Someone mentioned that in the US, the power is measured at the back of the amp.
Your rules don't stipulate where it's actually measured. Dave Leeson, and
other's,
contacted FCC officials, and the FCC said it was reasonable to measure the
power at the
load, IE: ant feed-point. US broadcast TX are measured at the feed-point, or
close to it, not the
output of the amp at base of tower.
.5db of feedline loss = 10% LOSS. 1 db = 20 %loss 2db = 37% loss 3db =
50% loss
IMO, most folks will have at least .5db loss..and a lot more on the upper HF
bands...esp
with the typ 140-400' length's of coax used. So the next time you tell the
fella on the other end of the
qso, that ur running 1.5 kw.... stick a pep meter at the top of the tower, and
get your friend on top
to give you the real story....via his 2m FM hand held.
I know a few folks who actually did that procedure, [including myself]....and
got a REAL eye opener...with the dismal
results. Broadcast TX manufacturer's have factored line loss into the
equation. [ ditto with cell sites, commercial vhf/uhf]
With just 2db of feed-line loss, you require 2380 watts OUTPUT..to get 1.5 kw
at the ant.
OK, all the above might be a moot point.... but your typ 30-46 lb plate xmfr,
when run at it's max CCS ratings,
typ has a high internal temp. If you want a real 1.5 kw at the feed-point..
you really need a 2 kw output rated amp...
which will require a 3.5 kva CCS hypersil xmfr..which will weigh 60-64
lbs..and will STILL run hot when maxed out.
When Roger was trying to calculate duty cycle on ssb/cw/rtty etc, you forgot
to toss in the IDLE current.
Unless EBS is used, that will throw your calcs way off. That 2 x hole QRO
/Commander amp with the russian
tetrodes does not use EBS...and the pair of tubes idles at a whopping 450
ma.....and 675 ma for the 3 x hole
version of the same amp. The heath idles at 180 ma. The stock drake amp idles
at 230 ma. Don't forget
processed SSB, or ssb with a lot of low freq content in it, like essb. That
will increase the duty cycle by a
whole bunch. Ham Amp makers want to stuff small xfmr's into table top amps.
IMO, the B+ supply should
be in a separate box.... on the floor, behind the desk. Then the weight is
split between RF deck..and B+ supply.
The HB folks have the advantage they can configure any way they want.
Jim VE7RF
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