[Milsurplus] Waveforms for Oscillator "Booster" in WECO 227B

[Bob Camp]

Hi

Keep in mind that most of the transistor adaptations of these circuits had pretty poor reliability. They spent a lot of time figuring out how to modify things like transformers so that solid state stuff would be happy. This is not as simple a project as it might seem.

Bob

> On Nov 10, 2014, at 8:01 PM, David Stinson <arc5 at ix.netcom.com> wrote:
> 
> I was asked about waveforms of the simple "oscillator booster" I'm using in the WECO 227B.
> 
> Sorry the MOSFET Gate waveform photo is bad.
> I needed one hand to hold the scope probe, one to
> hold the camera and one to key the PTT...
> 
> Here's the circuit again as a reminder:
> http://home.netcom.com/~arc5/oscbrd.jpg
> http://home.netcom.com/~arc5/oscbrdtop.jpg
> 
> Before we start talking about improving my primative thingie, remember the goal:  a cheap,
> simple and effective replacement when one doesn't
> have a crystal.  "Efficient" is not a priority.
> If it works without blowing itself up (or something else),
> I count it "good."  The thing can be improved many ways,
> but if we start adding too much we defeat the whole idea.
> 
> I don't think my scope is properly calibrated on the 10 V per division scale.  It says the input waveform is
> 10 V PTP but my supply rail is 5.5 V?
> 
> The GATE waveform is nasty.  I'm guessing
> at what the points I noted mean.  And you can see a little high-freq parasitic just like Arden said there would be, but it's pretty low level and happening
> while the MOSFET is not conducting.
> http://home.netcom.com/~arc5/GATE.JPG
> 
> Here's the waveform that appears at the 6L6 grid.
> The grid resistor is 100K.
> My scale ends at 60 VPTP and my 10:1 probe is busted so I'm estimating this waveform at 80V PTP:
> http://home.netcom.com/~arc5/PAGRID.JPG
> There's a series cap-inductor in the grid circuit
> which goes over toward the Modulator.
> Don't know why;  I still don't have a diagram.
> Maybe it's ringing?  But the inductor looks more like an RFC.  The cap is 50 pFd.
> Aside:  The little HC-25s work well in a lot of things, but won't oscillate in this circuit.
> They work OK in the receiver oscillator.
> 
> Here's the output at the antenna connection:
> http://home.netcom.com/~arc5/PAOUT.JPG
> Power out was 8 watts into 50 ohms resistive.
> 
> 73 DE Dave AB5S
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