[ARC5] Potentiometer value needed

[Kenneth G. Gordon]

On 9 Aug 2014 at 20:54, Jim Falls wrote:

> The rods have been broken off. I intend to use it for CW, but would like the AM
> option. I'm glad there is a mitigation. I thought they were fixed coil slug
> tuned units.

No.

The adjustments for alignment are variable capacitors at the tops of the 
cans.

The two coils are fixed-value non-adjustable coils, but the top coil can slide 
up and down about 1/4" or so, which varies the coupling between the two. 
Looser coupling, wider spacing, means greater selectivity.

There are two notches in the phenolic carrier that the coil is mounted on, and 
there are two fixed small metal "slides" with a "tit" on them that slide into the 
notches when you move the coil.

The coils are held in place with beeswax, which at this late date gets hard, 
making it difficult for the coil to slide.

That is why the rods break off. They are only some sort of fibre and are not 
very strong.

If you heat the can up a bit, the beeswax will generally soften enough to 
make the coil slide more easily.

But removing the can, removing the cover, and moving the top coil by hand 
is fairly easy when the rods get broken. It is simply a bit time-consuming.

Ken W7EKB