[hpsdr] Using External 10 Mhz on Hermes Board

[Bruce Beford]

It -can- be left on. However, in my experiments with Mercury, Penelope and
Excalibur (upon which the Hermes design was based) I noted that the 10 MHz
clock from Penny, the one from Excalibur and mixing products could be seen
in received traces. I modified my Penelope to allow disabling of it's
onboard 10 MHz osc when using Excalibur.

For most uses, it probably wouldn't matter. For some critical apps, it may
not be desirable to have an unused oscillator contributing to the received
signal spectrum. This is one of the reasons disabling the onboard clock was
made possible in the Hermes design.

73,
Bruce, N1RX

> Is it necessary to remove J23 to disable power to the internal 10 Mhz osc.
> or can it be left on when J20 pins 2 to 4 are jumpered for an external 10
> Mhz?
> If yes this would simplify the switch arrangement.
> Larry K4LED



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