On Tue, 15 Sep 2009 13:49:23 -0500, Ignoramus11401 wrote:

Any idea what might be he

http://cgi.ebay.com/ws/eBayISAPI.dll...m=110432769572

It will be a couple of weeks before I pick up. I mostly want it for just
the cabinet.

i

The six big cylinders with the adjustment knobs & rods are diplexers,
from which I deduce that the four boxes with heat sinks on the four
cylinders are amplifiers of some sort -- probably power amplifiers.

This does _not_ look to be the right size for GHz-band diplexers -- those
look more like the 146MHz diplexers that I'm used to seeing for amateur
repeater use. If I'm right then someone was piggy-backing on a cell
tower -- probably a 150-ish MHz band commercial repeater, although the
actual repeater is missing. If the stuff can be modified to work at
amateur radio frequencies there's definitely a market for it; there may
even be interest from a commercial radio operator.

--
www.wescottdesign.com

On Tue, 15 Sep 2009 14:21:06 -0500, Tim Wescott
wrote:

On Tue, 15 Sep 2009 13:49:23 -0500, Ignoramus11401 wrote:

Any idea what might be he

http://cgi.ebay.com/ws/eBayISAPI.dll...m=110432769572

It will be a couple of weeks before I pick up. I mostly want it for just
the cabinet.

i

The six big cylinders with the adjustment knobs & rods are diplexers,
from which I deduce that the four boxes with heat sinks on the four
cylinders are amplifiers of some sort -- probably power amplifiers.

This does _not_ look to be the right size for GHz-band diplexers -- those
look more like the 146MHz diplexers that I'm used to seeing for amateur
repeater use. If I'm right then someone was piggy-backing on a cell
tower -- probably a 150-ish MHz band commercial repeater, although the
actual repeater is missing. If the stuff can be modified to work at
amateur radio frequencies there's definitely a market for it; there may
even be interest from a commercial radio operator.

They look big for cell phone spectrum to me too. You'll have
to get numbers off the decals to be sure. Those coax
connectors alone used to go for ~$20 a pop, probably
superflex type too. A lot of techs don't like to re-use old
coax connectors, but if the price is right...

It may have gotten whacked by lightning too, something to
keep in mind if you try to sell it.

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

Bruce L. Bergman writes:


English translation for Iggy: Diplexers allow you to connect multiple
transmitters and receivers to one antenna (or one array of phased
antennas, like a Turnstile used for TV and FM.)


Translation translation. They are VERY sharp RF filters; so you can have
a receiver and a transmitter [or multiples thereof..] sharing one tower
or antenna array. Think of them as tuning forks in the RF octave, vice
Middle C.

They must be kept in a stable-temp room or they will drift off frequency.
They are tuned with the knobs you saw; they run the shaft into the
cavity; changing its volume ergo its resonant frequency.

They are usually used in two modes. First is a pass filter, tuned to the
desired frequency; the receiver has one set on its frequency to it hears
ONLY that, and the transmitter has one on its, so it emits only that [no
off-freq splatter].

Then the receiver will have a shunt one set to the transmitter freq. so
as to divert any of that signal to ground; and the ditto the transmitter
on the rx freq.

This cabinet seems to have multiple output amps but that's solely a guess.
I look forward to knowing what all the labels and PN's say.

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

David Lesher wrote:

They must be kept in a stable-temp room or they will drift off frequency.
They are tuned with the knobs you saw; they run the shaft into the
cavity; changing its volume ergo its resonant frequency.


The idiots who built one UHF TV station in Dayton, ohio put their
diplexer above the drop tile ceiling to hide it. That required it be
aligned at least twice a year. I think it was Ch.. 22 but it's been 25
years since I interviewed for the job. I was told later that the chief
engineer was two years from retirement, and I knew so much about the
equipment in the station that he was afraid he would be fired if I was
hired. He didn't believe in a strict preventative maintenance program
so when he saw the letter of commendation from the US Army for the one I
implemented at the AFRTS station in Alaska he told me the interview was
over.


--
You can't have a sense of humor, if you have no sense!