Conrad,
The 90 deg angle of the two dipole elements is necessary to excite the 2
orthogonal polarities. For the radiation to be circular, the signals in these
dipoles must differ in phase by 90 deg. To do this you can feed both amps in
phase, and then insert a 90 deg shift (1/4 wavelength) in the feedline to one
of the dipoles.
Just keep the elements orthogonal and the feed phase differing by 90 deg.
73
.... Bill K3HZP
---------- Original Message ----------
From: Conrad PA5Y <g0ruz@g0ruz.com>
To: "amps@contesting.com" <amps@contesting.com>
Subject: [Amps] Phase and amplitude of 2 tube amplifiers
Date: Thu, 13 Oct 2022 12:37:10 +0000
I am going to attempt to use 2 identical monoband tube amplifiers to generate
CP but before I start I have a question. The 90 deg delay for CP comes from the
array orthogonal physical boom separation. So the amplifiers must be in phase
at the outputs.
I presume that this has been done in broadcast applications and I would like to
know, assuming everything is tuned correctly how close the phase likely to be?
I have line stretchers for the inputs, I have extremely good phase matching on
the Wilkinson splitter and 2 identical directional couplers that I have tuned
for good phase and amplitude matching. I can also measure the relative
amplitude and phase of the 2 amplifiers accurately. Small phase and amplitude
adjustments are ok but I have no idea what to expect with tube amplifiers.
This was not really planned but a 2nd amplifier became available, so I thought
why not? The tubes are becoming scarce so this way I can be a lot more gentle
on them.
Regards, Conrad PA5Y
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|