[Elecraft] securing toroids in K2, why not?

[Don Wilhelm]

  Ron,

Forget the LCR meter with the K2 kit - other than to evaluate the 
effects of various "fixatives" for toroids.
Wind the toroids with the number of turns specified and all will be OK.

As far as conformal coating, again, it makes repair or rework a "pain" - 
but if you insist ...
What I can say is that I have worked on many K2s (over 600 to date), and 
some have been subjected to extreme environmental conditions (salt 
spray, high humidity, etc.), and on all of those, even though the 
exterior of the K2 shows signs of corrosion from that environment, all 
those I have seen look "pristine" on the surfaces of the boards.  Based 
on that, I would discourage using any conformal coating, it is just not 
necessary unless you intend to dip your boards in salt water.

I have no idea what problems may occur if you would use a conformal 
coating, other than that the coating must be "worked through" if any 
repairs or upgrades are needed in the future.

When measuring with an LCR meter, be certain it is working at the 
frequency that the toroid will actually be used.  Many LCR meters work 
at a low fixed frequency, and the results obtained from those meters can 
be misleading when the toroid is used at the frequency that it was 
designed for.

73,
Don W3FPR

On 7/2/2011 9:48 PM, Ron VE8RT wrote:
> Thanks Don,
>
>       I've received a few helpful responses already, which I
> appreciate.  I could do without the RTV, except I like it at RFC14
> because its jammed into a tight space, and as you mentioned, its a RF
> choke which wouldn't be critical.
>
>       For a very long time conformal coating has been used in my
> field, avionics.  Its great stuff to reduce board corrosion in damp
> environments, even if its just from condensation.  That is if its
> applied carefully and the board and adjustable components and
> contacts are well masked.  If it won't mess things up, when its
> finished I'd like to apply conformal to parts of the board,
> especially the underside of the board.
>
>       Back to the RTV on RFC14, there is a very small dab of it on the
> bottom of the core, just to keep it upright.  Anymore than a small
> dab would be a waste.
>
>       OK, future cores I'll leave alone unless the manual says
> otherwise.  And conformal coating parts of the board can wait until I
> look into this further.  I have spare cores and wire, and an
> reasonably good LCR meter at work, I'll see what difference the
> coating makes in the value of toroidal coil.
>