[UK-CONTEST] 20m vertical

[Chris G3SJJ]

Mark, the basic antenna sounds like a vertical half wave dipole but with 
the base earthed, although a true half wave in the clear would be 16.5 
ft per leg. I guess the coax stub provides some matching. A 5/8w would 
be about 41.5ft. The nice thing about the design is it puts the current 
portion (the bit that actually radiates the signal) 16ft above ground, 
as opposed to a standard 1/4w vertical where the current portion is at 
ground level.

I think it is worth a try. A couple of things to look though. What coax 
did the original design use? Presumably the 6ft length is based on a 
certain velocity factor so you would need to use coax with same Vf or 
calculate the correct length for a different Vf. The other thing is what 
length of radials, I presume again 1/4w ie 16.5ft and what angle are 
they in relation to the lower section? I guess there would be some 
inter-reaction of the angle was too steep. Also presumably the feed coax 
goes straight down the lower section.

Give it a whirl, but I think if you had an antenna analyser handy it 
would help. Make up 1/2w length of coax, eg 22ft of RG213 and use that 
to check SWR etc, then you can connect that back to the shack.

Let us know hows it works I could do with a better antenna for 30m!!

73 Chris G3SJJ

daviesruby at aol.com wrote:
> Hi Guys 
>
> Thanks for all the responses absolutely superb. I will reply to each but thought I would just say thanks for all the information. It was my first posting !
>
> Has anyone tried the wa7rai ?? Its a 16 foot vertical on a 16 foot metal mast (insulated apart), inner coax to the top end outer to the bottom mast, then a 6foot length of coax it connected?across the terminals (Inner to top braid to bottom) and shorted (inner and outer soldered together)at the end this hangs down but kept 2 inches from the mast. The mast is then earthed and 3 radials place at the middle at the feed point. It gives an overall length of 5/8th ?
>
> Thanks again
>
> Mark
> MW3UPX
> ________________________________________________________________________
> AOL Email goes Mobile! You can now read your AOL Emails whilst on the move. Sign up for a free AOL Email account with unlimited storage today.
> _______________________________________________
> UK-Contest mailing list
> UK-Contest at contesting.com
> http://lists.contesting.com/mailman/listinfo/uk-contest
>
>