On 7/4/2015 4:07 PM, rickman wrote:
On 7/3/2015 3:27 PM, Wayne wrote:


"rickman" wrote in message ...

On 7/2/2015 8:53 PM, Wayne wrote:


"rickman" wrote in message ...

On 7/2/2015 3:52 PM, Wayne wrote:

Why will the reflections not have losses?

Because the assumption I posed was for a lossless line. In that case,
with a conjugate match on both ends, wouldn't there be maximum power
transmission regardless of the SWR?

You aren't grasping the issue. Losses are *not* only in the
transmission line. When a reflected wave returns to the transmitter
output, it is not reflected 100%. If the output and transmission line
are matched exactly, 50% of the reflected wave reaching the output
will be reflected and 50% will be dissipated in the output stage.

I don't think I've ever heard that anywhere before. Could you elaborate?

I'm not so sure now. I think I mentioned before that I learned about
transmission lines in the digital context where source and loads are
largely resistive. Resistance dissipates power. So when matched the
source dissipates as much power as delivered to the load (or
transmission line). Likewise, matched impedance will not reflect power,
but rather it is all absorbed. That is what happens at the antenna for
sure. But I'm not clear about what this conjugate network is really. If
it is purely reactive, then it will not have losses other than the
parasitics.

I have to admit I am not fluent in the complex math of networks. So off
hand an impedance of 1063 -j0 says to me resistive. The imaginary part
implies phase shifting, no? With that term being 0 doesn't that say the
capacitive and inductive parts cancel out leaving only resistance? If
you can, please explain how I am wrong.


Are you suggesting that the conjugate match will reflect back to the
antenna 100% of the original reflected wave from the antenna?

Well, yes. Minus losses in matching networks and transmission lines.

In examples with lossless lines and lossless matching networks, wouldn't
it be 100%.

I don't get how the matching network will reflect the wave from the
antenna 100%. Is that something you can explain?


Yes, he is correct.

Think of it this way, without the math. On the transmitter side of the
network, the match is 1:1, with nothing reflected back to the transmitter.

So you have a signal coming back from the antenna. You have a perfect
matching network, which means nothing is lost in the network. The
feedline is perfect, so there is no loss in it. The only place for the
signal to go is back to the antenna.

In a perfect system, all power is transferred to the antenna, even with
a large mismatch between the feedline and the antenna. However, that's
still not the same as having a match at the antenna, because reflected
signals most likely will arrive out of phase with the original signal.


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