1) I strongly disagree with any interpretation that multiple amps driven
from a common signal source are somehow "multiple transmissions" on a band
and are somehow, by their nature, illegal.
2) I do not quarrel with any interpretation that would conclude that
running more than a total of 1500 watts output from all amplifiers (but
where measured is still debateable in my mind) is illegal. From any
external measuring point it is not possible to determine whether there is a
single amp or multiple amps.
Lets look at the possibilities and show that multiple amplifiers are not
multiple signals and are perfectly legal.
1) A single tube feeding a single antenna has no need for discussion.
2) A single tube feeding multiple antennas should have no need for
discussion but now we have "two signals on the band" by the logic that
says that if the two antennas are at opposite sides of my 160 acres,
separated by a 1/2 mile, and, say, are pointed in different directions.
I could go near one antenna and measure a strong field around it ("clearly,
one signal") and then go to the other antenna and measure a strong
signal around it ("clearly, a second signal"). If you support this scenario
as "two signals" at what point do they become one signal? When the
two antennas are mounted within each others near field? Only when they
are pointed in the same direction? Clearly a single amplifier feeding
multiple antennas (phased arrays or, separate antennas spraying in
different directions, or any other arrangement) really is a single
signal on the band. That UL7 will only hear you once (if you are lucky).
3) What about multiple amplifiers that are combined into a single feedline
then either used to drive a single or multiple antennas. Say I take two
SB-200s each running 750 watts and combine them using an external hybrid
combiner (which provides a measure of isolation between the amplifiers,
reducing their interaction). Is this illegal? I really doubt it!! In fact
this technique is used in solid state amps all of the time. The solid
state KWs often have 4 or 8 amplifiers (each with two push pull transistors)
that are combined in hybrids (internally) to provide a single signal.
4) So what if these two SB-200s (each running 750 watts) to drive two
dipoles in a phased array? These signal"s" get "combined" in the near
field around the array. There is no measureable difference in the
far field from this than driving the two dipoles with a single 1500 watt
amplifier and a power divider scheme. What about the case not of
two dipoles in a phased array, but of two Yagis (either co-located on the
same tower or on separate towers) pointing in different directions? This
is still a single signal!! The net result in the far field is the same
whether you use one amp running the legal limit and a power divider,
or two amps each running half the legal limit. That UL7 is still only
going to hear one signal.
5) The single signal rule means one RF carrier with one modulation signal!
How it is amplified and power divided and radiated is irrelevant. Only
one QSO can happen at a time! The same mathematical expression describes
this signal in the far field whether it is amplified by one, two, or a
hundred amplifiers.
6) Any interpretation that multiple amplifiers are inherently illegal would
go against the concept of innovation for which hams are suppossed to be
famous. Large phased arrays are often driven by a large number of small
amplifiers in other services. The reasons for this are valid for ham
applications as well. It is more efficient to drive each element of a
phased array with an individual amplifier rather than taking all of these
amplifier modules and combining them into a "single signal" with a
power combiner and then splitting them into individual signals again
with a power splitter to drive the individual antenna elements.
7) Again, multiple amplifiers are not multiple signals! Multiple signals
are only present when two separately time varying RF signals with
separate modulations are generated and radiated. (Maybe I should worry
about SSB being "separate signals"! With a spectrum analyzer I can see
multiple frequency components being radiated at the same time.)
Want to build a reliable, no tune amplifier and eliminate feedline loss
in a large array of Yagis? (My 4 stack of 8 element 10M Yagis has
100 feet of RG-213 in each sub feed, plus the 200 feet of 1/2 hardline
loss in the main feedline.) I think I will use four 400 watt solid state
amps and bolt one to each boom of each Yagi. With built in antenna
switches, receiver preamps, and separate receiver feedlines I could
not only reduce my feedline loss to zero (2db improvement), but also look at
the separate outputs of each receiver preamp and measure in real time the
phase differences between these signals and measure the angle of arrival of
each signal. And with independent phase shifters at the inputs of the
power amps I could steer the transmit signal in elevation to
correspond with the received signal. Adaptive arrays like this have
been around for a long time. Maybe CT-11 or whatever will also log
the angle of arrival of each signal for off-line propagation studies
and make sure the TX signal is steered properly in order to keep the
rate meter up. And, probably, the same people who have worried about CT-8s
DVP capability and where that is leading, will worry about the dynamic
beam pointing of CT-11.
Technical innovations are what drive me to contest. The zeros of the
world need all of the innovation we can muster to overcome the "east
coast advantage".
What are my limits, is nothing sacred, you may ask. The only "innovation"
of recent discussion,in my mind, that really seems beyond fair play, is the
practice of taping contests and doing the logging off-line after the contest.
This seems to me to be making a 48 hour contest (working and logging your
QSOs) into a 96 hour contest. You can't stop anyone from doing this, because
there is no way to know, but I feel like it is in the same league as using
packet when in single op UNassisted class.
Again, for emphasis, multiple amps are legal, but the power rule of 1500
watts limits the TOTAL power to 1500 watts. One 1500 watt amp. Two
750 watt amps. Ten 150 watt amps. But where do you put the wattmeter?
Somewhere in the feedline(s), but right at the amp with a barrel connector,
or with 6ft of coax, or maybe at the feedline after the coax switch (it has
a little loss). But what if this switch is a remote switch? Mount it
after the switch at this point (one wattmeter for each band, not so
ridiculous since the wattmeters are not perfectly calibrated and maybe
you calibrate each one perfectly for its particular band because you are
a perfectionist). Or at the RG-8 jumper from the hardline around the
rotator? Or at the feedpoint itself? This isn't any more power than if
I bolt my Alpha to the boom with a couple of big U-bolts and run a
220 volt line up the tower. It autotunes and would work great, run cool
in the winter, and be water cooled in the spring rains. 1500 watts at the
feedpoint. I am not taking a position on this, other than that Dave Leeson
has raised a valid point. (W6QHS runs an Alpha in his shack with lots of
feedline loss--so much feedline loss on 15 meters that an 87A doesn't have a
prayer to make it up. And he just turned in a great 15 meter score in
ARRL DX phone from the west coast, by the way) t. If it really means 1500
watts out from the amplifier at the connector on the back, then my desire for
technical innovation would tend to drive me to build remote amplifiers.
NOTE: I am still running 1500 watts out AT THE AMPLIFIER (IN THE SHACK)
with a Bird Wattmeter bolted directly to the amplifier with a barrel
connector, and will continue to do so for the foreseeable future.
Thanks for following along. (I am really doing all of this writing just
to distract everyone from the 24 hour issue. Is it working?)
73 John W0UN
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