At 9/6/2004 07:43 AM, you wrote:
>--- Kevin Berlen <[EMAIL PROTECTED]> wrote:
>
> > Over the weekend, I added a second UHF control
> > receiver at one of the sites
> > I take care of. The control RX antenna is up about
> > 150ft. Previous to
> > adding the new RX, I could easily access the first
> > RX about 25 miles out.
> > Since adding the second RX, I can only access either
> > one about 12-15 miles
> > out. I simply put a "tee" connector on the
> > polyphaser and connected both
> > lines to it. Not the best engineering practice, but
> > I have gotten away with
> > it before. Does anyone have an idea about how to
> > properly match two
> > receivers to one antenna? The receivers are located
> > in different racks in
> > different parts of the building. I know Motorola and
> > GE had passive devices
> > to do this job. Is there a way to build something
> > "homebrew" to do this
> > job? TIA, and 73,
> >
> > Kevin, K9HX
> >
>
>You will usually get a 3 dB loss (or more) by using a
>tee or a normal splitter.
In reality, the performance of a simple T connector used as a receive
splitter will vary greatly depending on the reactance of the
front-ends. In particular, if a receiver with a highly selective front-end
is connected to a T, it can look like a short at the other receiver's
frequency at the T depending on the length of coax connecting the T to the
first receiver. In that case the T can have over 20 dB of loss. Of course
you could get lucky & have an open reflected back to the T, in which case
the T will appear lossless in the other branch.
The safest approach is to use a properly isolated splitter. Fortunately,
the 75 ohm CATV splitters mentioned in previous replies are isolated. Due
to their short electrical length, they are quite usable even at 440
MHz. You just need adapters on all the inputs to go from type "F" to
whatever 50 ohm connector you prefer.
Bob NO6B
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