[TowerTalk] Loss in Alpha Delta Switches ?

[Tom Rauch]

> Was "shocked" to see that the contact was made when
>  the EDGE of a thin strip of metal was pressed down
> against the flat surface of another strip.  It was at such
> a contact I had experienced an arc or burning do to
> high swr,  I  guess.  Anyway,  the switch became NG.

Most of these indoor manual switches are imports, and I suspect 
many are from the same manufacturer.

The MFJ switches I looked at had a lightning protector with too low 
a rating. With a "typical" 1500 watt amp into a 2:1 SWR the 
lightning protection pills would sometimes conduct.

I am NOT a fan of gas tubes for lightning protection at HF with high 
power. They usually cause more damage than they prevent, but 
some people insist on using them.

Also the die cast housing had supports that were about 50 
thousands of an inch too high. This caused the small springs that 
push up on the board that forms the stationary contacts to be at 
the end of travel, and not apply any tension to the contacts.

Once the lightning pill voltage was increased and the housing were 
done properly that switch became very reliable.

You might look carefully at yours and see if the stationary contact 
board floats on four little springs. Maybe it has a mechanical 
problem like the units MFJ imported had.

I now use an RCS8V for my indoor (and outdoor) high-power 
switching.
73, Tom W8JI
W8JI@contesting.com 

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