[BC] Bay spacing

[Mike McCarthy]

Depending on power and height above the roofline, RFR and EMI 
considerations to the host building (and those surrounding it) could 
also become a factor based on bay spacing. Ask the antenna vendor of 
choice to create a few scenarios showing the main and minor lobes and 
how they would impart their signal onto the building and those within 
1000ft. I would also consider something more than a 2 bay not for the 
gain, but for the vertical pattern shaping possible to steer the minor 
lobe away from a direct roof and adjacent building reflections. Also, 
consider a reduced bay polynominal antenna as well which fattens the 
main lobe, but keeps steep downward radiation well managed.

These are but a couple of the scenarios which need to be carefully 
explored and modeled using the proposed antenna and it's relationship to 
the building (height above the roof) in the models.  Urban building-top 
antennas carry very different permutations than tower mounted antennas.

MM

On 2/20/2012 10:52 PM, Dana Puopolo wrote:
> I have an FM station that is installing a transmitter atop a tall building
> downtown. The reason is to penetrate the steel and concrete buildings there.
> The customer has asked for a 2 bay 1/2 wave spaced antenna. I told him I
> thought.625 wavelength spacing made more sense, because this antenna would
> just be forming a minor lobe, which would be large enough to improve the
> signal in the less tall buildings directly below the site, but not so large
> that it would cause the kind of multipath that a full spaced 2 bay would
> (think the minor lobing of a 3 bay half wave spaced antenna).
>
> Am I off base here?
>
> -D
>