Author Topic: How a classic diode ring mixer works  (Read 3947 times)

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Offline w2aew

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How a classic diode ring mixer works
« on: August 14, 2014, 12:01:27 am »
My latest video describes how a classic, double-balanced, diode-ring mixer operates.  The basic theory is presented, along with a circuit description and measurements on the bench.

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Offline bobcat

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Re: How a classic diode ring mixer works
« Reply #1 on: August 14, 2014, 03:00:43 pm »
Nice simple explanation of the basic function. Thanks---
 

Offline retrolefty

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Re: How a classic diode ring mixer works
« Reply #2 on: August 14, 2014, 06:27:36 pm »
Can't underestimate your statement about impedance matching requirements (on all three ports to some degree) to reach best rated performance of such passive mixers.

 

Offline Dongulus

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Re: How a classic diode ring mixer works
« Reply #3 on: August 14, 2014, 06:59:11 pm »
Thanks

I've always been completely mystified whenever I've looked a mixer circuit, now I'm not.
 

Offline Odysseus

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Re: How a classic diode ring mixer works
« Reply #4 on: August 18, 2014, 06:23:57 am »
Great video, just like the rest, as I've discovered! Seriously, watching your channel was all I did this weekend.
I had seen the diode ring mixer schematic and the use of diodes as switches before, but now it really clicks for me.

I'm curious about the feed-through / isolation characteristics of the diode ring mixer.  Seems to me that mismatch in forward voltage of the diodes would manifest itself as increased feed-through of the LO.  I've also seen schematics where the center tapped port is used as an input.  I wonder what advantages/disadvantages that has in a practical circuit.
« Last Edit: August 18, 2014, 06:27:32 am by Odysseus »
 

Offline T3sl4co1l

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Re: How a classic diode ring mixer works
« Reply #5 on: August 18, 2014, 06:38:02 am »
The ports are all symmetrical, but if it's transformer coupled, you obviously can't get DC out the two transformers, but you can between the CTs.  For BFO type SSB detection, you'd want the BFO on one transformer, IF on the other, and audio comes from the center taps.

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Offline idpromnut

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Re: How a classic diode ring mixer works
« Reply #6 on: December 12, 2014, 04:10:33 pm »
Excellent video, as always!  :-+

One question that popped up for me was how you choose the number of windings for the transformers? Is there some extra material you can link that helps explain that part? I can understand that if I wanted to adjust this mixer design for a different frequency range, that I would need to adjust the diodes used, but how would I go about figuring out what I need to change in terms of the transformers?

Thanks again!
 

Offline w2aew

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Re: How a classic diode ring mixer works
« Reply #7 on: December 12, 2014, 05:16:48 pm »
Excellent video, as always!  :-+

One question that popped up for me was how you choose the number of windings for the transformers? Is there some extra material you can link that helps explain that part? I can understand that if I wanted to adjust this mixer design for a different frequency range, that I would need to adjust the diodes used, but how would I go about figuring out what I need to change in terms of the transformers?

Thanks again!

Most broadband RF transformers for MF/HF bands are made using ferrite cores because the high permeability means that fewer turns are needed.  This makes it easier to wind several wires on the same core, and minimizes problems with resonant problems in the windings.  A good rule of thumb is to make the inductive reactance of the windings be 4-5x the impedance of the circuit that they're being used in.
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YouTube channel: https://www.youtube.com/w2aew
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