Re: [time-nuts] Advice on 10 MHz isolation/distribution
Date: Fri, 12 Feb 2010 15:32:55 -0500
From: Bob Camp lists@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
life speed wrote:
Date: Fri, 12 Feb 2010 15:32:55 -0500
From: Bob Camplists@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
Clay
Your design is subtly different from the one I posted.
The output amplifiers should have about 1K6 from the ZTX5179 emitter to
ground not the 95 ohms in series with 1k6 shunted by 100nF.
Among other effects your version will exhibit significant distortion
unless the current in the output transistors is increased.
You've also reduce R9 R10 and R12 to 10 ohms??
This significantly reduces the RF loop gain.
In particular the open loop RF gain of the ZTX5179 input device drops to
little more than unity.
They should be about 1K or so.
If you do the analysis correctly you will find that they have little
effect on the RF or low frequency noise.
My simulations indicate Vout-1 to Vout_2 is around 100dB at 10MHz with
the correct values for R9, R10 and R12.
This may be slightly optimistic.
Bruce
Clay
What's the effect of assigning the same label (Vout_2) to the outputs of
both output amplifiers as shown in your circuit schematic?
Bruce
life speed wrote:
Date: Fri, 12 Feb 2010 15:32:55 -0500
From: Bob Camplists@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
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
An easy way to make a 10 MHz distribution amplifier is the one from Stanford Research.
Manual can be find at :
http://www.thinksrs.com/downloads/man.htm
Download FS700
The schematics are in the back of the manual.
Met vriendelijke groeten
Regards
ElectronicsAndBooks@Yahoo.com
http://www.ElectronicsAndBooks.tk
Hi
Boy, that's an old circuit. I don't think I would want to try to buy the
chips in the "front end" of that amp. I also suspect the front end is a bit
noisy.
The output stuff with the 3904's looks very reproducible though. That end of
it certainly is worth looking at.
Bob
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Electronics and Books
Sent: Thursday, February 18, 2010 9:54 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Advice on 10 MHz isolation/distribution SRS FS700
An easy way to make a 10 MHz distribution amplifier is the one from Stanford
Research.
Manual can be find at :
http://www.thinksrs.com/downloads/man.htm
Download FS700
The schematics are in the back of the manual.
Met vriendelijke groeten
Regards
ElectronicsAndBooks@Yahoo.com
http://www.ElectronicsAndBooks.tk
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Using an amplifier with AGC like the MC1590 is a sure method of ensuring
high flicker phase noise and a high phase noise floor.
The emitter followers by themselves provide insufficient reverse
isolation for most applications.
Usually one requires 0dB (or perhaps more) gain so that an input preamp
with at least 6dB gain is required.
The widespread use of inductors precludes this circuit from
consideration if one wishes to avoid magnetic components.
Another issue for some applications is the relatively high dc emitter
current required by the emitter followers to produce the desired RF
output level.
For some applications this may be an issue.
Bruce
Bob Camp wrote:
Hi
Boy, that's an old circuit. I don't think I would want to try to buy the
chips in the "front end" of that amp. I also suspect the front end is a bit
noisy.
The output stuff with the 3904's looks very reproducible though. That end of
it certainly is worth looking at.
Bob
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Electronics and Books
Sent: Thursday, February 18, 2010 9:54 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Advice on 10 MHz isolation/distribution SRS FS700
An easy way to make a 10 MHz distribution amplifier is the one from Stanford
Research.
Manual can be find at :
http://www.thinksrs.com/downloads/man.htm
Download FS700
The schematics are in the back of the manual.
Met vriendelijke groeten
Regards
ElectronicsAndBooks@Yahoo.com
http://www.ElectronicsAndBooks.tk
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.