[BC] IBOC Antennas /was/ Kinstar Antenna Approval

[Phil Alexander]

On 31 Oct 2005 at 8:47, Cowboy wrote:

> On Monday 31 October 2005 07:42 am, Mike McCarthy wrote:
> >It's my understanding that it would play fine.
> 
> >At 10:05 PM 10/30/2005 -0700, KKTY wrote
> 
> >>Any idea if the Kinstar antenna plays nice with AM IBOC? Better or worse
> >>than a regular stick?
> 
>  My thoughts as well.
>  Being a "compromise" of sorts, and requiring some tricks to make it
>  play at all, would suggest that these same feed tricks should make
>  it, perhaps, even more IBOC compatible that a "standard" stick.

I concur, although it is possible that some boxes may require a
"cusp rotation" section at one end or the other of the feedline
to accommodate the internal matching network in the Tx. This is an
area of IBOC that has become important, and different boxes need
different compensations so the PA output can see a j0 load. In some
cases this is true between different models of from the same
manufacturer.

However, the best possible antenna for an non-DA IBOC may be the 
ancient and much maligned slant-wire fed shunt excited tower with 
a single vacuum variable adjusted for phase rotation that suits the 
box. If the attach point and slant wire angle are adjusted for 50 
ohms the match to the Tx would be near-perfect across a very wide 
bandwidth. Probably better than any other antenna system from the
standpoint of load flatness and hermetic symmetry.

Considering the modeling capabilities we have now, it might be
worth another look backward about 60 years. There is a possibility
that the shunt-fed antenna was another good idea quashed by 
competition with General Sarnoff. (WE promoted shunt-fed so RCA
promoted series excitation claiming the effects of the feedline
would cause unpredictable interference.)


Phil Alexander, CSRE, AMD
Broadcast Engineering Services and Technology 
(a Div. of Advanced Parts Corporation) 
Ph. (317) 335-2065   FAX (317) 335-9037





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