[WRL] Re: WRL digest, Vol 1 #69 - 1 msg

Tue, 23 Mar 2004 19:16:29 -0700

Thanx for the reply Larry.  I was hoping you would comment being a
recognized expert in WRL transmitters. (I certainly am not)
I replaced the Amperex 4-250a with a NOS RCA 4-250a just a few weeks ago and
it provided absolutely ZERO improvement in the sag problem.
Changing the plate blocking cap instantly corrected the problem.  I checked
the capacitance of the removed 500 pf doorknob and it measures 525 pf.
Under load and heat, who knows what it was doing!
I could put back the Amperex tube to see and probably will, out of
curiosity.

Now that the GK-500B is putting out full power, I am thinking about
modifying the pi inductor.  Dino, WA1KNX, measured the tank coil and we took
measurements with an LC meter.  It appears to him, that the pi inductor is
about 3 micro Henries too high to give an easy match considering the final
tube and the tank capacitors which were used.
Do you have any recommendations for winding and tapping a new pi inductor
that would give an acceptable match for 50 ohm tranmission line?  On 80 and
40 meters,  the switched, fixed padding capacitors have very little effect.
The 160 meter coupling design is another issue.
TNX and 73
Damon, W7MD

----- Original Message ----- 
From: "Larry Rau" <[email protected]>
To: <[email protected]>
Sent: Tuesday, March 23, 2004 6:14 PM
Subject: [WRL] Re: WRL digest, Vol 1 #69 - 1 msg

> MY GUESS IS YOUR TUBE WAS GOING FLAT.
>
> THERE ARE A LOT OF RF RATED MICAS ( WW II ERA SURPLUS)
>  OUT THERE.. IF YOU WANNA CONJECTURE..
> BUT HAVENT SEEN THIS DESCRIBED PROBLEM IN THE GLOBE KINGS I HAVE HAD OR
> WORKED ON.
>
> BECAUSE OF THE CONSTRUCTION OF THOSE DOOR KNOB CAPS ( ESSENTIALLY PRESS
FIT
> TOGETHER)
>
> MOISTURE CAN DEGRADE THEM OVER TIME.
>
> LARRY W6WUH
>
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