I tried sending some photos to the group but evidently they are not
allowed.. I have been using a new portable/Rover setup since the August UHF
contest. I have been using portable masts held up with guy ropes for years
(decades?) but it takes a long time and a lot of work to put them up and
take them down. Plus, the antennas for 11 bands take up a lot of room in
the car. So I got a car roof rack for the purpose of both transporting the
antennas on the car and holding up a mast.
I made this system with the 5-foot stackable mast sections sold by Radio
Shack (I hope they still sell them). A horizontal side-arm is made from one
mast section and is fastened to one of the roof racks with U-clamps. It has
a plate at the end to support the mast. At the bottom of the mast is a
tilt-over mount.
It is pretty easy and fast to set up and take down. The photos I have show
three antennas on a 15 foot mast used in the UHF contest, but in September
I had a 20 foot mast up with 144, 222, 432, 902 and 1296 all on the one
mast. It worked fine. I haven't tried this setup in winds over about 15
mph, so I don't know how well it will stand up in higher winds. I'm sure I
will find out soon, maybe in the January VHF contest. :-)
If anyone would like to see the photos, I can send them. Alternatively, if
someone knows of a place where I can upload them, I can do that.
73, Zack W9SZ
On Tue, Dec 27, 2016 at 10:33 PM, Patrick Thomas <p-thomas@mindspring.com>
wrote:
> Hey all,
>
> I've been considering augmenting the park-and-go rover setup with a
> push-up mast. However, I have noticed that the Rohn H50, etc., explicitly
> state that they are "not recommended" for use with yagis. And sure,
> physics would suggest that if you have a 15' antenna boom, you are likely
> to have more off-axis "arm" acting on the top of the mast, versus a
> vertical or even a dish. On the other hand, I don't know if they only say
> that to protect themselves against people who use H50s as semi-permanent
> rooftop installations in 80MPH wind zones with heavy ice.
>
> So what's the verdict? I'm sure it's "possible" but is it safe to use a
> large 2m yagi on an H50 when properly guyed, on a day with gentle breezes?
> Or is it indeed "not recommended" under any conditions due to instability,
> etc? For that matter, what about the weight of a rotor that high up?
>
> (And yes, I'm still working on the halo stack, so worst case I could
> always hike that up the line... but would love to have the extra gain and
> directionality from the yagi.)
>
> Thanks,
>
> Patrick
> KB8DGC
> _______________________________________________
> VHFcontesting mailing list
> VHFcontesting@contesting.com
> http://lists.contesting.com/mailman/listinfo/vhfcontesting
>
_______________________________________________
VHFcontesting mailing list
VHFcontesting@contesting.com
http://lists.contesting.com/mailman/listinfo/vhfcontesting
|