Multiple Power Amps

[0015017 at msgate.emis.hac.com]

From: Balmforth, Kevin D
Date: Mon, Mar 22, 1993 10:30 AM
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