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
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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