Date: Thu, 08 Dec 2016 12:48:20 +0800
From: Alek Petkovic <vk6apk@bigpond.com>
To: AMPS <amps@contesting.com>
Subject: Re: [Amps] 600W vs 1.5KW amps was: Re: SS amps and
autotune...
I know very little to nothing about the fineries of solid state amps but
I do know, that it's the first half kilowatt, whichever way its derived,
that does all the work and makes all the difference on the S meter.
73, Alek
VK6APK
## The old timers back in the day all said the same thing. The 1st 500 watts
does all the
work, the rest just heats up the shack.
100-200 = 3db
100-300 = 4.77
100-400 = 6.0
100-500 = 6.99
100-600 = 7.78
100-700 = 8.45
100-800 = 9.03
100-900 = 9.54
100-1000 = 10.0
100-1100 = 10.41
100-1200 = 10.79
100-1300 = 11.14
100-1400 = 11.46
100-1500 = 11.76
100-2000 = 13.01
100-2500 = 13.98
100-5000 = 16.99
100-10000 = 20.00
As you can see, a point of diminishing returns occurs. But dbs are
accumulative too.
Going from 600w to 1200w buys you a lousy 3db. But start doing stuff like
using a bigger
yagi, putting the bigger yagi up higher, or even putting the existing smaller
yagi up higher,
using lower loss coax, etc, then the additional 3db from the bigger
amp..combined with the
better yagi / coax setup can easily yield a net 6++ db improvement.... at
least on TX. A .5 db here,
and 1db there, and a couple more db from something else...all soon adds up.
Tiny incremental increases by themselves may not seem like its worth it, but do
a bunch of small
incremental increases, and it adds up...fast. Of course the bigger amp doesnt
buy you anything on RX,
but it will if BOTH stations at each end of the circuit use a bigger amp.
You cant work em if you cant hear em. Well you cant work em....if they cant
hear you.
You have to get practical too. Most folks on postage size city lots are lucky
if they can muster up
an inverted vee at 50 ft on 80m. 2 x similarly equipped stations may well
have a hard time talking
to each other on a noisy summer time 75m band...with each running a 100w Xcvr.
Simple fix is add at
least a 500w amp...another 7 db..at both stations. Lower bands with their
inherent ant limitations +
more noise on RX greatly benefit from more TX power.
For mobile applications, a 500w SS amp is almost mandatory....esp on the lower
bands.
Jim VE7RF
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