[ARC5] Selectivity improvement in ARC-5 receivers - another question.

[Kenneth G. Gordon]

On 2 Jun 2014 at 16:54, Dennis Monticelli wrote:

> Ken, 
> 
> I have not done any measurements but I'm pretty sure the plates only affect the
> electrostatic coupling not the magnetic coupling. The two coils are in the near
> field of each other so magnetic coupling is probably dominant. The designer must
> have had a reason to isolate the two coils from a capacitive coupling
> standpoint.

That makes sense, Dennis. Thank you. I agree that the designers must have 
had a reason. As far as I am concerned, all those folks who were involved in 
the design of the ARC-5 were sheer geniuses.

Ken W7EKB
 
> Dennis AE6C
>
>     Another question (to which you may not have the answer): in the ARC-5 
>     IFTs
>     there is often a small circular grounded metal plate between the two coils.
>     My first impression on finding one of these was that its purpose was to
>     reduce the magnetic coupling between the two coils.
> 
>     However, after further investigation, and thinking about it, I am not at all
>     sure that is its real or only purpose.
> 
>     Moving the coils further apart, rather than adding a second "plate" does far
>     more to improve the selectivity of those IFTs than adding that second plate,
>     spacing those plates so that one is nearer one coil, and the other nearer
>     the other coil.
> 
>     In fact, it seems that removing that metal plate entirely while in the
>     process of moving the coils further apart results in no apparent ill
>     effects.
> 
>     This apparent result, however, may be simply because my limited test
>     equipment did not show the effect.
> 
>     In any case, not knowing whether or not my removing the plate had any
>     effect, I put it back in, but centered it between the two coils.
> 
>     I have yet to complete my own "research" on this selectivity improvement
>     idea. I am FAR behind Jeep's work on it.
> 
>     Your thoughts?
> 
>     Ken W7EKB
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Kenneth G. Gordon W7EKB

"Courage is being scared to death but saddling up anyway."--- John   Wayne