Most interesting discussion.
Peter wrote: "On the other hand, if in a 10kHz wide band starting 6.75
kHz away, you aren't down 50dB, then you're somewhat antisocial
anyway."
It appears, from i.a. SM5BSZ's measurements, that "antisocial
behaviour" would be quite common
in current amateur radio transmitters.
Not having the text of ITU-R SM329 immediately available, I am
somewhat uncertain of the meaning of the required suppression, it may
be referring the total mean sideband power in the 10 kHz band, or it
may be referring to a normalized sideband power compared to a
normalized power within the "necessary bandwidth".
In either case I am quite convinced that very few amateur transceivers
meet the SM329 requirements "barefoot", especially when using liberal
amounts of ALC. The situation when
using an "amp" usually will not be better.
On another note, I find it most gratifying that the UK authorities
still refer to the ITU-RR in their regulations.
In Sweden, deregulation (as previously referred to) has progressed to
a point where the ITU-RR has no legal force any longer. The content of
the current amateur radio rules are not specifically derived from the
RR, as they previously were, but instead they are worded in a very
cautious and vague way not to infer any connection with the RR. As I
have understood the "legalese" from the PTS (Swedish Post and
Telecommunications Authority), any incorporation by reference of the
ITU rules would not be permissible by adminstrative law, and be turned
down by an administrative court in case of dispute.
Another complication is that the amateur radio service in Sweden has
become "license exempt",
which means that the legal protection (and responsiblities) that a
licensing arrangement used to provide are no more. This was "marketed"
as the suspension of the "licensing fee", which was applauded by the
SSA (the Swedish national amateur radio society) officials as a means
of attracting more new amateurs.
Little did they understand the long-term implications of this "offer".
"Brave New World..."
73/
Karl-Arne
SM0AOM
----Ursprungligt meddelande----
Från: g3rzp@g3rzp.wanadoo.co.uk
Datum: Jul 3, 2006 10:06:29 AM
Till: "W.F van Wyk" <zs6arf@telkomsa.net>, g3rzp@g3rzp.wanadoo.co.uk
Kopia: amps@contesting.com
Ärende: Re: [Amps] Maximum RF output in practical application: 4-250A
Wynand - and this applies generally, I think -
>WE are already in ZS in a grey area of owning equipment capable of
more than 400W so the last think we need is the regulator having to
enforce
the regulations<
We need to bear in mind the spurious emission requirements enshrined
in Radio Regulations by ITU-R Rec. SM329. Interestingly, the FCC
managed in their last update of Part 97 to implement the requirements
incorrectly - they have it as requiring harmonics and spurious as -43
dB, when it should be -43 plus 10log P, where P is the PEP, and for HF,
not needing to exceed 50dB. Even then, they didn't make as much of a
mess of things as the UK! The requirements for commercial equipment in
the EU are less than the Radio Regs, but the UK licence says we have to
abide by the RR! So you can legally buy a piece of kit that in theory
you can't use. Fortunately, the enforcement in the UK is so minimal it
doesn't have any effect........
However, we should aim for all harmonics to be at least 50dB down -
not exactly too difficult - but high order IMPs might be. To meet the
RR, emissions separated by 250% or more of the necessary bandwidth (say
2.5 times 2.7kHz) should be down 43+10log P, not exceeding 50dB for an
HF tx. Nobody is sure whether the number for harmonics above 30MHz from
a tx operating below 30MHz need to meet the 43+10logP not exceeding
70dB that applies to transmitters above 30MHz, or 43+10logP not
exceeding 50dB. That applied to the Chairman of ITU Task Group TG1/5
where some of these numbers came from, too! On the other hand, if in a
10kHz wide band starting 6.75kHz away, you aren't down 50dB, then
you're somewhat antisocial anyway.
Personally, I think that SM329 isn't very good: unfortunately, I
wasn't at ITU-R TG1/3 where a lot of this started. Incidentally, that
edition of SM329 was the first time there had ever been any limits on
amateur transmitters, and because nobody thought about the effects of
phase noise on narrow band transmitters, the limits at microwaves are
ridiculous. This has been changed somewhat after the satellite people
realised their tracking beacons are narrowband and thus have the same
phase noise problems as amateurs! Ironically, the whole thing on
spurious came about because of radio astronomy complaining about the
spurious emissions from Iridium satellites in radio astronomy bands,
and like Topsy, it 'just growed'. But an Administration enforcing the
rules and complaining to other Administrations about their amateurs
could cause us problems if we don't at least meet the RR spurious
emission limits. The use of HF isn't going away, and there are a lot of
people would like our ban
ds....
Hopefully this isn't considered too far off the amps topic....
73
Peter, this week SM5/G3RZP
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