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The Improved Three Diode Limiter

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Author Topic: The Improved Three Diode Limiter  (Read 2818 times)
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Posts: 1084

« on: March 05, 2005, 11:24:38 AM »

Has anyone got experience using Steve's (WA1QIX's) Improved three diode limiter? I'm thinking of adding this to my Home Brew 833's to tame the potential of excessive negative modulation. I have lots of audio power available and seem to run into over-modulation if I do not very carefully adjust the transmitter. I'm repairing my VoluMax today. It has a bad pot that tends to re-adjust the audio drive to the transmitter for me. But even after fixing that and carefully adjusting everything avoiding 100% Neg. will still be an issue. I'm wondering about the results of using the diode limiter here? Will I be able to adjust the transmitter for something like 120% positive & 99% negative? Like I said, 833's make the audio with a Peter Dahl BC-1T Mod transformer & Heising setup. I'm assuming that this circuit will work on the heising reactor just as well as the mod transformer. I'm considering this:
Any Input? Distortion issues? Explosions?

AM is Not A Hobby - It's a "Way of Life"!
Timmy, Sometime in 2007 on a Mountain Far Away..
Official Registered "Old Buzzard"
Steve W8TOW

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Posts: 367

« Reply #1 on: March 07, 2005, 08:46:06 AM »

Hi Keith,
I was using a previous version of this in my Johnson Valiant from about 1998 til 03. When this "Improved" version was offered, I modified my neg cycle loading circuit to this...I noticed a little difference over the earlier 3 diode circuit.
I could increase my AF gain from "3" to about "4.5" without clipping!
B4, it would clip and cause serious problems...of course.
The circuit drawn, can also be found in an old ER MAG, perhaps Issue  #3 or #5 offered by KD0HG, Bill....
gl es 73 steve

Always buiilding & fixing stuff. Current station is a "Old Buzzard" KW, running a pair of Taylor T-200's modulated by Taylor 203Z's; Johnson 500 / SX-101A; Globe King 400B / BC-1004; and Finally, BC-610 with SX28  CU 160m morn & 75m wkends.
73  W8TOW
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