Sounds like the "greatest-good-for-the-greatest-many" Ultimate "any ham
can use this" portable Antenna Support Structure design project!!!
Have you considered using a portable light tower trailer, as seen on
construction sites everywhere near you? Also solves the electrical
generation problem, too! Might have to remove the "stock" generator and
replace with something lighter to permit towing behind really small
vehicles, but would put the power generating capability into reason for a
"single op, no Kilowatt" portable. AND the tower sections on these are
usually short enough that when collapsed but stood vertical, the top
likely wouldn't produce an overheight condition. This would allow an "M"
frame configuration to mount Yagis on either side of the telescoping
"tower",
so can be used while moving possibly... When stopped, extend the trailer
outriggers... wind up the mast to
operating height, no other "setup" required. This assumes all antennas
are cabled to their station equipment...
I still have the telescoping mast I mounted on top of the roof of my VW bus
to do something similar... I only got around 4.5 feet of extension with
that setup, but this was enough to raise the 4 element 6 meter beam up to
"minimum optimum operating height" when stopped, and collapsed, was around
13ft.2in. vertical clearance. The two meter yagi was hung a foot below
the 6 meter Yagi, and didn't mind the roof and rack steel about 4 feet
below when collapsed. 222-1296 were hung slightly below and to either
side of the 2 meter Yagi on the "m" frame. Running and Gunning on 903 and
1296 with those high-gain looopers made for some interesting QSOs! (The
"aurora" stopped when I did:-)
Safety Note: NO ROTATOR MADE that I know of is capable of directly
supporting antennas on a moving motor vehicle! They were not designed to
deal with near-hurricane force winds occurring simultaneously with
Magnitude
10+ earthquakes! I found this out the HARD WAY! (Dragged antennae behind
vehicle, held by their feedlines until I could dynamite the brakes and
finally get stopped, an hour before the start of a June VHF contest:-(
So whatever you do, if your setup involves hauling the antennae on a
support structure in a "operational" or "ready-to-run" configuration, some
means for
mechanically isolating the rotator from the antenna support assembly is
essential for survival of the rotator. A well-designed pair of thrust
bearings or thrust collar should do the trick, as long as this can support
the intended windload and array weight without the assistance of the
rotator. Also wouldn't hurt to have some sort of "auxilliary brake" or
locking mechanism to prevent overcoming or destroying the brake within
your chosen antenna rotator in the event you get caught in a side-wind, to
prevent the antenna array from suddenly appearing as a much wider load
than intended!!!
Along your design thoughts, I have a "parts VW Bus" I may take the time
to add a tiltover crankup tower to, similar to the one I already built...
then prepare a comfortable operating position/sleeping area within! With
the engine and transaxle removed, there is a huge space under the vehicle
where batteries and a generator could be carried. I would leave in the
stock fuel tank as fuel storage for the genset. Perfect for Single Op
portable operations!
Eric
KB7DQH
> On Mon, Jun 22, 2009 at 5:00 PM, <kb7dqh@donobi.net> wrote:
>
>> Guess it depends on what kind of hills you got...
>
> Hills, there ain't no hills in S/E Texas to speak of unless you count
> the two bridges over the Houston Ship channel. The coast plains are
> FLAT period. If I were to move up into the piney woods where there
> are some hills the number with public access are few and then we have
> huge trees to deal with.
>
> I'm trying to come up with something light weight and small enough to
> be towed by even the smallest of automobiles. This will increase its
> versatility and can be used for other events like field day a the
> MS-150 that I work each year. I've looked at used mini-buses, bread
> trucks and like everyone dreamed about a used ENG van. Those are all
> far more expensive than a small trailer, the insurance & registration
> is a fraction of additional vehicle, it doesn't have to pass emission
> testing and the general maintenance is a heck of a lot less.
>
> Nor am I trying to activate 9 grids, maybe just 3 or 4. At some time
> I may shift my focus and try to do more but I just don't see that for
> now.
>
> --
> Mike Urich, KA5CVH
> http://ka5cvh.com
> http://twitter.com/KA5CVH
>
> Life is hard, faith shouldn't be
> http://fairmontpark.org
>
> And help defeat Harry Reid
> http://simcoxforsenate.com/
>
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