Topband: Cushcraft MA-160

[Herb Schoenbohm]

Paul,

I really don't know if it makes a difference as the top wire is only 
supposed to do top loading and the goal is to minimize high angle 
radiation from the horizontal portion.  I saw the crow's foot antenna in 
a US Military Antenna book once and it had three on the top and three 
wires on the bottom Marconi style feed.  Maybe this would be a good 
configuration for someone to model. Personally I prefer the Marconi T 
with a symmetric ground system.  Maybe Guy K2AV has had some experience  
with the three over three crows foot spread for top band. This seems to 
be right up his alley.


Herb, KV4FZ





On 3/20/2012 12:20 AM, Paul Lambert wrote:
> Hey Herb,
>
> Enjoy all your replies and articles.
>
> Old question for you. With an inverted "L" is there a
> favorite direction with the "L" or the opposite direction?
>
> Had a "crows-foot" many years ago an remember the
> direction went with the "L" direction.
>
>   _________________________
> II_________________________
> II_________________________
> II
> II
> II
> II
> II
> II
> (.)------------------------------------------------------------coax to 
> shack
> on the ground radials
> ____________________________
> ____________________________
> ____________________________
>
> The Crow's Foot story is from an old Marine "Forward Observer"
> experienced in the S. Pacific during WWII. A story for another time.
>
> Anyway, what do you think or know?
>
> Thank you,
>
> 73, Paul
> N8ABS
> --------------------------------------------------I
> On Sat, Mar 17, 2012 at 7:50 AM, Herb Schoenbohm <herbs at vitelcom.net 
> <mailto:herbs at vitelcom.net>> wrote:
>
>     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
>     >
>     >
>     > _______________________________________________
>     > UR RST IS ... ... ..9 QSB QSB - hw? BK
>
>     _______________________________________________
>     UR RST IS ... ... ..9 QSB QSB - hw? BK
>
>