Q1 (input) is HP 1854-0091--no "2Nxxxx" equivalent transistor listed in HP equivalent list. Q2 (output) is HP 1854-0332, again no equivalent transistor listed. Both are TO-5/TO-39 case. I think a 2N5109 is a reasonable choice for trying the circuit in the breadboard.

Steve

On 9/16/2022 10:18 PM, Tom Lee wrote:

Thanks for checking that, Steve.? Unless the 2N5109 has a surprisingly high parasitic emitter resistance, there's still about a 10x gap to be closed.

--Tom

-- 
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070

On 9/16/2022 22:14, Steve Ratzlaff wrote:

And the output capacitor I used was 100 uF/25 volts, with measured 100 kHz ESR of 0.26 ohms.

Steve

On 9/16/2022 10:00 PM, Steve Ratzlaff via groups.io wrote:

As noted, first test was at -40 dBm. I raised the level just now to max, -17 dBm--very little change from before--the output impedance decreased about 0.03 ohms for each frequency.

Steve

On 9/16/2022 8:55 PM, Tom Lee wrote:

Those numbers have a believable trend, but the magnitudes seem too high. I don't know what the parasitic emitter resistance is of a 2N5109, but I would be surprised if it were bigger than an ohm. The output capacitor's ESR adds to that, of course, but a good cap shouldn't have several ohms of ESR. So, if you include realistic parasitics, the output resistance should be an ohm or less. The milliohms number I gave earlier is the ideal value you would get in the limit of no parasitics.

How large an excitation are you using to probe the output Z?

Tom

-- 
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070

On 9/16/2022 19:48, Steve Ratzlaff wrote:

I breadboarded the circuit just now using 2N5109's and swept the output Z with the DG8SAQ VNWA, 10 kHz-30 MHz. The circuit draws 117 mA; the output transistor draws 84 mA. The output impedance is mostly flat, gradually rising after about 10 MHz.

50 kHz 4.23 ohms

1 MHz 4.42 ohms

10 MHz 5.27 ohms

20 MHz 6.80 ohms

30 MHz 8.77 ohms

Steve AA7U

On 9/16/2022 5:44 PM, Mikek wrote:

Someone sent me a private messaged and corrected me on the output impedance of the 50 to 1 transformer,
it is 0.001Ω or 1 milliΩ. So, impedance ratio of 2500 x -.001 = 2.5Ω primary impedance. I'm not sure I know how to figure the output impedance of the
power amp in the HP4342A, I would have thought 220Ω.
I'm posting the schematic of the impedance converter the drives the injection transformer primary and asking,

What is the output impedance of the impedance converter?

????????????????? Thanks, Mikek