Exhibit 11
2
Tuning procedure
Tuning is possible only in the OPR mode.
a.
Preliminary Information
Tuning the amplifier involves a procedure of matching the impedance of the antenna and
transmission line to the tubes characteristic load resistance. This will ensure maximum plate
efficiency and RF gain at nominal output power, with minimal distortion and spurious output.
Note that REFLECTED POWER readings depend on the antenna and transmission line
impedances only, and not on amplifier tuning. If the load impedance is not a nominally resistive
50 Ohms, the REFLECTED POWER reading will always show a reading, no matter what the
tuning settings. Proper tuning is always necessary, however, and will allow you to operate at a
high power level, without distortion or any danger to the amplifier. Note also that the real
OUPUT POWER presented to the load (the antenna and transmission line) is equal to the
difference between the FORWARD and REFLECTED POWER readings. For instance, with a
2.5:1 VSWR, readings of 800W and 150W FORWARD and REFLECTED POWER respectively,
the real OUTPUT POWER is 650W. At very high VSWR levels, such as when no antenna is
connected or a badly mismatched antenna is used, the FORWARD and REFLECTED reading
will be almost equal, while the real OUTPUT POWER (the difference between them) will be
zero. The amplifier can operate safely as long as the REFLECTED POWER is LESS THAN
350W. Matching is assured for loads presenting a REFLECTED POWER of up to 350W.
Nevertheless, for some loads and bands, matching is possible at even higher REFLECTED
POWER levels, but the drive power must be reduced to prevent the REFLECTED POWER from
exceeding 350W. Failure to comply with these guidelines will cause the protection circuits to trip.
For example, if the antenna VSWR were 5:1, the maximum attainable FORWARD POWER
would be 540W, 240W of reflected power and real output to the antenna and transmission line
of only 300W. in the event your antenna cannot be adjusted to produce a lower VSWR, an
external antenna tuner may be deployed.
CAUTION
At elevated VSWR levels, high voltages and high currents are distributed along the coaxial
cable to the antenna, risking internal arcing and heat generation, and likely damage to the cable
and any antenna switches that may be used. It is recommended that VSWR levels of more than
2:1 not be permitted with coaxial cable above 14MHz.
It is advisable to adjust amplifier tuning when antennas have been changed, snow has fallen,
new objects are in the near field of the antenna, etc. Such changes may affect antenna
impedance.
NOTE
If you use more than one antenna on a band, the proper antenna must be selected prior to
performing the tuning procedure outlined below.
CAUTION
To avoid damage not covered under warranty, do not switch the BAND while transmitting. As
discussed above, hot switching will damage the amplifier’s band switch.
CAUTION
Also, never apply drive longer than one minute continuously without pausing for at least one
minute to allow tube to cool.
