On 10/3/2015 1:29 AM, Jeff wrote:

Having done a few quick calculations; with a vswr of 20:1 at the
antenna, and a feeder having a loss of 0.5dB, and an ATU matching at the
Tx end, the total power wasted in the cable with a 100W transmitter is
over 55W, with only about 45W actually reaching the antenna.

Even reducing the cable loss to 0.1dB results in about 20W being lost in
the cable.

Reducing the VSWR reduces the loss significantly.

What is the reflection coefficient at the ATU/feedline interface?


Assuming a 'perfect' ATU and a prefect conjugate match, giving 1:1 at
the TX, then it is 1. ie all of the reflected power that reaches the ATU
is re-reflected back up towards the antenna.

Is that good? If the cable length is 1/4 wavelength (as it is in the
info provided for this case) the reflected power is nearly 180 degrees
out of phase with the initial power at the antenna. I think reducing
this through cable losses would not be so bad, or better to dump it in
the ATU?

--

Rick