[time-nuts] Firmware and antenna for Stanford Research FS700 Loran C frequency standard

[Attila Kinali]

On Fri, 17 Jul 2015 12:55:07 +0100
"Dr. David Kirkby (Kirkby Microwave Ltd)" <drkirkby at kirkbymicrowave.co.uk> wrote:

> Thank you Ole. That at least gives me something to start from. I guess the
> op-amp design Poul-Henning Kamp used offers more flexibility for gain
> adjustment. I might look at that too. If the amplifier is in a box with a
> couple of banana jacks and a BNC socket, it is fairly easy to change one
> amp for another. I assume from what you say that the FS700 will report the

I would probably replace the AD797 with it's younger cusin the AD8099.
The noise performance is very similar, but it has a GBW-product of
>3GHz (instead of 110MHz), which potentially allows you do get much higher
gain in the first stage. And best is: you can run it from a +5V supply
and don't need to bother with a +/-5V supply (keeping in mind that the
AD797 specs are for +/-15V, so they are likely to be worse at +/-5V).

Please note that neither of those opamps are rail-to-rail. You need
to stay 1.3V clear of the rails for the AD8099 (both, input and output)
and 2.5V and 3V for input and output respectively for the AD797.
The datasheet does not specify what happens when you cross the input
rails limit, but I would expect nasty stuff like gain reversal and such.

Also, the absolute maximum ratings have a maximum differential input
voltage of 1.8V and 0.7V respectively. Do not cross that line, lest
you want to smell magic smoke (ok, not really, but it might at least
detoriate the input protection diodes, if not fry them)

			Attila Kinali

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