[Amps] Readout power linear amplifier

[Réjean Léveillé]

Hi everyone

SWR meters are not created all equals and only few will get under the 5%
accuracy in reference with the Birds models.

I use the Autek WM1 with the remote rf sensor head and I am satisfy with its
accuracy and its peak mode. I will get the same reading with a steady
carrier or a pulsed transmission.

The same result with BPSK or tune mode the power output will be exactly the
same.

The same thing in AM mode with 100% modulation I get four times what I was
without modulation.

Even if I got the latest Yaesu Ftdx5k, its peak meter gives poor result.
What I like the most is the accurate Rf power adjustment on one of the LCD
display for few seconds, it perfectly matches my external power meter by 5
watts steps from 10-200 watts. Then I feel safe not to overdrive my linear
amplifier

I always tune up with the PTT or MOX, cw mode  with the keyer turned off
with the keyer paddle.

In old linear amplifier with average readout with SSB modulation
instructions, saying the word “four” without any compression you add a
factor of four and you will be very close to a peak reading. Of course your
average power must be calibrated.

 

I am happy to own a Marconi BH30 modified for all 9 amateur bands that is
over 40 years old looking like new (no rust), kind of gold color inside the
rf deck, weighting 160 kg, unlimited transmission time at 1200 watts (rtty)
-20c to +50c. Each component is 2-3 times greater than what is needed. The
rf deck could easily handle >3 kw, the diameter band ring switch diameter is
at least 8 cm with coated Teflon metal strap. It was designed around 2x
3-500Z tubes, at near maximum power (1.7kw) the HV only drops 200 volts from
3500 volts and it will recover 50-75 volts after 10 seconds. 80-10 meters
with 55 watts drive I get 1.5 kw, it needs more drive for 160 m and the
plate tubes will only get half red even after 1 minutes carrier and thanks
to its cage blower, smooth air duck curve with Eimac glass chimney. There is
a second muffin fan for the transformers and HV bleeder resistors with many
sensors monitoring transformers, tubes, HV full wave rectifier solid state
block and safety kill switches that will trigger both breaker fuses in case
of a problem. It was modified for free harmonic for 26-30 mhz, zener diode
in series with the HV bleeder resistors used for –B with optical isolation
trigger circuit for bias cut off, big vacuum relay, Led white light for the
meters, 9 bands selection, 1:100 turn ratio counter for the vacuum capacitor
(Original synchro motor driven). RTTY contest you just forget it and the
panels will not get hot at all at 1kw running station for hours none stop.

 

I have learned many things from all the experts found on this site.

 

73, Rejean (va2am)