[Discuss-gnuradio] Daughterboard progress

[cfk]

Dear Matt:

    I have the schematics, thank you very much. We are making progress.

    I do have a PADS license, thats no problem. Its just that I am quite a
bit more proficient with Orcad Layout, but reading a PADS database is
manageable from this end. If you could post that on the Wiki, or send it to
my e-mail, then I can turn around a schematic and layout with the 4702 back
to you in a few days for your review.

    I am going to list my current questions, of which some of them will be
answered by the PADS file, but you can see where my thoughts (or lack of)
are going.

1. I have tried to find pin 1 (or pin A1) on the Molex web site to no avail.
I did find in the Molex reference for their spice model the designators
A1..A32 on one side and B1..B32 on the other. Do you *really* want to change
the pin numbering? I will certainly go with whatever you decide. I suspect
the PADS database will allow me to avoid mirror imaging the connector.

2. It may be that we might want to use the AUX_DAC_A line instead of a
MAX518 I2C DAC for the AGC. Is this what you might want on this
daughterboard?

3. I wonder if you have a source for T1 (or T2, I assume they are
identical). Having a source for this part would allow me to get the
footprint right. Without it, I currently have an 8pin DIP that we can solder
the leads into. That usually works for transformers, but the "right"
footprint is always better. I know that we could use many different
transformers. I would just feel more comfortable with at least one source.

4. I assume that in the case of the 4702, that we are going to go through a
transformer with its Ifout1 and Ifout2 on one side, and then to VINP_A and
VINN_A on the other side? Perhaps with or without impedance resistors? I
think the 4702 is 300ohm output, so we will need to go from 300ohms to
50ohms to match the AD9862 input. I'll take a swag at that and send you the
schematic and layout.

5. Do you want me to link the schematic and layout files from my web site
http://home.pacbell.net/cfk similarly to the way you have done with the Rx &
Tx daughterboard schematics. I can update them from my end and include the
Orcad data base files for the schematic and the layout in addition to the
.pdf files.

6. I dont know what the output level of the 4702 is yet. Do you know if it
is more or less then 100mv P-P? If greater then 100mv, no problem. If less
then 100mv, we may lose some dynamic range without a buffer.

Charles