Specifications

4
DOCNUMBER 9500
Document Issue 1, Revision 7
June 2009 Page 4–3
Alpha Radio Products Alpha 9500 HF Linear Amplifier Operating Manual
Product Release 1 Preparing Your Station
Many antennas that are suitable for general use are unsuited for operation
with a full 1500 W of power. At this power level in a 50-ohm circuit, the
RMS current is 5.5A and the peak RF voltage is 387 V. With a 2:1 SWR,
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. Instances of melting or flashover of traps have occurred in
many installations where insufficient thought has been given to their
ratings.
If you have deployed an antenna for a long period of time, take it down
now for inspection. Double-up on insulators and replace any that are
cracked or show signs of tracking. If there is any chance of people,
animals, or objects coming close to the antenna, move it higher or place
barriers to prevent access. Adjust the antenna for minimum SWR in your
favorite part of any band.
Step 4 Provide adequate RF cabling.
The importance of a well-constructed feed-line system cannot be
overstated.
After all, the purpose of the amplifier is to provide approximately 2 S
units (12+ dB) of improvement in your radiated signal. All too often,
however, installation problems result where cheap, poor, or underrated
coax and connectors are used. These often are responsible for at least one
S unit of degradation. In other words, you could have bought a 375 W
amplifier and achieved the same radiated signal by buying good-quality
feed-line components!
Use the lowest-loss 50-ohm coaxial cable that you can obtain. Use new,
clean connectors installed according to the manufacturer’s
recommendation. Clean the connectors after soldering them and before
mating them with the amplifier. Remove any excess solder and fragments
of braid and the like from the connector. Never use old coax, which may
have had moisture penetrate under the jacket.
Run the coax in straight lines as much as possible. Support it frequently
using noncompressive clips so that it does not hang or stretch under its
own weight.
Avoid sharp bends (most manufacturers specify a minimum bend radius
for their product). Ensure that the connection from feedline to antenna is
waterproof. Provide for disconnection of the feedline when it is not in use
to protect against damage caused by power surges and lightning strikes,
which are not covered under the amplifier warranty.