[Lowfer] 600MRG> Why put a coil under the top hat ???

[Andy - KU4XR]

Hi All:

I hope everyone is having a peaceful Christmas, and HNY 2010 to you.

Since I posted the original question on this topic, I thought a
follow up might be in order. The information I wanted is primarily
to see if I can improve my 1750 meter antenna any further, so PSE
forgive the intrusion into the 600 meter group. I have been reading
lots of material on coil placement, and dimensions the last few days
Cebnik, Rauch, Flory, and Koehler. All of them pretty much say the
same thing; Center placement will provide optimum results for a
very short antenna with limited top hat length.
I am still not persuaded on the optimum L/D of the coil though.
I'll use thin walled 4" white PVC as a form, wound with #14 AWG
with thin insulation ( 15 amp rating ). A 2:1 ratio allows for
about 68 turns over 8" for around 189 Micro-Henries.
A 4:1 ratio allows for about 136 turns over 16" and about 415 uH.
At 185 KHz; neither of these coils provide a significant load
in the antenna line I don't think. It would appear that the biggest 
advantage would be in getting the current farther up the antenna,
and the hot end of the coil about 15' above ground. I will need to
rewind my variometer at the transmitter for fine tuning.
Finally; IF !! adding a center mounted loading coil will make the 
antenna more efficient than base loaded alone, I certainly want 
to give it a try. The only question I have now is on the optimum
L/D ratio of the loading coil. Any replies on this matter will
be appreciated, and thought thru.

73 all :::



Andy - KU4XR - EM75xr - Friendsville, TN.
LOWfer Beacon " XR " @ 185.29866 KHz ( QRSS-60 )
Coordinates:  N:  35* 43' 54" - W:  84* 3' 16"
http://www.myspace.com/beaconxr
http://webpages.charter.net/ku4xr/
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