Elenos T30000, Handbook

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Hand Book T30000 -
21
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TUNING INSTRUCTIONS
NOTE: The T30000 unit is factory-adjusted (if no other request has been made) to operate at 98MHz. The
tuning adjustments are motorised and controlled by 4 controls (UP/DOWN) on a switchboard located
on the front panel. Two choices are available: FAST adjustment and SLOW adjustment, depending on
the position of the selector key on the front panel. The four switches vary the following parameters:
ANODE IMPEDANCE, top left; ANODE TUNING, top right; INPUT TUNING, bottom right;
INPUT IMPEDANCE, bottom left. If one of the four switches is lifted up, the parameter is increased
and vice versa. Adjust the modulator power for an anode current consumption of about 500-600mA on
the T30000. Move the selector key to the FAST position and simultaneously move the ANODE
TUNING switch (top right) in one of the two positions: up, to tune to a frequency greater than 98MHz;
down, to tune to a frequency of less than 98MHz. Continue with this adjustment to obtain a maximum
reading on the P.W.R. meter located on the front panel. Increment the excitation power of the
modulator, keeping under control the reflected power reading of the preceding driver stage; this should
be less than the threshold at which the protection mechanism intervenes to allow other adjustments to
be made. With the key in the SLOW position, adjust alternately the two input tuning adjustments of
the final stage; first INPUT TUNING (bottom right), then INPUT IMPEDANCE (bottom left) in order
to minimise the reflected power reading of the preceding driver stage. Increment again the modulator
power, keeping under control the I.A. and I.G. values of the final stage and the driver's reflected power
value. Make adjustments to obtain the maximum relative power output of the final stage using the
ANODE TUNING control (top right) and, if necessary, adjust the two controls INPUT TUNING and
INPUT IMPEDANCE to optimise matching with the driver stage. If neither the I.A. or I.G readings of
the final stage approach the threshold of protection intervention, proceed with the same sequence of
operations until a final power output greater than 50% of the maximum is obtained. At this point
evaluate the tendency of the tuning characteristics which can be of two types: the I.A. value tends to be
too high with low values of I.G.; or the value of I.G. tends to be too high with I.A. relatively low and
low power output. The two tendencies can be normalised with the ANODE IMPEDANCE control (top
left). This adjustment is important to obtain equilibrium between the I.A. and I.G. parameters but must
be adjusted in small steps IMMEDIATELY FOLLOWED by a compensating adjustment of the
ANODE TUNING control to maximise the relative output power reading of the T30000 P.W.R.
meter. The rule is as follows: if incrementing exciter power results in excessive anode current (I.A.),
increase ANODE IMPEDANCE by lifting the corresponding switch (top left) (simultaneously
compensating ANODE TUNING). In this way the output power will increase, reducing I.A. and
compensating I.G.