User's Manual

ALPHA 9500 Interim OPERATING MANUAL

www.alpharadioproducts.com

result in outlet air being drawn back into the ampliﬁer air intake and recirculated, thus getting

hotter and hotter and resulting in degraded ampliﬁer performance or even failure. If you are

designing your own console, consider putting in additional fans and/or ducting to deal with

waste heat. Try to minimize the possibility of dust or other contamination getting drawn into or

falling on the ampliﬁer. It is also advisable to periodically (at least annually) clean the dust out

of your ampliﬁer, paying particular attention to the tube ﬁns, for continued ﬂawless operation.

Alpha Radio Products recommends the use of compressed air for dust removal.

3.4 Antennas

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 5.5 amps and the peak RF

voltage is 387 volts. With a 2:1 SWR, these values double to 11 amps and 775 volts. 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

an antenna has been deployed for a long period of time, it may be worth taking it down for

inspection prior to full power operation. If any insulators are cracked or show signs of “tracking”,

3”

To ensure adequate cooling

make sure the top and rear

of your ampliﬁer have at

least 3” of clearance to allow

unobstructed airﬂow.

Figure 3.3 - Minimum clear-

ance for proper airﬂow