I remember that Natioanl had a transceiver called the NCX-1000, which
supposed ran a kW input on SSB. This was before I got into ham radio. Did
it really deliver 600 watts output as it should have, and was wondering why
it was never duplicated by anyone else?
Joe W4AAB
----- Original Message -----
From: "Karl-Arne Markström" <sm0aom@telia.com>
To: <g3rzp@g3rzp.wanadoo.co.uk>; <amps@contesting.com>
Sent: Sunday, July 23, 2006 4:34 AM
Subject: Re: [Amps] 3cx3000A7 driver
> Peter,
>
> You are certainly right...
>
> Making a medium to high power HF transmitter with "close-in" noise
sidebands of
> -160 dBc/Hz would be a very difficult task indeed.
>
> It is not only the spectral purity of all oscillators involved that count,
but
> also the aggregated noise properties of the amplifiers and level control
loops.
>
> Having been deeply involved with military "co-located" HF systems in the
past,
> I fully appreciate the efforts put into "high-end" HF hardware by their
designers,
> i.a. the necessity of building the input end of an HF power amplifier in
the
> same way as a receiver low-noise amplifier, not to degrade the overall
SNR.
>
> Despite these efforts, it is still uncommon to find better noise floors
than -150 dBc/Hz at 20 kHz spacing
> for "production" HF equipment.
>
> An account of the design philosophies required to approach these levels of
performance can be found
> in a paper "A New Generation of HF Power Amplifiers" by K G Nygren in the
Proceedings of the Nordic HF Conference HF92, which goes into the design
considerations for the ITT-Standard Radio SSA1020 1 kW MOSFET amplifier.
>
> Having accomplished transmitter and receiver sideband noise floors of -160
dBc/Hz, at, say, 10 kHz spacing, the next major task would be finding a way
of reducing the IM sidebands of tunable SSB transmitters to corresponding
levels....
>
> 73/
>
> Karl-Arne
> SM0AOM
>
>
> ----- Original Message -----
> From: "Peter Chadwick" <g3rzp@g3rzp.wanadoo.co.uk>
> To: "Harold Mandel" <ka1xo@juno.com>; <g3rzp@g3rzp.wanadoo.co.uk>; "'Frank
Goenninger'" <frgo@mac.com>; <amps@contesting.com>
> Sent: Sunday, July 23, 2006 9:14 AM
> Subject: Re: [Amps] 3cx3000A7 driver
>
>
> > Hal said:
> > >This radio is built for the future.
> >
> > In tomorrow's world -160dB(c) per cycle may actually be
> > a force to contend with......<
> > It may be, although I have severe doubts about the technology needed.
This is because, in the final analysis, low phase noise requires high power.
S/N becomes osc power over thermal plus implementation noise. Modern IC
technologies are pushing to smaller geometries, which mean lower voltages
and so SNRs are tending to drop. Implementing a DDS to go fast without
needing a BIG heatsink (e.g. the old Plessey SP2001 500MHz ECL DDS) becomes
a bit of a difficulty - you need to do it in CMOS. But reduced geometry CMOS
has reduced SNR, because of the lower voltage swings. It also has leakage
problems, which can also degrade SNR, as well as lead to higher current
consumption - which is why in the company I work in, we're still pretty well
confining ourselves at the moment to using 0.18 micron CMOS, especially as
we need RF analogue characterisation. In any case, until everyone else on
the band has rigs of equal performance, there's not that much advantage, and
as far as IMD goes, f
> or
> > the majority of people, need. See my 2002 QEX article.
> >
> > 73
> > Peter G3RZP
> > _______________________________________________
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> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
> >
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