On Thu, 17 Jun 2010 09:05:11 -0700 (PDT), "R.Scott"
wrote:

The problem with holding a few parameters constant is that you have to
accept whatever gain, patterns and such that come with the deal.

Well I did find plans for a 6 elem on a 17.5ft boom. The boom on the
old A4S is 18Ft. If I use the parts off my old A3
and my A4 I should be able to come up with all the parts for the 6
element. And its direct connect.
I'm a bit late to the party, but...

To me that seems like a lot of elements on a short boom, (I use 7L on
a 29' boom) but properly adjusted they can give more band width rather
than gain as gain is more a function of boom length. Also, how do they
get 50 ohms at the feed point of a dipole driven element in a 6L
Yagi?

Direct connect can work, but how well is another question. It may
give a good match, it may transfer the power efficiently, but again
the question is, how well does it work.

Jim Brown's (K9YC), A Ham's Guide to RFI, Ferrites, Baluns, and Audio
Interfacing ...
www.audiosystemsgroup.com/RFI-Ham.pdf is well worth reading. when it
comes to using toroids and the old "coil of coax" as a rather
inefficient current balun (which I used for years).

I worked a station down in Central America (on six) who had his new
rig on the bench testing it with a short piece of wire stuck in the
coax connector...I'm in Michigan. He could have said, that short piece
of wire on the bench was a good antenna...at that moment.

But given you get a good match, the pattern is still going to be
distorted. You can take 4 2.4" OD toroid cores with 4 or 5 turns of
coax through them to make a very good current balun (bout 5,000 ohms
isolation) and center feed a split driven element, then the antenna
is not really "direct connect" as the "matching device" is between the
feed line and antenna even though it can be the end 5 to 8' of coax
wound on the cores.

BTW, run the coax through the toroids before installing the connector



I wonder how far above the A4 the 6 meter needs to be. I only have a
5ft mast.

Should be and what you can get away with are often quite different. A
friend has a bunch of antennas on one tower that are all way closer
than they *should* be, but he gets acceptable performance, at least to
him and that's all that counts. Having said that, 5' would be
considered very close and 10' would be much better. OTOH you will
probably be satisfied with the performance over a simple antenna.
All antennas are a series of compromises as are installations. IOW we
use what we have and hope for the best. You only have a 5' mast, so I
assume that a taller mast is out of the question which makes "how far
apart do they need to be" a moot question. Then the real question is:
Will they work with only 5' of spacing? The answer is ... Probably and
they probably will work fairly well.

One element to keep in mind (no pun intended) is with the antennas
only 5' apart they may tend to detune one or both a bit and also lower
the feed point impedance. But it's what you have and you won't know
until you try.

Getting things to work is half the fun, at least it is to me...as long
as getting the project to work does not run into frustration. :-))

73 & Good Luck.

Roger (K8RI)

my DX800 rotor should handle it.