[R-390] Receiver 51J-4

[mikea]

On Thu, Jun 30, 2005 at 01:12:31PM -0400, Patrick wrote:
> Not an R-390 question, but with all of the knowledge here, perhaps I can get 
> some help.
> 
> The 51J-4 has tunning slugs about 1 1/2 inches long, what would be the
> impact on replacing broken ones or all of them with slugs that are 1 1/4
> inches long? (R390 type)
> I can make the length of the flexible cable  the same as the one on the 
> 51J-4...or should it be 1/4 inch longer???
> 
> Thanks in advance to any and all advive.

I can't see that it will be a drop-in replacement. If the 51J-4 slugs are
the same material as the R-390 slugs, then I suspect the inductance will 
go up some -- maybe a lot -- with the R-390 slugs. If they're not the same
material[1], then you'll need to experiment. 

OTOH, if they _are_ the same material, then you should be able to cut the 
R-390 slugs down to the right length for the 51J-4. I'd try a Dremel and a
cutoff wheel. Wear eye protection. 

But try to find some 51J-4 slugs first, please. R-390 slugs aren't all that
common any more, and there probably won't ever be any new ones. 

[1]	Just how does one go about determining this? GDO, standard coil, etc.,
	and measure inductance change per unit length?

-- 
Mike Andrews, W5EGO
mikea at mikea.ath.cx
Tired old sysadmin