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Author Topic: Random wire antennas and counterpoises  (Read 6218 times)
N9AOP
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Posts: 641




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« Reply #15 on: July 02, 2017, 01:31:34 PM »

I used to worry a lot about half wave, random length and counterpoise.  Now I just toss out what wire I have and make contacts.  Less brain strain.
Art
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W1ADE
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Posts: 5




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« Reply #16 on: July 09, 2017, 09:33:35 AM »

To go on further about getting supports up into the trees, I have to share what I discovered just a little while back and use now-nearly every time.  Also, an added bonus that I discovered long ago, but gets little discussion.

When I first learned to hang wire antennae, I used the bottom section of a surf-fishing rod with 20# mono and a wrist-rocket to launch a painted sinker.  So many years later my wrist rocket has fallen apart and one day I was eying the location i wanted a line and thought--hey, that's an easy CAST!  

So now I use the entire surf rod with (17-20# line) and just yesterday was able to put lines where I wanted-sometimes with the first cast.  Also, I now use surveyor flagging to highlight the sinker (1/2 or 1 oz bank style is best, but I've used all shapes.  

Also, I rarely hear other hams speak of it, but non-metallic clothesline is what I have been using for lift/support "ropes"  since the very beginning. It's cheap enough, strong, holds a knot well, and available just about every where laundry soap is sold. It will eventually turn gray/black, but I've never had any snap (under normal use) or show sun damage. I started using it in 1996 and have found it handy in camp, also as fish stringers, etc.

For portable, sure maybe something else is plenty (a Snoopy rod?), but for putting it WAY up there-right where I want it, I'm casting.  Hey, I started catching trees on a fishing rod in about 1972!  Grin Tongue



BYU's ideas are good ideas on how to get your wire up into a tree.  I used to use various types of twine, however I always felt bad if a piece of twine or rope got stuck in a tree.  It looked awful and probably will still be up there 100 years from now.  When backpacking or traveling I often just use a piece of (cotton ?) kite string and often just tie it to a half full water bottle.  It throws OK and if it gets tangled I can just break it.  I usually use the string to pull up my antenna wire.  For car camping I often carry a 31 ft telescoping pole which I can bungie to something, or I often use it just lay an antenna wire or twine over a convenient branch near the picnic table.  Probably the easiest way to get a line up moderately high without too much risk of a tangle is to buy a arborist kit.  There is a beanbag looking weight and some really slippery line which seems to drop easily through the branches.  In theory you should be able to go quite high with practice, and I have found that something like 25 or 30 feet is rather easy.  There are many other methods for getting wires up high in the trees, however if you can get your 26 foot wire over say a 15 or 20 foot branch this will be plenty high to give you many happy QSO's.  I used to spend an hour or more on set up, but more recently have enjoyed a 5 minute set up time, and enjoyed more operating time.
       KL7CW
« Last Edit: July 09, 2017, 09:37:33 AM by W1ADE » Logged
WB8LZR
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Posts: 40


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« Reply #17 on: July 09, 2017, 11:53:17 AM »

AOP: Less brain strain = good.  Now that's truly a "random" wire.

ADE:  How high can you cast it?  I've never been able to throw a weight with a trailing line more than maybe 30 feet (vertically).  So to get my dipoles high in the trees (90 footers here) - I used the slingshot.  The rubber's so old it probably isn't safe anymore, so that'll need replacement before the next antenna farm project.
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K0UA
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« Reply #18 on: July 09, 2017, 02:54:26 PM »

I have been using my 31 foot long piece of #14 wire and my homebrew copy of the EARCHI 9 to 1 balun.  I have tried it with and without counterpoise.  With the counterpoise it seems to work, a bit better.  I use a 31 foot elevated counterpoise.  It all seems to work pretty well.  I have talked across the frog pond from here in Missouri on SSB.  Most contacts were made with 5 watts, some with 20, but I had to cheat and use 50 to get to Ireland on 15 meters.  It works pretty good on 40, and really good on 20 and 15.  So so on 10 and 6.  I can load it on 80 meters, but it really sucks.  I made a few contacts on 80 but "your really weak" was the average  signal report.  Take it for what it is worth, but I was pleased how well it worked for the very small investment in money and time.
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W1ADE
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« Reply #19 on: July 10, 2017, 07:40:16 AM »

AOP: Less brain strain = good.  Now that's truly a "random" wire.

ADE:  How high can you cast it?  I've never been able to throw a weight with a trailing line more than maybe 30 feet (vertically).  So to get my dipoles high in the trees (90 footers here) - I used the slingshot.  The rubber's so old it probably isn't safe anymore, so that'll need replacement before the next antenna farm project.

Have yet to need more. Helps to have 7' or longer rod with moderate stiffness. Heavier line won't go as far, and a too soft a rod won't load up enough energy for good tip speed.  Casting reels take a little heavier weight to get the spool spinning, but I always use spinning reels for super accurate lobs and no backlash.  My tallest trees are 80-90' but as they line the edges of the woods there's no way to get right over the tallest part. I catch limbs on the field side.  

de W1ADE a/k/a Wade
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WB8LZR
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« Reply #20 on: July 11, 2017, 10:38:08 AM »

AOP: Less brain strain = good.  Now that's truly a "random" wire.

ADE:  How high can you cast it?  I've never been able to throw a weight with a trailing line more than maybe 30 feet (vertically).  So to get my dipoles high in the trees (90 footers here) - I used the slingshot.  The rubber's so old it probably isn't safe anymore, so that'll need replacement before the next antenna farm project.

Have yet to need more. Helps to have 7' or longer rod with moderate stiffness. Heavier line won't go as far, and a too soft a rod won't load up enough energy for good tip speed.  Casting reels take a little heavier weight to get the spool spinning, but I always use spinning reels for super accurate lobs and no backlash.  My tallest trees are 80-90' but as they line the edges of the woods there's no way to get right over the tallest part. I catch limbs on the field side.  

de W1ADE a/k/a Wade


90 feet?  You promise now, this isn't any fish story.   :-)   Else - I'm heading straight for the Bass pro shop.
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AK0B
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Posts: 267




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« Reply #21 on: July 11, 2017, 12:42:40 PM »

The ZM-2-ATU is a nice design.  it should be able to tune anything you use.   I like about 45 ft and I have a 2 ft ground rod I drive into the ground about 8 to 10 inches so I can get back out when I go home.   Smiley

My rule of thumb if it is shorter than a half wave I tune with a tapped or variable coil.  If longer than a half wave I tune with a series cap.  If one doesn't ork try the other either a var cap or var coil will tune most pieces of wire.

I like the ZM-2 it  is small and easy to use.

Stan AK0B

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WB6BYU
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« Reply #22 on: July 11, 2017, 03:10:37 PM »

Quote from: AK0B

...My rule of thumb if it is shorter than a half wave I tune with a tapped or variable coil.  If longer than a half wave I tune with a series cap...



Then perhaps your thumb needs recalibration.

Typically wires shorter than one quarter will have capacitive reactance, so need a series coil.
Over 1/4 wave and up to 1/2 wave will be inductive, so need a series capacitance to tune them to resonance.
That sequence continues alternating between inductance and capacitance every quarter wavelength as the wire
is made longer.

But that just matches the reactance, not the resistance.  If your wire is 250 - j600 ohms, canceling the reactance
with a series coil still leaves you with a 5 : 1 SWR.  For short wires (less than 1/4 wavelength), the resistive component
will be less than 50 ohms, but the ground losses will often bring it up enough to get an adequate match, especially for
portable work where you have a limited ground system.  But for longer wires you will often have a high SWR even after
canceling the reactance.


This year for Field Day I used an L-network with an external balun in place of the Johnson Matchbox for my doublet:


Tuning was much smoother, and it had no problems matching the antenna, while last year I with the Matchbox I couldn't
get the SWR below 2 : 1 on 20m.  Yes, I know that this isn't exactly sized for convenient backpacking, but if you use
a wire over 3/8 wavelength it should match it on any band, even using a small L network with a variable capacitor
and a coil tapped with a clip (or a toroid built onto the wiper mechanism of an old rheostat.)
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AK0B
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Posts: 267




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« Reply #23 on: July 11, 2017, 07:48:40 PM »

Then perhaps your thumb needs recalibration.


Chuckles,

I agree you're correct ---  Stan AK0b
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ZR1PJA
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Posts: 62




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« Reply #24 on: July 14, 2017, 06:07:42 PM »

I have had this discussion with Bonnie Crystal a while ago.
From her experience a good countrepoise system for backpack and long or random wire antennas is 3m, 6m and 12m which i have tied together.
Alternatively i have used the KISS countrepoise system.
These cover from 80m to 10m

Regards
Paul
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LUCYAJONES
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Posts: 16




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« Reply #25 on: October 11, 2017, 08:37:12 PM »

Something I've never done but is in my bucket list, hopefully to be done before I punch out.

I want to go to a park, set my QRP gear up on a table, run a single wire to a tree limb and lay out a counterpoise.  Then see what I can work.

My questions are, do I make the antenna itself a specific length according to band/frequency or can I just string out what I can and used my tuner to match it to my radio?

How long do I make the counterpoise with the correct above information at hand?

This subject has been asked and answered on this forum before but I can't find it now that I need to learn it.

At that point simply utilize one for the reception apparatus and another as the counterpoise and check whether

your tuner matches it. Or, on the other hand simply unroll the counterpoise wire to a helpful
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