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

Luciano Paramithiotti timeok.it at gmail.com
Sun Apr 21 07:22:27 UTC 2013


Hi all ,
normally the external frequency standard input are not 50 OHms , but  all
the distribution amplifier have 50 Ohms of standard output impedance. This
because the standard cables used to connect the devices are 50 ohms.
Case one: External Zi input 50 ohm: direct connection with rg58 cable.
Case two: External Zi input 1k or more (as example) use the RG58 cable with
a 50 ohm as termination in parallel to the instrument input.

This second setup is to avoid any standing waves on the cable that produce
unwanted phase and amplitude modulation; this is a  cost-less  best
practics to apply .

Luciano
www.timeok.it

On Fri, Apr 19, 2013 at 2:54 AM, <dlewis6767 at austin.rr.com> wrote:

> 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.
> >
> >
> >
> > _______________________________________________
> > time-nuts mailing list -- time-nuts at febo.com
> > To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > and follow the instructions there.
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>



-- 
Luciano
Timeok
visit : www.timeok.it



More information about the Time-nuts_lists.febo.com mailing list