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Author Topic: antennas for QRP portable  (Read 1299 times)
KD5RNN
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Posts: 44




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« on: June 10, 2002, 07:26:14 PM »

I am checking into geetting either an Electracraft K1-2 or a k1-4. I am looking for a fully portable antenna I can set up in a short time and take down in a short time. It has to be multi-ban...And just to let you know I will hopefully get the K1 with the ATU...so give me your I deas on portable antennas I can run QRP off of.
I would like something thats not getting Negitive gain!!!

73 KD5RNN Neil
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AD5X
Member

Posts: 1430




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« Reply #1 on: June 11, 2002, 09:10:40 AM »

Check the December 2000 issue of QST for a multi-band (20-10 meter) dipole I use for QRP portable.

73,
Phil - AD5X
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WB6BYU
Member

Posts: 13147




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« Reply #2 on: June 11, 2002, 04:05:16 PM »

I've had excellent results with a set of wire dipoles.  I put an
insulator on the end of 25' of RG-174 coax with a pair of wing nuts
for attaching the ends of the wire.  The wires are cut and pre-tuned
in the backyard or the local park - if tuned at a height of about 12'
(3.5m) they should be close enough in most portable installations.

When I stop to set up the station, I decide what bands I want to
use and tie those wires onto the center insulator.  (I tie the wires
through a hole in the insulator for strain relief, then twist the ends
together and put them under the wing nut.)  Throw a rope over a
tree branch, tie it to one wire, pull the whole thing up in the air, and
tie the remaining wires off to handy bushes.  When were are no
trees, I've supported it on fence posts and rock outcroppings.

One of my favorite features of this approach is the flexibility: I can
put up different combinations of bands for mountian-topping on
10m than when I make camp for the night and want to work 40 and
80m.  Or I can combine the wires in other ways, such as using one
of the 40m wires for a full-wave loop on 10m.

Having enough practice at using the kit, I have put it up in 5
minutes.  I've put up all 5 bands in the dark.  Use #22 to #24 or so
stranded, insulated wire, and learn to wind it across your palm in
a figure-8 which makes it much easier to unroll without kinking.
If you color-code the wires it will make it easier to pick the ones
you want.  I carried a 50' (15m) length of braided cord for a throwing
rope, and lots of shorter lengths of mason's twine for tying off all
the loose ends.  (Dental floss also works, and comes in a handy
dispenser.)  The whole antenna kit including feedline fits in a small
nylon pouch (2" x 4" x 6") with room to spare for battery cables,
microphone, telegraph key, headphones, etc.

My kit has a lot of miles in my backpack, with either the Argonaut
or HW-8.  And I never used an antenna tuner with it.


Another option if you want to carry a tuner is a longwire.  I used
a 135' wire in Alaska with good results.  If you choose a multiple
of half a wavelength, the wire will have a high impedance and
you don't need much of a ground for good efficiency (a pack frame
or bicycle will probably work - I've used nothing at times.)  Such
an antenna requires only a simple 2-element "L" network to
match it, and you can simplify the tuner even more if you always
use the same piece of wire, because the impedance will be fairly
predictable once you get it tuned the first time.

Whichever type of antenna you use, you will enjoy it the most if
you practice using it, and, particularly, tying knots that will hold
it up but that are easy to untie when you want to take it down.
A bowline, sheet bend, and tautline hitch will go a long ways - and
I make them all "slippery" so I can pull the loose end to untie them.
(Wind the ropes up in a figure-8 just like the wires.)

If there are no trees where you are going, consider a WorldRadio
fishing pole for an antenna support.

For a convenient single-band antenna, I've had good results with
a J-pole.  If you use twinlead for the matching section and regular
wire for the radiator, they are not very bulky, even for 20m.  This
requires just one rope over a branch to hoist it and start opeating.
No trees?  Hang it from a kite.


There may be times when a base-fed vertical is a good solution,
but I haven't encountered them any of them.  They can be efficient
if you get the base far enough above the ground and use enough
radials... you can always put one up and use as a support for a
dipole.

Good luck and 72,

 - Dale WB6BYU

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WB2WIK
Member

Posts: 20567




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« Reply #3 on: June 11, 2002, 07:13:58 PM »

Previous ideas were great, here's another one:

If you are operating portable but plan to return at least once to the same site, such as a favorite campsite, you might consider installing a tree-supported antenna, and just leaving it there for "next time."

I've done this several times and surprisingly, most of the semi-permanent antennas installed stayed up for years, verifying my theory that not all kids are vandals!

I installed a 40m wire inverted vee in a pine tree, about 30 or 35 feet above ground at the apex, with about 60' of RG58/U coax attached to it, in a public park at the summit of a large hill overlooking the ocean about ten miles from where I live.  It used to be one of my favorite "go up there and operate" spots when I lived in a condo without good home antennas.  When I was finished using the antenna, I'd coil up the coax and hang it over a lower branch about 8' above ground, just at the limit of my reach and (hopefully) above the reach of most kids.

I went back and used that antenna probably twenty times over a period of two years, and it was always there!

Something to keep in mind...

WB2WIK/6
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KD6JLS
Member

Posts: 38


WWW

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« Reply #4 on: June 13, 2002, 06:07:22 PM »


A LOT of people who use radios while backpacking or working portable swear by a commercial antenna called the SuperAntennas MP-1. You can read about it here:

http://www.superantennas.com/___Products/MP-1_Portable/MP-1_Details/mp-1_details.html

It is widely available at ham radio stores, or online at various web sites. It costs around $60 bucks at HRO, if memory serves. One advantage is you can hook it up to the side of your backpack, run a counterpoise behind you, and talk while walking. It also sets up in about two minutes if you just want to use it stationary at a local park. People have worked all over the world with 5 watts on that bad boy.

Another popular option is to use a random long wire with an antenna tuner. The LDG Z-11 tuner is very popular with backpackers, especially those operating QRP. You can buy a kit from the manufacturer, or an assembled unit from most ham radio stores:

http://www.ldgelectronics.com/z-11.html

The down side to both of those options are that they have power limitations, so they aren't ideal for a permanent station. They are a great match for a K-1 or K-2, however, or my personal favorite, the FT-817.

The Yahoo group HFPack is just about the best place to find information about portable antennas and operating. Scroll through the message board there and you will find hundreds of solutions. They also did a shootout between a large number of different portable antenna options to see which worked the best. Just click on the antenna link from the main page.

http://www.hfpack.com/

You'll have to join to have access to the message board and some other features, but it doesn't cost anything. You just have to fill out a form and give them your email address. Well worth it.
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KD6JLS
Member

Posts: 38


WWW

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« Reply #5 on: June 14, 2002, 02:14:25 PM »

I have a typo in the above post. The MP-1 was $160 last time I priced it, not $60.
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KD5IVP
Member

Posts: 22




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« Reply #6 on: June 27, 2002, 02:08:59 PM »

Of all the QRP portable antennas I 've messed with, the one I always return to is the 1/2 wave wire and 1/4 counterpoise.   Whether back packing, hoteling, parks, car camping, etc. this antenna works great, requires no coax or other feedline, is matched with a very simple L-C network, and wire is cheap!  I use 24ga wire cut to 1/2 wave on the lowest freq. I plan to opperate.  A 1/4 counterpoise wire  is strung out on the ground.  The antenna can be strung straight up in the air (depending on how tall your trees are), low over the ground, inverted L, end fed V, over door frames and ceiling fan blades as I've done here in the house, or over hotel balconeys dangeling in the breezes.  Try it!
Paul, KD5IVP
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AE5X
Member

Posts: 382


WWW

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« Reply #7 on: July 16, 2002, 05:07:52 PM »

I have the same rig (K1-4) and have had excellent results with a dipole cut for the lowest band you intend to use and fed with 300-ohm Radio Shack twin lead. Tunes easily on all four bands. I usually install it as an inverted V with the apex up around 25-30 feet.
More details at:
http://www.ae5x.com/backpack.html
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