----- Original Message -----
Subject: RE: [AMPS] RE:
Dan wrote:
> I haven't actually tried the faster speeds to see what differences there
> would be in the final outcome. I usually just leave the keyer where it was
> last.
>
> This would be a good test to try to see if there are any end result
> differences (power out and where the tune/load end up) with different dit
> speeds.
Here is some data I collected this morning; your results
may be different, hi!
Peak powers read out via RF Applications VFD RF Power
meter; dit speeds set via use of AEA MM-3 "Morse
Machine", using *630 for 30 wpm dits, and *660 for 60 wpm.
Tests performed at 7200 kHz, power out into a Bird
8890 dummy load.
Now will see if I can set up a table that will email properly.
...............................1500 watts PEP.......2500 watts PEP.
Drive Power...............40 watts....................69 watts.........
.......................30 wpm.......60 wpm.........30 wpm.....60 wpm.
Tune Control...353.............356................353...........356......
Load Control...559.............550................562...........576......
Grid Current....20 mA.........38 mA............60 mA........60 mA
Plate Current..200 mA.......245 mA...........300 mA......300 mA
Plate Volts......5400 volts at all key down tests.......................
For the SSB test, I just had to increase the setting of
the drive control on the Omni VI to come back up to the
indicated 40 and 69 watts peak drive into the linear; got
the same VFD indicated PEP's and with no improvement
by re tweaking the Tune and Load controls.
The linear used is a Henry 8K. Both tune and load controls
are 10 turn precision pots which are part of a Wheatstone
bridge circuit which, when unbalanced, provides a signal
to drive DC servo-motors; one connected to the vacuum load
capacitor and the other, to the rotary inductor Pi and L
network variable inductor coils. There can be some
hysteresis in the operation of these motors in such
a bridge circuit. The shafts of the motors and capacitor
and inductor drives have timing pulleys on them; a
timing chain interconnects theses timing pulleys and
motors. Note also that Henry wires the Load control
such that minimum reading of the Load control pot
corresponds to maximum loading and minimum
load capacitance.
However, the data collected today seems to be
consistent: no delta in the tuning for either of the two
power levels or the dit speeds tested. And a small
decrease in optimum loading (increased load cap
setting) as both dit speed and power output are
increased, but not much. Very tiny delta in the tuning
pot between 30 and 60 wpm dits; no tune L delta at all
between 1500 and 2500 watts into the dummy load.
Tube currents and voltages read using the Henry
amp meters of the remote controller unit. Question:
why did both grid and plate current increase when
going to 60 wpm dits at 1500 watts out, but did
not increase with the same speed increase at
2500 watts output?
Summary: Appears no real delta exists between tuning
up at 30 or 60 wpm dits. Also does not appear to be
any benefit to amp performance, presumably also
including IMD performance, in tuning up first at a
higher power, then reducing drive back to bring the
desired operating mode to the 1500 watts out
we are permitted.
As Jon, KE9NA, has written, probably best for the tube
and amp performance, to tune up at the peak output
power you plan to reach as the PEP in the mode you
expect to use.
I ran this data several times, bringing the tune/load
pots away from the settings, then re tuning/loading
to verify results, and to assure minimum/zero hysteresis
in the data.
Have we learned anything?
73, Jim, KH7M
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