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From: Eric NO3M <no3m@no3m.net>
Message-ID: <c7ee7c98-78c6-3d45-92a0-5a2c4e700d60@no3m.net>
Date: Tue, 26 Feb 2019 07:04:43 -0500
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Subject: Re: LF: Class D current spikes
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Don't have a U3S to test with here, but the normal drive chain is:

K3 (10.137 khz out)
xvtr (137 khz out)
137 khz LPF
Doubler (trifilar xfmr, BAT41 schottky diodes)
Tuned filter (parallel coil + cap between signal and ground)
LM311P squarer (80-90mV level detect)
4013 flip-flop
MCP1404 driver (4.5A) with ability to key supply line (per G0MRF circuit)

I'm primarily interested in CW, WSPR, JT9...

CW not a problem with a constant carrier and keying the driver. Don't 
intend to run Opera but understand Jay's method of doing so.

So running the exciter at 2x excitation and WSJTx at 2x tone spacing 
works flawlessly?  Guess that's an option...

But, going back to what Rik was eluding to... a hanging driver output.  
Can anyone capture the end of the RF envelope from a U3S when running 
WSPR?  Just a thought, perhaps the RF is ending exactly at a zero 
crossing, whereas a typical PC/soundcard + exciter may not be and that 
is causing this issue.  I can't imagine anything else that would be 
different; after all the filtering and processing, my driver outputs to 
the FET gates are very clean.

73 Eric NO3M


On 2/26/19 6:18 AM, Chris Wilson wrote:
>
> Hello N1BUG,
>
> Just to add things were MUCH worst using a X2 multiplier circuit
> (Jay's). I now use an exciter frequency of X2 direct both from the
> U3S, and as of late X2 from the TS-590 into a simple squarer and use
> WSPR in the "Advanced" X2 mode to correct the WSPR tones. No issues at
> all with either. OPERA is a no no as of this time, it is a FET killer
> :)  Don't  know  why though. It would be great to get to the bottom of
> all this!
>
>