MEMBER PROJECTS


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N7WS - Wes


 2 Meter 8877 Amp

 


2 Meter KW Amp

Split Band Processor

Two-Meter 8877 Amplifier

Here are some photos of my Two-Meter 8877 amplifier based on the W6PO design.  I used this for tropo and meteor scatter and EME operation.  I did all of the metal fabrication, passivation, silver plating and panel engraving.  

Front Panel

Left Interior View

Front Inerior View

Cathode Bias Network

Bottom View

Cathode Compartment

Rear View

Left Side View

Right Side View

Top View

Two-Meter KW Amplifier

This was a Two-Meter KW amplifier using two 4CX250Bs in parallel.  To my knowledge no one had done this before; other designs were all push-pull.  The plate circuit is a stripline with an integral DC blocking capacitor.  Tuning and output coupling are via two "flapper" capacitors.  As in my 8877 amplifier, I designed and fabricated everything from scratch.


Front View


Top View

Side View

Bottom View

Input Compartment View

Plate Compartment View




Split Band Speech Processor 2nd Edition

 

In the September 1979 issue of Ham Radio Magazine, my paper, "Split-Band Speech Processor" was on the cover and was the lead article.  The processor featured an input stage that used a moderate amount of compression to maintain a more-or-less constant input to the following speech clipping circuitry.  The article was very popular and I eventually received about 200 letters from folks, literally around the world, who wanted circuit boards.  I didn't have any initially, but eventually contracted for 100 sets to be manufactured for me. 

Just after placing the order I received a set of boards from Circuit Board Specialists who had decided to sell them too.  I called the magazine editor asking for some help, since the article was copyrighted and both their logo and my callsign were on the boards.  He offered no sympathy and went on to inform me that my design was coming out in kit form from a new company named, "Radio Kit."  I learned later that Radio Kit just happened to be owned by the editor! 

Despite this "competition," I went on to sell all 100 sets and actually placed an order for and sold another 100.

Unfortunately, it turned out that the compressor Plessey Semiconductor IC that I used, while available locally, was essentially unattainable anywhere else in the world.  I wound up purchasing and reselling (at zero profit) all that I could locally and eventually purchased some directly from Plessey and sold those. 

The version in the photos was a prototype that I built for myself that has a discrete compressor with a noise gate and LED indicators for compression threshold, noise gate open and clipper overload. It also has much lower distortion than the Plessey device.  There are two circuit boards, the original unmodified clipper board is underneath and the compressor and power supply board is on top.

 Here's the link to Number 1.

 

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