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Author Topic: Portable antenna suggestions  (Read 5915 times)
WM6Q
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Posts: 37




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« on: October 04, 2017, 03:23:30 PM »

Would appreciate hearing suggestions on portable antennas (40m - 10 or 6) for emcomm use. I'm thinking in terms of a vertical rather than some kind of wire dipole or other configuration. If there is a thread on this already, please point me. Thanks

Bob WM6Q
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KM4DYX
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Posts: 63




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« Reply #1 on: October 04, 2017, 04:38:18 PM »

What distance(s) are you planning to communicate? Verticals are good for Ground Wave paths and long-haul Sky Wave paths, but not for short-skip Sky Wave paths. I always approach this sort of thing by first determining what path I want the signal to take and what the conditions are on that path. Then I select the frequency. Then I select the antenna.

73,
Al
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NA4IT
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Posts: 52


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« Reply #2 on: October 05, 2017, 03:27:03 AM »

http://www.earchi.org/92011endfedfiles/Endfed6_40.pdf

Made one with a 4:1 UNUN. Works. Can be put up vertical with UNUN at bottom, sloper with UNUN at top, Inverted "L", etc. Works with my 857 and LDG tuner, all freqs between 3.5 and 55 MHz.
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K7RBW
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« Reply #3 on: October 05, 2017, 03:51:19 PM »

I've used the Buddipole and the Crank-IR, and each is good at what it's for. The buddipole folds down into a notebook and the Crank-IR covers 80-6 meters. (40-6 without the extensions). For gain, the Crank-IR is better, without question, but for portability and flexibility, the Buddipole wins.

Of course, a wire dipole trimmed to length beats them both in gain and portability, but can be harder to deploy.

I've yet to find an antenna that's good at everything.
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WB6BYU
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« Reply #4 on: October 05, 2017, 09:49:31 PM »

You really do have to define what sort of "EMCOMM" you are imagining using the antenna for.

Here in Oregon, the ARES/RACES units use mostly dipoles or inverted vee antennas for
40 / 60 / 80 / 160m SSB NVIS work around the State.  (Yes, I've put up portable dipoles
for 160m across the lawn of the County Courthouse.)  That's what works best for relatively
local (out to 300 miles or so) HF communications.  Because of the overhead null, a whip or
vertical is NOT a good choice, especially for distances less than 50 miles or so.  While 40m
gives good daytime coverage around the State under current conditions, as we approach the
bottom of the sunspot cycle we often need to use 80m during the day and 160m at night
to maintain coverage.

We're also part of the Oregon Amateur Digital Network, which uses WinLINK to connect
to internet-connected nodes outside the disaster area.  For that we may  need to cover
longer distances, typically on 80m through 17m depending on the node location and the
current propagation.  For that purpose, a vertical may be a better choice, though again
it depends on a lot of factors, including the available supports and the local ground
conductivity (which tends to be rather poor in much of Oregon due to the volcanic soil.
But on the beach of a tiny island in the Pacific, a vertical would be much better.)

While an antenna at 20' is adequate for most NVIS work, and even lower antennas can
be used with some decrease in efficiency,  for longer distances we might try to get our
dipoles up higher, and now we've added 30, 20 and 17m to the mix.


On the other hand, if you are part of a group such as SATERN, you may be more involved
in communicating back to a base at a much greater distance, and 20m or 17m may be a
better choice.  You can use VOACAP to see which bands have a greater chance of being open for a
path at different times of day.  (It also allows you to specify different antennas at each
end of the path, and see how changes in the sunspot number affect the various bands.)


That's why the suggestions to start by defining the path you want to cover, and using that
to choose the bands and antennas that will best accomplish that.


Personally, I've been stringing up portable dipoles for over 35 years, and have found them
to be simple, cheap, and effective.  The whole kit for the 5 pre-WARC HF bands fits in a
small pouch and weighs about a pound, including 25' of feedline, and I don't need a tuner
once I've tuned up the wires initially.  I have the center insulator attached to the coax and
sets of wires for each band that I can attach to it  depending on my needs each time I set
it up (and re-purpose the wires for other antenna types when an opportunity presents itself.)
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NQ3M
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Posts: 48




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« Reply #5 on: October 08, 2017, 07:34:45 AM »

Would appreciate hearing suggestions on portable antennas (40m - 10 or 6) for emcomm use. I'm thinking in terms of a vertical rather than some kind of wire dipole or other configuration. If there is a thread on this already, please point me. Thanks

Bob WM6Q
I have a socket on the rear of my truck that supports military fiberglass poles. Made an insert that supports an holds 3 of the brackets one would use to make a Ham Stick dipole with. All three are connected together so one coax feeds them all. Spaced them about 16" apart and at 120* to each other. I can use any combo of bands I want with the same coax, plus still have another mount on the side of the camper shell that everyone assumes is a CB mount w/o an antenna on it, for another band if need be. Then there is a socket on the rack on the R/F of the camper shell that holds another fiberglass pole/s that supports a 2/1.25/440 antenna. From the time I stop until everything is ready to operate is less than 15 minutes.

I also have a ALS 500M if needed, supported by 2 group 29 deep cycle battery's (that also feed the radios) I can charge them via the truck if need be but they are normally charged via a 6.5HP Honda that powers up to 3 (if need be)100 amp single wire DC alternators. Most of the time I just run the Honda at 1400RPM an use 1 alternator, but a 1.5KW inverter is hooked to the battery's as well hence the 2 extra alts. The Honda is very quiet but also use old carpet to knock the sound down even lower when it's running if in a crowded area. 
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WM6Q
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Posts: 37




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« Reply #6 on: October 08, 2017, 11:36:51 AM »

Thanks everyone for the comments. I will probably be using this set up Field Day and other portable ops; my actual emncomm work is VHF/UHF. I have been leaning towards a buddypole, but wondered what others thought. The ease of set up and take down is important, but I suppose there's no reason I shouldn't also carry some kind of end-fed wire.

Thanks again!

Bob WM6Q
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K5LXP
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« Reply #7 on: October 08, 2017, 07:59:00 PM »

The ease of set up and take down is important, but I suppose there's no reason I shouldn't also carry some kind of end-fed wire.

I would recommend you try a buddipole in your intended application before you go down that road.  I've contended they're a solution waiting for the right problem to come along.  Having deployed numerous kinds of antennas in the field, I would not rate the buddipole as being "easy".  They are inherently inefficient, they're expensive and not terribly portable, unless you consider a large heavy bag "portable".  Just about any kind of wire antenna and a simple support like a crappie or jackite pole will be easier to transport, quicker to set up and more likely to net you contacts than the buddipole contraption will.

Mark K5LXP
Albuquerque, NM
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WB6BYU
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Posts: 17190




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« Reply #8 on: October 10, 2017, 12:07:26 PM »

Quote from: WM6Q

... I will probably be using this set up Field Day and other portable ops...



Hams have very different pictures of what "portable operation" looks like, and this is
one of the reasons why you get a wide variety of recommendations for antennas.  For
some it means backpack QRP operation, or operating from a local park, or setting up
beams on 60' towers for Field Day.  All are "portable operation", but have very different
requirements for antennas.

So a good first step is to define what you want to do.  Picture the types of situations
where you want to be able to set up, and how you are planning to get there.  Do you
have trees or other natural supports available?  Can you pound in stakes for guy ropes?
How much space do you have around you to set up?  Do you have to share your space
with lots of other people?  How long do you plan to operate each time you set up?
Are you planning to operate overnight, or just for a few hours during the day?  Do you
have other limitations, such as weight, size, aesthetics, wind, salt water, etc?  Is your
operating location fixed (a picnic table in the middle of an open park, perhaps), or can
you set it up in a more convenient location for antennas?

And how important is antenna performance to the amount of enjoyment you get out
of your portable operation?

These are personal questions that you have to answer about what you find enjoyable.
The choice of antenna(s) to meet your needs depends on the answers.



For example, the Buddypole is a convenient commercial package that can be free standing
(in case you don't have other available supports).  Efficiency isn't that bad, particularly on
20m and up, and it can be used on multiple bands in different configurations.  If you have
to set up in the middle of a parking lot with other vehicles driving all around, it may be
a good choice.  On the other hand, tuning on 40m can be fussy, and efficiency drops off.
If you a regularly use it in a similar configuration, you can set it up to tune pretty quickly,
but changing bands requires lowering the antenna and readjusting the coil taps and maybe
fine tuning the whip lengths, so isn't something I'd necessarily want to do in the dark or
in a storm.

My backpack wire dipole kit, by comparison, is considerably smaller and lighter to carry
(and a lot cheaper, but I had to build it myself.)  I rely on using available supports, usually
trees (though rocks, sign posts, and/or my hiking staff have been pressed into service).
But the places I'm likely to go usually have trees, so that isn't a big problem.  I've put up
dipoles for the 5 pre-WARC HF bands on a common feedline, allowing me to hole up in
my tent and operate during a howling storm.  It takes more space to put up full-sized
dipoles, particularly on 80m and 40m, but I've managed that, even in a camp ground,
where I would pitch my tent on the far edge by a tree.

For ARES use, I use similar dipoles for 160m through 40m NVIS, but with heavier wire
(#18 perhaps) and larger coax (RG-58) because weight isn't a problem.  Sectional masts
provide supports when there aren't convenient trees.

For Field Day we use those same dipoles, but we have more time to set up antennas and
optimize performance beforehand, so we may string the dipoles up at 50' in the trees, and
add at triband yagi on a 32' sectional mast, plus whatever other designs I've cooked up to
take advantage of the specific operating site.  From the West Coast, a beam of some sort
helps, and even yagi or quad configurations using wire and rope can improve your signal
strength on the Eastern Seaboard.

If you just want to spend a couple hours sitting on a bench on a hilltop, then a vertical
of some sort secured to the back may be a more convenient installation that doesn't
affect others walking by as much.

If you're operating from city parks, particularly with a lot of people around, they have more
strict rules on stringing antennas in trees or pounding guy stakes than at an unimproved site
in a National Forest or open BLM land.  That affects your choice of antennas and supports, too.



So first figure out what sort of operation will be most enjoyable for you, where you are likely to
operate from, and choose an antenna system that is best suited to that.   And nothing says that
you can't have multiple antennas for different types of trips:   while a general purpose kit may
work, special needs (a week backpacking the Pacific Crest Trail, perhaps, or a cabin in the
redwoods) may present different limitations and/or opportunities that may call for a different
choice of antenna.

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ONAIR
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Posts: 3536




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« Reply #9 on: October 10, 2017, 02:59:16 PM »

Balun Designs makes a combination 9:1 and 4:1 unun!  You can build a variety of portable antennas with it.  www.BalunDesigns.com
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KF4ZGZ
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Posts: 40


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« Reply #10 on: October 19, 2017, 03:25:50 AM »

The EARCHI endfed is very portable, and can be configure any way needed.
I have even removed the wire and attached the 9:1 to a 30ft. support mast and used the mast as a vertical antenna.(the mast was insulated from ground)
So, any thing you can stick in the air that will radiate, can be put to use.

Matt
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