[linrad] Re: Linrad via Ethernet

[<leif@xxxxxxxxxx>]

> LO (Xtal osc) (What freq?) ->74AC14 X6  -> AD6644 -> AD6620 -> AD6620 ->
> ethernet -> PC
The frequency would be the highest possible. The data sheet says maximum
guaranteed sampling speed 65 MHz. The SDR-14 uses 66.66667. I think
65.000 MHz would be fine. It becomes easy to lock it to a 10 MHz
reference one way or the other:-)

> If we were to do one AD6620, then a second one wouldnt be too hard.
Absolutely:-)

> Could one do all this on a double sided board?
Maybe. The AD6644 data sheet suggests a design with 4 layers.
The clock is supplied via a transformer and two schottky diodes
limit the amplitude. Probably one could feed the transformer
with a sinewave directly from the LO.

> Alternatively a multilayer board would be possible, though I have never
> done one
Maybe it would be a good idea to make a small 4-layer board with
the X-tal oscillator, the AD6644 and appropriate buffers just as suggested
in the AD6644 data sheet. This should be a very low risk project.
As far as I understand one can buy this board for USD 200 from Analog Devices
http://www.analog.com/en/prod/0%2C2877%2CAD6644%2C00.html#price
Then one could connect it to a two-layer board with two AD6620 and an
ethernet interface.

> I still use the old Autotrax (1991 - precursor of Protel)
> As of a couple of years ago, a local board house still accepted this

73  Leif / SM5BSZ



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