[Lf] More on Red X Corona Dope

[Andre' Kesteloot]

les at highnoonfilm.com wrote:

> Lyle responded to my earlier question about if this stuff could
> actually improve the "Q" of a coil as stated in the QST article.
> I thought his comments were worth sharing...
> ----------------------------------------------------------------------------
> -----------
>
> It's a little hard to believe that there is anything you can spray on a
> coil that will actually *improve* the Q. Hard to beat air as an
> insulator. I would expect the Q, as measured with a Boonton type of Q
> meter, to *decrease* a tiny bit because the added dielectric between the
> windings will cause a slight increase in distributed capacitance.
> However, the coil dope should help to keep the Q from going to pot
> because of moisture, insulation degradation, etc, so all in all it
> sounds like a good idea.
>
> My present coil is wound with enamel insulated Litz wire, and even
> though it is protected by the upside-down 5 gallon plastic bucket, it
> seems to take several dry days after a very wet period for the antenna
> current to recover fully. This could be due to moisture in any number of
> things like nearby trees and the antenna support ropes, but I don't
> remember it being that much of a problem with my old basket-wound coil.
> By the way, when I first put up the #14 basket-wound coil, I covered it
> with a plastic bag, which blew to shreds in the first wind storm. After
> that, the coil hung out there in the weather for more than 5 years
> before it was replaced with the Litz coil. I did spray the Litz coil
> with some Krylon to stabilize the floppy windings, but the can was
> almost empty, it was probably the last warm day in fall, and I didn't
> feel like running to town for a new can of spray. Maybe it would be
> worth hitting the coil with some of that Red X spray before the next
> LowFER season.
>
> _______________________________________________________________
>
> My own thought is that the dope might actually help to improve the
> dielectric properties of lossy insulators such as PVC that are
> often used as coil forms. Especially if they were carefully coated
> by hand using the "brush" type dope. Allowing each coat to try
> and building up a thick coating.
>
> Then after construction, as Lyle suggested, it would be worth
> coating the actual coil itself, if just to reduce moisture problems,
> such as "de-tuning". And to extend the life of the coil.
>
> Back to the PVC problem. I've heard it suggested that using
> a sabre saw to cut away as much of the PVC from the coil
> form as possible can improve "Q" (By exposing as much of
> the coil as possible to an "air" insulator rather than PVC.
>
> Has anyone tested this? How much of an improvement could
> this yield?
>
> Les Rayburn, KT4OZ
> (XMGR)
>
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