The QRPp Attenuator...

As a QRP enthusiast I came to the point when I thought "how low can you go". I want to find out what is possible with an output power much lower than 5W or even below 1W. Most commercial transceivers have a low output power limit of 5W. To reduce this power without any hardware manipulation inside the TRX or by changing hidden menue parameters (...on newer TRX's) I decided to build this switchable attenuator. It is constructed as a chain of 3 seperate attenuation stages (3db, 6dB, 10dB). It is possible to switch the chain between the TRX and antenna during transmit or during transmit and receive. Furthermore the attenuated output can be used for measurements. The first intention was to use the attenuator with a YAESU FT-897. The ACC connecotr offers a permanent supply voltage pin as well as a PTT (GND on transmit). See the pictures for details. The housing is made of copper clad boards. The top cover is a sheet of alloy