[time-nuts] 10 MHz clock distribution for the lab

dlewis6767 at austin.rr.com dlewis6767 at austin.rr.com
Thu Apr 18 20:54:42 EDT 2013


External reference inputs are definitely not all '50-ohms.'

'Learned the hard way.

You need to read the specs on each piece of equipment.

Input impedances will vary all over the map, even within the HP line.

-Don









---- Hal Murray <hmurray at megapathdsl.net> wrote: 
> 
> caf at omen.com said:
> > I have a FlexRadio 1500, Racal 1992 counter, HP 3586, Advantest U3641, and
> > Gigatronics 6061A daisy-chained off my Thunderbolt.  Don't throw out those
> > BNC T connectors. 
> 
> I thought most boxes would have an internal 50 ohm terminator so at first, 
> I'm a bit surprised that it works.
> 
> If cables are short (which is not hard at 10 MHz), it would just be a 
> resistive divider.  If the source impedance is low, it's just more work for 
> the driver.  If the source includes 50 ohms, that's a 5:1 (1/6) divider so it 
> probably works if the receivers are reasonably sensitive.
> 
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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