[BC] Arrays On-the-Cheap - Was: Two-tower array designed for 990 running on 1030

[Phil Alexander]

On 8 Jul 2005 at 15:51, PeterH5322 at aol.com wrote:

> 
> >While short spacings may appear to have the benefit of a slight gain
> >over a non-D counterpart, the downsides are high RSS:RMS ratio,
> >poor bandwidth and low drive point impedances. The vectors in the
> >main lobe do not add up to the total i.e. there is a residual.

Directionals are never as good as the real thing. <g> And the more
complex they become, the less good they seem to be. ;-)

> Both are asymmetric designs with unequal spacings. One is as short as 55 
> degrees.
> 
> A benefit is a relatively broad, very deep null towards the Class A, 
> off-axis, with a very broad minimum, also off-axis, towards a distant 
> co-channel Class B in the first case, and towards a local first-adjacent 
> in the second case.
> 
> Yes, the RSS:RMS ratio does stink in these cases.

That's not all that stinks. Trying to align one can be VERRrrrry
interesting, even when everything is near perfect. Can anyone say
mutuals without a grimace when the spacing gets that low?

> I'm sure all other considerations aside, the goal was maximum power at 
> minimum cost, while fitting within a fixed site.
> 
> The sites were existing, and were not originally intended for the 
> ultimate use (both cases), or even for the same frequency (the second 
> case).

The should be really fun sites to try to implement IBOC. :-(

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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