Hi all, This might be a good time to bring up "height above average terrain"
for a 6 meter beam. I'll digress here a little then will get back to the point. I used to
rove with the lower 6 bands. Antennas were all mounted on a rotor fixed to roof racks on
my truck. There were ~ 8 ft yagis and loop Yagis on 2 thru 1296 BUT on 6 meters I had an
old 4 element Yagi on a 12 foot boom. This got mounted right above the rotor so was maybe
7 feet off the ground. (Yeah the ~9-10ft long 6M elements hung over the sides of the
vehicle a little - never was a problem with law enforcement hi). Everything worked great
except 6M. It had reasonable SWR and I knew the Yagi worked because I had used it on the
tower.. but signals were weak except when the band opened for e-skip.. Well that should
have tipped me off right there but It wasn't until I had a talk with Pete, K9PW, who used
to operate with the AA9D multi-multi VHF contest station in central Illinois. They had
done some experiments with
their rovers and found that just a HALO antenna at 25 feet WAY out performed
a multi-element Yagi at 10 feet.. Well duh, of course the Yagi's pattern in the
vertical plane got more and more elevated off the horizon the closer it got to
the ground and at 10 feet there was practically no response on the horizon. I
haven't done any of the math BUT just experimenting with it, I arrived at about
20 feet for my rover 6M antenna. I built a 2 element beam on a four foot boom.
This could easily ride on the roof racks with the elements pointing fore and
aft. I put together a 20 foot mast and that got stowed up there too.. So, yeah,
no operating 6m while in motion, but with a trailer hitch sort of mount for the
mast, it really only took a couple minutes to get the 6M beam in place..
Armstrong rotated for me, but here in Maine pretty much everyone is in the same
direction and with abroad pattern it was pretty much set it and forget it.. The
results were quite amazing and all of a sudde
n I worked stations on tropo at several hundred miles..
To get back to the back-packer antennas, folding up the antenna and making it
"packable" is one thing but then you need a 20 foot mast too and a way to keep
it up in those high mountaintop winds!! The gain of the antenna is not doing you any good
if it's peak is above the horizon and there is a null AT the horizon!
just saying..
bill, k1DY in Maine
________________________________
From: VHFcontesting <vhfcontesting-bounces@contesting.com> on behalf of Mark Spencer
<mark@alignedsolutions.com>
Sent: Thursday, February 15, 2018 4:22 PM
To: Bob K0NR - email list
Cc: vhfcontesting@contesting.com
Subject: Re: [VHFcontesting] Portable 50 MHz beam antennas
Thanks All. I got some great on and off list responses.
Yes I believe the 40" length limit is a reasonable one. (I have found carrying
48" mast sections via backpack to be a bit awkward for me.)
73
Mark S
VE7AFZ
Aligned Solutions Co.
mark@alignedsolutions.com
604 762 4099
On Feb 15, 2018, at 7:17 AM, Bob K0NR - email list <list@k0nr.com> wrote:
Zack,
I'd be interested in the 144 MHz yagi design for backpack portable operating.
Its got to be compact and easy to assemble, otherwise it tends to get left at
home.
For me, compact is nothing longer than 40 inches.
(I'm actually thinking SOTA more than VHF contesting but I sometimes combine
the two.)
73, Bob K0NR
On 15-Feb-18 7:57 AM, Zack Widup wrote:
I got a design from VE3BFM for a four-element 6m beam on a 13 foot boom.
It's a great performer. Since I operate portable 95% of the time, I built a
version I could quickly assemble and disassemble at a portable site. The
boom and each element is in two pieces. I never formally wrote up an
article about how to build it, but I did talk about it at the VHF forum at
Dayton a couple years ago. Maybe I should write it up.
I have similar portable Yagis for 144 through 432 MHz. I can assemble and
disassemble them pretty quickly. My 144 MHz Yagi has six elements
wide-spaced on a 12 foot boom. I believe the gain predicted by Yagi
Optimizer is about 12 dBd. I haven't measured it yet.
73, Zack W9SZ
On Thu, Feb 15, 2018 at 8:23 AM, jon jones <n0jk@hotmail.com> wrote:
Mark:
Another idea is to build your own portable 6 meter beam. I have found a 2
element yagi is easy to build, break down and re-assemble quickly. A 2
element yagi offers about 3 - 4 dB gain over a dipole. It is easier to put
up and take down than a 3 el.
I use one for my VHF contest and portable operations. A picture of it is
in the NCJ March/April 2016 pp. 32. It works... have WAC with it on 6 with
100 W from KS on ssb/cw.
A plan for one is here: http://www.qsl.net/k7yo/6m2Yagi.htm
[http://www.qsl.net/k7yo/6m2yagi.jpg]<http://www.qsl.net/k7yo/6m2Yagi.htm>
6 meter 2 element yagi - QSL.net<http://www.qsl.net/k7yo/6m2Yagi.htm>
www.qsl.net
6 meter, 2 element yagi. A simple, compact and effective antenna for 50 Mhz.
This antenna was built in about an hour after using K6STI's AO simulation ...
- Jon N0JK
________________________________
Hi:
I finally took delivery of a suitable LiPo battery to facilitate "back
pack portable" operation at the 50 to 100 watt level. If any of my
Canadian colleagues are interested I can provide the contact details for a
Canadian distributor.
At this point I'm planning on simply taking my 50 MHz three element beam
apart and re assembling it on site. In my view the beam I have isn't
really intended for that type of use and I'm curious if anyone knows of any
suppliers for small 50 MHz beams that break down and re assemble quickly
and easily. Google searching on my part didn't turn up anything that is
currently in production.
I'm hoping to shift my focus a bit this year and actually reach the true
summit of at least one local mountain (vs simply driving most of the way up
via logging roads.) Having this ability would also have been useful
earlier this year when I had to abort my CO81 visit during the sept
contest. In hindsight I suspect I could have activated the grid for a few
hours on foot.
73
Mark S
Aligned Solutions Co.
mark@alignedsolutions.com
604 762 4099
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