[UK-CONTEST] 20m vertical

[James Thresher]

Hi Mark,

A beam correctly setup and at the right height will almost always outperform a vertical (1/4 or 5/8) regardless of ground conditions.

A ground mounted vertical on or near a large expanse of salt water will perform very well (Salt water is about as close to perfect ground as you can get), the advantage of this is that they are far simpler (and usually cheaper) to buy or build. They also don't require a tower to get them to the correct height or a rotator, this is probably the reason why they are favoured by some Dxpeditions near salt water (they will also weight a lot less).

However the most gain you are likely to get from a vertical in near perfect conditions is going to be around 1dbi (1/4 Wave) and about 2-4dbi (5/8 Wave, can't remember the exact figure for a 5/8ths). The gain will be at a very low angle of radiation when on salt water (good for DX).

There are some disadvantages though, in crowded band conditions you will have no directivity or F/B ratio unlike a yagi, so in big contests it can be difficult to get rid of that unwanted QRM from Europe while you are trying to work the US.

How high is your G5RV? I suspect that you will find a big improvement by moving to vertical's for 20m and 40m, especially if putting up a tower with yagi and rotator are out of the question. The cost is also much less, get yourself some fibreglass poles they are pretty cheap for the 5m and 10m variety then it's just the cost of the wire. You can probably build both the 40m and the 20m for less than £70.

Hope that was helpful

Good luck with the Intermediate exam.

73 de James M3YOM

-----Original Message-----
From: uk-contest-bounces at contesting.com [mailto:uk-contest-bounces at contesting.com] On Behalf Of daviesruby at aol.com
Sent: 12 November 2008 13:11
To: uk-contest at contesting.com
Subject: [UK-CONTEST] 20m vertical

Hi Guys

Ive been reading about people on DXpeditions/contests who swear by verticals over beams when located on or near the sea. I was thinking of doing similar as I am about 50m from the sea (esturay and salt marsh) and was looking for some good designs Im thinking of the WA7RAI as shown on his web site (1/4 wave with shorted stub so acts as a 5/8 vertical) being in my location the ground (sand) ?is very damp and salty, I can put a 10 foot earth rod down and be in the wet stuff ! Ive got a\20 foot pole?I could mount it on if needed.

Also thinking of a vertical for 40m

Any advice would be very much appreciated

Ive got a G5RV at the moment

Mark

MW3UPX (intermediate exam next week !)

Anglesey
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