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[AMPS] Transceivers high 3rd order IMD

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Subject: [AMPS] Transceivers high 3rd order IMD
From: (Peter Chadwick)
Date: Fri, 19 Feb 1999 14:27:40 -0000
The nearest professional standard equivalent to the amateur service is the
maritime service. Here the standard is -31dB rel PEP, -25dB rel
tone.(There's an ETSI Standard, I think it's ETS 300-377) For ISB work, it
is usual to go some 10dB better.

The methods of measurement vary considerably between countries. There is
some attempt to obtain standardisation at ITU - R level, in Task Group 1/5,
which is concerned with Out of Band emissions. OoB Emissions are those whose
frequency lies between the necessary bandwidth, Bn, and 2.5 Bn. So an SSB Tx
in the amateur service with a 'necessary bandwidth' of 3 kHz has to meet
spurious levels  at more than 2.5 Bn, or 7.5kHz away from the centre
frequency of the emission, of 43 + 10log P, not exceeding 50dB, in the HF
band. The OoB emission limits proposed at TG1.5 are pretty lax,
deliberately, as we wanted the minimum possible restrictions on the amateur

For HF, with modulation of tones of 1100 and 1700 Hz, the limits are:

from 4.8kHz away from the centre frequency (1400Hz away from the carrier) to
8.9 kHz away from the carrier, all products are -31dB or more rel PEP,
measured in a 100 Hz bandwidth.

>From 8.9 to 10.0 kHz away from the centre frequency, all products are -38 dB
rel PEP.

from more than 10 kHz away, products are more than 43 + 10 log PEP down rel
PEP, without exceeding needing to be more than 50dB rel PEP.  

Does this help?


Peter G3RZP

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