COIL FORM DETAILS



14.7 Uh
Dia:  0.75"
Length:  4.5"
Turns:  67 - #14 AWG


33.5uH
Dia: 1.0"
Length:  6.0"
Turns:  89 - #14 AWG

 


 

The coil form must be strong enough to support various lengths of top-sections.  I chose a solid fiber-glass rod for strength and insulating qualities at RF frequencies.  I had the coil end-caps manufactured at a local machine shop from this drawing.  I have two (2) different diameter coils, one is 3/4" in diameter and the other is 1.0" diameter.  The drawing above is for the 1.0" diameter coil form.  The end-caps are drilled and tapped to accept a 3/8"X24 thread which is the standard used for most antenna's and mounts.

The "Q" of the coil could have been improved by using a larger diameter coil but the only way to accomplish this would have been to use a piece of 2" or 3" coil stock from Air-Dux which is rather expensive.  I tried to keep the IR loss to a minimum by using #14 AWG enamel wire to wind the coil.  The result is ver4y satisfactory. 

After winding the coil, I assembled the complete antenna by connecting two (2) Hustler mobile bottom sections together using a 3/4"X24 thread-coupler available at most hardware stores.  This provides an 8 foot bottom section for the antenna.  The coil is then screwed into the top of this eight foot section and the 6' top section is then screwed into the top end of the coil.  The top section was a piece of an old 102" CB whip.

At this point I disconnected the coax line from the base of the mobile antenna mount so I could make an impedance measurement using my Autek antenna analyzer.  The antenna measured 45 ohms resistive at resonance and +J 34.  I began cutting small pieces off of the top section making measurements after each cut.   The goal was to resonant the antenna at 10.110 MHz. Reconance was finally achieved with a top section length of 4.5'

Power was applied to the antenna and the SWR shecked on the rig and found to be almost zero.  Next it would be necessary to field test this antenna for performance.  IAs luck would have it, my good friend Bill, WS4Y was going to make a trip to Florida and agreed to take the antenna with him for testing between Florida and Kansas on 30 meters.  The testa were conducted over a seven day period at various locations in Florida and proved to be extremely successful.  The antenna performance was as good or better than a full-size dipole.


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