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Re: 10.0 - 10.5 GHz LNBs and upconverter-TX units.



Hi Ed and all..
as I already posted earlier in another thread, commercial 10 gig lncs
are no good for narrow bandwidth ssb, because of bad phase noise. The
frequency drift and stability of a dro might be sufficient though
annoying because it surely will drift around a couple of 100 khz's..
But the problem of phase noise is as follows: imagine you have a cw
signal normally audible with your cw-filer with say 500 hz width.. now
imagine this cw-signal on 10 gig will be downconverted to your IF by a
signal with a width of a couple of 10 khz (10000 Hz !). As converting
means mixing, your mixed IF signal will be something with similar width
(10 khz).. now imagine listening to this with a 500 Hz Cw filter. I did,
and it was not very promising.  8(
Same assumptions are valid for SSB, though the effect is not so strong,
but nevertheless you have a loss in SNR.. which is very undesireable for
weak signal reception like sat-ops..

The most promising device seems to me the downconverter of Michael Kuhne
(www.db6nt.com). He already made transverters for terrestrial ssb with
conventional crystal multipliying, so I guess this is the way to go,
although I also would like the DRO thing.. 8(

73s Achim, DH2VA


"Edward R. Cole" wrote:
> 
>
> 
> Doug,
> 
> If you checked on Downeast and SSB's web pages you will have discovered
> that they both have or plan for 10 GHz P3D down convertors.  I have one
> pre-ordered from Downeast when they begin production.  I certainly agree
> that we should patronize our ham-microwave suppliers.  But its only
> typically "ham" to scrounge or build our own.
> 
> If you have the time, skill, or willing to acept the risk then go for it.
> If not, then DEM, SSB, Kuhne, Parabolic, etal offer a good selection.
> 
> See you on x-band :-)
> Ed
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