[hpsdr] New kid on the block --> TransFox SDR

[Curt, WE7U]

On Fri, 8 Oct 2010, Phil Harman wrote:

> Re the TransFox, my concern would be trying to maintain an acceptable
> image rejection over such a wide frequency range. Whilst 70dB may be
> acceptable on the HF bands, since images may be hidden under the general
> band noise, at VHF and UHF this will not be the case.

Looking at the block diagram I see what I think are two PLL's, one
labeled "Wide band loop" and one labeled "Auxiliary loop", created
in the left box with an ASIC and other components external to the
ASIC.

In the right box, I & Q signals are combined with the "Auxiliary
loop" output, run through a 1 GHz IF filter, then mixed together in
a high-level mixer with the "Wide band loop" output.  From there it
goes through RX/TX switches to switch between PA's and LNA's, then
to RF bandpass filters.

The whole thing looks more like a two-PLL-loop HF rig, but with an
extremely wide IF designed for I/Q signals, rather than something
like an HPSDR that processes the RF directly.  I admit I'm not
trained in RF so my understanding may be incomplete (Digital EE &
S/W spoken here).

Comments from the experts?

-- 
Curt, WE7U.                         <http://www.eskimo.com/~archer>
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