Hello Tom,
I run a 68 foot half sloper (1/8 wave length on 160 meters) mounted on my 40
foot tower, and really have a blast on 160 with it. You can see my antenna
in the March 1998 issue of QST.
Here are a few different lengths for your sloper, and a few different coil
locations. Efficiency is not as good with the coil at the feedpoint, but I
found it very convenient to place it there for my situation.
I calculated the values below using 14 gauge wire as your sloping wire. The
formula I use is right out of the ARRL antenna handbook (Limited Space
Section). The handbook also has a chart that yields similar values. I
calculated the antenna for 1.8MHZ. You can just shorten the end of the
sloper to make it resonate up higher in the band.
For coil at feed point :
Coil Coil
Half sloper length XL (ohms) L (uH)
80 feet 376 33.25
70 feet 484 42.80
For coil at mid point :
Coil Coil
Half sloper length XL (ohms) L (uH)
80 feet 731 64.6
70 feet 927 82.0
Let me know what kind of coil form you want to use (diameter, gauge wire,
etc.), and I can give you some different winding combinations for the coil.
I had no problems getting my 160 meter half sloper to resonate, but the half
sloper is dependent on many factors such as ground, top loading on the tower,
etc, so be patient.
I am sure Tom (W8JI) and many of the other big guns on 160 meters laugh when
they see such designs for antennas. Nevertheless 160 meters sure is a fun
band and I recommend putting up anything that will get you on the Top Band.
73's
Don Kirk (WD8DSB)
P.S. here are just a few of the countries I have worked in the last two
seasons on 160 meters with my rinky dink 160 meter antenna.
VK, ZL, KH6, GW, G, TI, C6, HC8, HR, G, OZ, EI, HI, DF, IV
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