Hi Jeff,
> To what degree are AM broadcast stations required to suppress their
> third harmonics?
The law is simple.
1.) They are not allowed to cause harmful interference no matter
what level of spurious emissions are allowed in technical
standards. This is a blanket rule that covers all cases.
2.) The level allowed normally, when interference is not an issue, is
normally 43 plus 10 log times the power in watts. An upper limit is
set at -80 dB. This formula is given in part 73.44 of the rules
For example, a 1000 watt station is 43 plus ten log 1000, or -73 dB.
A 5,000 watt station would be -80 dB, as would a 100 kW station,
because at 5 kW the limit of -80 dB is reached. The lower limit is
65 dBc in all cases.
So the correct answer is -65 to -80 dBc, depending on power, as
long as they aren't causing problems.
Even if a station meets these requirements, they are not still
allowed to cause problems. But it is also very unlikely they will
cause problems if they meet the normal restrictions!
I'm working now on getting an IMD product from the Meadowlands
(near New York City) corrected. It is WBBR mixing with some
other station(s), and the product is over 40 dB above ambient noise
level here at times!!!
Help please!!!
If anyone (close to NYC) can ID the other stations mixing with
WBBR, it might speed things up. This WBBR mixing thing is loud!
Sometimes this stuff goes slow, but it is always possible to get a
problem repaired. There have been seven problems corrected in the
past year alone, so the FCC does work on this stuff!
73, Tom W8JI
w8ji@contesting.com
--
FAQ on WWW: http://www.contesting.com/topband.html
Submissions: topband@contesting.com
Administrative requests: topband-REQUEST@contesting.com
Problems: owner-topband@contesting.com
|