--- Jeff DePolo <[EMAIL PROTECTED]> wrote:
> > When you put the Bird between the TX and the
> duplexer, you
> > have changed the
> > length of the jumper cable, which upset the
> tuning.
>
> Adding a wattmeter or any other length of cable
> between the transmitter and
> the duplexer Tx input port has no effect on the
> tuning of the duplexer. It
> may change the load Z the transmitter sees, which
> may make the transmitter
> happier (or sadder) depending on the resulting Z,
> but in no way does it
> alter the tuning of the duplexer itself.
>
> Adding or removing cable lengths between the
> transmitter and duplexer also
> does not change the VSWR as seen by the transmitter
> (minimal cable loss
> effects notwithstanding).
>
> --- Jeff
>
Jeff you have just made two statements that are the
exect opposit of each other. If changing the length
of cable makes a differance, then the swr as seen by
the transmitter must change.
As some transmitters can not be tuned for impedance
mismatch, adding lengths of line may change the
impedance where the transmitter will produce the
maximan ammout of power out.
If say the duplexer is setup for a 50 ohm load and the
transmitter wants to load into a 60 ohm load, then
changing the length of cable between the duplexer and
transmitter may let the transmitter see 60 ohms
instead of 50 ohms. The swr will not really change on
the line as a whole, but at a given point it may match
the impedance of the transmitter for maximum power
transfer.
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