoot your repeater in the foot
> type thing. A generic rule of thumb might assume each
> coax connector is about .2 dB of loss added to the
> system.
You know, has anyone actually measured those losses?
I've heard all sorts of numbers, from 1dB (insanely high) to 0.1dB.
I talked it over with a friend, who is a microwave contester, and
he's thinking it's way closer to the 0.1 number, and maybe lower.
If I get curious, I might build up a string of adaptors and do that
test tonight.
> The above is helpful when you duplexers are not so
> great or the pass-reject type.
Wacom BP-BR, but I don't know the model number offhand. Four cans,
about 10" diameter, with sliders for the rejects.
> If you have a wide band filter (ie the DCI type...)
> there might not be a great place to run it in the system
> unless adding it into the system at a very busy repeater
> site can help protect it from other equipment in operation.
> I've used a large number of DCI wideband filters for
> frequency agile and rx pre-selection applications.
Known local interferers are paging transmitters at about 1kW on a
nearby hospital, in about 152 MHz At the other repeater site
somewhat closer, I measured a couple millivolts on the antenna from
these signals. They have a "hideous noise" problem that's been
happening for a couple years. Occasionally, like once every few
months, and usually when it's raining, an earsplitting mess of noise
erupts. I've never been able to catch it and record it, but I do
think that I hear audio "echo" in it.. The repeater has about a 40mS
delay in the audio, so it could be an intermod problem allowing the
repeater to hear it's own output. At one point the group was
convinced that it was caused by activity on the machine I now own,
but we disproved that when the problem happened again, and we shut
this machine off totally. There's been a lot of theories on that one.
> I have mixed bag opinions about running a smaller (standard
> size) DCI filter in a high powered repeater tx application.
>
Similar to a DCI-145-2H apparently.
>
> What you do with the filter also works with where your
> repeater is, the quality/type of equipment you're using and
> how busy the site/location is.
>
> We'd need a bit more information about the filter...
And the site..
Unfortunately, I won't know the RF picture until I haul the gear up
there, and am sitting in a pile of repeater parts.
The equipment is Daniels MT-2 series VHF and UHF radios, specifically
the VT-2, VR-2, UR-2, and UT-2A Generically speaking, the front end
on the VHF is a four section 1" dia helical resonator with preamp,
feeding a conventional mixer into a 21 MHz IF, and motorola IF chip.
The LO passes through two 1" dia helical cavities before injection,
which I thought was interesting. On UHF they use a five section
helical filter, but otherwise same.
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/Repeater-Builder/
<*> To unsubscribe from this group, send an email to:
[EMAIL PROTECTED]
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
