Topband: Fire tower as support for 1/4-wave sloper

[George (K8GG) & Marijke Guerin]

John & fellow Topbanders:

"John Harper" <john at ae5x.com>wrote:

Subject: Topband: Fire tower as support for 1/4-wave sloper


> Hello,
>
> I have obtained permission to operate from what I hope will be an ideal
> location (better than my home QTH) for the upcoming ARRL 160 Meter 
> Contest -
> a fire tower-like tower, 90 feet tall way up on a hilltop above the
> surrounding terrain with a building at the base with all the creature
> comforts. My plan is to put up a sloper. Although I've never used a sloper
> before on any band, I understand they can be hit or miss as far as
> performance goes.
>
> My question is:
> To achieve resonance, is it better to trim the length of the sloper or
> experiment with the height of where it's fed on the tower?The tower in
> question is steel, about 20' on a side with a steel stairway going up the
> center.
>
> Thanks,
>
> John Harper AE5X

John,  I would consider a different approach as well.

An inverted-L 160 feet long, about 80 - 85 feet vertical with the rest 
sloping out at less than 30 degrees below horizontal will put out a great 
signal over decent radials.  I have used such an antenna over 40 - 50 
radials each averaging 80 ft length with great success.  One does need a 500 
pfd variable capacitor to tune out the reactance, as the impedance is about 
Zant = 50 + 200j ohms.  I have used 500 pfd vacuum variables and 300 pfd 
vacuum variable with a 250 pfd vacuum fixed padder with good success.

Another idea:  Add 2 to 4 each 40 ft top loading wires to the fire tower and 
shunt feed it!

Good luck        73        George    K8GG