[TowerTalk] frustrating rain and connections... update

[Bob K6UJ]

I have always noticed a slight change in the swr with hf yagis when it 
is raining.  Just a
minimal change though.  Nothing like what Gary, K9RX reported.

Bob
K6UJ


On 4/12/16 7:36 PM, Gary Huber wrote:
> 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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