[TowerTalk] Looking for a Short Rotatable Dipole or...

[Kevin Stover]

Agreed with all of that. I don't think were talking anywhere near 50' 
certainly not 100'. 30' maybe. It's a rooftop tower.
At 100' EZNEC  says the 40m dipole kicks butt, 50 feet not so much and 
30 feet even less.

On 4/29/2016 4:59 AM, Jim Thomson wrote:
> Date: Thu, 28 Apr 2016 18:54:17 -0500
> From: Kevin Stover <kevin.stover at mediacombb.net>
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] Looking for a Short Rotatable Dipole or...
>
> K9YC has given the best advice.
>
> A dipole, any dipole at less than 1/2 wavelength isn't going to have any
> lobes to rotate so scratch the dipole idea. It'll be pretty much
> omnidirectional.
>
> R. Kevin Stover
> AC0H
> ARRL
> FISTS #11993
> SKCC #215
> NAQCC #3441
>
>
>
>
>
> ##  tell that to the folks with 80m rotary dipoles up 100’.....
> or folks with 40m rotary dipoles up 50’.   That null off the
> ends is nothing to sneeze at.  6-14 db, depending on whether its local or
> dx.    Some will use  2 x wire dipoles at  90 deg apart..... but they are
> configured more like a T, when looking down on the pair of dipoles.
> And try and get the center of one dipole,away from the end of the 2nd dipole.
> Dont  cross them in the middle like an X.   But that mess requires  4 x supports
>
> ##  Inverted vee.   Now they are omnidirectional.   Even a vee with a 90 deg angle
> between legs will radiate off the sides...and off the ends.
>
> ##  Put the apex of the vee at the same height as the dipole, and the dipole
> will be 6 db stronger off its sides.   Dipole also has the nulls off the ends.
>
> ##  Inverted vee is good, a dipole is better, and a rotary dipole is better still,
> or 2 x  crossed dipoles.   6-14 db null off the ends might not sound like much,
> until the station  you are trying to work is in the null.
>
> ##  I have tried  40m GPs, with the very top at 70 feet, and they worked good,
> as did the 40m  GPs, with the very top at 56 feet.  Both had  loads of elevated radials.
> Surprisingly enough, neither  config had an issue with noise, they were fairly quiet.
> Only issue with a GP is.... with no nulls obviously, you hear everything, from every direction.
>
> ##  any shorty 40m, 2 el yagi, even as low as 60 ft, will  make lunchmeat out of any vertical array,
> even a ground mounted  4 square.
>
> Jim  VE7RF
>
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-- 
R. Kevin Stover
AC0H
ARRL
FISTS #11993
SKCC #215
NAQCC #3441


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