Sunday, May 13, 2007

Progress on the 80m challenge transmitter

Finally making progress on the NSW Home Brew group's 80m challenge project to build a 20W 80m AM transmitter.

I'm a bit daunted as I have never made anything that puts out more than about 500mW and have very little RF experience, but progress is finally being made.

A design has been cobbled together based on the Hendricks QRP TwoFer design, built for 80m.

So far I have the oscillator and a buffer stage running nicely and I'm looking for an RF power transistor to get to 2W. I can't seem to source a 2N2553 or 2SC799 so I've ordered from the U.S. but disappointingly they say it won't ship for up to 3 weeks.

The smoke from an MPF102 was released along the way due to wiring it in reverse.

In other news, I picked up 20m of RG213U co-ax from the MWRS at a great price. I've run this through a hole, up between the double brick walls, through the ceiling and to my newly stretched out 40/80m dipole upstairs.

Reception is great but when I transmit all hell breaks loose from RF getting into audio amplifiers. Once again, my long wire antenna looks like being the most practical transmitting system here.


Anonymous said...

could I please buy this 80m transmitter on am from your country ?.

Peter Marks said...

Richard, you are a man of simple taste!