From: Balmforth, Kevin D
Subject: Multiple Power Amps
To: CONTESTMAIL
The concept of driving multiple 1.5 KW amps in parallel to different antennas
is an interesting legal/ethical problem. At first examination, this seems
blatantly wrong. However, I believe it is technically allowed in Part 97,
since an RF wattmeter anywhere in the system will not indicate greater than
1500W.
If a station has two antennas (each driven in parallel by a 1.5 KW amp) with
one beaming VK/ZL and the other beaming EU, then the only advantage this
station would have over a station with the same antennas, but one amp, is the
reduced time to CQ on one antenna, then the other (OK ... this will also keep
stateside QRM off your frequency!). If the two antennas are beaming the same
direction, this is tantamount to using one antenna at 6 KW (ERP gain = 3 dB
amp gain + 3 dB stacking gain, other things being equal). But wait - I could
put out the same ERP with 1.5 KW and four antennas, which not illegal.
In fact, Part 97 doesn't regulate ERP or antenna gain. It does say that
power should be limited to the minimum necessary for communications. However,
most would argue that the minimum necessary is the maximum allowed because of
the contest QRM.
In the old days, max power was regulated at the input level because it was
easy for the average guy to measure. The regulation was updated to reflect a
more current technical capability to measure power output. It seems a shame
that Part 97 might have to be updated to limit ERP, since that would cripple
the revolution in huge antenna arrays that contesting has experienced over the
last 10+ years.
Kevin NC6U
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