Re: [IRCA] More coax experiments

[Rick Kunath <k9ao@xxxxxxxxxxx>]

Patrick Martin wrote:

> I fiqure I am going to need the metal box anyway, so why not start
> there. It will be interesting to note, if the s meter readings go down
> by attaching the cap on the end of the coax anyway.

Yes, that will tell the tale. Until you get that (the coax) RF tight, 
nothing else will matter.

> The choke idea
> sounds a bit involved, so I would do that as a last resort. The metal
> box first, then the coax,  To test the coax with the cap to terminate
> it, what kind of s meter readings would be exceptable?  Anything?

I'd say extremely low readings, if any at all.

As to chokes, Radio Shack has some ferrite clamp-on chokes available. 
They have some that open in half and you wind the coax through it, but 
coax generally can't be bent that tight and the chokes are a ferrite mix 
that works better at HF. Plus the inter-turn coupling affects the 
ultimate ability of these to choke at MW.

There are some you might try, part number:

273-105.

You'd need 3 or 4 of these. You have to modify the plastic holder by 
cutting off the ends of the holder so that when you place them on the 
cable, end-to-end, the ferrite touches the next choke in line. With the 
plastic still on the ends of the holder, the ferrite is too far apart, 
and you wind up with less choking effect.

Ferrite material designed for medium wave is better, but these might be 
worth a try if you need to see if they'd help.

As to the ferrite toroids for choking, these just slide over the coax, 
and you tape them in place, one touching the next, in a big stack.

Rick Kunath
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