The AM Forum

Wayne WA1SSJ just completed a new 450 Watt (carrier) Pulse Width Modulator /Power Supply for his transmitter.  Wayne completed the RF amplifier a few years ago.  Wayne had been using an analog modulator (with the existing RF amplifier from a few years ago), but built this one because it is considerably more efficient and is a lead-in for a more powerful unit in the future.

This modulator / power supply uses 3 IRFP260N MOSFETs in the modulator output section, mounted on a small heat sink.

Wayne is a superb builder, and takes great care to properly lay out front panels as well as the internals (as the pictures show).

Also shown is the resulting modulation waveform of a 250 cycle triangle wave.  The action of the negative peak limiter (set to around 90%) is clearly visible in the modulation display, as well as the perfect rendering of the triangular waveform in the modulation pattern.

Please excuse the poor pictures.  I used my phone, and it's not too good with pictures unless you're outside in bright sunlight.

Here is the front of the modulator / power supply.
(http://www.classeradio.com/wayne_pwm_front.jpg)

Here is the inside of the unit looking down.  The PWM generator and Overload/Efficiency board are near the front, and the PWM filter and output are visible near the back.
(http://www.classeradio.com/wayne_pwm_inside.jpg)

Here is a closeup of the PWM filter.  Note the filter is constructed completely using cores, reducing the filter's size considerably.   This can be done at the kW level as well.
(http://www.classeradio.com/wayne_pwm_filter.jpg)

Here is the resultant modulation display of the modulator modulating a 450 watt carrier class E RF deck with a triangle wave.
(http://www.classeradio.com/wayne_pwm_waveforms.jpg)

Some really great looking work.  Wayne does do a great job with HB projects.

Something to note is the total power input to the modulator is shown by the 2 meters on the left.  The input voltage is 130V and the input current is 3.5A or 455 W.

The meters on the right show the output voltage and current.  The output voltage is 45V and the output current is 9.7A, or 436.5 W.

The efficiency of the modulator is 96% (95.9% to be exact).  This is typical for good pulse width modulators.

And it sounds great too.  Ran into QIX Steve testing out this modulator on Sat. on 3885 khz and we had a nice chat.  Great audio and big signal as usual. Very nice piece of work.
73s  Nigel

Wayne is an artist.

It's nice when a plan comes together. Metal work and layout and wiring, out of this world.

It is a work of art. I imagine the one clip lead in the picture is simply there in honor of your visit, Steve.

This should be an inspiration to us all! bill

Impressive work Wayne.  Steve, thanks for posting.

So Wayne's modulator is actually at my shack, so there are clip leads pretty much everywhere  ;)  The neat, organized construction is certainly an anomaly in my shack.

I should take a picture of the RF deck that I've got hooked up to the modulator.  I built that one (and it definitely does not resemble Wayne's construction in any way!).

Wayne built me a VFO a couple of years ago.  It looks like a commercial, factory produced piece of equipment.  I'll take some pics at some point and post them.

I had always heard great things about Wayne's homebrew work, but frankly had no idea the attention to detail until I saw those photos.  Countersinking all of the flat head screws and even engraving the lettering on the front panel.  Then the well-thought-out component layout.  A far cry from what I do for sure!  Wayne is incredible!

And I've never heard Wayne bragging about his own work either, although if he did it would be perfectly justified. 

Unfortunately Wayne will never read these compliments online because he is averse to computers.  Hopefully someone will print out this thread so he can read it on paper.

Thanks for posting that, Steve.

Eric

Wayne makes beautiful stuff. After the Henniker 'fest in 2007 he invited the AM crew over to his place. I remember seeing his 4-400 rig and was amazed not only at the construction quality, but also by the front panel: no labels, decals, tags, all engraved. Talk about looking 'factory'.

He also shared a story with us about meeting his wife, and how she was one of the Collins girls, building S-Lines and/or KWM-2s back in the day. Some guys get all the luck.  ;D

Yeah, and she's smart, really pretty, a good cook and just a nice person in general !

So how did she meet Wayne then?   ;D ;D ;D

Actually I think Wayne does look at a copuker on occasion....Fran allows it! 

Todd I was at that party....it was the first time I saw his work up close.   I felt bad....realizing the crap I build in comparison.   8) 8) 8)

We may need to do an intervention to get his antenna back up....then we should go north to the home of that K1REC guy. ::)

~ps