Since I first threw this project up on the web, I've received a
number of emails with comments, suggestions, and -yes- questions,
and -yes-yes- compliments. Thank you one and all. It
is nice to know that something I have done is found "interesting"
by someone else.
HI!HI!
I had always planned to do this page -- when and/or if I had any
response to the Home Brew, Mobile 6M Halo. It has come to
pass that there are enough responses from the visitors to this web
site to warrant cranking out this final page.
Not everyone wanted their emails quoted here. From some of
that material I may do '
third
person' references.
E.g.: "Someone told me that painting the halo sky blue improves the
gas mileage by 3 mpg."
Something like that....
The folks whose emails you'll find below have given their
permission for such publication. One item, though: You'll not find
their email addy's here -- they probably get enough spam. If you
want to get in contact with them, you'll have to proceed in "the
usual way(s)".
First we have an email from
Goody, KF6PBN out in CM95:
From: Goody <KF6PBN CM95>
To: Jonesy <W3DHJ DM68>
Date: Tue, 19 Aug 2003 23:09:33 -0700
Subject: Halo
Jonesy,
Hi, and thanks for the tips and the initial work.
I used your idea and built a 6M halo, I too used the serial
capacitance, however I used 3/8 instead of 1/2 inch internal
tubing. It required that the tube be 6 3/8" long and set off center
3/4" toward the shield side.
The insulator I used was a nylon core from a roll of adding machine
paper and a few pieces of heat shrink. My other problem was the
gamma match, mine ended up 15 inches long and wraps around the
corner, works good at 49 ohms.
My antenna is centered at 50.8 with the 2.0 SWR points at 49.9 and
52.0 -- I wanted to make sure that I covered the Pacific DX window
since I live on the ocean.
I have yet to make a contact as it is designed to be mounted on my
travel trailer, right below the dual band J-pole mounted on the
bumper. I made the mount so it will fold down when the mast is
retracted and then open up when raised. I have an 18 foot mast on
the back of the trailer. The J-pole is my design, made out of 3/8"
aluminum rod, cost is around 20 bucks and needs no match.
pat goodyear (goody)
kf6pbn cm95oh
Next we have an email exchange with
Rick, KD5UVA down in EM22 - - this was my
in-context reply:
From: Jonesy <W3DHJ DM68>
To: Rick Davis <KD5UVA EM22>
Date: Wed, 3 Mar 2004 13:24:53 -0500 (EST)
Subject: Re: 6M Halo
On Wed, 3 Mar 2004, Rick
Davis wrote:
Hello from Texas!
I'm Rick Davis-KD5UVA, and my Friend Kurt-KD5UVB and I built a halo
per your design. Wow! Now everyone wants one! I have some questions
and some info on what we found.
"Hello!" from Gunnison! It's heartwarming to hear from folks that
share the 'excitement' in some of the stuff that I do!
Question: The Gamma
Match, about how long is the copper wire inside the tube? I know
this is subject to tuning but we didn't know a starting point. You
are great at explaining the operation in laymen's terms, so if you
don't mind, I'd like to know how the match works, more
specifically, what is the relationship of a longer/shorter copper
wire? I know what the grounding strap does.
The copper wire -- really a "copper rod" -- together with the outer
alum. tube, make up a capacitor. Building it this-a-way creates
(when designed for "proper" proportions) a 'long capacitor' which
then is able to 'reach out' to the proper tap point on the driven
element. The matching of it all, then, involves adjusting the
amount of rod inserted into the tube (capacitance) -- together with
adjusting where the strap attaches to the driven element
(feed-point impedance). IJFM. So, even if you use the
identical same scrap as I did, it will probably be WAY
different in adjustment for you than it was for me. Well, maybe not
WAY, WAY different -- but, enough so that your tuning of
your antenna will require as much futzing as I had with
my antenna.
Originally, my copper rod -- when assembled somewhat 'close' to
what the final assembly was -- extended nearly to the end of the
tube. That's why I mentioned wrapping the rod with the teflon tape
starting out at the end of the rod -- it makes for 'cleaner'
snipping of the rod without the tape coming unraveled so easily (At
least, that's the theory....) I was Very Fortunate, and only needed
to whack about 1/2" off the rod before that and the adjustment of
the strap gave me a match.
If you find the gamma match "needs more rod" - and you are using a
full-length piece to start with -- you need to use:
* a larger diameter rod (e.g. 10 ga. Cu versus 12 ga. Cu) ,
* or a tube with a somewhat smaller i.d. ,
* or a longer tube together with a longer (same size) rod).
Moving to a longer gamma tube is not much of a concern -- since the
shorting strap between it and the driven element is where the
"magic" is. But, with a halo antenna, the tube eventually can be
too long -- both mechanically and aesthetically.
We got our loop to reach
1.7 swr on the MFJ analyzer, but only by with a match long enough
to nearly touch the Halo. That's not bad, but we'd like it to be
lower of course to allow more bandwidth.
Maybe you're trying to tune it with the MFJ attached directly --
not a good way to do it. Use a short piece (5-6 feet) of coax to
get yourself out of the "field of influence". I knelt down when
fiddling with the MFJ -- trying to stay out of the horizontal plane
of the antenna. Too, make sure the halo is clear of any nearby
"objects" -- by 4-5 feet -- while trying to tune it.
Now, here is what we did
to solve our internal tuning capacitor. We made the same plastic
part as you did, but instead threaded a stainless all-thread 5/16"
though it. This resulted in dropping from our original 63mc to 53,
we then simply ran on two nuts, one on each end of the all-thread.
Viola! The freq fell right into the SSB range. Perfect! A few drops
of hot glue and all is wonderful. The all-thread makes tuning a
breeze.
Kewl! Very neat trick!!
And, for the perfectionists out there, I believe I have seen brass
all-thread -- which would yield a higher-Q capacitor. (But, then
again, is high-Q necessarily what we want there? hmmmmm...)
My early brain-storming revolved around something similar. I had
thought of attaching the internal tube to a piece of plastic
all-thread that would come out at one of the nearby corners where I
would have a nylon nut mounted. Then I could adjust the thing from
outside -- at anytime I wanted.
But, as I prototyped the thing I found that the internal capacitor
-- once set -- offered plenty of bandwidth and would require no
further adjustment. KISS.
Here are some specs that
you might want to include in your site: First run report: QRP rig
running 9 watts, RG-8 mini coax (yuck) at 30' elevation above
ground and ground is 460' above sea level. Conditions: zero
enhancement (verified by two stations barely making contact locally
despite running beams and 100 watts at 35 miles, typical for the
area and terrain) Local Signal reports s7 signal at 12 mi (2
people), 5/9 at 15 mi., s3 with a bit of white noise at 12 mi by
station running vertical only. And the best was a 5/9 report at 19
miles. All without a rotator, and with an unusually low noise floor
compared to the vertical. Noise with vertical was s3 to s5, with
this halo it was zero to s1.
You might see humor in
this: When we saw your site, we immediately wanted to build one of
these, so we left work at lunch, drove to the scrap yard, walked up
to a pile of prospective goodies. Right there were three 21" lawn
chairs. When we picked them up, immediately below them was a pair
of aluminum crutches! $9 and ten minutes later we were just plain
giddy and still had time for a burger, our wives laughed at us and
thought we were nuts. The 59 signal reports spoke for
themselves!
Great Story!!
Don't you love it when A Plan Comes Together? HI!HI!
My wife frequently wonders about me, too.
Again, Thank you!
es 73
Jonesy
Now for some email snippets:
From a VE3:
Great article on the 6m
mobile-lawn-chair-halo!
From Mass.:
I loved your pages concerning
the 6m halo setup. Very concise. The pictures are clear
and very helpful. Thanks for taking the time.
From R.I.:
I just read your
implementation of the six meter lawn chair antenna. That's a
very nice piece of engineering and scrounging! And a very
nice presentation, too! I've collected enough broken chairs
with rounded leg corners to build two of those. I'm
interested to see how a stacked pair would behave.
From Minn.:
Just wanted to drop you a
note that I really enjoyed reading your 6m halo site. LOTS of good
ideas. Thanks for taking time to put the site up. I
know it's a lot of work.
From Germany:
I have seen the 6m HALO
project on your homepage... really cool stuff. I will build a
HALO, too! ;-)
Feedback is appreciated.
There are a few other web site operators that felt my project was
unique enough to warrant
adding a link to it from their web site(s).
Rod, AC6V (now a
SK) linked
to this project from his (still maintained) "
antennas"
page.
Then, there's this nice reference on
JL1IRB's web site:
HI!HI!
Interestingly, I've gotten quite a few
short comments on 6M QSL cards along the line of: "Great 6M Halo
web page". Nice touch, that!
Feedback, "stories", suggestions welcomed:
Constructive comments and/or discussions:
Last updated: 21-Feb-10
