Re: LF: Soldered joints on antenna wire

["john sexton" <computernetworks@excite.com>]

Thanks to Bob, Markus and Alan for their helpful comments.
On the question of multistrand wire, it occurs to me that the problem might be even worse with Litz which has not been adequately cleaned. If only some of the strands are connected and the antenna is used for transmit with perhaps a couple of amps or more, some of the connected strands could fuse and set off a chain reaction.

My thinking with soldered joints was that at RF, skin effect means that the current is flowing through the solder not the copper and solder quickly tarnishes when in the open, so even though the DC resistance remains low, the RF resistance might be quite high as a result of the badly conducting outer surface. Whether the RF will then migrate inwards toward the copper or not is unknown to me.

It might be a good idea to paint over newly soldered joints with a compound that weathers well. Any thoughts?

73, John, G4CNN



--- On Mon 02/18, Vernall

wrote:
> John,
>
> One thing that has worried me with multistrand wire is whether there can
> be
> arcing or intermod if one conductor in the bundle has a break in
> continuity.
> This could also arise if the centre wire in a 7 strand bundle is not
> soldered properly. It is very hard to tell if solder has penetrated
> "right
> through", especially for wire that has been out in the open and
> weathered
> somewhat. What I am saying is that at RF there can be potential
> differences
> due to transmission line effects, and a conductor that has one end
> floating
> is like a stub, but as the gap is small it can easily arc over. Arcing
> could cause broadband QRM.
>
> So while soldered joints in antenna wires appear to be fair game, it
> would
> pay to have the individual wires cleaned to a "bright copper"
> condition
> before firing up the solder bolt.
>
> I have seen crimps used to join antenna wires, and crimping could be
> suspect
> for multistrand wire.
>
> I would not worry about losses in soldered joints, but as Markus has
> commented, corrosion could be a limitation in the longer term. In any
> case,
> you will probably want to experiment with changes to your antenna well
> before corrosion has a chance to show up :-)
>
> 73, Bob ZL2CA
>
>
>
>

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