[BC] AM Protection

[RSTYPE@aol.com]

In a message dated 7/2/2005 7:40:52 AM Eastern Standard Time, 
dan.strassberg at att.net writes:
Henry Turner wrote:

Hello all,

I have the following question.

Does one have to protect non class A international stations pursuant to
domestic interference rules?
If not, what if any protections apply to international non class A at night?

Thanks
Henry
----

As I understand it, a foreign (i.e. Western hemisphere) non-Class A station
must be protected within its national borders from co-channel and
first-adjacent-channel nighttime 10% skywave interference from stations in
other Westen hemisphere nations to the greater of A) the foreign station's
50%-exclusion NIF contour or B) its 2 mV/m groundwave contour. The foreign
station's groundwave service must be protected within the station's national
borders from groundwave interference from stations located in other Western
hemisphere nations to the station's 0.5 mV/m contour. That is, at the
station's 0.5 mV/m daytime groundwave contour within its national borders,
groundwave interference from stations in other Western hemisphere nations
must not exceed 25 microvolts/m co-channel, 250 microvolts/m
first-adjacent-channel-channel, and 5000 microvolts/m second-adjacent
channel. I am unaware of any critical-hours protection requirements for
non-Class A statopns.

--
Dan Strassberg, dan.strassberg at att.net
eFax 707-215-6367
The nighttime protection requirements from U. S. AM stations to other AM 
stations in Region 2 (western hemisphere) are specified in several different 
international agreements including the Region 2 AM agreement and separate 
individual agreements with Canada and Mexico, which supercede the Region 2 agreement.  
(Protection to the Bahamas (and possibly Haiti) is still dictated by the old 
North American Regional Broadcasting Agreement, since they never signed the 
Region 2 agreement.)  The Region 2 agreement also provides for different 
protection criteria to countries in different parts of the hemisphere through the use 
of a "noise zone" concept which divides the hemisphere into two different 
noise zones which are subject to different protection requirements.  The 
protection requirements also differ based on whether or not the station being protected 
is on IFRB List A (fully complies with protection requirements to stations in 
other countries or other IFRB lists (B, C, D), which indicate that the 
foreign station does not comply with the protection requirements to AM stations in 
other countries.  The requirement to protect stations in Cuba has also varied 
over time, but at the moment I believe that they must be protected pursuant to 
the Region 2 agreement.  (It's all really quite complicated.)

None of these international agreements require nighttime skywave protection 
to foreign strations operating on first adjacent channels, which is only a 
requirement of the U.S.'s domestic AM protection criteria.  Only the agreements 
with Canada and Mexico (and NARBA) specify the use of 10% skywave values for 
calculating protection and interference to the foreign station.  Nighttime 
protection calculations to all stations subject to the Region 2 agreement are based 
on 50% skywave calculations, rather than 10%.  In evaluating all of this, the 
FCC (when evaluating a an application for a domestic station) employs their 
domestic standards when evaluating interference and protection to a domestic 
station (even if it involves interference received from a foreign station) and 
the appropriate international agreement when evaluating protection to a foreign 
station.  (As I said above, it is all really quite complicated.)

Roy Stype
Carl E. Smith Consulting Engineers