[SixClub] Re: [50mhz] New 6M antenna array up

[Bill VanAlstyne]

Hi Gary,

There's just been a good thread on the TowerTalk reflector about this exact
subject, to which I made a modest contribution.  :-)

It's true that a stacked array (particularly a very HIGH stacked array) doesn't
do well on sporadic-E paths, for the reason you stated: The radiation angle of
the stack is just too low. In my post, I related an experience I had recently
that illustrates this:

"Just the other night, for example, I was working stations in the midwest over a
very typical sporadic-E path of about 1000 miles. Most of the signals from this
area were S9 or better. I finally came back to a call from a comparatively
weak station in the same area and gave him a 5x5 report, only to find that he
was running a kilowatt to stacked 9-element yagis at 150 feet! If 6M had been
open to Australia via F2 propagation, he would have cleaned everybody's clock --
but not over this typical sporadic-E path to New Mexico."

Your solution is exactly what I recommend for 6M. You get even better results by
stacking the antennas further apart than you did, though. Probably the best
stacking distance I've seen for 5 or 6 element yagis on 50 MHz is 30ft/60ft. As
modeled on YT (over nominal flat terrain), you get a set of elevation plots that
cover every elevation angle from 3 degrees to 16 degrees within +/- 3 dB or so.
This, of course, assumes use of the StackMatch so you can use antennas A / B /
A+B as you describe.

Good luck with your antenna and let us know how the system works out on
sporadic-E propagation. I'll be looking for you on double-hop!

Bill / W5WVO
DM65


Gary Mitchelson - N3JPU wrote:
> Spent the past couple of weeks preparing and finally installing a new
> 6M antenna with some new features I hope will be useful. I had a C3I
> 6 element (great, super robust, but heavy) up at 50' for the past
> couple of years but always felt that the previous 5 over 5 stack
> (Rutland's) seemed to play well. Actually that 5 over 5 got me 6M WAS
> in the 1998-2000 timeframe with 100W from the east coast.
>
> But the stack always did not do well on shorter E skip, but did great
> on the low angle stuff. So in order to get the most out of both
> worlds I added a Array Solutions 6M StackMatch II. This allows me to
> select Top, Bottom or both in phase and without 75 ohm phasing lines.
> Just 2 equal length 50 ohm lines. There is an option to do an Out of
> Phase selection but am not sure that will be to worthwhile on 6M.
>
> My new stack is comprised of a pair of Directive Systems (they make
> the antennas for Down East Microwave) DS50-5's, which are 5 elements
> on a 18' boom with 9.1dbd gain each. I also replaced all the flexi
> 9913 coax with 1/2" Heliax to help improve my receive as much as
> possible. The lower antenna is at 38' and the top at 51'.
>
> There has been no openings since I put up the stack up but have
> noticed that the lower antenna by it's self picks up more noise than
> the top, and with both phased the noise really drops and signals pick
> up slightly.
>
> As I get to play with the stack switching I will be noting which
> setting is best (Top, Bottom, Both) and will build up a spreadsheet
> as I get enough data to input. Hopefully this will show the
> usefulness (or not) of this kind of configuration.
>
> There are some pictures on my website.
>
> Gary Mitchelson
> N3JPU Montgomery Co. MD  FM19
> http://www.mitchelson.org/
>
> Moderator: Ray Brown, KB0STN
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