The AM Forum

Clip Lead Alley strikes again  ;D

This is a low power (about 80 watts in this example), simple class E transmitter using a class H modulator.

The design is easily extensible to 225 watts by adding MOSFETs to the modulator and RF amplifier.  The transmitter will function well at as low as 10 watts output, if this is needed for a linear amplifier.

The class H modulator is capable of 200% positive modulation, and includes a negative peak limiter.  The RF amplifier features a single tuned circuit (drive is digital), and covers 160 through 40 meters.  Much smaller RF components may be used - these are what I had lying around the shack, so I used them.

Here is the modulator schematic:
(http://www.classeradio.com/easy_class_h.jpg)

The overall modulator, as built:
(http://www.classeradio.com/easy_h_1.jpg)

A closeup of the modulator itself:
(http://www.classeradio.com/easy_h_2.jpg)

And, the RF amplifier:
(http://www.classeradio.com/easy_h_3.jpg)

Steve

DON'T SNEEZE!   ;D

 :o  ::)  ;D  ;D

It sounds much better than it looks.

I have had bad luck with those clip leads. They look like Radio Shack ones. The crimp connections cannot be trusted.

Great idea coming up with a power level where the xmtr can directly substitute for a ricebox.

The Radio Shack clip leads have morphed over the years.  The old ones were crimped, and in order to use them successfully, had to be soldered (which I did every time I bought a pack).  But, recently, RatShack has been using a different clip lead supplier... and they ARE (or were) soldered!  But, I do always check - because like your experience, I've had bad connections in clip leads cause problems.

Great!

JUST what I've been looking for.   ;D

Thanks for posting it Steve.

Good gawd, man!  Have you no shame?...  :o   ;D


(I want the finished circuit to build as my next project)


Can the exisiting H-modulator board be used for this without much trouble?  I understand the RF section will need to be point-point based on our conversation?

T

Steve, I'm speechless...

As Dave said, it certainly does sound excellent. Hey, I was only kidding yesterday when I said to have those plans on my desk by today. Hope you didn't stay up all night taking pictures and drawing up the schematic!

That does look like a very slick way for someone without a lot of solid state experience (who has been procrastinating) to give the FET design a try. A board kit would make it a done deal! I love the fact that it will do 160m - 40m too!

73,

Rob

Hi Tom,

The existing class H implementation is *completely* different, from soup to nuts. 

I need to add a couple more "features" to this one for completion.  One important feature is an overload detect, but I want a no-brain variant of my existing overload shutdown, with a low parts count and an easy adjustment to set up.

The idea of the project is simplicity.  Whether I can keep it that way is the challenge  :D

Steve,
Your clip lead specials amaze me! 

Have you thought about a PDM version?  As your well aware, they are not that complex. 

It would be a great starter kit for those that have never built much before. 

Joe, GMS

Looks like I'll need more clip leads!

Hi Joe,

Well, there were several reasons I went with analog for this simple kit  ;)

The biggest reason is the wide range of power.  With this setup, one can load the RF amplifier from less than 1 amp, to up to 3 amperes (with one MOSFET in each portion of the modulator), and the modulator is perfectly content.

The circuit is very simple.  A lot of components required for a PWM implementation are not necessary (such as an input filter).

This one is very easy to debug with DC instruments.

And since the circuitry is all analog, it is very forgiving with respect to construction techniques.

Of course the advantage of PWM is a lower weight, no power transformer (if an off-line design is used), and greater efficiency  8)   This is the only analog transmitter I've got at the moment.  Everything else I use is PWM, but of course all of those other transmitters run a lot more power, so PWM is really the only way to go.

And of course, analog signals travel over clip leads much better than do digital signals  ;D ;) :) :D

Regards,

Steve

Those clip leads are making me hungry looking like tri-colored pasta  ;D

How do you remember what you are clipped to?

And here I was thinking that my bench was too messy and I should clean it off ( amounting to sweeping it into a cardboard box with my forearm). Welp. Guess I wont now!

Steve ,
That conglomeration hasn't changed very much. Maybe 15 more clip leads.
And on your thread about sub-woofers........While we have you here.........Why do you need to hear or feel audio down to 10hz?..........HUH?

Fred

clip leads are an art. You really have to understand current loops to get away with it.

My wife got a bigger kick out of these pics than I did.

My stuff does not look so bad anymore and I had to tell her that you are smarter than I.

I keep telling her that the amount spaghetti is directly proportional to genius.

js

Steve, I gather you are getting ready to win the clip lead category in the Feb. 6 rally.  Congratulations I think the award should be given now--why wait hi hi.

Can't wait to hear the new rig and if there were ever a RIG, this is IT  ;D

73

Rob

STEVE!!!

Please please please don't design anything with quad TL074 chips!!

At least go with a 5532/5534 family??  Singles or duals??
Many many potential subs vs. almost none??

Not to mention the new ultra ultra low distortion chips from National and LT??

Please?

:D

               _-_-bear

I've got a pretty nice overload shutdown circuit going.  Although this adds some parts, it is a very important feature.  I'll document the changes when I'm not so tired  ::)

I built this whole thing point to point, clip leads and dead bug.  But, I think a PC board is in order to facilitate construction.

It would be reasonable to make the board accept up to 3 MOSFETs in each class H bank, for up to 225 watts of power input.  Configuring the board with 2 MOSFETs in each bank will give you 150 watts in, and a single in each will give you up to 75 watts dc input to the final.

Makes a nice DX100/Apache/Valiant power level transmitter.

Above 225 watts? Use PWM  ;D

Regards,

Steve

Hey Steve,

Great idea,  and nice implementation,  as usual.  Am buying more 'Cliplead Futures" !

73  Vic

Steve,
I put a LED in series with the NPL transistor collector so it flashes when the npl is turned on. I mounted the LED on the front panel of the modulator as a monitor.
It could also go in the base circuit if you need more than 10 ma of NPL current.

Steve do you think one could stuff one of your overload shutdown circuit cards into a K7dyy box???? Thaht might be the answer to the class D issues.

It would work....

Of course you'd have to have a power supply... That's isolated from the rest of the DYY circuitry. Not even a ground...

And find the right traces on the DYY board to cut, to route the Modulated DC through the overload board..
Maybe there is already a jumper? going from the modulator section to the final FETs?

May be a little tricky, since almost all the circuitry in the DYY is floating.. (which is probably the root cause of some failures)

But I bet it can be done   ;D

Hummmm I wonder if a isolation transformer can be shoe horned into the box... Well if I could figure out how to reduct the size of a Class E into one box, I'd just try that.

Yes, it's been done a number of times  :)   The goal of this project is to do a compact, one box transmitter.  I did it with the 500 watt "class E ranger" transmitter - and that included EVERYTHING, power supply, VFO, etc!

Steve you would not have a pic of the insides of such a beast to share would you. If I can find a case the size of a ranger and the big parts I know where I can get the boards and small components. By the way I'm real corfused on wether to use H moders or PWM for 350W and above.

There are a couple of ways to go.   For the ultimate compact transmitter, I used PWM (and still do).  It is MUCH smaller if you use the correct design.  I have a complete power supply - modulator 450 watts modulated DC that fits in a 7 inch high, 7 inch deep 19 inch space.  That's the complete modulator-power supply.  No power transformer.  This one uses a direct line rectification (and it is isolated using pulse transformers) design.  This is what was done with the class E ranger.  There was no space for a power transformer!

If you have a little extra space, you can add a power transformer and use a much simpler PWM design.  This modulator is well documented on the class E web site and has been reproduced a number of times.  Also talk with Bruce KF1Z, as he has built a number of PWM class E transmitters.

For class H, you will need CONSIDERABLY more heat sink area, and a much larger power supply - both with respect to the transformer(s) and the filter capacitors.  For power levels around 300 to 400 watts, class H generally takes up about twice as much space, and weighs more than twice as much as similar power pulse width modulators.  At higher power levels, class H gets even larger because the power supply requirements become quite large, and everything else grows as well.

Hope this helps  :)

Regards,

Steve

For 250-300 watts and up, use PWM...

Class H requires a larger heatsink, larger power supply (much more "stout")

PWM much more efficient.

They both preform equally well, but PWM wins out at high power for ease of construction etc...


Well, I see Steve has chimed in while I'm typing this.....

My PWM is in a 3RU (5" high)   12" deep , 17" wide (inside space)  box.
That's power supply and all. WITH a transformer  :D
It's good for approx 320 watts out to the RF deck.. Limited by my too-small toroid power transformer,,, could be 400-450 with a bigger one in there...


With Steve's new "Easy-H", The modulator/power supply, AND a class-E RF output stage for about 120-200 watts will EASILY fit in a  box the same size as my modulator alone.
Though maybe needs to be a 4RU box, just due to the heatsink mounted board's "circumference" with devices installed, and the height of the inexpensive power transformer that Steve has made available....

Haven't actually built one YET, because I don't have a board    :'(

So as I digest this I should for a 300-400w class E plan on the PWM moder and possibly plan on using a transformer. That would put the moder powersupply and all components in a single box. From that point I would then have to build the powersupply and rf deck into the same box. That puts both powersupplies into the same box. Would I need to shield the RF side from the moder side? Starting to look like maybe a VKII size box to do this.

What is a good source for the box? Thanks

There is only one "large" power supply, and then a couple low-voltage supplies.
(think of the modulator as a modulated power supply)

Yes, you will need a transformer, but a toroid doesn't take up too much room (3" tall, 6" diameter MAX)

Yes, a shield between the RF side, and the modulator side will be needed.

Try here..... lots of options... cheapest I've found..

http://par-metal.com/

I bet a VKII case with a new front panel painted Johnson Purple would look kewl with the metering VFO and flashie lights on the front and I bet it would fit as well. Just have to find some metal to make a front panel and cover the bottom of a carcus. Cut the back out for the heat plate and heat sink. Hummm I'm going hunting.

Might become the VKIV. I have never worked with solid state and my layout ability has alot to be desired. We'll see