Larry,
It depends. If your transmitter PA is exactly 50 ohms source impedance
(not likely) and your duplexer input cavity is exactly 50 ohms load
impedance (not likely) and your interconnecting coax is exactly 50 ohms
(pretty likely if it's good quality), then the length of the coax is
irrelevant. Ah, but we know that nothing in this world is exact,
especially PA source impedance!
Perhaps the best course of action is to make up the interconnecting
cable to neatly and conveniently fit the installation, and see how it
works. If the power to the antenna, measured with a thruline wattmeter
at the antenna connector of the duplexer, is more or less what you'd
expect after the loss in the duplexer and cables, then you probably
don't need to do anything.
If you determine that the power to the antenna is significantly less
than you think it should be, then you might try installing an impedance
matcher ("Z-Matcher") right at the transmitter output connector, and see
if you can tune the PA for the expected output. If that makes a huge
difference, you can either leave the Z-Matcher in line and get on with
your life, or you can experiment with varying lengths of cable to find
the length which transforms the impedance to a value similar to that
created with the Z-Matcher.
73, Eric Lemmon WB6FLY
Larry Kemper wrote:
> Anyone have any idea what length of coax I should run from the
> transmitter and receiver to the duplexer? I have a Sinclair Q2220E
> and freq of 147.225 Transmit.Any info about this will be greatly
> appreciated.Thanks in advance. WA0VUS
> Larry Kemper
> Muscatine, Iowa [EMAIL PROTECTED]
>
>
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