[TowerTalk] frustrating rain and connections... update

[Gary Huber]

So if the SWR returns to normal with a towel, what would a gentle 
shaking of the antenna using the rotor to rock the antenna back and 
forth do? I'm sure some of those rain drops would drop....

73 ES DX,
Gary - AB9M

On 4/12/2016 7:02 PM, StellarCAT wrote:
> An update to my post on rain and connections for those that might be interested...
>
> I’ve had beams since 1978... I was off the air from 1990 through 2005 and when I returned it was in Arizona where rain is rare and when it comes, generally during the summer monsoon, EVERYTHING is disconnected. I don’t remember seeing the sort of effects I’ve seen with both the 15 and the 20 yagis here. And that I remember no one in their replies said “that’s normal” ... except one private email I received from an antenna manufacturer that asked to be unnamed...
>
> he said indeed it IS normal and it is caused by the dielectric change with the rain acting as a covering (impartial and uneven thickness) and thus changes the tubings velocity factor and in essence lowers the antenna resonant frequency. That is what I saw on the 15 – not what I saw, or at least I wasn’t able to confirm it since my rig (and my license) won’t allow operation lower than 14.0 which is where I saw the SWR’s worse change on the 20... I found it difficult to believe ...
>
> so ... now I have the 20 on the test tower and the 15, now with a run of new coax (common suggestion – replace the coax, even though coax can’t change properties off and on in a matter of a few hours) on saw horses... it rained last night and BOTH antennas indeed saw the same increase in SWR high in the band. And both after a number of hours (about 5 again) returned to normal.
>
> So it rained again a little while ago and the 15 went up again ... so this time I went out and I dried all the elements with a towel. Before drying it I noticed that all of the elements had water beading along their bottom along the whole element length. Didn’t do a great deal – just ran a towel over the elements. And lo-n-behold the SWR returned to normal! This over a matter of 4 minutes from the test showing it was high to the test showing it was back to ‘normal’ after I had dried the elements.
>
> So ... that to me is proof positive it is normal. I’m not sure why I don’t remember seeing it before – or why no one else mentioned it (many comments with many yagis/antennas) ... but now I know definitively that there is a direct relationship between water on the elements and high(er) SWR. [note – the SWR shifts downward so indeed it might lower the SWR on the low end of the band thus in that case being beneficial]
>
> Thanks again to all that replied. (And my apologies for doubting! )
>
> Gary
> K9RX
>
>
> From: StellarCAT
> Sent: Saturday, April 2, 2016 5:03 PM
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] frustrating rain and connections... also Noalox?
>
> Thanks for the comments – it is a hairpin design. It is an M2 6 element 15 that was built using their 15M6-125 antenna and converted to their 15M6DX ... so I refer to it now as a 15M6DX-125. Anyway it has a fiberglass center insulator with thick donuts to ensure there isn’t any creepage along the fiberglass... and if it were anything related to that it should have done it when I hosed it down (lowered to 8’)... I couldn’t really get it to change with a hose.
> Its off the tower now – had to move on (take advantage of clear days) to testing the 20M5LGS made from a 20M5 ... its now on the tower at 8’ up with high winds so its not going up any higher until the hills are calm.
> I’ll continue to test the 15 on saw horses. What I was seeing I’m sure will show even at that height. And once again: whatever design wise might be suggested it has to be remembered this is a near exact duplicate of another one that didn’t have this problem. So I’d guess it has to be either related to construction or possibly a deficiency caused by being used. The latter shouldn’t be a problem – I’ve dealt with used antennas before and never had a problem... but it could be. Please write direct if you have any other thoughts that come to mind.
> Gary
>   
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