[hpsdr] Proposal for a 'low-end' RX/TX board for HPSDR

[Philip Covington]

Hi Ahti,

On 7/27/06, Ahti Aintila <oh2rz.sdr at gmail.com> wrote:
> You are talking so nicely about the active integrator, so I have no
> alternative  but admit. Being a simple and silly person myself, I love
> KISS. Here is my latest simple schematic
> diagram:<http://kotisivu.dnainternet.net/ahti/sdr-1000/newmix4.pdf>
>
> I figured out that the OPA1632 is a combination of two inverting
> amplifiers, so why not they could not work as two integrators.

This configuration is what I started out with using the AD8139 and I
have been going back and forth in my head on whether the two are
equivalent since then (the individual AD8021 op amps verses one AD8139
fully differential op amp).  I know that discussions of fully
differential op amps mention that you can think of it as two inverting
op amps that share a common non-inverting input, but I am not sure
this is exactly equivalent.

> Unfortunately, I am still waiting for the ordered components to come,
> so no tests made yet. This is just a paper exercise. If this idea
> works the QSD (and QSE likewisw) can be put to a really small area.

You are right, these circuits need to be built up and tested.  If your
configuration is equivalent to my AD8021 circuit then it is much
simpler as far as part count and I would definitely prefer it over the
more complex circuit.

> By the way, I like isolating tranformers to separate the dirty digital
> world from the sensitive analog circuits.
>
> What do you say, and what am I missing this time?
>
> 73, Ahti OH2RZ

Obviously we need to build these and get some real numbers.  I am
keeping my fingers crossed that your configuration is equivalent to
the one I posted earlier.

73 de Phil N8VB

 1154031732.0