QRP

[K9ACT]

Not sure where to post this but as I am not committed to Class E (D might do just as well), I will put it here.

I have my PDM generator up and running and am ready to move on. However as I am only at the Cub level of achievement and understanding, I want to keep it simple. Pondering 18" rack sections filled with stuff is rather intimidating. When I started out as a homebrewer it was a progressive process, one tube, 2 tubes, CW then AM, QRP to QRO.... you get the idea.

There has to be an easier entry than leaving a few FETS and diodes out of a rack full to get one's feet wet.

Can someone point me to or whip up a simple design for a 5 or 10W modulator and RF deck?

In addition to the PDM gen I have some 11n90's, IRF510's and DD414's thinking I could work something up myself but am hopelessly over my paygrade.

js

[G4CPV]

Hi,

Check out Dave's page http://www.shortwaveradio.co.uk/fat5_nov2009.htm. Cheap as chips FET's up to 100W.

Bob
G4CPV

[K9ACT]

Hi,

Check out Dave's page http://www.shortwaveradio.co.uk/fat5_nov2009.htm. Cheap as chips FET's up to 100W.

Bob
G4CPV

Some really neat projects there but as near as I can tell, it is not PWM which is what I am trying to get a handle on in a small way.

js

[kf1z]

Jack,

About the simplest thing that I am aware of is the K7DYY stuff.

But, still not the power level or simplicity I think you're looking for.


You've built, or almost built the PWM anyway... why not just use it?

No one says you have to drive a 400 watt carrier rig with it.

As a matter of fact, I used to run mine in "tune" posistion 80% of the time. (70 or so watts carrier)

By the time you go through all the work, and expence, you've done almost as much to get 20 watts, as you would to get 200-400 watts.


If you want to start "light", just build a smaller RF deck, and plan your PWM filter accordingly to mach the impedance the "QRP" deck is designed around.

Maybe something like Jay W1VD's 100 watt class-D RF deck.

The problem with really simple PWM designs, is that the things that are left out to make it simple, are the safety factors!

[Gilly]

Hi Jack

This is a photo of my 160M TX....



It is a baby compared to others here on the forum....but in Australia we are only allowed 120Watts carrier..
I have settled on IRF840 fets and use from in all my TX's......
Although have changed the VFO the TX is unchanged and is reliable....
Looking at it ..... its far from complex.....the minimum level is about 50Watts up to well have only pushed it to 150Watts....

You will be happy having decided to build Steves PWM ... you just don't realize it yet and going by your pictures is going well....


Hope this helps ...


Wayne

[kf1z]

Hi,

Check out Dave's page http://www.shortwaveradio.co.uk/fat5_nov2009.htm. Cheap as chips FET's up to 100W.

Bob
G4CPV

I had looked at Dave's page a while back... maybe last year....

Thanks for reminding me to go look again!

I've had a couple email exchanges with him, and they have kits available now, which is very cool.

I'll be sure to start a thread on the FAT5 when the bits and pieces arrive.

Always love a new project!

Bruce
kf1z