The 4815A probe is becoming unobtanium and repairs are around $800.
Ive been staring at my analyzer sitting on a shelf for several years now.
For what I want to do in the shop up to 6M can be done with the TS-617C Q
Meter. I just wish I had something that worked for easy tuning of 160/80M 4
Squares. The MFJ 259B is junk in that area and also takes up shelf space
after initial dissapointment.
Carl
KM1H
----- Original Message -----
From: "John Lyles" <jtml@losalamos.com>
To: <amps@contesting.com>
Sent: Wednesday, March 31, 2010 6:18 PM
Subject: [Amps] real component measurements at RF
> W7IUV's recent posting makes sense as to the pitfalls of measuring L and C
> with the various commercial instruments. There is one other device that
> wasn't mentioned, but is a less expensive
> alternative and uses the Hp-optimized IV approach. But it isn't portable!
> The old Hp 4815A vector impedance meter has an active probe with the
> sampling device in it. This meter covers from 500 KHz to 110 MHz, over the
> HF range
> and has specified accuracy from like 10 ohms to 100 Kilohms over same
> range. They can be found for a hundred dollars or so used, but make sure
> the probe is good. Also, the later 4193A digital version is superb, I use
> that one at work a lot as the 4815A is prone to having intermittents from
> the air variable tuning capacitor in oil inside. They have been
> discontinued by Agilent, but these are the workhorses for amplifier
> component testing, once you figure
> out how to fixture the device to fit the tiny probe. That is done with
> copper strap and homebrewed holders and clips from N and BNC. The 4815A
> cannot be run through HPIB but the 4193A can. About 15 yrs ago, I started
> writing a
> software calibration routine that would do OSL normalization at the probe
> tip, to allow the 4193A to read down to below an ohm at RF. This allows
> one to do a better job of knowing the Q of a series resonance and of
> bypass capacitors
> effects at RF. I had found a similar program in an Hp app note for the
> 4191A impedance analyzer. I never finished my routine due to time, but
> continue using the 4193A everytime i need to know what a component value
> is at an RF freq. ]
> I have measured things like B&W chokes, Ohmite Z144s, disc caps, doorknob
> caps, chip components, Miniductors, tank circuit components, vacuum caps
> with it. I also use an ESI meter that works at KHz, and a Boonton,
> both disagree on inductors somewhat, as Larry points out the causes.
>
> John
> K5PRO
>
> -------------------
>
> Message: 2
> Date: Wed, 31 Mar 2010 10:31:35 -0700
> From: Larry <larry@w7iuv.com>
> Subject: [Amps] LCR meter & measuring components
>
> Very complex (spelled H E A R T - A T T A C K) instruments like the
> HP/Agilent network analyzers that are marketed as component test sets,
> (sorry don't remember the model numbers offhand) use a system known as
> RF-IV for the detectors. They actually measure the RF voltage and the RF
> current at the test ports and use that to calculate the complex
> impedance. Since this system is capable of accurate phase and amplitude
> measurements over a VERY wide range of frequencies, these instruments
> are the best there is for evaluating components, especially high Q
> inductors, over a wide frequency range. The N2PK VNA has a RF-IV option.
> I have the RF-IV bridge but have not yet put it together so have no
> first hand knowledge, but it is reported to show accuracies similar to
> the Agilent instrument (within the N2PK's normal frequency range).
>
>
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