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Coil Loaded Dipole build - photo diary

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  #9  
Old 10-26-2008, 06:58 PM
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Quote:
Originally Posted by moleculo View Post
Since my other thread got hijacked...
Sorry about that!

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  #10  
Old 10-27-2008, 12:46 PM
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Hello Mole:
I have one of those Alpha Delta Dipole Antennas; it covers 80, 40, 20, 15 and 10 meters, or better put it’s supposed to cover those bands.

I made a 1 to 1 Current Balun to feed the Alpha Delta Antenna, 8 or 9 turns or paired 12 gauge wire around a 2.4 inch Toroid Core from Amidon. I think this throw off the dipole design from the manufacture. As I needed to tune this dipole antenna for 20, 15 and 10 meters.

The original coil inductance can be measured on your MFJ Antenna Analyzer, just set the frequency to 80 or 40 meter band and duplicate the new coils measurement in uH.
Connect the coil leads to the anaylzer SO-239 and be Xl mode.
Or figure the original coils inductance in uH from a Coil Calculator from a search engine. Then make the new coils to have the same analytical uH as the original coils.

Anyway sounds like you are having fun with experimenting around and a walk to the park.

I noticed that the 40 meter band was very broad banded, and worked well. 80 worked ok, but the other bands I had to tune. Like to hear your results when done.

My antenna easily took 1000 watts PEP without catching fire.

Jay in the Mojave

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Old 10-27-2008, 01:03 PM
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Quote:
The original coil inductance can be measured on your MFJ Antenna Analyzer, just set the frequency to 80 or 40 meter band and duplicate the new coils measurement in uH.
Connect the coil leads to the anaylzer SO-239 and be Xl mode.
That's a good idea...I never thought of that. I wonder if anyone has the inductance of the Alpha Delta coil published? If not, I suppose I'll have to get on the roof and measure mine (after disconnecting the wires, of course).

BTW I was able to get my Alpha-Delta DX-CC to have very good, if not perfect SWR on each of the bands it is made for but it took some time messing with the wire lengths. I've run as much as 2+ KW through mine on the higher 75m frequencies (actually MARS) with no problems!

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Old 10-27-2008, 04:58 PM
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I found this link today which is the same project with slightly different dimensions. It's a good read:

Coil loading of an 80m dipole for restricted space

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  #13  
Old 10-27-2008, 05:00 PM
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Yo Mole:

Yeah ok good deal, great info there. I have built a 80, 40 20, 15, and 10 meter dipole all with seperate lengths for the bands, but haven't had the time to put it up, and tune it.

I am also thinking of a remote automatic tuner in the Barn to tune a long dipole antenna having the tuner do all the work after programming in all the bands so the tuner will slam there real quickly and handle all the power. But at around a grand plus for the tuner you would be able to have a effictive dipole. See:

Welcome to Palstar.com Model AT Auto 1500

But that wouldn't allow you to experment with the tuning of the dipole. 2000 watts+, you city people run a lot of stream as compared to us poorer folk who live on dirt roads and in the Desert! Hahahhahaha

Jay in the Mojave

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Old 10-28-2008, 08:43 AM
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Hello All:

Ok I posted this yesterday but the computer out smarted me again, and it didn't get posted!

The Alpha Delta Dipole Antenna has a real great performance on the 40 meter band. That is, it has a wider that normal bandwidth and works well. I believe the 40 meter wider bandwidth is due to the coil on the end of the dipole antenna length for 40 meters, seeing a inductive reactance.

This can be verified or not verified by making a dipole antenna that has the coils for a dipole antenna for 160/80 meters, or even 40/20 meters. Food for thought here.

If this is true then one might want to make a 160/80 meter dipole antenna that worked somewhat on 160 meters, but had a very wide SWR Bandwidth on 80 meters.

Your comments....

Jay in the Mojave

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  #15  
Old 10-28-2008, 12:52 PM
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Jay,
"I believe the 40 meter wider bandwidth is due to the coil on the end of the dipole antenna length for 40 meters, seeing a inductive reactance."

I'm afraid not. That coil is a loading coil for 80 meters, has nothing to do with the 40 meter antenna which is located below the 80 meter antenna. I think if you measured that wire segment below the segment with the coil in it, you'll find that it's for 40 meters. (That's going only by the posted picture of the 'Alpha-Delta' antenna, don't have one so can't do that measuring myself.)
The bandwidth of that 40 meter antenna is sort of typical, not really all that extraordinary.
Now, if that loading coil was a 'trap'... but it isn't.
- 'Doc

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  #16  
Old 10-31-2008, 04:16 AM
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Hy Power Antenna Company I run the loaded 40/80/160 dipole.These are great antennas.

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