[BC] Re: AM Daytimers (Field Strength)

[Phil Alexander]

On 23 Feb 2006 at 11:03, Bailey, Scott wrote:

> I wished the FCC would revisit the Field Strength Requirements for Class
> D's. Phil, Barry, Scott, and others....you might think I'm crazy saying
> this, but lowering the required minimum field strength on Class D's from
> 282 mv/m to 241 mv/m, (like Class C's) might help the noise floor at
> there during Critical Hours and PSRA/PSSA hours as well....plus making
> the antenna requirements a slight lesser of a headache for the licensee,
> as far using a shorter, vertical, radiator in areas of zoning problems.
> I'm I (kind of) right at thinking this?

I don't know for sure, but there may be an international treaty involved
in the requirements for station classes. Maybe Peter can tell us.

Strictly from a theory standpoint, if everyone used shorter antennas for
Class B, there would be somewhat greater high angle radiation in
comparison with groundwave, although with the short antennas permitted,
this would tend to be marginal. Now, if all Class B's were required to
have at least 180 degree radiators skywave would be significantly
reduced and groundwave f/s would go up substantially. The problem is
the expense of installation, especially toward the lower end of the band.

I think if you check the Class D's with tall towers (there are a few 
where FM's were added to old III-D's) you may find the nighttime power 
significantly above that typical for the stations with shorter towers. 
For example, I know one that has a tower about 195 deg. that has about 
60 W nighttime where you might expect a limit of 20 or 30 W if the tower 
were around 90-100 deg.


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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