On 9/27/2015 9:46 PM, Wayne wrote:
"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.
Incorrect. Return loss increases with an increased SWR. An SWR of 1:1
has no return loss because there is no returned signal to lose. 100% of
the signal is radiated.
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.
You cannot have a return loss when there is no returned signal. 0
divided by anything is still 0.
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.
But that is where the loss occurs. The loss will be dependent on the
SWR and the length of the coax. If your coax is short, you won't have a
significant loss with a reasonable SWR.
I believe we are all talking about the same thing.
I don't think so.
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