RE: VERTICAL ANT IDEAS HELP!!

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From: Bob Nygren (rnygren@epix.net)
Date: Thu Dec 07 1995 - 17:21:59 EST


You wrote:
>
> Gang: Two quickie antenna questions for you to ponder ===
>
> 1.I've seen a Delta Loop antenna mentioned here several times, but I'm
> not too familiar with its construction. Here's what I had in mind
> to build for 40 meters:
>
>
>
>
> | ====> high end abt. 30 feet (fed here with coax or twin)
> |||
> | | | ====> each side abt 47' (1005/7.04)
> | | |
> | | |
> | | |
> | | | ====> low end supported by wooden fence 8' above
> ------------- ground
>
> Is this the basic idea behind the Delta? Is the formula correct?
>
> 2. I've wanted to try out the DX possibilities of a vertical ant,
> but don't want to shell out big bucks for a GAP or similar, only
> to be disappointed by its performance. Can I just throw up about
> a 33' piece of wire on a vertical support, attach this to the
> center lead of coax, create a radial or counterpoise system
> under the vertical wire and attach the coax shield to it?
> Is this the basis for a cheap and dirty "experimental, see
> how I like it, see if it works" vertical system?
> If so, how many radials are best? How long 1/4, 1/2 wave?
> For 40 meters, can I get away with less than 33' or so of
> vertical?
> In all cases, I'd be using a tuner with the setup.
    
>
> 72/73 de Dave KK5HA
> QRP-L #25
>
Dave,
     I've run a delta loop on both 30 and 40 meters. If you can,
turn your design upside down. The flat side as high as possable.
Feed at the opposite angle. (Which is now closest to the ground.)
You need a quarter wave section of RG-11 or RG-59 to act as a
transmission line transformer, but you can find that that formula
in the Antenna Book or Handbook. 234/f(MHz)* Vf(velocity factor
of the coax, something like .66) The antenna plays well!!
     Question 2, YES! If you can get a few 1/4 wave radials, good.
But I belive that as the current in the radials is greatest close
to the antenna, is is more important to have many short radials as
opposed to having few longer radials. But I have not quantified my
own results. The conductivity of the soil may be a factor.
     Good Luck,
     Bob WA3YON


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