[NLRS] 50Mhz antenna modeling question

[Dr. Gerald N. Johnson]

On Wed, 2007-05-16 at 17:23 -0500, Matt Burt wrote:
> 
> I have built a few antennas for six and now feel the need for something small
> enough for the rover and yet capable of a little forward gain.
> The last three roves my delicate 6M moxon has been damaged due to a mis-hap with
> a tree on my route (one tree is 6 blocks down the road on the only road that
> leaves the subdivision).  As always I will try to get my antenna up as high as
> possible ... but not much more than 20 ft is very practical. Of course I have
> used 3 or even a four element at 15-18ft and had good luck. 
> 
> Any way armed with an old DOS program for calculating dimensions I came up with
> a 2 ele 50MHz antenna of the following specs:
> REF 117.3"
> DIR (DRV) 116.53"
> BOOM: 30.7"
> expected forward gain 4.74 dBd
> F/B not very good
> element size .375" (maybe .50" at center)
> My plan is to feed the driven element with a T match and 1/2W length piece of
> coax tuned for 50.140.
> The "Z" looks like 49 ohms with some inductive component
> Any modelers out there that can duplicate my numbers?
> 
> KF0Q 
> 
> 
If the feed Z at the modeled driven element is 49 ohms, the T match will
have to run all the way out to make it a folded dipole. That's a design
feature of DL6WU long yagis. Its not structurally so good, but a split
driven element with a 1:1 balun should work though the feed impedance
will be drastically affected by proximity to ground and the rover
vehicle.

I generally can work MSP, Chicago, and Lincoln NE with my two element
remains (of a 5 element commercial beam) on 6m with it about 14' up. And
have good results working sporadic E. One hopes for much E in the June
contest as some have given in past years.

73, Jerry, K0CQ