If the duplexers for each system are only 50 ohms at each receiver and
transmitter, then I should see 4 frequencies where there is a 50 ohm
load, and they are all different. Why would I need more than some sort
of phasing harness to connect the two duplexers to the single
transmission line, assuming the BpBr duplexers have enough isolation
to keep the two repeaters from bothering each other?
On Feb 20, 2008, at 2:22 PM, DCFluX wrote:
Isolators work with transmitters only. That would do nothing for
getting signal from the antenna into the repeaters.
What you need is a diplexer. That is a low pass / high pass filter
network. These can be constructed with L/C high pass and low pass
filters, but that usually only has enough Q to work with a super wide
split, like VHF low pass and UHF high pass.
It looks more like you need a pair of interdigital band pass filters.
These can be tuned 5 MHz wide so the filter passes both TX and RX and
depending on the number of poles will be the isolation, I'd say 5
poles should be around -60dB, 20 MHz out.
They are kind of a pain to build as copper is expensive and aluminum
is really hard to weld, that aluminum solder crap never worked for me.
And then they are a real nutbuster to tune, don't even try it without
a spectrum analyzer with a tracking generator.
But before you spend any money, I would do a VSWR test with watt meter
and a hand held to see if the antenna is broad band enough to support
the 2 machines.
--
Cort Buffington
H: +1-785-838-3034
M: +1-785-865-7206
