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Author Topic: end-loaded horizontal dipole  (Read 609 times)
N5EIL
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Posts: 121




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« on: May 21, 2003, 10:02:37 PM »

I am going out of town and am trying to construct a dipole for qrp'ing on 17m,30m,40m. on 17m i have a full size dipole. I can put up, then on 30m I have added coils at the ends of my 17m dipole to give me reasonace on 30m when hoked to the 17m dipole ends.
then on 40m I have another switchable coil on rite behind the 30m coil. which are 2.5in coils. used with 18ga plastic speaker wire.

will this work for me on 30/40m w/o any sort of tuning device ?
what should i expect from it on 40/30m?

thanks 73's
N5EIL , Neil  

 
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KT8K
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Posts: 1490




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« Reply #1 on: May 22, 2003, 09:38:43 AM »

If you designed the coils properly it should work fine, though the bandwidth will be limited as it is with all shortened antennas.  Sounds like a good idea, for low power at least.  Hope to C U on the air.
- Tim
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AC5E
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Posts: 3585




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« Reply #2 on: May 22, 2003, 10:50:35 AM »

It's a feasable design. If I understand you correctly you have a full size 17M dipole you want to add a pair of resonant coils, "traps,"  to for 30 and another pair for 40.


It does not matter whether you use a self resonant "solenoid" type coil, some other style trap, or the self resonant coaxial trap described in QST, and subsequent ARRL Antenna Compendiums. Although for QRP the coaxial traps are somewhat more efficent and less affected by wet weather.

You will need a fairly short section between the 30 and 40 M traps to and another outside the 40 M trap. You will want the 30 M traps to resonate just below 18 mHz, and the 40 M traps to resonate around 10 mHz. This greatly increases trap efficency.

73  Pete Allen  AC5E
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W6HB
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Posts: 38




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« Reply #3 on: May 22, 2003, 03:01:26 PM »

If you can get up a tuned feeder fed doublet 44' long you will have a predictable pattern and better performance. Look up the details at www.cebik.com/aledz.html

73 - Doug - W6HB
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N5EIL
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Posts: 121




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« Reply #4 on: May 22, 2003, 03:49:00 PM »

thanks for the info...

I hope to operate psk-31 and other similar modes with this antenna at qrp levels.i think that this idea should work for me on 30/40m w/o any tuning or matching device. i think overall it will be more effeciant to load it at the ends so it won't effect my radiation pattern that much.

73's and good Dx'ing
N5EIL, Neil
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