Phil,
So the solution to the autotransformer action was in your case to short out
the 160 meter section with a relay when not in use? I have a similar problem
with my HB 3-500Z deck. When on 75 meters it arcs big time around the 160
meter position on the switch. I have a few RJ-1As laying around. Wonder it
that would be suitable to short out the unused turns?
Lane
Ku7i
PS sorry abt responding to this older post so late.
-----Original Message-----
From: Phil Clements <philk5pc@tyler.net>
To: amps@contesting.com <amps@contesting.com>; Alek Petkovic
<vk6apk@eon.net.au>
To: <amps@contesting.com>
Date: Friday, July 30, 1999 6:12 PM
Subject: Re: [AMPS] explain this one
>
>>When I tune up on 10m, I get arcing on the 160m position on the
>bandswitch
>>to the frame of the switch. This position switches in the 160m
>padding
>>capacitor. Nothing in the 160m circuit is connected when it's on 10m.
>The
>>tubes also get extra warm in the 10m position.
>>
>You have an autotransformer going for you. With the addition of the
>WARC
>bands plus 160 meters a coupling problem exists within the tank
>circuit.
>
>If you will notice on the schematic of any of the late model 9 band
>amps,
>they utilize a band switch that shorts out 3-4 of the unselected
>positions
>Just shorting out the unused part of the Pi coil is no longer
>effective due to
>the autotransformer action. Even with roller coils, as in the Henry
>3-K and
>8-K Ultras, half of the Pi roller coil is shorted out with a relay in
>addition to
>the shorting strap on the roller itself. This problem will show up on
>other
>bands also, depending on your layout and components. I pulled my hair
>out a few years ago when constructing my first 9-bander. Instead of 10
>meters
>arcing the bandswitch, it was 40 meters in my case. This has nothing
>to do
>with any oscillations, it is because 160 meters is a LONG way up the
>coil
>from 10 meters!
>
>GL!
>
>(((73)))
>Phil, K5PC
>
>
>
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>
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