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Author Topic: Antenna is up, tuning is next.  (Read 1572 times)
KE7DJQ
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« on: October 08, 2012, 07:03:03 PM »

A box from DX Engineering arrived today containing 300 ft of 14 ga polyethylene covered wire, a Comtek 4:1 balun, 200 ft of 3/16 rope and a polyphaser lightning protector.

In just over 2 hours, the XYL and I got all 4 corners of the 80M loop up, and then ran out of daylight.  Tomorrow I'll solder the antenna to the balun. Right now it is just twisted on so I could get the loop up in the air.  The corners are about 22 feet up.   I know that is less than optimum, but is the highest I could go right now.  The wire is hanging loosely since it is too long.

I have an MFJ 259 analyzer and am ready to use it, although it may be that I will just cut the wire so it is snugly up based on spacing between the 4 masts.  Never  having done a loop before, this is all new.
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KD8GEH
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« Reply #1 on: October 08, 2012, 07:33:05 PM »

Make it 270 feet total for starters and google 80 meter loop. If you need help email me at my call at arrl dot net. Run the MFJ thru the 80 meter and bends below and look for your dips in SWR, tweak as needed  Grin
73 DE Dave KD8GEH
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WX7G
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« Reply #2 on: October 08, 2012, 09:57:25 PM »

Ate you feeding the loop with coax?
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KE7DJQ
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« Reply #3 on: October 09, 2012, 08:59:16 AM »

Yes, I'm using coax to feed the loop.
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WB6BYU
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« Reply #4 on: October 09, 2012, 10:08:12 AM »

Since you are using coax to feed the loop, you want to cut it to resonance to keep
the SWR reasonably low.

In my experience this usually means about 3.55 MHz in order to get the higher resonances
suitably placed on 40m, 20m, etc.  This turns out to be great for a CW operator, but you'll
need a tuner for 75m operation (and some other bands as well).  Typical length is 270 to
280 feet.

As an example, a model of a square loop 70' on a side (total of 280') using #14 bare wire
shows resonances at:
 3.6 MHz,
 7.05 MHz,
 10.75 MHz,
 14.3 MHz,
 17.8 MHz,
 21.25 MHz,
 24.8 MHz,
 28.3 MHz.

That will depend somewhat on the height above ground, wire insulation, etc.

If you have a particular band of interest, you can adjust the loop length until the SWR is
low where you most frequently operate - as long as it is one of the bands where you
would expect the antenna to be resonant.

I put up loops by tossing a rope over a tree some distance out from each corner.  The end
of the rope can either be tied to the corners of the loop, or (as is often the case when the
trees aren't evenly placed) I use an electric fence insulator that easily slips around the wire
and the rope ties to that:  that allows the insulator to slip along the wire as I pull the loop
up into place.

Then pull up all the ropes to raise the loop.


I would NOT tie the wire directly to each of your masts - use a pulley and halyard instead,
as that makes it much easier to lower it for adjustments, etc.
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KE7DJQ
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« Reply #5 on: October 09, 2012, 07:40:07 PM »

Thanks, WB6BYU.  Each of the 4 masts has a rope so I can lower each corner.  Tomorrow I'll start the cutting and tuning process.  I have a tuner.  I'm looking forward to getting on the air with a real antenna.
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KE7DJQ
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« Reply #6 on: October 10, 2012, 06:28:37 PM »

Well,  I got on the air with the new antenna.   It ended up to be about 276 feet long, based on what I cut off.  It is lots quieter and I can hear lots more stations.  About 5:30 pm MST,  I made a contact  on 20M in Atlanta, Georgia.  He could hear me very well.  Then I switched to 40M and called CQ.  Got the west coast, about 250 miles north of Los Angeles. 

Overall, I am happy, so far.  In a little while I'll arrange a local QSO on 40M and see how it performs there.

I still need to get it into the shack, though.  It's in thru an open window right now.
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KE7DJQ
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« Reply #7 on: October 11, 2012, 01:26:24 PM »

So far, so good with the antenna.  I talked with a couple of friends less than 10 miles away on both 40 and 80 meters, checked into a state net, and talked to stations on both US coasts.   So far, I don't have any RF issues, not even thru my computer speakers.  I did have that issue with the temporary antenna that was inside the room.

Now I need to put the polyphaser protection on and run the coax through the wall into the shack.

Thanks for all your  help.

« Last Edit: October 11, 2012, 01:31:54 PM by KE7DJQ » Logged
WB6BYU
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« Reply #8 on: October 11, 2012, 02:46:36 PM »

Glad it is working for you.

How is the SWR on the various bands without a tuner?
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