[time-nuts] Agilent appnote

Magnus Danielson cfmd at bredband.net
Mon Jul 25 15:00:14 EDT 2005

From: "John Miles" <jmiles at pop.net>
Subject: RE: [time-nuts] Agilent appnote 
Date: Mon, 25 Jul 2005 11:30:15 -0700


> Also... it might seem obvious, but check your 5370's reference levels to
> make sure they're both 0.00.  I don't remember which button calls up those
> settings to the display, but if they don't match exactly (and/or your 5370
> is not in calibration), the Start and Stop channels will trigger at
> different phases of the signal.
> > Belden RG-58A/U 50 Ohm is 0.66 (where as the 52 Ohm is 0.73 and
> > 53.5 Ohm is
> > 0.75, all is "RG58A/U")
> Is this genuine Belden cable, or whatever was on sale at Radio Shack last
> week?  It does make a difference. :)

The above numbers all came from Beldens catalogue on the web, and whatever
Radio Shack or its local equalent is having a sale on can indeed vary from
this. Basically, with cables you need to know exactly what cable it is to
beleive the specs, and beyond that we have manufacture variations (they only
give a mean value anyway), effect of handling etc. Propper measuring is surely
needed. If we really care, we should also take the rise-time of the cable into
acount, so that we could combine the cables rise-time with the signal rise-time
and also the counter input channels rise-time and compensate for the effective
risetime if we do not measure that separately.

HP has a nice little patent on calibration of time interval counters. Much
recommended reading.


More information about the time-nuts mailing list