A question showing my ignorance.

illegible

The rest of us have dumped dropbox.

NT

Huh? Perfectly legible here.

Having my own website, I don't have a need for such as dropbox... My website only costs me $4.99/month. ...Jim Thompson

V301 is a cathode-follower rectifier.

And then what do you use? Mikek

OK great, I have a legible schematic that you can zoom in on to read. How are they using a DC meter in a circuit I think would be delivering AC. It is obviously working, so, what don't I understand about the circuit?

Thanks, Mikek

And the gate is modulated with an AC signal of 8mv to 20mv. So, why don't I have an AC signal on the cathode that then drives the meter.

I might be in a situation where the answer is so obvious, the question is so far below your level of thinking that it is not understood.

Note: A coil goes where it says coil, this is resonated by C201. Series resonance.

I use several hosted sites. They're all a semi-organized mess but good enough for posting images and documents of all flavors. I build the web site on my home computah, and upload any changes to the real web site. The major problem is keeping the two properly synchronized.

For my personal hosting dumpster, I use 1&1

For images, I use an old version of JAlbum:

For file transfers, I use WinSCP:

For backup and replication, I use WinHTTrack:

For building web pages, I use Amaya: Development seems to have stopped in 2012, so I'm looking for a replacement.

There are probably better and more up to date tools and services available. I just use whatever worked at the time I needed it and stayed with it as long as it continued to work.

Note that the semi-organized mess is very portable and can easily be moved between hosting providers. I haven't had to do this for my mess, but have moved friends and customers (the only difference is that the customers pay me) to other providers without drama. Don't get locked into a proprietarized presentation and CMS (content management system) from a single provider.

Tim

-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website:

Gotcha beat for ancient... I use FrontPage Editor v3.0.2.926

Works just fine since I don't need any fancy-pansy features. ...Jim Thompson

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I'm looking for work... see my website.

'Gate' in tube parlance is 'grid'.

Did you notice the 0.1 uF bypass capacitor from the cathode line to ground?

Thank you Tim, So now as I understand it, "the device (tube) is biased almost completely off" only one side of the AC signal on the grid pushes the tube into conduction. The half wave pulsed output is smoothed by C301 a

You sir are a gentleman and a scholar, you have my undying gratitude.

Mikek

PS. My plan was to double the FS voltage of the meter, in my quest to measure Q's over 625, the limit of the Boonton 260A. I'm hoping to measure up to 1250. The meter has an internal resistance of 1,210 ohms. I paralleled it with a 1,210 ohm resistor and then added a series 605 ohm resistor to keep the same resistance in the circuit hopefully keeping the circuit aligned. This messed up the linearity when adjusting the input drive. A drive voltage of 13.33mv gives a Q of 325. A drive voltage of 8mv gives a Q of 388. Without the meter modification, the Q's read the same. Seems odd. Removing the series resistor didn't solve the problem. I did this with 4-9" wires run out to a switch, so I could have a normal and a times two setting. I don't see how the wires could affect linearity with a dc circuit. Maybe the filtering is not as good as I thought.

Yep.

Mikek

There's a bypass cap from the cathode to ground.

(It's not a gate, it's a grid!)

The tube is a peak detector at high amplitudes. At low level, the grid nonlinearity makes some DC output, sort of a diode square-law detector. The advantage of the cathode-follower detector is that it minimally loads the series LC, which loading would kill the Q.

The voltage at the grid is the voltage across R202 times the Q, so it's likely to be substantial at higher Qs.

I made my own Q-meter: a signal generator drives a low value resistor, then the series LC, then a super-low-capacitance sampling scope probe.

This unit test Q with a series circuit. Tt is my understanding that the maximum voltage across R202 is 20mv. That is one amp of current. There are several warnings to not exceed that. 20mv is 1 on the multiplier meter, to measure higher Q's, you reduce the voltage on R202 to 10mv for a 2 times multiplier and 8mv for a 2.5 times multiplier.

I may end up using my scope and 3db points, but certainly would like to get my Boonton configured to measure much higher Qs. My 6-5/8" dia x 6 " inductors would not fit very well on your circuit board. I need to stay 2ft away just to not affect the Q.

Mikek

Tinypic, flickr, picturehosting.com,

NT

M201 reads a thermocouple that is heated by the AC.

M301 is in series with the cathode ov V301, so also gets DC.

Jon

You didn't say which meter is confusing you.

M201 is measuring the voltage on a thermocouple, which is heated proportionally to the RMS voltage on R202 -- it probably IS heated by R202, but it could have an internal resistor.

M301 is measuring the rectified voltage on the cathode of V301, per John Larkin's comments.

Oh, sorry it was the Q meter.

Yes, I didn't understand the rectification, but it has been explained. Although if you read my post where I got understanding, the bottom part explains another problem I don't understand. I have a feeling any gurus would need a little more understanding of how operate a Boonton 260A in order to give insight on my question.

I've used one of those, back when I was in EE school. It was ancient even then!