ARRL

ARRL General Bulletin ARLB004 (2001)

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ARLB004 ARRL Takes Part in ITU Study of Unwanted Emissions.

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ARRL Bulletin 4  ARLB004
From ARRL Headquarters  
Newington CT  February 1, 2001
To all radio amateurs 

SB QST ARL ARLB004
ARLB004 ARRL Takes Part in ITU Study of Unwanted Emissions.

The ARRL Technical Relations Office in Washington participated in
just-completed International Telecommunication Union studies of
''unwanted emissions'' in the radio spectrum. Unwanted emissions
consist of out-of-band and spurious emissions. The
ITU-Radiocommunication Sector has conducted two multi-year studies
of out-of-band and spurious emissions during the past decade.

ARRL Technical Relations Manager Paul Rinaldo, W4RI, chaired a
second-round task group with an international membership, drafting
out-of-band emission specifications. ARRL Lab Supervisor Ed Hare,
W1RFI, and his staff participated in task group meetings and
provided technical support to the League's Washington office.
Representatives of the International Amateur Radio Union also took
part.

''Had we not invested all those hours and travel, the amateur and
amateur-satellite services probably would have some unwanted
emission limits that would be more difficult to meet and make
amateur equipment more costly,'' Rinaldo said. The panel's
recommendations are being circulated to governments for final
approval.

Out-of-band emissions are those falling outside the necessary
bandwidth of a signal and are the result of modulation. ''Amateurs
know them as key clicks and splatter,'' Rinaldo said. The ITU defines
spurious emissions as emissions beyond 250% of the necessary
bandwidth, but the definition is still under debate. Spurious levels
already are spelled out in the international Radio Regulations. ARRL
Lab tests have shown that amateur gear could meet a standard of -50
dB relative to main signal for HF and -70 dB for VHF bands and
above.

Out-of-band limits for amateur equipment were agreed upon at the
final task group meeting last year, and Rinaldo says these are
consistent with the idea of establishing a safety net--not stringent
levels of emission. A suite of ITU-R recommendations on unwanted
emissions is being circulated and should be approved by mid-year.

More work lies ahead for the ARRL Washington staff. Radio
astronomers and earth-exploration passive services are not satisfied
with present levels of unwanted emissions from satellites and are
concerned about interference to their sensitive receivers. A new ITU
task group is studying the issue and preparing information for
presentation at WRC-03.
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