Thread: Parallel coax
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Old September 28th 15, 02:46 AM posted to rec.radio.amateur.antenna
Wayne Wayne is offline
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First recorded activity by RadioBanter: Jul 2006
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Default Parallel coax



"John S" wrote in message ...

On 9/27/2015 1:20 PM, Wayne wrote:


"rickman" wrote in message ...

On 9/27/2015 10:41 AM, kg7fu wrote:

Matching the antenna won't make the Return Loss go away but it will make
the transmitter happy.


Can you explain this? I thought matching the antenna would *exactly*
make the return loss go away because it would eliminate the mismatch.


Not wanting to put words in his mouth....
I read that to mean that the high SWR between the ATU and the antenna
would remain, but the transmitter would be happy with the SWR on the
transmitter/ATU coax.



# Rick is correct. If the antenna (load) is matched to the line, there is
# no return loss, hence no SWR. The ATU will be adjusted (hopefully) to
# make the transmitter operate properly with the impedance as seen at the
# transmitter end of the line.

# Yes, the SWR due to mismatch of the antenna (load) and line will remain.
# Even if the real part of your load impedance is matched to the line, you
# will still have a high SWR if the reactance remains.

# Does this make sense?

Yes. That's what I was trying to say using SWR instead of return loss.
Return loss numbers get bigger with lower SWR.
For example: SWR 1:1 = infinite return loss.

But I assumed that Rick was talking about the reflected power used in the
return loss calculation. That part goes to zero for a perfect match, hence
the infinite return loss.

Since my ATU is closer to the transmitter than the antenna, I tune for
lowest SWR from the transmitter to the ATU and don't worry about the ATU to
antenna SWR.

I believe we are all talking about the same thing.