--- Ron McKean <wd5fun@earthlink.net> wrote:
> You are absolutely right. Scott, stated in his
> informational release that
> the Orion would utilize both methods. He also said
> that the main receiver
> (using the crystal filters) would be ham band only,
> so I assume it will use
> a crystal mixed oscillator like the Omni V and VI.
> The sub-receiver will be
> full coverage and use only DSP technology.
>
I didn't get the impression at all that the main Orion
RX is going to be crystal filter based, at least not
in the sense that the Omni VI et al have been.
>From Scott's 25 January post:
"Main receiver is amateur radio bands only, utilizing
both analog and IF-DSP stages, 10-160 meters. Sub
receiver is IF-DSP, general coverage."
Nothing in those two sentences implies that the main
RX will not be DSP based, in fact plainly says it will
have DSP. I interpreted his comment to reflect that
there will be a mix of analog elements and DSP in the
IF chain. Much the same as Ten Tec's DSP radios to
date already are. This makes good sense because 130+
dB dynamic range A/D devices are rather rare or at
least very expensive. I?m sure that much of the
top-notch performance will come from choosing more
capable analog devices in the RF/IF chain before the
signal gets digitized.
What I did get out of Scott's posting was that they
will likely have relatively narrow band pass filtering
for the ham band frequency ranges. Relay switched?
Perhaps combined with this will be a synthesizer
design that is similarly narrow (tuning range), again
a methodology that was already used in the Omni V and
up series. But I also doubt if it will be a crystal
mixed scheme like the later Omni's for cost reasons.
There are several really low phase noise synthesizer
chips out there already that rival crystals.
Did you realize that the K2 and Pegasus/Jupiter share
the same Motorola synthesizer chip? One has exemplary
phase noise specs and the other is mediocre by today?s
standards. The low phase noise K2 doesn't use a VHF up
conversion scheme whereas the Pegasus/Jupiter does.
The main reason up conversion became so appealing to
designers was to provide for continuous no gap HF
coverage. The main Orion RX will not do that, hmmmm.
Bottom line is that current crop of DSP IF radios
aren't being limited so much by the DSP design issues
themselves. They are instead mostly limited by other
architectural design issues that would/do impact
analog only designs equally.
73,
Duane
N9DG
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