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airborne receiving function sensitivity of 30 microvolts per
metre may be assumed.
2.3.2.3 Effective acceptance bandwidth for 100 kHz,
50 kHz and 25 Ediz channel spacing receiving installations.
When tuned to a channel designated in Volume V as having
a width of 25 kHz, 50 kHz or lOO'kHz, the receiving function
shall ensure an effective acceptance bandwidth as follows:
2.3.1.2 Power: On a high percentage of occasions, the
effective radiated power shall bc such as to provide a field a) in areas where offset carrier systems are employed, the
strength of at least 20 microvolts per metre (minus 120 receiving function shall provide an adequate audio
d13w/m2) on the basis of free space propagation, at ranges and output when the signal specified at 2.3.2.2 above has
altitudes appropriate to the operaiional conditions pertaining to a carrier frequency within 8 kHz of the assigned
the areas over which the aircraft is operated. frequency;
7/11/96
No. 71
Annex 10 - Aeronautical Telecommunications Volume 111
b) in areas where offset carrier systems are not employed,
the receiving function shall provide an adequate audio
output when the signal specified at 2.3.2.2 above has
a carrier frequency of plus or minus 0.005 per cent of
the assigned frequency.
2.3.2.4 ESfective acceptance bandwidth for 8.33 kHz
channel spacing receiving installations. When tuned to a
channel designated in Volume V, as having a width of
8.33 kHz, the receiving function shall provide an adequate
audio output when the signal specified at 2.3.2.2 above has a
carrier frequency within plus or minus 0.0005 per cent of the
assigned frequency. Further information on the effective
acceptancebandwidth is contained in Attachment A to Part 11.
Note.- The effective acceptance bandwidth includes
Doppler shif.
2.3.2.5 Adjacent channel rejection. The receiving
function shall ensure an effective adjacent channel rejection as
follows:
a) 8.33 kHz channels: 60 dB or more at plus or minus
8.33 kHz with respect to the assigned frequency, and
40 dB or more at plus or minus 6.5 kHz;
Note.- The receiver local oscillator phase noise
should be suflciently low to avoid any degradatiort of
the receiver capabili~to reject off carrier signals. A
phase noise level better than minus 99 dBc/Hz 8.33
kHz away from the carrier is Iiecessaly to comply with
45 dB adjacent channel rejection rtnder all operating
conditions.
b) 25 kHz channel spacing environment: 50 dB or more
at plus or minus 25 kHz with respct to the assigned
frequency and 40 dB or more at plus or minus 17 kHz;
c) 50 kHz channel spacing environment 50 dB or more
at plus or minus 50 kHz with respect to the assigned
frequency and 40 dB or more at plus or minus 35 WZ;
d) 100 kHz channel spacing entvironment: 50 dB or more
at plus or minus 100 kHz with respect to the assigned
frequency.
2.3.2.7 Recornmendation.- In the case of receivers
complying with 2.3.2.3 above used in areas where ofset
carrier systems are in force, the characteristics of the receiver
should be such that:
a) the audio frequency response precludes harmful levels
of audio heterodynes resulting from the reception of
two or more ofset carrier frequencies;
b) the receiver muting circuits, if provided, operate
sati&ctoriIy in the presence of audio heterodynes
resulting from the reception of two or more offset
carrier frequencies.
233 Interference immunity
performance
2.3.3.1 After 1 January 1998, the VHF communications
receiving system shall provide satisfactory performance in the
presence of two signal, third-order intermodulation products
caused by VHF FM broadcast signals having levels at the
receiver input of minus 5 dBm.
2.3.3.2 After 1 January 1998. the VHF communications
receiving system shall not be desensitized in the presence of
VHF FM broadcast signals having levels at the receiver input
of minus 5 dBm.
Note.- Guidance material on immunity criteria to be used
for thc performance quoted in 2.3.3.1 and 2.3.3.2 above is
contained in Attachment A to Part 11, 1.3.
2.3.3.3 After 1 January 1995, all new installations of
airborne VHF communications receiving systems shall meet
the provisions of 2.3.3.1 and 2.3.3.2 above.
2.3.3.4 Recommendation,- Airborne VHF communications
receiving system meeting the immunity performance
Standards of 2.3.3.1 and 2.3.3.2 above should be placed into
operation at the earliest possible hte.
2.3.2.6 Recommendation.- Wheneverpracticable, the
receiving system should ensure an effective adjacent cltannel
rqjection characteristic of 60 dB or more at plus or minus
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