[time-nuts] Advice on 10 MHz isolation/distribution

[life speed]

Date: Fri, 12 Feb 2010 15:32:55 -0500
From: Bob Camp <lists at cq.nu>
Subject: Re: [time-nuts] Advice on 10 MHz isolation/distribution

Hi

There are a few differences between what you are simulating and the schematics Bruce posted earlier. The collectors of the input stages (q1, q4 and q7) seem have to come unglued from the bases of the output stages. The 95 ohm / 100 nf roll off networks seem to have vanished from the emitters of Q1 and Q7. There are  a few other minor things. 

I suspect that once you get it back to a node-node feedback circuit, the impedance at the splitting point will drop and the isolation will go up quite a bit.

Bob

Hi Bob,

I see I fumbled the mouse, thanks.  I had to spend a couple days working on other parts of the design, but I am back at the 10 MHz circuit again.  I don't see the RC networks in the emitters of Q1, Q7 in the original schematic (design 3), although I tried them and also with a 1.6K ohm resistor and did not see much difference.

I notice that the gain of 2 (6 dB voltage gain) happens in the first stage, and the second stages seem to have an equal amount of loss, which is a reasonable outcome for buffer/isolator circuit.

The isolation, while improved, seems to be only 50 dB from Vout_1 to Vout_2.  To make this circuit really effective, I think I would have to parallel two Q4/Q1 two-stage amps.  Either that, or there are still some mistakes.

Clay


      
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