[Icom] Icom Pro II and PW-1 (Do I have a problem here!)

Thu, 27 Jun 2002 09:02:17 -0400

Bill,

I don't think you have a problem... aside from what looks like wide
tolerances for wattmeter calibrations.

My PW-1 disagrees with my wattmeter by about +10% at the high end of the
scale - which is to say that when my wattmeter reads 1000 watts the PW-1
reads about 1100; and by about -10% at the low and of the scale - wattmeter
says 100 watts, PW-1 reads about 90. I adjusted my PW-1 based on the
wattmeter reading 1KW and the PW-1's ALC meter at the set point. [why do I
trust my wattmeter more than the PW-1 meter? -- because it allows me to get
more power out! ;-]]

The interesting reading is when you reduce the drive power from the
transceiver (an IC-746 in my case) to see at which point the ALC clamps the
amp's output power. [Reduce drive power to minimum, then slowly advance
drive until output reaches max (the 1000 watt point). Put the amp in
standby, and measure output power from your transceiver.]  For me, it only
takes about 55 watts of drive to hit 1 KW out from the PW-1... which means I
can run my transceiver much leaner (and cleaner I hope) and still deliver
max out from the amp.

Probably the only modes where you would need to worry about 1000 versus 1250
watts is one of the solid carrier modes like RTTY or PSK -- and I never
operate those modes at full output anyway. So, at least for me it would not
be an issue.

-larry
K8UT
----- Original Message -----
From: "Bill Tarkington" <[email protected]>
To: <[email protected]>
Sent: Thursday, June 27, 2002 12:07 AM
Subject: [Icom] Icom Pro II and PW-1 (Do I have a problem here!)

> Having recently purchased a Pro II, I followed the owner manual
instructions
> for both the amp and radio to set the ALC level on the amp so as not to
> overdrive it and risk FET damage.  Once all proper connections are made,
> book says to adjust the exciter (Pro II) output to 100W, then turn ALC
> adjustment screw clockwise slowly while key down on either CW/RTTY and at
> same time reading the ALC scale on the PW-1 control head until meter needl
e
> is dead on the ALC adjust mark. Once adjusted thusly, key down at 100W
from
> the exciter and check PW-1 power meter to insure 1KW output.  Did all this
> and all looked to be okay.  HOWEVER, I noted that the RF power knob on the
> ProII was not fully clockwise (wide open).  Advancing it to full open
seemed
> to indicate the Pro  II was putting a little something in excess of 100W
per
> its power meter.  Bottom line is, I do not know what meters to trust here.
> Out of curiosity, got out the Bird 43 Watt meter with 1000W slug therein
and
> did some checking. First used the Bird meter with 100W slug to set
barefoot
> output on the ProII at precisely 100W and left it there(  little less than
> full open). Further testing with the Bird in and out of the circuit with
the
> PW-1 output seems to indicated the Pro's watt meter is pretty accurate,
but
> the power meter on the PW-1 is reading low.  If do the ALC adjustment
using
> the PW-1 power and alc meters per book,Bird says full amp output is 860W,
> not 1KW the PW-1 watt meter indicates. If do the ALC adjustment using just
> the Bird meters readings while ignoring the PW-1, the ALC goes into the
red
> some little way, and the output per the Bird is about 1250W.  All this
> leaves me wondering which watt meter to trust to obtain the full 1KW
output
> of the amp. If use the Bird and guess wrong, will 1250W out with ALC being
a
> little in the red likely cause me some amp damage?  The safe thing to do,
of
> course, is go with the PW-1.. BUT, I want them to agree more or less with
> one another or understand why not.  Incidentally, if it matters, all tests
> were done into a  1500W dummy load.  Am I missing something here?
Comments
> please. Bill, K3YC
>
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