[time-nuts] HP 4193A 4815A probe compatibility?

Mark Kahrs mark.kahrs at gmail.com
Thu Oct 17 09:47:13 EDT 2013


Except that if you blow the 54701A front-end, the IC is made of
unobtanium.  Likewise, buying an untested probe...

As for the 4193A, if you know of an instrument without probe for $1, please
let me know ASAP!!!

The connector of the 4193A is the same awful connector as the 8411A so if
you wanted to build your own, you could start from there.





On Wed, Oct 16, 2013 at 4:42 PM, Tom Knox <actast at hotmail.com> wrote:

> I agree the 54701A is really a great product. Great point on attenuation,
> I always forget the 10x attn value changes when not being used on a O-Scope
> as a voltage probe.
> Thanks;
> Thomas Knox
>
>
>
> > From: SAIDJACK at aol.com
> > Date: Wed, 16 Oct 2013 15:22:13 -0400
> > To: time-nuts at febo.com
> > Subject: Re: [time-nuts] HP 4193A 4815A probe compatibility?
> >
> > Hi Rick, Tom,
> >
> > one little bit of knowledge I learned: I like the HP 54701A FET probes
> for
> > frequency-domain stuff.
> >
> > Available for $300 on Ebay sometimes. I built a small power supply for
>  one
> > of mine, and use it as a probe for my Spectrum analyzer and scopes.
> Almost
> > indestructable.
> >
> > It works really well up to about 3GHz and beyond, especially for relative
> > measurements.
> >
> > The only disadvantage is that it has 100K resistance to ground which may
> > affect sensitive capacitive circuits, and that it has 20dB attenuation.
> >
> > Otherwise it works really well for Spectrum analyzer and Network analyzer
> > applications.
> >
> > bye,
> > Said
> >
> >
> > In a message dated 10/16/2013 11:33:11 Pacific Daylight Time,
> > richard at karlquist.com writes:
> >
> > The  4815A used P channel FETs which were available 50 years ago
> > and are now  unobtainium.
> >
> > The 4193A used N channel FETs which were available 10 to  30 years
> > ago and may even be currently available.
> >
> > They are  DEFINITELY NOT INTERCHANGEABLE.
> >
> > This is according to ex-HP'er George  Standford, who used to
> > support vector impedance meters with HP's  blessing.  He held
> > the worlds remaining supply of P channel FETs for  fixing probes.
> > He was in New Jersey, but my contact info for him is no  longer
> > valid.
> >
> > I don't know how to identify them, but in principle an  ohmmeter might
> > be able to identify the polarity of the FETs.
> >
> > While  we are on the topic, it turns out that the market is such
> > that a 4193A with  probe might sell for $5000, but if you break
> > up the set, the probe is worth  $4999 and the instrument is worth
> > $1.  Well, maybe I exaggerated that  a little, but not much :-)
> > I actually know someone who paid $5000 for just  a 4193 probe.
> > He made the mistake of purchasing an instrument without a  probe,
> > and paid way too much.
> >
> > It is also worth noting that now you  can buy a very nice vector
> > impedance meter from Tomco in Austrailia for  only $3000 new.
> > I A/B'ed one of these with an HP one, and I will have to  admit
> > that the Tomco is the real deal, not a cheap knockoff.
> >
> > Rick  Karlquist N6RK
> >
> >
> > On 2013-10-16 09:15, Tom Knox wrote:
> > > I hope  this is not to far off topic. Does any one know if the 4193A
> > > and 4815A  probe are physically interchangeable and electronically
> > > compatible? If  not does anyone know the differences and how to
> > > identify which is  which? If you feel this is to far off topic please
> > > contact me  directly. Thanks very much.
> > >
> > > Thomas Knox
> > >
> > >
> > >
> > >  _______________________________________________
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> > --
> >
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