Fw: ITU and Out of Band Emissions

[DavidC]

Thought y'all would like to read this.  (see below)

-  73, DavidC  K1YP in Hudson, FL

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> Hi David,
>
> I saw your post on the Boat Anchors Digest. I don't subscribe, but I do
take
> a look.
>
> As the guy who started all this, let me explain.
>
> Back in the depths of time at a WRC, the ITU asked its Study Group 1 to
> re-examine the requirements for spurious emissions in the light of new
> technological advances. The ITU SG1 set Task Group 1/3, and they reported
> back to WRC97. Spurious emission limits were introduced there for the
> amateur service, and spurious are things like harmonics, parasitics, mixer
> products and so on which, after the TG1/3 work, existed more than 2.5
times
> the 'necessary bandwidth' away from the centre of the transmission.
> 'Necessary Bandwidth' has a particular meaning in the Radio Regulations:
it
> is the bandwidth that a signal may be passed through for a given level of
> degaradtion. (As a definition, I find that as much use as teats on a
bull!)
> The limits on the Amateur and Amateur Satellite services are much less
> stringent than for other services, although they are 10dB more stringent
> than existing FCC and European levels. They come into effect on Jan 1st
2003
> for new transmitters, and from Jan  1st 2012 for existing transmitters.
> These limits are in  ITU-R Recommendation SM.329, which is incorporated by
> reference into the Radio Regulations. The Radio Regulations have the
status
> of an international treaty, which is why when the US signs up to the final
> acts of a WRC, it takes about 5 years, as although the US has agreed
matters
> through FCC and NTIA, the departments of Commerce and State are involved,
> and then the ratification is approved by Congress. However, it isn't known
> if the FCC is actually going to get around to implementing the
requirements
> of the Radio Regulations into Part 97. I digress.
>
> Following on from the work of TG1/3, WRC 97 wanted Out of Band Emissions
> defined, primarily because the wide band emissions (outside the allocated
> band) of certain satellites causing trouble to the radio astronomers, and
so
> SG1 set up Task Group 1/5. The whole Out of Band emission thing came up
> there. I got involved professionally, and saw what had happened for the
> amateur service in SM329. One problem is that no one considered the
> microwave narrow band case, and the spurious limits give problems with
phase
> noise.
>
> Although I tried hard at CEPT and IARU tried hard at TG1/5, it was not
> accepted that amateurs should be left outside this regime. On this basis
> (GI8AYZ when he was RSGB President expressed it as 'It's better to be
inside
> the tent pissing out than outside pissing in') I came up with a set of
> figures.
>
> So to get around the problem of specifying emissions very close to the
> carrier for narrow band emissions, especially at UHF and above, I
introduced
> the concept of a 'minimum necessary bandwidth'. What this does is to say
> that no signal is ever considered to be less than the minimum necessary
> bandwidth, so we'll consider a CW signal to be 4kHz wide at HF. Then we
> don't look for spurious closer than 10kHz away (2.5 times the 'necessary
> bandwidth'), and key clicks are only looked at from 4kHz to 10kHz (beyond
> that, they're  spurious). AM doesn't fit in to this, so we say 'AM is 6kHz
> wide (you can have 7 if you like) So we don't look for spurious until we
are
> 2.5 times 6 or 15kHz away from the carrier. (17.5kHz if you said 7kHz
wide)
> If you're splatter isn't 50dB down 15 or 17.5 kHz away, there's something
> wrong!
>
> So the bottom line is that the width of signal is going to be primarily
> limited by Part 97.
>
> Note that at 10GHz, we consider a CW signal to be 100kHz wide, because of
> phase noise problems.
>
> This concept has found wide acceptance for satellites and other areas
where
> narrow band signals get into trouble, although the terminology is
constantly
> changing.
>
> The bottom line is that there's no problem for AM or anybody else - at
least
> to 2012. Even then, an ATU should be enough to clean up the signal. Of
> course, unless your harmonics cause a problem, who knows that they are
> there?
>
> So that's the story. Feel free to explain what the situation really is.
> Anyone with questions can e-mail me at peter.chadwick at ieee.org.
>
> 73
>
> Peter G3RZP
>

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