On Apr 21, 2004, at 3:35 PM, AA6DX wrote:
Hmmm. OK .. guess everything is bigger in Tejas ... including Ohm's
law!
HIHI ...
Let's do a "what-if" ... IF you had 24Ø VAC Single ~ --- you ran it
down
25' of #16 copper ... and you were running a "Tejas KW", of 5.7 KW
input,
key down (say, FM, RTTY, Digital, AM, or CW with a brick on the key) --
which should get the 1.5KW legal output rather handily, actually more
like
3+KW .... a single 4-1ØØØ does 2.5 KW handily, capable of a wee bit
more ...
depending on amp design, of course ... THAT would require 25 amps.
So, we
have 24Ø V, 25 amps, 25 feet of "waaaarrrrr" ... AWG 16 --- the
voltage
drop would be ... tah dah! 6.1 volts.
With a resonant-choke filter, pretty close. With a C-filter, not
even in the ballpark. Phil knows the score.
233.9 VAC delivered to the xfmr. Do the math, Phil ...
By the way, of course, on the OTHER hand, by increasing the wire size
to
#1Ø, there is considerably less voltage drop .... you get 4.6 more
olts - All the way to 238.5 at the business end! Mind you, this is
assuming you're running over 5KW input to the amplifier. About 1ØØ
Volts
on the output side ----- again, if you are running 5.7 KW. By the
time
the rest of the power supply components get into the mix ... the caps,
the
choke(s), the diode losses, the bleeders, metering, etc .... that
voltage
difference is essentially nil. (With number 4, you would only lose
about
1/2 volt.)
But, you are correct ... if one is to run a 4CX-1ØØØØ at full tilt,
you need
some serious "waarrrrr". Holy Cow, the filaments require over 56Ø
watts! As
to rewiring the ham shack ... does the term "3-Phase" strike a bell?
Maybe for the 8171's big brother, the 8281, but the li'l brother can
be run easily on SSB from 1-phase 240v -- provided it is tuned up with
a tuning-pulser.
You might want to consider some other coax too .. Andrews line, with
dryer!
The first FM transmitter that I was chief for used one of these ...
For 20m, RG-213 can handle an 8171 on anything but full-bore RTTY.
Cheers, tnx conversation ..
From: "Phil Clements" <philk5pc@tyler.net>
To: "AA6DX" <aa6dx@pacbell.net>; "Jim Isbell"
<millenniumfalcon@cableone.net>; "Mail list Amplifiers"
<amps@contesting.com>
Sent: Wednesday, April 21, 2004 2:19 PM
Subject: Re: [Amps] Serious design stage
Hmmm .. just wonder why the large wire requirement, Phil? We are
not
connecting a restaurant size `lectric range here. Assuming we are
talking
AWG size wiring, the current carrying capabilities @ 230-240 VAC,
single ~
is about:
#4 = 37,000 watts
#6 = 27,000 watts
#10= 13,800 watts
#16= 5,750 watts
(Approximately, safely ... your mileage may vary!)
Is that not correct?
That is not correct because you did not specify a length.
I don't like warm wiring inside my walls, so I spring for a few bucks
more for cable
when I wire a ham shack. My service here is 37 kva from the street
transformer.
The power company chose to run size 0 wires for the 50 foot run to my
service
entrance panel. I guess we are conservatives down here in Texas!
The bottom line is that you do not want anymore system voltage drop
than is absolutely
necessary.
I was also advising the wire size not for a 4-1000A, but for the
monster transformer
the guy has there. If Rich convinces him to try a 8171 amp at a later
date, he will not have to
rewire the ham shack.
(((73)))
Phil, K5PC
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Rich Measures, AG6K, 805.386.3734. www.somis.org/
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