Alpha 8410 Linear Amplifier User Manual
RKR Designs LLC
Preparing Your Station
DOCNUMBER 8410
Document Issue 1.1
Page 3–2
August 2015
33
3
It is critical that airflow around the amplifier remain unimpeded at all
times and that the top of the amplifier remain clear of any restrictions.
Maintain at least 3 in. of clearance around the amplifier and at least 4 in.
of clearance around the air intake and exhaust areas to allow for
unobstructed airflow. Ensure that exhausted air cannot recirculate back
into the amplifier air intake. We recommend that you do not stack
equipment on top of the amplifier.
If you are mounting the amplifier in a console, ensure that the exhaust air
is properly and fully removed from the console. If outlet air is drawn back
into the amplifier air intake and recirculated, the amplifier gets hotter and
hotter, resulting in degraded performance or even failure. If you are
designing your own console, consider putting in additional fans and/or
ducting to deal with waste heat.
Minimize the possibility of dust or other contamination getting drawn into
or falling on the amplifier. Periodically (at least annually) clean the dust
out of the amplifier, paying particular attention to the tube fins. We
recommend the use of compressed air for dust removal.
Step 3
Ready your antenna for 1500 W.
Ensure that all antennas are rated for 1500 W and that they are carefully
tuned and installed for minimum voltage SWR.
Many antennas that are suitable for general use are unsuited for operation
at full 1500-W power. At this power level in a 50-ohm circuit, the RMS
current is 5.5 A and the peak RF voltage is 387 V. For SWR = 2:1, these
values double to 11 A and 775 V. The actual voltage and current at various
points in or on your antenna may actually be many times these values.
On a simple dipole with sharp wire ends, corona (localized ionization) can
easily occur. Corona can (and has!) led to fire in nearby objects. Traps in
beams and verticals can heat up significantly during high-power
operation. Melting or flashover of traps have occurred in many
installations where insufficient thought has been given to their ratings. If
an antenna has been deployed for a long period of time, take it down for
inspection before full-power operation. If any insulators are cracked or
show signs of tracking, replace them.
Step 4
Provide adequate RF cabling.
Use good-quality low-loss coaxial cable.
Use new, clean connectors and install them according to manufacturer
recommendations. Clean the connectors after soldering them and before
mating them with the amplifier.
Remove any excess solder from the connector; likewise, remove any
fragments of braid and the like.
