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Author Topic: What is your ideal PORTABLE QRPp antenna?  (Read 51837 times)
KE7FD
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« Reply #15 on: November 18, 2010, 06:36:45 PM »

BYU, you mentioned a kite... Funny thing was that from the hill outside of Prescott Valley back then my wife and I brought a couple of paper kites with us and having forgotten tail material I fashioned something from litter that had blown up there.  The kites were so high up we couldn't see them due to the strong updrafts and winds around Mingus Mountain.  As we walked down the hill whenever we encountered more litter, I would pass it up the line where the draft carried it up towards the kite.  By the time we made it back to the base there was quite a long trail of trash I was able to reel in.

Here's a portable antenna of the genre I was thinking of:
http://www.w0ch.com/travel_antenna/travant.htm

Glen
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N3OX
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« Reply #16 on: November 18, 2010, 08:33:21 PM »

I ran some models and I think it's going to be a close call  in terms of performance between W0CH's "whip" and replacing the other half of a whip with another quarter wavelength wire laid out in the same way as the single "counterpoise" wire.

Note that Dale talks about propping up his dipole on really short things.  A couple-foot-high dipole might beat or equal the short whip and one counterpoise wire.  An eight foot high boulder might be like a tower for a dipole in this context.  I'm almost tempted, based on my modeling this evening, to call the type of antenna you're proposing a "short half-dipole with a heavy, loss-adding, breakable, bandwidth-narrowing, loaded counterpoise whip."

People build them all the time and try them and they work, and people think of it as a short ground plane vertical.  But it's just not quite right.

You might be tempted to figure that if you have to put  "counterpoise wire" right on the ground, it will radiate better if you have a short whip than a dipole on the ground.  But it doesn't really.  It's actually going to become very directional in the direction of the radial.  In that direction it will work only a couple dB better than a dipole right on the ground, but in the other direction it will be 20dB down or so.  Not really necessary to have a beam out in the field if you're going to run a few watts to a -15dBi antenna in either case.  It really only helps for reception, and you probably don't need help with that in the wilderness working people who can hear you.

I tried another case with the feedpoint up about four feet, and the four-foot-high-apex inverted vee seems to beat W0CH's design a bit (again, the whip+counterpoise seems directional)

These predictions would bear field testing (which I think Dale has already done a lot of), because we need some verification of really-close-to-the ground stuff.  I trust it a little more since N6LF's radial studies, so I think this might be the real situation.  And what it looks like to me is that there's not much reason to not take out the whip and coil and use another quarter wavelength wire in its' place.  It might seem against all that's holy in ham radio to use a two foot high or even an on-ground dipole, but that might actually be the better option

On the ground isn't a good antenna, not by any stretch of the imagination.  But it might not be especially worse than a 7 foot whip loaded with a PVC coated high reactance loading coil fed against one wire on the ground.  This is the thing you need to go ahead and test out.  Ultimately, you want the best antenna, not the one that makes you feel less weird.  It's deeply weird to me to consider a zero-height dipole or one propped up on a backpack or something.  But what if that's a better radiator than a more complicated and more easily broken antenna like W0CH's?


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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
WB6BYU
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« Reply #17 on: November 19, 2010, 09:19:10 AM »

I've hoisted 150' of wire with a kit in a slight breeze (because that was all we had that day), but
it would require a bit more wind to keep it steady.  But that is a whole different discussion...


I'm certainly not saying that a small loaded whip won't work.  Again, a lot depends on each operator's
personal preferences.  It is much easier to make a short portable whip work well on 10 or 20m than
on 40 or 80m, for example.  A low dipole on 40 or 80m typically won't work much DX, but usually the
radiation pattern will be better suited for local contacts than a whip.  And if you are sitting by salt
water (especially in an aluminum canoe) it is hard to beat a vertical antenna for low angle radiation
on any band.  There is no "one best solution" for all operators.

Going back to N3OX's analysis - it is actually quite difficult to predict the performance of antennas
installed in irregular rocky terrain, especially the volcanic peaks that characterize much of the west
coast.  First of all, you don't know how much of the antenna will actually be close to the ground,
since the surface typically is very irregular.  Second, you don't know the characteristics of the
rocks:  some of the magma is heavy, with a high iron content.  Some is very light, like pumice.
The RF characteristics are very different.  I remember talking to a station in Nome who just
laid his dipole wires on the ground, because it was dry sand and nearly transparent to RF - the
antenna was effectively 100' high.

If the ground isn't flat you get other effects:  a low dipole can have a very low angle of radiation for DX
when installed at the proper height over sloping ground.  Looking off the edge of a cliff changes
the pattern as well (or tying the antenna between two rocks with a 300' drop beneath it, which may
be possible with old semicircular volcano remnants.)


In the end, perhaps the best recommendation is to try a number of antennas and see how they work
for your needs.  It's not hard to build the W0CH whip and a dipole and take both to the top of a hill
to see how they compare in the situations you typically encounter, on the bands you like to use.
People make different tradeoffs between convenience, size, and efficiency.  For temporary testing you
can use any sort of whip and a chunk of coil stock tapped with a clip lead.  Similarly, try the dipole laying
on the ground with one wire raised as a semi-vertical.

Experiment. Try different things.  Be creative.  And have fun.
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KE7FD
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« Reply #18 on: November 20, 2010, 06:30:41 AM »

Two very good lines of thought, N3OX and WB6BYU.  At the locations I spec'ed out, one would allow a dipole to be draped across the rock outcroppings while the other might not with dirt and small shrubs making the vertical the better option.  BYU's closing thoughts of build and take both is where I think I'd like to leave this train of thought.  Between now and the spring I'll have time to build two antennas for this purpose then try them out.  The results of such a test might not be all that conclusive but I suppose if there were hordes of hams that did this there might be some marginally meaningful information that would come of it.  I do think one item on the list of things to take will be a couple of collapsible fishing rods; light and small enough to stuff into a backpack with the rest of the gear without adding very much weight at all.

Thanks again.

Glen - KE7FD
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N3OX
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« Reply #19 on: November 20, 2010, 08:42:26 AM »

I suppose if there were hordes of hams that did this there might be some marginally meaningful information that would come of it. 

Yeah there would.  It's a shame that more people don't really test things.

A lot of people build an antenna, feel that "it works just fine,"  and then go ahead and recommend it with no further testing.  This really puts a kink in the process of people trying to figure out which antenna is best for them.  There are a proliferation of "antenna designs" by individual amateurs and commercial firms that have no accompanying predictions or test data, even simple solid A/B testing over a long time.  Sometimes I feel like people build a thing that isn't so terrible as to shut down all contacts and on that basis claim it's a "design." That's why I wrote this article:

http://www.eham.net/articles/20174

It's like "OK, fine, it "works" on the air, but why should I make my life complicated by building it?"  A simple scientific method is the best way to assess antennas, and I don't mean "with lots of fancy techniques or test equipment" when I say "scientific."  I mean:

1) Make some sort of guess or prediction for how your new idea is going to work compared to something else simple, like a dipole or ground plane.
2) Actually test that prediction and see if you were right or not.  If it's a tight race, be very skeptical and make the new antenna prove itself despite your best efforts to show that it's NOT working the way you predicted.

This is the hard thing, I think.  People don't seem to like to be self-skeptical.   It gets so bad that there are sometimes reported "results" on people's antenna websites that are literally impossible.  The more common thing is that people report stuff that's just not objectively useful, like "of course, it doesn't work as well as a dipole," without telling you how bad it is.  But every once and a while their design cannot possibly work like they say.  They've managed to badly mislead themselves, either messing up their on-air tests badly or by not including all possibilities in their explanation.

Oh well.  The ham who does solid comparison testing has a leg up on those who don't...
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
K4AHO
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« Reply #20 on: November 20, 2010, 02:28:27 PM »

I have used several configurations of portable antennas in the local parks over the last few years.   I tried a 52’ center fed doublet as an inverted V and flattop using a balanced feedline, balun and K1 internal tuner with mixed results.   About a year ago I purchased a PAR 40/20/10 QRP EFHW antenna and have had amazing success with it…  I tried vertical, sloping and dipole configurations.   The most successful configuration has been the sloping configuration. After reading “Sloper Antennas” by OE5CWL I realized that anything less than 50 degrees of slope was a high angle radiator… I cut a ½ wave piece of very lightweight wire, hung  it from the top a MFJ mast, sloping at 60 Degrees and used the PAR Balun as 20 meter matcher. I had what I thought was a very successful 4 hour run during the QRP Afield Contest, 33 contacts, 5940 points and 3rd place.  And I am not much of a contester… Last weekend, I tried another site that allowed me to hang the PAR from a Pine tree and keep the lower end about 10 feet off the ground. Worked several SOTA guys.  Seem to work very well on 40 as well…

I also tested the issue of using a counterpoise with the PAR EFHW with an AIM 4170 completely isolated from ground and computer(using a Bluetooth RS-232 link).   I found that the PAR 40/20/10 EFHW only needs about a 3 foot counterpoise to work well and will happily work with any feedline over that. 

I think what really counts here is matching your mission Antenna to the prevailing propagation and available resources.  If you want to make close in contacts then a low dipole on 40 or 30 is great, On 20 you are wasting RF.  For DX contacts using a EFHW at 90 degrees vertical will do wonders, see the W1PID site. If you want  stateside contacts 90 degree vertical radiates at a too low Angle of Radiation to be effective. Spends too much time in the D layer and gets attenuated.   A 60 degree sloper has a slightly elevated Angle of Radiation which spends less time in the D layer, less attenuation and more successfully with  stateside stations. Of course working Washington/Oregon state from Florida, all bets are off.   Whatever works…

72

Jim
K4AHO
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AURICH
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« Reply #21 on: November 20, 2010, 07:33:03 PM »

My ideal portable QRP/QRPp antenna is the Par End Fedz 10/20/40. Short (40ft), end fed, rolls up small, 3 bands/no tuner, setup in any configuration, relatively inexpensive. I feed mine with 25' of RG-174.

With one support I can be operating in a matter of minutes while the next guy will be untangling wires and fiddling with seperate baluns, tuners, counterpoise wires, etc.

With the antenna horizontal a mere 6ft off the ground I have worked the Caribbean and Hawaii on 20m. In a near vertical/sloper configurations I have worked Europe and east to Russia, all with 5w or less SSB phone from here in Colorado. The furthest contact with the least power was to Austria on 2.5w which comes out to about 2100 miles per watt. Obviously good band conditions helped, but band conditions mean nothing if your antenna sucks.

Sure, with QRPp some sort of beam would really help, but in terms of KISS (Keep It Simple Stupid), and portability, the Par End Fedz excels.

Luke
KD0FIN
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KB1GMX
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« Reply #22 on: November 21, 2010, 11:08:23 AM »

I have some portable work and FD experience and the antenna has been either the PAR EF40/20/10
or a home brew 20M endfed and for 10M a dipole or a 10M end fed.  Both cases for the mono band
end feds were oriented vertical using a tree or crappy pole to get it erect. That vertical configuration
is not a compromise antenna as it's full size and high enough.  The other I've done a sloper using
the EF 40/20/10 as thats 40ft long and with the far end at about 35ft from a tree and the feed end
at about 10ft using a fiberglass pole also proved to be very effective as well for even 40M.  Since
my preferred mode is SSB QRP and efficient antennas are a must and on 20M a 33ft half wave is only
limited by how high you can get it.  But at 10M it's not hard o get it a half wave or more up (16ft).

The other bands i like to run QRP from the field are 6 and 2M and the usual antenna is a square loop
or a small portable beams.  On those bands a portable antenna and mast of 10-15ft need not
weigh more than 10 pounds all up with 20ft of rg8x. This usually means a 3 element of 6 and
5 element on 2M.  From the hills I've tried that works very well. with 1-5W SSB.

Allison
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W8MKH
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« Reply #23 on: November 22, 2010, 09:59:56 PM »

I use a Pac 12 vertical from pacific antennas  have great luck with it it is light and fits into my go bag easily
also have used the super antennas mp1.
Ft 817 pac 12 has done me well for several years  also used mini mite 40mtr 350mw txer with it and have been amazed how well it works
did make new ground radials and it has improved it greatly from the stock ones.

No you cant beat a dipole but this is the next best thing
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N2QGV
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« Reply #24 on: December 05, 2010, 02:22:59 AM »

Keeping it simple, Par endfed 10-20-40 w/Icom 703+. No stories or history. It just works.

73
Art
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AE6RF
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« Reply #25 on: December 08, 2010, 10:04:11 AM »

Keeping it simple, Par endfed 10-20-40 w/Icom 703+. No stories or history. It just works.

I've used the Pac-12 and the Par end-feeds, both to reasonable success.

One suggestion is the W2FMI "umbrella" 40m vertical. But you'll be putting out radials. Not too big an issue on remote, rocky ground.

Another is one of the short vertical dipoles like some of the Force antennas. I have a buddy who really likes his Sigma-5 for portable work...

73 de Donald
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AD6KA
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« Reply #26 on: December 08, 2010, 10:49:38 AM »

Quote
what I'm asking for is what can you cram into a backpack and run out the door with and maybe hike up a hill side where there aren't any trees.
 
If I'm operating from a motel room, most 40m dipoles just aren't going to work, and for that reason I wanted to know what other non-dipole antennas were working.

First you say outdoors on a hill, then you say motel room. Big difference!

Quote
we can't pack cumbersome poles with us.

Not ALL poles are cumbersome or heavy. The thin wall telescoping fiberglass (or whatever) ones from MFJ and others are light and can be easily strapped to your backpack or day pack. I've used one in the field to make both wire verticals with and to support an inverted vee. (Not at the same time).
Use twin lead and a BLT for lowest loss, especially if you are going to use the antenna on more than one band. You may have to guy it if it's windy, and you'll have to put down some radials with a vertical, but there's no such thing as a free lunch.
Which, can I say, seems to be you are looking for.

73, Ken AD6KA
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KU2US
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« Reply #27 on: December 12, 2010, 07:46:01 PM »

Use the Par 3 band qrp end fed longwire. Find a tree and you are on the air. No radials, no tuning, weighs less than 1 lb. and works great!
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AD6KA
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« Reply #28 on: December 13, 2010, 10:18:30 AM »

Use the Par 3 band qrp end fed longwire. Find a tree and you are on the air. No radials, no tuning, weighs less than 1 lb. and works great!

A good plan, but the poster said:
Quote
"what I'm asking for is what can you cram into a backpack and run out the door
 with and maybe hike up a hill side where there aren't any trees. "



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KE7FD
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« Reply #29 on: December 13, 2010, 09:11:31 PM »

Wow, I'm very surprised this question has been going for over a month. (Your milage may vary.)

Ken, whether I'm hauling a QRP rig up a hill or operating from a motel room it's about the same.  The reason I would be in a motel room in the first place is because I'm probably somewhere on business and have other things to lug around  so toting a 20 amp supply isn't an option (for me anyway).  The backpack is quite literal.  I know this means I've got a compromised-compromise radio/antenna but if I can work a few QSO's instead of wasting time watching HBO or howling at the moon, I'm content.  I think we can look at most of the posts on eHam and can clearly see that assumptions are par for the course.  In this case, the way I operate while on the road or from a backpack differs from how I would say at home or even mobile.  IMHO, as a group we need to be open to the possibility that operating objectives will vary from site to site and situations.

There's been a lot of replies for various wire antennas and some commercially made antennas.  If I can come up with something that would work well enough for a motel room/balcony, I would probably use it as a backpack-portable antenna as well.  Lots of ideas from guys who have tried some different things which I may try too.  I did just pick up a pair of 40m hamstick type antennas so before I take to the road I'll take the time to get them tuned up.  If they work after various tests then I'll report back, if not, then maybe I'll try something else.  I realize there is a certain amount of reinventing the wheel going on here but I enjoy the tinkering too, about as much as making contacts on-the-air.  Life isn't too short for QRP, but if we always use beams, quads and big amps, how will we know if it's our own skills and talents coming together to make a contact and not some products doing it for us?

Thanks to all!

g
« Last Edit: December 13, 2010, 09:15:06 PM by Glen Roberts » Logged
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