I would check reflected power at the PA output it should be no more than
if you were fireing the pa straight into the antenna. If it is then you
will need to adjust your cable length by trying different lenghs increasing
an inch or two at a time (on Vhf) until you reach the equivilent of 1/4
wavelength of added cable. Somewhere during the process you should see
minimum reflected power / maximum foreward out. This does work I tried it
with my 2 meter repeater when I changed recievers the new reciever was
experiencing bad desense and by adding small jumpers between amp and
duplexer reflected power went away and so did desense. I think this whole
process as I have described it exists on the repeater-builder web site in
the Wacom manual.
http://www.repeater-builder.com/wacom/wp6xxVHFtuninginstructions.pdf
hope this helps.
tom n8ies
> [Original Message]
> From: Eric Lemmon <[EMAIL PROTECTED]>
> To: <Repeater-Builder@yahoogroups.com>
> Date: 3/11/2005 10:50:01 PM
> Subject: Re: [Repeater-Builder] repeater coax duplexer leads
>
>
> 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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