Data redazione: 25/07/03
R.V.R. Elettronica S.r.l. (BO)
VJ30000-TE - R.F. Tube Amplifier
39
Make sure that the contacts between pipe and tube, clamping verywell the clip placed on the
bottom part of the tuning pipe (fig.9C). Then, clamp the other clip placed on the top of the
tuning pipe. Check inside the R.F. cavity so that there aren’t anything and then close the
cover. Switch off the equipment and then place on the ON position the protection switch of
the blower.
Now, after these operations is possible to close all covers and panels.
3.7 TUNING AND SWITCH ON PROCEDURES
The high power switching on operations must be executed only when you have ended all
other operations, placing mains voltage and antenna connections.
PAY PARTICULAR ATTENTION TO THE ANTENNA CONNECTION, because it isn’t
admitted, when you work with radio frequency systems, to use a connection to a non
adequate antenna or to not sure connections.
For the frequency tuning operations on the equipment is useful to have a spectrum analyzer,
but it’s possible to operate in any case with the help of the measures available on the front
panel, but the time necessay is longer.
Before to switch on the equipment verify that the modulator is setted for the minimum
output power, then it’s necessary to set the indicator meters of the variuos equipment for the
reading of the following parameters: Reflected power for the driver and VG1, VG2, IA and
Forward power for the final amplifier.
At the moment of the switching on, the transmitter executes a sequence of programmed
operations. If all prestart parametrs are correct, a warm-up timer ends its counting after 90
seconds. Then, the equipment is ready to start the working at high power.
Set the service switch on the stand-by position; with this operation the anode and grid 2
power supply are inserted in two different steps at 2 seconds one from the other, at last, is
enabled the modulator working.
In this transmitter configuration, the tube is supplied on the anode; for this reason it’s
impossible to detect a small anode current of 100/200 mA.
Increase slowly the output power of the modulator by its control power.
Check that the modulator reflected power remains under 40/60 W.
Then, increase again the driver output power until the anode current is 350/450 mA.
If the reflected power is greater than 40/60 W, make various attempts alternatively on the
two regulations of the input tuning of tetrode (on the bottom position) until this value is
correct. When on the tetrode is possible to detect an anode current of 350/450 mA, adjust the
tetrode output tuning (on the top in the right side) moving the push forward to (+) position
until compares a reflected power indication in antenna.
Adjust this push button forward to (+) or (-) for the indication of the maximum relative
power in antenna. Increase lightly the modulator power checking and correcting always the
input tunings of the tetrode until to obtain the minimum value of the driver reflected power.
After the frequency tuning operation of tetrode, is necessary to execute the according
antenna operations. This last operation is advisable when the output power has exceed the
value of 8-10 KW. If tetrode isn’t correctly according to antenna, the values of the anode
current and the two grids currents aren’t correct, and in this case the amplifier doesn’t
increase the output power with a relative increase of the input power.
The push button of antenna tuning (on the top in the left side) allows to correct the IA, IG1,
and IG2 currents values in according to output power. Each once it’s been necessary to
adjust the antenna coupling (push button on the top in the left side) IT’S ABSOLUTELY
NECESSARY TO ADJUST THE OUTPUT TUNING (push button on the top in the right
side) to obtain the maximum value of the forward power in antenna.
