Re: Wretched interference from WPRX (Was: Things you can do on AM)

[Dan Strassberg <dan.strassberg@worldnet.att.net>]

At 02:52 PM 6/11/97 +0000, you wrote:

>WPRX makes WBBR unlistenable within
>about a 15-mile radius of Bristol in the daytime (including places just
>65-70 miles from Central Park). At least part of this area must be in the
>WBBR 0.1mv contour, which I thought was protected from first-adjacent
>interference.

No, I'm pretty sure it isn't. I'm pretty sure that a Class A AM's 0.1 mv/m
daytime groundwave contour is protected only from co-channel interference.
The 0.5 mV/m daytime groundwave contour is protected from adjacent-channel
groundwave interference. That means WPRX, on the first adjacent channel,
should not deliver more than 0.25 mV/m daytime groundwave to WBBR's 0.5 mV/m
daytime groundwave contour.

>So why was a 1 kw day/500 night station assigned there? I
>believe the history is that WPRX once upon a time was WBIS on 1440 with 500
>watts. I think it was a daytimer and may have been dark for some period.
>Then it comes back, I guess, when the clear channels were trashed further
>and 1120 became available.

WADN was granted before what is now WPRX was granted a move to 1120.
Originally, WBIS's facilities on 1120 were 250W DA-2. I think the day
pattern must have protected WBBR. How WPRX got an increase in day power, I
don't understand either. But I have a theory about the night power. I think
the extent of WADN's nighttime protected service is determined not by
co-channel interference but by skywave interference from WBBR. Unless the
rules have changed (and they may have) I think that a first-adjacent channel
skywave signal is not deemed to interfere unless it is five times as strong
as the desired groundwave signal more than 10% of the time. If WPRX could
show that the increased interference to WADN would not exceed 1/20 of the
WADN's protected groundwave field intensity more than 50% of the time, I
think the FCC would grant the nighttime-power increase.

- -------------------------------
Dan Strassberg (Note: Address is CASE SENSITIVE!)
ALL _LOWER_ CASE!!!--> dan.strassberg@worldnet.att.net
(617) 558-4205; Fax (617) 928-4205

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