Re: [Amps] Output Filter PCB Available for Solid State Amp

["Dr. William J. Schmidt, II" <bill@wjschmidt.com>]

A couple of comments on your filtering approach:

1.  There are better filter designs today than those published in Helge's 
paper (which he admits in his papers).  I agree the Rockwell Collins HF-80 
series amps are extremely advanced from filter design technology.  I use 
them myself... You should look into their design.

2.  I never did see a specification/ scope document on the design of the 
amp.... rather a website narrative on some things it should do or some 
designs it should or should not emulate, or technology that can be bought 
that can be cobbled into your design.  I suggest you put together a good 
solid specification document with input from the AMPS group. Then I suspect 
you will get more design help than you can stand.

3.  I suggest you incorporate the RF T/R switching and the line section 
sensing unit for FWR/REF power into the filter board.  Otherwise you will be 
building yet another board for that purpose later.

4. Breadboard your designs before you order PCBs.  It won't take more than a 
few  afternoons to do.  I don't order boards that aren't final production 
and neither should you.

5.  The SGC-500 power cube incorporates some very simple yet effective 
control circuitry.  You will glean a ton of ideas from their schematic.  I 
can send it in PDF format if you don't have it.

This is a worthy project and I'd rather not see it fail....

Sincerely,

Dr. William J. Schmidt, II  K9HZ
Trustee of the North American QRO - Central Division Club - K9ZC

Email: bill@wjschmidt.com
WebPage: www.wjschmidt.com

"If computers get too powerful, we can organize them into a committee; that 
will do them in."  -- Bradley's Bromide


----- Original Message ----- 
From: "Dan Levin" <djl@andlev.com>
To: <amps@contesting.com>
Sent: Sunday, February 13, 2005 12:57 PM
Subject: [Amps] Output Filter PCB Available for Solid State Amp


As part of our "open source" project to create a reference design for a 1500 
watt solid state amplifier ( http://www.k6if.com/ssamp/ ), we have designed 
a printed circuit board to implement Helge Granberg's six band, five pole 
Chebyshev low pass filters as shown in his QST article "MOSFET RF Power, An 
Update."  These filters are designed for use in a legal limit amplifier to 
attenuate harmonics.

The PCB is roughly 6" x 13", double sided.  We are going to have them made 
by ExpressPCB, a quality commercial fab house.  The design uses relays and 
capacitors available from Digikey, and inductors that you need to wind 
yourself.

As you might expect, the cost of a PCB like this goes down when they are 
ordered in quantity.

If you are thinking of building such an amplifier at some point, and would 
be interested in a filter board, please let me know by email.  The boards 
will cost $50 each (unless we get a bunch of folks, in which case the price 
will go down from there).  Please note: these boards are a new design, they 
have not been tested and are not guaranteed to work.  Some rework may be 
necessary.

The ExpressPCB file for the board is on the web site - see the link on the 
"Output Filters" page.  If you find any bugs or have suggestions on how to 
improve the board - I'd love to hear them too!

                         ***dan, K6IF
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