Topband: Ground loss query (re inverted L, antenna radiation resistance, & Jerry Sevick)

[Herb Schoenbohm]

On 10/19/2011 2:28 PM, shristov wrote:
>
>
> Folding has nothing to do with either radiation resistance or ground losses.
> It is impedance-transforming device only.
>
> You've just performed 1:4 impedance transformation, nothing else.
>
> 73,
>
> Sinisa  YT1NT, VE3EA
Sinisa,  A well known broadcast consulting antenna group Mullany and 
Associates made a detailed NAB presentation in the 60's on why a folded 
unipole and a cage feed made significant improvements for stations with 
questionable ground systems. They presented  FSM reading with and 
without to prove their point.  From that point on it became sort of an 
urban legend.  Other studies have discounted the claim completely. The 
acid test by du Treil, Lundin, & Rankin out of Sarasota, FL, was 
ungrounding and directly feeding a tower and hooking the cage to the 
feed point and getting exactly the same FSM reading at 1 mile with when 
the cage was fed unipole style! Their findings were presented at the 
1996 NAB Broadcast Engineering Conference.  The original Mulany papers 
in the early 60's suggested that by raising the feed point impedance 
less current was flowing in the ground system thus improving the overall 
efficiency.  Many hams still believe that is still true.  Thanks for 
the  clarification.  But the legend continues to have legs.


Herb Schoenbohm, KV4FZ