[TowerTalk] frustrating rain and connections... update

Wed Apr 13 08:54:55 EDT 2016

Remote control leaf blower to blow the water off the elements.
or
Remote control small semicircular squeegee.
or
Eccentric weight on a motor's shaft to shake the mast to vibrate the 
elements of the antenna
or...

On 4/12/2016 11:09 PM, Bob K6UJ wrote:
> 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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>>
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