Greetings Jon,
Again, I must admit that I only have time to skim. There are folks waiting
to use this computer and I have bout 9 minutes.
JOHN:
At the 3 dB points, half the power that is transmitted at that frequency by
the source or whatever, gets passed through to the load or whatever is on
the other side of the filter.
So where does the other 3 dB go? Is it dissipated? Hardly. To understand
where it goes, one must look at the magnitude of S11 and S22 of the filter.
At the 3 dB point, the values of S11 and S22 are getting large and all of
that power is being REFLECTED back towards the source.
BILLY:
I need to study this further and think on it but I have a problem thinking
that power can just be reflected back to the source and done away with. It
has to go somewhere. If we have a conjugate match at a given frequency--and
we can only have a CM at one frequency--then the output will be attenuated
at any other frequency. Just as we cannot create power, we cannot destroy
it either. We must dissipate it in a manner that does a job for us such as
transmitting an rf wave or dissipate it as a loss.
(I believe that this is related to the "law of the conservation of energy".
It's been years since chemistry so I could be wrong.)
Back to the Tuner instead of the filter:
I have never had the need of thinking this out before but since we are
discussing the Conjugate Match (rather than a band-pass filter), if there
is a loss of 3db which, of course, is at a frequency that is close to but
removed from the CM point, a portion of but not all of that power will be
re-reflected toward the load. It would seem that some of it must get by the
re-reflection point of the tuner to the source and a portion of it should be
re-reflected to the load. Does this just continue to go on and on until it
has made so many trips up and down the feed line that it has dissipated in
the resistive losses of the line? And what about the part that will get past
the re-reflection point to the source. Does it not dissipate in the
lossiness of the source output impedance. My main point is that it has to
go somewhere! I wish I had more time to spend here but I will take the file
with me.
Please re-send yesterdays letter to me privately. I copied it to the
A-drive and the disk was no good and I have already deleted it from my
hotmail account.
Billy
Billy
_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|