[eagle] Re: Eagle 10 MHz Clock
kk7p at wavecable.com
Wed Apr 11 10:14:38 PDT 2007
> Good points about keeping the command receiver on 100% - no issue there.
> But I think the matter is somewhat confused (at least for me) since I
> believe the command receiver that John has designed is also the
> data/analog receiver. I don't recall that being the case is the past
> satellites. If command and data function stay combined, then that's all
> the more reason for considering John's suggestion.
In the past, the "command receiver" used the same front end as the
transponder receiver. The difference was an IF tap that was then
downconverted to baseband to drive a hardware command decoder.
Thus, all uplink that had command capability had receivers that were
One rule learned the hard way is you *never* turn off a command
receiver. It's also why command receivers, at least, were never
frequency agile. It's bad enough to recover a spacecraft if you are
commanding it in the blind - it's even hardware if you have no idea
where the receiver might be tuned. So, we always used crystal
oscillator/multipliers, or PLLS with pins-selection of dividers. Using
a serial-load PLL adds a lot of risk -- not sure what the reward is for
Not to say we need to always do what worked in the past, just that we
should have compelling reasons to change things that relate to
spacecraft safety and health.
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