[SECC] Sept VHF

[K4SB]

"David L. Thompson" wrote:
> On Saturday I picked up the Cushcraft 6 el beam from Ron, W4WA.  Some of the
> hardware will need to be replaced and one side of D4 is broken.   I pulled
> the 5 and 6 element from their web page as I thought I might try the 5 el
> version on 1/2 of the boom but did not like the old equal spacing.

Just a couple of comments. First of all, the premise that gain of a
yagi is a function of boom length is well established, so I'd forget
that 1/2 of the old boom stuff.

If the elements are of equal diameter, you might consider replacing
that broken element with copper tubing since the length is so small.
If not, I'd consider replacing all the elements with copper tubing. 

As for a design, you might look at the modified 4 element W2PV beam (
think it was DJ6SY who added an additional element. ) It has direct 50
ohm feed and reduced boom length versus a long boom yagi I designed. 

I am presently building a 20 meter version. It shows 15.48 dbi forward
gain and 48.38 
F/B ration on a 41' + boom, vs the 54' boom of my old design.
Impedence is 50.09 -j.07 ohms at resonance. (SWR = 1.003:1 ) Beamwidth
will more than cover the entire band with less than a 2:1 SWR. I'm
building it for the low end of 20, and the SWR for that area is less
than 1.2:1 for the first 150 kc or so. 
1.1 

Just guessing, but if that 20 were resized for 6, the boom length
would be about 10+'

73
Ed