On Jul 25, 10:44 am, DeanO wrote:
On Jul 23, 10:27 am, szilagyic wrote:



Hello,

I have two antennas that I am trying to combine, and have a question
in regards to the best way to do this. The first antenna is a
Winegard HD7084P (FM/VHF/UHF lpda) that is hooked to a preamp and
tuned in perfectly. I want to add my other antenna (Winegard PR-8800
UHF bowtie) that is also tuned in and points in the opposite direction
(almost 180 degrees) to pick up some UHF stations. The two antennas
are side by side, but the ends of the elements are about 4 feet
apart. When I disconnect the HD7084P from the preamp and connect the
combiner and hook the HD7084P to the combiner, the signal strength for
HD stations maintains about the same. But when I hook up the second
antenna to the combiner, the HD signal strength from the HD7084P drops
by 10-40% (depending on the channel). I tried two combiners/splitters
and got the same results, one is a RCA brand splitter, the other is a
Radio Shack hybrid splitter/combiner. Would something like the
Channel Master 0538 or the Winegard CC-7870 work better for this?? I
read up and these models mention "high isolation" which I can't seem
to find any information on. It seems like a powered combiner would be
ideal so that there is no loss at all, but I haven't seen anything
like that. I am looking for any suggestions or ideas that anybody
might have.

I really appreciate all of the help and feedback.

Thank you very much,
--
Chris

The problem is phasing of the signals at the combiner. You only
need
to lengthen one feedline
from one source prior to the combiner, this will be done by
experiment. You could also shorten feedline a little at a time and
observe the changing signal levels. You will not get them perfect
(due
to slightly different frequencies/wavelenghts). You will also
effect
the impedance 'coupling' slightly which may work in your favor.

The whole point of a diplexer (jointenna) is to filter out individual
channels so that 'phasing' is no longer an issue for combining the
feeds. The actual insertion loss of a jointenna should be aound 1 dB
on a pass through channel

GG