In message , rickman
writes
On 10/5/2015 7:29 AM, Jeff wrote:





NO. It covers the reflected power from the antenna. There is no
reflected power between the ATU and Tx if the match is 1:1.

You keep saying that, but it isn't true. Power can come through the
ATU circuit into the TX even when there is a 1:1 impedance match. In a
silly case lightning can strike the antenna. I don't think the 1:1
impedance match will prevent that power from reaching the TX.

Am I mistaken, or is the discussion starting to get a bit silly? The ATU
is certainly NOT a one-way device!

Of course power can flow back through the ATU. If it didn't, when the
rig is receiving (assuming it's a transceiver), you would never hear any
of the signals that the antenna picks up. This includes a lightning
strike! For the same reasons, if you have any strong radio transmissions
in the neighbourhood, these too pass through the ATU to the TX output,
and you may not be possible to get a 1:1 reading on the SWR meter!

However, apart from these sorts of situations, if the SWR meter is
responding to only to the signal transmitted by your TX, and it is
showing a 1:1 SWR reading, none of the reflections of TX signal are
coming back through the ATU and into the TX output. The portion of the
TX signal that is not making it into the antenna can only be accounted
for by it heating up the coax, and the ATU.


--
Ian