Posted by
Geoffrey Mackenzie-Kennedy-2 on
Mar 08, 2005; 7:26am
URL: http://elecraft.85.s1.nabble.com/Receivers-tp375444p375448.html
Morning Lyle,
Lyle Johnson KK7P wrote:
> >> ...Assuming the use of strong mixers (+50dbm)...
>
> Hmmm. +50 dBm = +20 dBW = 100 watts! That's some mixer!!!
>
Could never get a job typing ! It should have read '( with an
IP3in of +50dbm). The mixer is the H Mode mixer developed by G3SBI some
years ago, and is a real performer.
> >> ...Great will be the day when a DSP unit running at VHF,
> >> with a high IP3in etc, and low noise figure becomes practical.
>
> An interesting approach to this is the SDR-14 from rfspace. It directly
> digitizes the entire HF spectrum -- and by using input bandpass
> filters can digitize up through the 222 MHz band. I have listened to 2
> meter signals on mine.
>
> The front end isn't as strong as a contesting station would need -- yet.
>
That is interesting, and they will get there.
> Meanwhile, for high-performance, a strong front-end followed by a
> crystal filter suited to the mode and signal level, enhanced by a DSP
> seems to be the best practical implementation.
Agree, provided the LO(s) very close in phase noise does not
compromise the filter, or at any further out offset the phase noise does not
compromise the dynamic range (PNGDR).
Tnx es 73,
Geoff.
GM4ESD
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