[amsat-bb] Shack re-wiring: RTL-SDR options?

[Jim Jerzycke]

I don't think an RTL dongle will tune down that low.


Jim  KQ6EA


On 03/02/2017 10:46 PM, Greg D wrote:
> Hi folks,
>
> Has anyone used an RTL-SDR dongle on the 10.7 MHz IF output from another
> receiver?  Is that better than going direct?
>
> My cable TV provider is forcing us to go all-digital.  With the new
> "cable box" comes the opportunity to re-wire the shack and simplify the
> many layers of cables, splitters, and lash-ups that have accumulated
> over the years.  The proverbial camel is crying out for help.
>
> What this has to do with Ham Radio is that part of the lash-up mess is
> an old pre-CATV deep fringe TV antenna that I have in the attic, aimed
> to the southern horizon.  We are well outside the range of any of the
> digital OTA stations, and never one to leave a perfectly good piece of
> RF equipment go to waste, I currently have it fed to an old Icom R-7000
> scanning receiver (previously used as the AO-40 downlink IF) and to an
> RTL-SDR dongle by way of a TV 2:1 splitter.  I've tried hooking the
> dongle directly to my 2m ham antenna for satellite use, but for some
> reason that was less than satisfactory.  Never really did hear much of
> anything, and never could figure out why.  At least with the TV antenna,
> I can copy some stuff with the dongle, though the Icom is generally
> better.  But the Icom doesn't do the various digital modes that are
> better suited for SDR.
>
> Looking at the back of the Icom, I see that it has a 10.7 MHz IF output,
> so the thought is that the SDR dongle might perform better hooked there
> (with a DC bias block) instead of to the antenna itself through the
> splitter.  Both receivers have similar frequency coverage, but perhaps
> the Icom, while somewhat deaf by modern standards, might still make for
> a better front-end to the dongle?
>
> I think the down-side is that the Icom's IF bandpass is narrower than
> the Dongle's, so I'd lose some flexibility there.  I would also lose the
> ability to software-control the frequency of the receive chain, outside
> of the IF bandpass.
>
> What do you think?  Would this be a net win or loss for the RTL-SDR?
>
> Thanks,
>
> Greg  KO6TH
>
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