Gentlemen,
An appeal for help - I need your comments. ITU Recommendation SM329 on
spurious and unwanted emissions is currently being revised, and the idea
is being introduced that the spurious emissions (inclusive of
intermodulation products) limits should be met outside of a band which
is 250% of the necessary bandwidth, centred on the centre frequency of
the signal. This would mean that at outside of a 7.5KHz band centred
around an SSB signal, the intermodulation products would need to meet
the spurious output levels - currently to be 43 + 10log P, where P is
the PEP output, or 50dB (whichever is less stringent) down. This would
be the PEP of all IMD products, adjusted to (not necessarily measured
in) a 10KHz bandwidth
VHF would be slightly different, since the measurement would be a 100KHz
bandwidth, while 1296MHz would be in a 1MHz bandwidth.
The question is; Is this reasonable?
I don't think so; the 250% figure has been adoppted because it's fine
for wideband systems, such as CDMA, pi/4DQPSK, m-ary QAM, OFDM etc, but
it seems wrong for narrow band systems.
I'll be interested in your comments ASAP, as I need to put in an input
to CEPT and ITU this week.
73
Peter G3RZP
PS W8JI - Tom, ITU recommendation SM328 has quite a bit in it on noise
loading of SSB transmitters for tests - I found that out yesterday.
There ain't nothin' new!!
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