[Johnson] A question from A New BA operator.

Thu, 21 Mar 2002 13:13:37 -0500

Ray & all:
KWS-1 manual Section 3.2.3
a. Tune the transmitter exactly as for cw ....
b. Switch to AM operation
c. Back off the CARRIER LEVEL control until power drops 1/4 the cw value
(1/2 antenna current). This corresponds to a plate current of about 275
ma.

NOTE: Section 3.1 c. Turn the PA PLATE voltage on. Advance PA grid bias
control until PA idling current is 100 ma. 

The PA grid bias control and the front panel carrier level control are
two different things. Review Section III "Operation" in the manual.

Pete

On Thu, 21 Mar 2002 11:33:07 -0500 "Ray, W2EC" <[email protected]>
writes:
> 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
> > > > > > >
> > > > > > >
> > > > > > _______________________________________________
> > > > > > Johnson mailing list
> > > > > > [email protected]
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> > > > >
> > > > >
> > > > > _______________________________________________
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> > > > >
> > > >
> > > > _______________________________________________
> > > > Johnson mailing list
> > > > [email protected]
> > > > http://mailman.qth.net/mailman/listinfo/johnson
> > > _______________________________________________
> > > Johnson mailing list
> > > [email protected]
> > > http://mailman.qth.net/mailman/listinfo/johnson
> > >
> > 
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