I have 220 MHz and 440 MHz antennas. They are mounted on the same
mast, the 440 ontop and about 3' under that is the 220. I would like
to feed both antennas with one piece of coax. How can I do this?
I'm not interested in SWR as they will not be used to transmit, only
for receive. I want to do this with as little loss as possible as the
stations I want to receive are located a long distance away.

Bill

Billy wrote:
I have 220 MHz and 440 MHz antennas. They are mounted on the same
mast, the 440 ontop and about 3' under that is the 220. I would like
to feed both antennas with one piece of coax. How can I do this?
I'm not interested in SWR as they will not be used to transmit, only
for receive. I want to do this with as little loss as possible as the
stations I want to receive are located a long distance away.

Just parallel them. The 440 should have a high impedance on 220 and the
200 should have a high impedance on 440. The frequencies that you have
to worry about are the 3x frequencies, i.e. 148 x 3 = 444.
--
73, Cecil http://www.qsl.net/w5dxp



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"Billy" wrote in message
om...
I have 220 MHz and 440 MHz antennas. They are mounted on the same
mast, the 440 ontop and about 3' under that is the 220. I would like
to feed both antennas with one piece of coax. How can I do this?
I'm not interested in SWR as they will not be used to transmit, only
for receive. I want to do this with as little loss as possible as the
stations I want to receive are located a long distance away.

Bill
the 'proper' way to do this is with duplexers. these are basically bandpass
filters that only pass the frequency you want from each antenna onto the
single coax and prevent interaction between the two antennas.

the cheap way is to just connect the two of them with a T connector and hope
for the best...

the experimenters way is to cut the coax between the two antennas and the T
connector to minimize interaction. for this i would start with 1/4 wave at
440mhz feeding the 220 antenna, and 1/4 wave at 220mhz feeding the 440
antenna.... listen to a source on 440 with just that antenna and connect the
220 antenna and see if the signal drops, if it does add another 1/4 wave at
440mhz to the 220 antenna feed and try again, if that doesn't fix it try
removing 1/8 wave... then hook the 220 antenna to the receiver and listen to
a signal on it, connect the 440 antenna and see if the signal drops too
much, if it does add 1/4 wave on 220mhz to it's feed line and try again...
etc, etc, etc... if you have access to a network analyzer you can save lots
of time. make it fancier by adding stubs and you end up building a duplexer
in coax.