The Project Gamma ( http://www.k6if.com/ssamp ) team is pleased to announce
that the V2 output filter board has passed initial qualification testing
with flying colors. This board is designed to provide harmonic attenuation
for our open source 1500 watt solid state HF amplifier design (or any
similar design that you may be working on :-) ).
You may recall that the R1 board was based on Helge Granberg's design as
published in QST, and that that design had over-heating issues in our high
power testing. The R2 board is based on the diplexer filter design
published in QEX by William Sabin, W0IYH and adapted by Steve Friis, WM5Z.
The team modified the diplexer components for 1500 watt contest use and
designed a new PCB to house all six filters on one board. Key contributors
included W3NQN and N6RCE.
Qualification testing began with insertion loss, SWR and harmonic
attenuation tests using an HP vector network analyzer. This was followed by
high power testing at 1500 watts at a 50% duty cycle (key down dits at high
speed) for an extended period, and 100 watts at two bands above the
fundamental at a 50% duty cycle (to check the high pass section). Results
were excellent. While final acceptance testing will have to wait for the
rest of the amplifier to be completed, we are confident that this design
will meet or exceed our requirements.
All elements of the Project Gamma design are or will be available to the
public. The board design, parts list, and VNA test output can be found at
http://www.k6if.com/ssamp/ - follow the link on the left to the output
filter section. Boards are available at our cost - email me for details, or
you are welcome to order them from PCBExpress directly using our design
file. Detailed assembly instructions will be forthcoming once a few more
boards have been built.
Photos of the R2 board in various stages on completion can be found at
http://www.k6if.com/Gallery1/diplexer .
Various members of this list have assisted in the development of these
filters, and we thank each of them for their thoughtful input.
If you are interested in contributing to Project Gamma, we are always
looking for new members of the team. See our web site for details, or drop
me an email.
The Project Gamma Team
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