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I note the MPSA18 has a HFE of 500 to 1500, will this work as the first transistor to lower output impedance even more?? FT is 100MHz. Mikek

Before I put time in making a documentation package (will take me couple of days) I would check if it is interesting for somebody -- don't want to waste my time on something nobody needs. It is

Added to: https://www.kn5l.net/Q-Meter/ New T50-2 36T measurement is a V-Meter Bandwidth Q measurement and a SimSmith model demonstrating Injection Transformer fixture loss when driven with 50ohm

Jacques, Thanks, makes sense with full scale actually being 3.0. I'm used to AC voltmeters full scale actually being 3.16 even if only marked up to 3.0. John KK6IL

Evaluating frequency range can be performed by removing DUT from Injection Transformer fixture, adding a wire between input and output of Injection Transformer fixture and evaluate output of RF

Success! Some emails ago Jacques mentioned using a capacitor divider at RF voltmeter input. It may be a requirement! https://www.kn5l.net/Q-Meter/ is updated with new RF voltmeter schematic and Q

John, The attenuator must adjust levels according to the Q range selected. To go from a Q range of 30 to 100 requires a level change of 100/30 = 3.333 Attenuation in dB = 20 * log(3.333) = 10.46 dB To

Tom, Quite so, I over-simplified the description to make it easier to visualise the oscillator circuit. PeterS??? ??? G8EZE

Nowadays, fixed attenuators are available for pennys in SMT packages. Don't know what was available in 1975, and the photos of the A3 assembly in the on-line manuals aren't clear. R2 and R4 have the

I should have noted a small nit to pick with swallop's answer: Q1 is not a variable load. It supplies the bias current for Q2. More current = higher amplitude (up to a point). That's the relationship

Thanks, I see it now. Mikek > > >

Renee got it right. Q1 is a common-base (non-inverting) amp, around which there is a positive feedback loop formed with a tapped inductor and capacitor. Q2 is a current source for biasing Q1. This

A1 Q2 operating as a grounded base oscillator.? Q1 is a variable emitter load which regulates the amplitude of oscillation, driven by the ALC control voltage from Q12 on A8. Follow the heavily

Just for fun, now that I look at the oscillator, where are the active components, I see the tuning, but what makes it oscillate? Thanks, Mike

Updated HP4342A schematic, includes ALC and Oscillator. https://www.dropbox.com/s/zsdcl5ckkt37bhy/HP4342A%20Injection%20transformer%20more%20complete%20driver%20jpg%203.jpg?dl=0

The RF Power Amplifier output level is set by detector CR1 at the input of the attenuator on board A3.? The ALC action reduces the output impedance of the PA to almost zero ohms, i.e. a constant

John, 50 ohm series input may be built into R2 attenuator input series resistor. Don't know, as attenuator resistor values are not marked. In "30 3" switch position, connection is straight through,

Yes, exactly why I did it, the schematic I'm using doesn't have them in order, Pages away from each other in fact, so I had to keep scrolling to find them, so I? put them together. For those

We have 1 GB of storage space at /g/Test-Equipment-Design-Construction/files Please upload any files you think might be interesting to others there. -- Dr. David Kirkby, Kirkby

Thanks for the combined schematic - hard to follow flipping through pages of a PDf. The input impedance of the Impedance converter is 50 Ω (R1, R2, R3 in parallel). The steps of the attenuator would