Yagimax, a possible 20m design

[exces3]

does anyone use the Yagimax program?,
here is what I have come up with.
ANY comments welcome.
I just can't get it better than this
at 18 ft boom length

20 meters, dims in feet
rf. 34.4... 0
dv. 33.2... 5
di. 32.2 ... 18

which results in, gain of,,,, edge, 14.2 , edge,,,, of
8.52, 9.01, 8.99, db over a dipole .

very different than your typical commercial design, btw.

 

[BJ radionut]

Sounds a little hot on the gain figures...9dbd at peak...
I would expect a 3 element to be more around 7dbd and 9dbi....
What is the matching system?....with that offset spacing...
>20ohms impedence (just a swag)
All the Best
BJ

 

[W5LZ]

I have to say that your program is very 'optimistic'... at best. Not the typical commercial figures? No, even the commercial people aren't quite that 'optimistic'. 80% of your numbers is more realistic I think.
- 'Doc

 

[exces3]

nut...

matching, I am thinking about...
a 9 to one, quarter wave matching section,
three coax in parallel, to get to 5.5 ohms or so.
driven element would be adjusted resonance at low-phone.
lumped elements would have to be switched in, for CW.
spacing is as indicated. 0 (reflector), five feet, 18 feet.

LZ.
is there something wrong with Yagimax?
if I wanted 7 db,
I would copy something commercial
commercial designs seem to be more
concerned with matching,
than with maximum gain.

Its not like 2 db is all that much on the other end,
I just want the best possible pattern
for receive.

 

[W5LZ]

The "...best possible pattern for receive", isn't always the highest gain with a directional antenna. Forward gain is always at the expense of 'F/B' ratio, the better the gain forward the less the attenuation to the back. It can turn into a double-edged sword quicker than you might think. I guess it just depends on how much that 'F/B' beans to you.
- 'Doc

 

[exces3]

LZ...

In my opinion,
the 'figure of merit' for a beam, is forward gain,
( an exception, would be some kind of
'steerable-null' antenna for receive)
as the backlobe is just another sidelobe to me.
as QRM comes from random bearings, not just 180.

as an aside, I am also considering some type of
shorty 8JK antenna for 40m, if there is such a thing,
and a 8JK has a F/B ratio of zero.