Topband: Cushcraft MA-160

[Herb Schoenbohm]

Dave,


If you ground the top of the wire of a quarter-wave sloper to the tower 
and feed the bottom of the slant wire instead (assuming a ground rod and 
some radials laying on the ground at the feed point) you will IMHO do 
much better. Some matching may be required at the feed point but it may 
be no more than a series capacitor to remove the reactance of the wire.  
There my be a very slight bit of directivity in the direction of the 
slant wire,  but the overall efficiency of this as a TB radiator may be 
significantly better even with a short tower of 50-60 feet.  If the 
tower is more than 60 feet tall and with a beam on top I would suggest 
shunt feeding the tower with a cage feed again assuming you can have at 
least 4 or more radials on the ground even if you need to fold or bend 
the ends a bit to fit in your yard.

All half slopers from metal towers do IMHO is try to backward excite the 
tower with RF.  Losses can be high and performance is generally less 
than adequate.  If you are able to shorten the slant wire to get your 
feed point closer to 50 ohms may also be beneficial and should also be 
considered.

Good luck,

Herb Schoenbohm, KV4FZ




On 3/16/2012 10:57 PM, David Novoa, W4DN wrote:
> Has anyone in this reflector installed a Cushcraft  MA-160 short vertical
> with a couple of  elevated radials or the K2AV Folded Counterpoise?  If
> so, results? Any  recommendations?  I need to do something before the TB
> season ends.  My quarter-wave sloper doesn't work properly.
> Thanks,
> Dave, W4DN
>
>
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