Hello Gary - Thanks for the interest and the info on Helical Winding of
my vertical antenna..
It really seems to do the business on 20 & 40 Metre Bands, but so far in
the 3 days the antenna has been up, I have heard nothing on 15 or 10.
Another point is, that using my ATU (The Kenwood AT-230), gives the
same 'S' reading, when peaked on receive, as when it is switched
'straight through'.
Today on SSB 20 Metres running less than 50 Watts, I have worked K1, N2,
KE4, CM8, 9K4 from UK, with reports of Signal strengths of between S6 to
S9+ - so as you suggest, it is hottest on 20M when the band is open,
which for the last couple of days has been from about 1300 to 1630 UTC
here. I heard no DX PSK, but quite a bit of RTTY - I think there was a
contest on.
For the benefit of this thread, I have today photographed the actual
antenna, with a view of the helical winding up it - but is this really
what could be classed as 'helical winding', to qualify as the half
effective length you describe ? The turns are quite widely spaced, as
you will see. Also, are you not sure that there is more to the formula
you quote,probably involving diameter size and spacing of the turns?
Its here, at the bottom of the page ....
http://www.john4music.tv/7.html <http://www.john4music.tv/7.html>
Thanks to all who responded in this thread.
John
(in central UK where the temp is 24 F', or minus 4.5 C , and snow
forecast over the next few days! = Global warming ??? Brrrr !!!)
........................................................................\
...........................................................
--- In [email protected], "Gary Nixon" <garylni...@...>
wrote:
>
> A few thoughts...
>
> One old-time rule on Helical antennas is that it takes about twice the
amount of wire to accomplish what a straight piece of wire would do;,
so, for this case, that would be about 75/2, or and effective wire
length of 37.5 feet, or ~125 Meters (of I did my math right). That
length represents between 1/2 and 5/8 wavelength at 20 Meters, so it
(theoretically) would be ground-plane independent with a very low angle
of radiation.
>
> Sounds like it's working in any case! Congrats...
>
> Happy New Year to the group,
>
> Gary, WA6HZT
>
