RF voltmeter purchase...

[amdx]

I\'m looking at buying a couple of RF voltmeters for measurements from
audio to 2MHz, mostly input output measurements.
This will be hobby use only.
 I have Boonton 92EA RF meters, but they are 50Ω terminated with BNC
connectors. I would prefer a scope type probe, or even an
active probe with for capacitive loading. A simple active probe build
would be nice! I would like a digital display although a little ambivalent.
 Any thoughts about what I should be looking for?

 Another thought, high impedance active probe with a 50 ohm output to
connect to my 92EA 50 ohm probe.

                                    Mikek

 

[server]

On Fri, 19 Aug 2022 07:32:14 -0500, amdx <amdx@knology.net> wrote:

I\'m looking at buying a couple of RF voltmeters for measurements from
audio to 2MHz, mostly input output measurements.
This will be hobby use only.
 I have Boonton 92EA RF meters, but they are 50? terminated with BNC
connectors. I would prefer a scope type probe, or even an
active probe with for capacitive loading. A simple active probe build
would be nice! I would like a digital display although a little ambivalent.
 Any thoughts about what I should be looking for?

 Another thought, high impedance active probe with a 50 ohm output to
connect to my 92EA 50 ohm probe.

                                    Mikek

Why not use a scope? Most will measure RMS and most have FFTs these
days.

 

[whit3rd]

On Friday, August 19, 2022 at 5:32:24 AM UTC-7, amdx wrote:

I\'m looking at buying a couple of RF voltmeters for measurements from
audio to 2MHz, mostly input output measurements.
This will be hobby use only.
I have Boonton 92EA RF meters, but they are 50Ω terminated with BNC
connectors. I would prefer a scope type probe, or even an
active probe with for capacitive loading. A simple active probe build
would be nice! I would like a digital display although a little ambivalent.
Any thoughts about what I should be looking for?

Why not a simple moving-needle voltmeter? Calibrated in dBm, these are easily
available (if a bit old-school).

 

[Phil Hobbs]

On 8/19/22 1:03 PM, whit3rd wrote:

On Friday, August 19, 2022 at 5:32:24 AM UTC-7, amdx wrote:
I\'m looking at buying a couple of RF voltmeters for measurements from
audio to 2MHz, mostly input output measurements.
This will be hobby use only.
I have Boonton 92EA RF meters, but they are 50Ω terminated with BNC
connectors. I would prefer a scope type probe, or even an
active probe with for capacitive loading. A simple active probe build
would be nice! I would like a digital display although a little ambivalent.
Any thoughts about what I should be looking for?

Why not a simple moving-needle voltmeter? Calibrated in dBm, these are easily
available (if a bit old-school).

Right, such as an HP 3400A--10x crest factor, 10 MHz bandwidth.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
https://hobbs-eo.com

 

[amdx]

On 8/19/2022 10:02 AM, jlarkin@highlandsniptechnology.com wrote:

On Fri, 19 Aug 2022 07:32:14 -0500, amdx <amdx@knology.net> wrote:

I\'m looking at buying a couple of RF voltmeters for measurements from
audio to 2MHz, mostly input output measurements.
This will be hobby use only.
 I have Boonton 92EA RF meters, but they are 50? terminated with BNC
connectors. I would prefer a scope type probe, or even an
active probe with for capacitive loading. A simple active probe build
would be nice! I would like a digital display although a little ambivalent.
 Any thoughts about what I should be looking for?

 Another thought, high impedance active probe with a 50 ohm output to
connect to my 92EA 50 ohm probe.

                                    Mikek
Why not use a scope? Most will measure RMS and most have FFTs these
days.

 I do, but I want better than 15pf/10MΩ.
                                Mikek

 

[amdx]

On 8/19/2022 12:48 PM, Phil Hobbs wrote:

On 8/19/22 1:03 PM, whit3rd wrote:
On Friday, August 19, 2022 at 5:32:24 AM UTC-7, amdx wrote:
I\'m looking at buying a couple of RF voltmeters for measurements from
audio to 2MHz, mostly input output measurements.
This will be hobby use only.
I have Boonton 92EA RF meters, but they are 50Ω terminated with BNC
connectors. I would prefer a scope type probe, or even an
active probe with for capacitive loading. A simple active probe build
would be nice! I would like a digital display although a little ambivalent.
Any thoughts about what I should be looking for?
Why not a simple moving-needle voltmeter? Calibrated in dBm, these are easily
available (if a bit old-school).

Right, such as an HP 3400A--10x crest factor, 10 MHz bandwidth.

Cheers

Phil Hobbs

OK, paid $120 with shipping for a \'working\' unit ;-).
                                 Mikek

 

[Gerhard Hoffmann]

Am 19.08.22 um 20:48 schrieb amdx:

On 8/19/2022 10:02 AM, jlarkin@highlandsniptechnology.com wrote:
On Fri, 19 Aug 2022 07:32:14 -0500, amdx <amdx@knology.net> wrote:

I\'m looking at buying a couple of RF voltmeters for measurements from
audio to 2MHz, mostly input output measurements.
This will be hobby use only.
  I have Boonton 92EA RF meters, but they are 50? terminated with BNC
connectors. I would prefer a scope type probe, or even an
active probe with for capacitive loading. A simple active probe build
would be nice! I would like a digital display although a little
ambivalent.
  Any thoughts about what I should be looking for?

  Another thought, high impedance active probe with a 50 ohm output to
connect to my 92EA 50 ohm probe.

                                     Mikek
Why not use a scope? Most will measure RMS and most have FFTs these
days.

 I do, but I want better than 15pf/10MΩ.

My Agilent 54846B scope has 1152A probes, 100K, 0.6 pF 2.5GHz.
It has a special BNC plug to the scope with 9 additional pins
that will probably not fit on very much else.

I also have some 54701A probes with N-connector that are less
integrated into the system. They have an additional LEMO
connector that needs +- some volts, forgot how much since I have
a sampling scope that happens to fit.

Then there is the Tektronix P6201 FET probe. Needs a +-15V
supply IIRC. I tried it in front of a spectrum analyzer, OMG,
an IMD generator if there ever was one.
But good enough for the time domain.

Finally, there are level meters like R&S URV-35. They don\'t only
have mW power heads, there are also rf voltage probes AFAIK.
I only have kept the thermal Z-51 mW head, I will never ever
give that away. Only heat is true power. Heads with Schottkys
are for kids.

Cheers, Gerhard

 

[amdx]

On 8/19/2022 12:48 PM, Phil Hobbs wrote:

On 8/19/22 1:03 PM, whit3rd wrote:
On Friday, August 19, 2022 at 5:32:24 AM UTC-7, amdx wrote:
I\'m looking at buying a couple of RF voltmeters for measurements from
audio to 2MHz, mostly input output measurements.
This will be hobby use only.
I have Boonton 92EA RF meters, but they are 50Ω terminated with BNC
connectors. I would prefer a scope type probe, or even an
active probe with for capacitive loading. A simple active probe build
would be nice! I would like a digital display although a little ambivalent.
Any thoughts about what I should be looking for?
Why not a simple moving-needle voltmeter? Calibrated in dBm, these are easily
available (if a bit old-school).

Right, such as an HP 3400A--10x crest factor, 10 MHz bandwidth.

Cheers

Phil Hobbs

Thanks for the advice Phil! I now have two Ebay purchased HP3400As.
Neither worked, of course.
I replaced two bad caps in the first amplifier section, (measured low
ohms) perked right
up after that. It still has a minor needle pulse swing on some ranges,
0.001V, 0.003V, 1V, and 3V ranges.
the 0.01V, 0.03V, 0.1V, and 0.03V are all stable.
Here\'s a video showing the worst case,
https://www.youtube.com/watch?v=nq_lC_WtJX4
It gets much better after a short warm up, reduces to about 5% of full
scale.

 It looked like the other one had a bad tube, I couldn\'t get it to
calibrate, I swamped the tube
with the working one and then it calibrated, I put the original tube
back in, and then it calibrated
just fine. ¯\\_(ツ)_/¯

 Still working on flatness from 100kHz to 10Mhz, 7 or 8% error and the
adjustment cap does not change anything.
The cap tested good though.

If anyone has experience with these problems, please add your input.

 I also had no luck using my oscilloscope to help troubleshoot the
unit. It had to much 60 Hz riding on the signal.
I tried no ground connection, (3 to 2 pin adapter), I tried both scope
and HP3400A ungrounded,
I tried an isolation transformer, with ground and without ground. Just
could not get rid of 60 Hz. Then I thought,
maybe it\'s power supply ripple, nope very low ripple, I also lifted and
tested each cap on the
PS board for capacitance and dissipation, all tested good.
 Any advice appreciated.
                   Thank, Mikek

 

[John Larkin]

On Fri, 19 Aug 2022 13:48:02 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 8/19/22 1:03 PM, whit3rd wrote:
On Friday, August 19, 2022 at 5:32:24 AM UTC-7, amdx wrote:
I\'m looking at buying a couple of RF voltmeters for measurements from
audio to 2MHz, mostly input output measurements.
This will be hobby use only.
I have Boonton 92EA RF meters, but they are 50? terminated with BNC
connectors. I would prefer a scope type probe, or even an
active probe with for capacitive loading. A simple active probe build
would be nice! I would like a digital display although a little ambivalent.
Any thoughts about what I should be looking for?

Why not a simple moving-needle voltmeter? Calibrated in dBm, these are easily
available (if a bit old-school).


Right, such as an HP 3400A--10x crest factor, 10 MHz bandwidth.

Cheers

Phil Hobbs

https://www.dropbox.com/s/d1js1c8nbs2ulud/HF_Ammeter.JPG?raw=1

That\'s most likely a thermocouple converter.

Mo found it at a garage sale for $5.

 

[amdx]

On 9/21/2022 3:46 PM, John Larkin wrote:

On Fri, 19 Aug 2022 13:48:02 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 8/19/22 1:03 PM, whit3rd wrote:
On Friday, August 19, 2022 at 5:32:24 AM UTC-7, amdx wrote:
I\'m looking at buying a couple of RF voltmeters for measurements from
audio to 2MHz, mostly input output measurements.
This will be hobby use only.
I have Boonton 92EA RF meters, but they are 50? terminated with BNC
connectors. I would prefer a scope type probe, or even an
active probe with for capacitive loading. A simple active probe build
would be nice! I would like a digital display although a little ambivalent.
Any thoughts about what I should be looking for?
Why not a simple moving-needle voltmeter? Calibrated in dBm, these are easily
available (if a bit old-school).

Right, such as an HP 3400A--10x crest factor, 10 MHz bandwidth.

Cheers

Phil Hobbs
https://www.dropbox.com/s/d1js1c8nbs2ulud/HF_Ammeter.JPG?raw=1

That\'s most likely a thermocouple converter.

Mo found it at a garage sale for $5.

Having a discussion on Q meters on an OI group. The Boonton 260A uses a
thermocouple to drive a meter.
 An oscillator drives one amp though the heater of the thermocouple to
a 0.02Ω resistor to get the meter to full scale.
If you set the current at 1/2 amp, that is a mutliplier so you would
double the Q reading.

https://www.dropbox.com/s/chq1r7ies4x7w6k/Boonton%20260A%20thermocouple%20meter%20driver..jpg?dl=0

 Just for more fun, I picked this from am old post of a production
engineer at Boonton back when the 260A was built, he posted about the
0.02Ω resistor.

\"The problem was with the 0.020 ohm injection resistor. It was a fired
platinum on porcelain disc construction and the value was fine tuned
with an abrasive powder. If the platinum was worn too thin, the
resistance would become inductive. That inductance would increase the
injection voltage and lead to very high Q readings especially above 20
MHz. The production procedures for measuring the flatness were lost
and/or ignored by this time- a big OOPS that was too late to remedy.

Mikek