[time-nuts] Practical considerations making a lab standard with an LTE lite

Dr. David Kirkby (Kirkby Microwave Ltd) drkirkby at kirkbymicrowave.co.uk
Sun Nov 23 04:46:58 EST 2014


I would like to make a unit with multiple 10 MHz 50 Ohm outputs to feed my
various bits of test equipment.  I am thinking about some practical
considerations.

1) It would be great if there was a circuit published which can give 50 Ohn
output impedance from a 12-15 power supply,  which

a) Doesn't load the TCXO
b) Doesn't degrade the phase noise.
c) Powered the LTE lite.

Ideally one for both 10 & 20 MHz crystals.

Better still if there was a PCB available.

2) How should I mount the components?

My preference would be a metal box with
* IEC mains socket
* antenna input socket
* 9-pin D for reading dats
* 15  BNC's outputs

With a power amplifier to provide the output for 15 sockets, some
ventilation possibly requiring a small amount of forced air cooling would
be needed. But given the TCXO"s sensitivity to temperature changes, I don't
know whether it might be preferable to mount the LTE lite in its own box
without any power supplies in it - perhaps with some thermally insulting
material around the LTE lite so the crystal doesn't experience any fast
temperature changes. Then have the power hungry bits completely separately.

I don't have a particularly big lab, so wherever I mount the LTE lite, the
temperature is going to change with the air conditioning unit blows hot or
cold

There are fairly large temperature changes when I am not using the lab, as
I don't run the air conditioning unit 24/7.

I am interested in people's thoughts on the best way to go about this.

For testing I have a couple of  signal generators that have ovens that are
powered 24/7. Also I should soon have the SR620.

Dave.


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