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: [email protected] > Date: Wed, 16 Oct 2013 15:22:13 -0400 > To: [email protected] > 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, > [email protected] 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 > > > > > > > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > -- > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
