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Re: Making a Q-meter /

 

Thanks for the combined schematic - hard to follow flipping through pages of a PDf.

The input impedance of the Impedance converter is 50 ¦¸ (R1, R2, R3 in parallel). The steps of the attenuator would be sized to present 50 ohms at it;s input regardless of the range switch settings.

Q3 & Q4 of the power amp are identical circuitry to the impedance already analyzed to have a very lot output Z, so I would expect to see a 50 ¦¸ resistor between the emitter of Q4 and J1 to make the power amp output match the input Z of the attenuator.

John KK6IL

On 9/18/2022 10:53 AM, Mikek wrote:
On Sat, Sep 17, 2022 at 03:06 PM, MAX wrote:
The output impedance of an emitter follower is the source impedance
driving the base divided by the current gain of the transistor plus
one.? This value is in parallel with any resistors that may be
connected to the emitter either DC or AC coupled.? So it goes back
to the impedance of the generator that is connected to J6.
For those playing along, Here is a drop box schematic put together from the Oscillator to the injection transformer. I was thinking it may help to see the impedances.
I don't have a clue what the attenuator does to the output impedance of the RF Power Amplifier.
?If I got something wrong notify me, and I'll correct it.
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