[UK-CONTEST] Vertical Dipole

[Darren G0TSM]

I've tried vertical dipoles in the sea and when you get salt water 
around them and they are as *low* as possible without getting them wet 
then your 100W will easily compare with a local 400W+Yagi station. But 
move the vertical away from the water (both up and away from the sea) 
and you loose the advantage. I've carried out 100s of A/Bs between 
10/15/20M vertical dipoles, a rotary triband dipole and mobile 8ft 
whips. The mobile whips are great if you can get the car up close to the 
water but the performance of the vertical dipole in the sea is quite 
outstanding. The only thing that really caught me out was how much the 
SWR varied, from setting the ants up at home in the garden, to plonking 
them on the beach at low tide and then that all changes when the tide 
comes in.

The way you have described the way you intend to set them up is pretty 
much perfect, with the exception that can you get them closer than 5M? 
The closer the better.

I'm not sure if I'll be out and about this year as I lost my spiderpole 
in SV5. Hopefully the replacement will be here this week and I can go 
out and play.

73 Darren G0TSM



On 25/07/2011 14:49, mm0bqi wrote:
> Following some very helpful and interesting comments last year about my IOTA
> contest ground plane antennas I have gone for a change this year.   During
> our recent EU108 expedition we tried vertical dipoles beside the sea and
> they seemed to work.  However I am not fully convinced but feel it is worth
> having a go!  I have two questions.
> 1.  Will there be any great performance difference between the two types of
> antenna?  My main target area is EU and I have a clear sea path to VK/JA
> should the bands open....
> 2.  The antennas will be on 12m fishing poles, does the height of the feed
> point matter or should I just make it as high as possible?
> Each antenna 10/15/20m will be taped to a separate 12m fishing pole and
> they will be within 5m of the sea.  The coax will come away at right angles
> along a cane for about six feet then slope to the ground at about 45
> degrees.
> Thanks
> Jim,  MM0BQI
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