[Johnson] A question from A New BA operator.

Thu, 21 Mar 2002 11:33:07 -0500

That's interesting. As I said, I hadn't tried it on the Valiant. I
mentioned it only because that is the method indicated by Collins to run
the KWS-1. According to the Collins manual, you load the KWS-1 (pair of
4X250B's) to full output, then reduce the grid drive (watching the plate
meter and a power output meter) until you get to a power output level
you want. For example, I load the KWS-1 to 500ma which gives about 575
watts CW out. Then I reduce the grid drive to a plate reading of about
275ma, which gives about 140 watts CW out. This is the exact procedure
as depcited in the Collins Manual for reducing power and is how I run AM
with the KWS-1.

Without thought or investigation I just took it that dropping the grid
drive a bit in the Valiant would provide the same power reduction. What
would be the different forces at play that would make it OK to do it on
the KWS-1 but not on the Valiant?  

73, Ray  W2EC  

[email protected] wrote:
> 
> Always run the 6146's at their rated grid drive voltage. Loading up the
> Valiant to full power and then using the grid drive control to reduce
> power is wrong. It will cause AM distortion and drastically reduce the
> life of the tubes. If you want to reduce output power, put a 3, 6, 8, or
> 10db pad between the transmitter output and your antenna. A less
> attractive way, and not normally recommended, would be to put a variable
> pot for the screen resister of the driver tube. Always run the output
> tubes at their rated grid voltage.
> Pete,WA2CWA
> 
> On Thu, 21 Mar 2002 09:12:55 -0500 "Ray, W2EC" <[email protected]>
> writes:
> )........
> >
> > Another thought, and I haven't tried this, is to load the Valiant up
> > to
> > full power (330ma for AM, 450ma for CW), peak the grid then back off
> > the
> > grid drive (normally 8ma) until you get the power level you want.
> >
> > 73, Ray  W2EC
> >
> > "Guy Olinger, K2AV" wrote:
> > >
> > > Correct. Run it at specs.
> > >
> > > The plate voltage is fixed, the screen voltage is fixed, the L/C
> > > ratio's in the tank circuit are only partly variable since the L
> > being
> > > used on a given band is fixed. The whole shebang is at maximum
> > > efficiency at the specified settings.
> > >
> > > I've seen guys operate a Valiant AM until the cows came home.
> > Just
> > > don't drop a book on the mike switch and get up and leave. When
> > your
> > > voice starts to hurt let the other guy transmit :>)
> > >
> > > ----- Original Message -----
> > > From: "Dr. Clifford L. Coleman" <[email protected]>
> > > To: <[email protected]>
> > > Sent: Wednesday, March 20, 2002 4:23 PM
> > > Subject: Re: [Johnson] A question from A New BA operator.
> > >
> > > > While restoring my valiant, I found(as the manual suggests )
> > that
> > > less
> > > > loaded causes high modulator current-so I tune it up to full
> > power.
> > > cliff
> > > > k9jts
> > > > ----- Original Message -----
> > > > From: "Mullin, Edward J." <[email protected]>
> > > > To: <[email protected]>
> > > > Sent: Wednesday, March 20, 2002 1:40 PM
> > > > Subject: [Johnson] A question from A New BA operator.
> > > >
> > > >
> > > > > Hello All,
> > > > >
> > > > > I've been lurking on this mail list for a while, as I've been
> > > > > working on my Valiant.  So far I have gotten it working
> > again,
> > > (recapping
> > > > > and replacing a couple of tubes was all it needed:)   Now I
> > want
> > > to use it
> > > > > on the air.  (I've been testing into a dummy load during
> > > restoration). I'm
> > > > > new to BA's (and Ham operations) in general, and  I've been
> > > reading the
> > > > > manuals alot.  What I want to know is: What is the correct
> > method
> > > for
> > > > > transmitting at less than full power. The manual is good at
> > > describing the
> > > > > tuning process, but it doesn't really cover this
> > information.(at
> > > least I
> > > > > didn't figure out where it was.)
> > > > >
> > > > >
> > > > > 73 de KB1HYS
> > > > >
> > > > >
> > > > > > Edward Mullin
> > > > > >
> > > > > >
> > > > > _______________________________________________
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> > > >
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> > >
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> >
> 
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