Re: [Discuss-gnuradio] ICOM 706 MKIIG as input to GNURadio

On 12/31/2010 02:24 PM, Brad Hein wrote:
>
> I'm looking for a way to tap into the unmodulated signal in my ICOM
> 706 MKIIG (I don't have a SDR BUT I do have a sound card, and lots of
> ham equipment :) ).
>
> Referring to the product service manual[1], I have found the "product
> detector" signal before it reaches the AF stages.
>
> Also it appears (hoping I'm wrong) that the second IF runs at about
> 9Mhz. So does that mean that I need to down-convert the signal from
> 9Mhz, to something the soundcard can handle?
>
> Or is there a better place to tap the IQ signal coming from the VDO...?
>
> Anybody else had any success in tapping the IQ in a receiver and
> feeding that into GNURadio?
>
>
> 73
> K1GTO
> BH
>
Pulling off a signal from the 2nd IF would likely be doable. But you'll
need to convert it to quadrature baseband somehow.

Most "traditional" receivers *do not* have a quadrature architecture.

You might look into getting something like a "SoftRock 40" and modifying
it to produce a quadrature conversion to baseband from
9MHz, instead of the nominal 7.1MHz that the "Softrock 40" is
designed for. I think the "SoftRock" series uses a Tayloe
detector, whose crystal clock runs at 4X the nominal conversion
frequency.

If you can identify the point in the receiver where the 9MHz IF is at
roughly 50Ohms impedance, it should be quite straightforward.

--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org

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