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Kamikaze · #65 01-10-2011, 03:23 PM

Quote:

Originally Posted by VA3ES

Interesting observation. I completely overlooked that aspect. Now why would the neg. cycle load resistor affect NFB, when that resistor is not in circuit except during neg. cycle cut-off?

The final's load and the negative cycle load are in parallel. The negative cycle loading is there throughout the neg cycle. The postive cycle only sees the final's load.

Quote:

Positive opeak stretching can only go so far before you start to overload simple diode detectors. I believe that a simple diode detector will start to distort at about ~130-140% positive. (Thus the broadcast standard of maximum 125% positive.)

Common diode detectors start distorting above 30%. They really fall apart above 125%. Some distortion is tolerated as a tradeoff for improved SNR.

Quote:

Timtron (Tim, WA1HLR) has promoted the concept of "Turbo-modulation", where the standard mod transformers in Heath and Johnson rigs are rewired as an autotransfomer. He claims 120% positive peaks with this mod. Having several DX-100's and Apaches, I haven't tried it.

Timtron knows what he's doing. The "turbo" connection for mod transformers along with inverse feedback to make the modulators act more like triodes as far as load impedance really wakes those rigs up.

479tx · #66 02-13-2013, 06:43 AM

Quote:

Originally Posted by Toll_Free

If you REALLY want to increase the complete talk-power on those units (I've been working with the 858 Unidens and the processors / clippers in them for about 25 years), add a diode or two to the POSITIVE side. This will still allow for some amount of clipping (good), but will INCREASE the positive side.

OR, keep a SILICON rectifier diode on the positive side, and a germanium or shottkey on the negative side. I did just this in a Lou Franklin clipper, and it make it about twice as loud: Not bad when you consider the processor gets the same compliments by itself!

--Toll_Free

I have a TRC-457. I'm interested in the two mods above to the diode pair/clipper that comes stock. What net effect would adding a diode or two in series with d21 (positive side on my radio) or replacing the stock diode @ d22 (negative side) with a schottky have? I assume you'd create favorable conditions for higher positive peaks while still keeping the negative peaks in check? (Asymmetric modulation instead of ~100%)

Anyone try this on an 858 radio's clipper? I have a schottky diode sitting right here...

scorpion · #67 02-14-2013, 05:51 PM

What is this supposed to do in the radio
if you don't mind me asking and would this
work in a Texas Ranger 936ffc.

longhaireddwb · #68 02-19-2013, 09:02 PM

I finally remembered about this mod and built the circuit on a perf board. Hooked it up in a Cobra 25 on the D10 diode (anti-spike), ran the ground and B+ and it did nothing more to my audio as herd from others around town. Not louder, not more.
Its possible I did something wrong but this is so simple I know I didn't do it wrong.

Whats up with this?

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