Hi George:
You have obviously done you homework. And I agree that in the
majority of cases 1-2 dbs won't make a lot of difference. The main
reason for the article is that there is a ceiling, and how we might make
the most of it. The ceiling could be a linear amplifier with a 800 watt
ceiling. The same circumstances would apply if that is what a man has
to work with. The legal ceiling is different than it was, not just
because of the problem of power reduction but in the fact that it is a
hard ceiling not soft as it was in the old days. One KW DC input limit
could easily be a rectangular wave modulated micro wave with a PEP of
10KW and still be legal.
All I'm saying is that with a ceiling, either legal or
equipment, that there may be better ways to operate with less distortion
and bandwidth while improving the level of reception at the same time.
I must admit that it was the legal limit that prompted me to
write the article since it's a little bit of a cramp in my style to be
forced to turn the variac down to 220 watts input to the final for a
carrier output of 165 watts. Because my voice is so asymmetrical I must
reduce the carrier to this low level in order to stay with in the 1500
watt PEP limit. So the next time I get on 75 mtrs I'll have a switch
that will flip the microphone phase and increase the voltage on the
final at the same time. Then I'll get reports on this for about a month
and see what every one says. I'll try to keep good records and post the
results.
It's all in the fun of experimentation as for as I'm concerned.
Heck, I've seen a 4-6 DB gain just by putting 20 dollars into some
material to get the antenna up a little higher and that leads me to a
subject that is very interesting to all I'm sure. I'll always use open
wire feeds if it is at all possible.
Good luck,
John, WA5BXO
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of George Pritchard
Sent: Monday, September 30, 2002 7:30 AM
To: [email protected]
Subject: RE: [AMRadio] New link to Info on AM and legal power limits.
Would anyone consider using the transmission line loss of 1dB as the
"output
power of the transmitter" into the antenna? That would mean 475 watts
carrier for symmetrical sinewave instead of the "understood" 375 limit.
Just
more fuel for the fire. Just have a power sensor at the antenna input
terminal. Claim it's the final output of the station. Consider this: 1KW
DC
input. Transmitter is 70% eff at TEN METERS. 700 Watts out into the 1dB
transmission line. That gets power down to 550 Watts carrier into the
antenna which is .87 dB over the "spec" if considering symmetrical
modulation. If one were to drop the audio gain by .87 dB, the station is
in
compliance with the 1500 Watts at the ANTENNA input terminal. Its all
"fly
doodoo" in the ocean as far as I'm concerned. I the end... most people
see
the potential 3000 Watts PEP (750 watts X4)old limit versus the 1500
Watt
new limit as the 3 dB cut in power. Maybe, but it is only 1/2 S-unit
using
the worst case math loss. I include my PATH loss in the math loss to
justify
using my homebrew rig. Actually, the new rules give the SSB operators at
least 300 watt more PEP. 2000 X 60% class B = 1200 watts old rules. My
opinion is that there was no intention to reduce power, since it really
didn't for the MAJORITY of the hams. Only a "convenient global" power
measurement method was needed. The AMers (myself include) brought
attention
to the AM power issue). Maybe it was (and is) un-necessary. Lets not
forget
that the "DC input rule" change was also for SSB guys as well. Since the
SSB
manufacturers were not burdened to include both Plate voltage and Plate
current on their linears (or rigs), The FCC did not want to dig into the
final's circuitry to make the frivolous and dangerous measurement. These
are
the words (paraphrased) by Steven mendohlson, director of the Hudson
division during those power struggle days. I think you are all loosing
to
much sleep over this... Just forget about it, use your rigs in a polite
manner, operate and be happy. Nobody cares about a few dB anyway. 10 dB!
yes
of course. 1 to 3dB? be real. Most meters are 1dB best accuracy anyway.
George AB2KC
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of John E. Coleman
Sent: Sunday, September 29, 2002 11:32 PM
To: AMRadio
Subject: [AMRadio] New link to Info on AM and legal power limits.
I've be working on a document that might be of interest to many folks.
With the help of K4KVY, WA3WDR, W5TOB and a month or two of night work
I've come up with something good I hope. Anyway here it is.
http://www.qsl.net/wa5bxo/asyam/aam3.html
I hope it is of some use to someone and encourages experimentation.
John, WA5BXO
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