[Antennas] 40m Apartment antenna saga continues <g>

[Sam Morgan]

On Fri, 03 Jun 2005 00:24:45 -0400
valerwin at aol.com wrote:

> Sam:
>  
> FWIW..............you may want to give thought to placing a mobile
> screwdriver-type antenna up on the roof. More expensive yes, but I
> doubt if the landlord is going to want you tromping around on his roof
> to change taps and tweak tuning, etc. on a fixed coil type bug
> catcher.......This would give you some frequency agility as opposed to
> just 40M. 
>
Correct this is going to be a set it and forget it deal. Any further
adjustments will be with a tuner in the shack. I had understood the
type setup I was considering was more efficient than a screwdriver
would be? Heaven knows any tiny bit better would be an improvement.


> Check with Henry Allen of TX Bugcatcher fame as he also
> markets a screwdriver-type antenna. With that type of antenna, you
> could feed the 12 VDC up the coax and adjust the antenna from inside
> the comfort of your apartment 
>
True, but in a previous corrispondance with Henry Allen
(I had ask if I needed a balun) .... he said:

 >>   do I need a balun at the feedpoint?
      You will need some way to match the feedpoint inpeadence.
      I sell a small coil (HD80) that goes at the feedpoint and a
      small amout of inductance is tapped to ground to handle this.
      With out any matching the feedpoint impeadence of the
      BugCatcher on 40 meters will be around 10 to 12 ohms.
      The matching can be done several ways, capacitor, torriod or
      even with your tuner.
      It is always better to do the matching right at the
      feedpoint and then just use the tuner to move aroud in 
      frequency.
      With the setup we are talking about (40 meters) you will be 
      able to work several other bands by using the tuner without
      retapping the main coil or the matching coil.
      Probally 20, 15, 12 & 10 meters. It might tune on 75 meters
      but the performance would be poor. 
 
         Henry

-----------****------------
now the rest of the story...
the above was in reference to a 5' mast
with the #640 coil
then 2' of mast 
and then the 20" hat
no stinger

...so the mini design I'm now limited to may change his responce as to
the matching situation??? 

comments?

Sam Morgan
KA5OAI
mailto:ka5oai at cox.net