New plans for the RFzero

When I bought the RFzero my plan was to use it for a beacon on 8M (40MHz) band but after doing some reading online I decided agaisnt it, plus sourcing a decent amplifier to boost the 13dBm that gave me a few watts was hard to find for this band and making one having to experiment with low pass filtering without the test gear wasn't a option either.

Then I thought, "what I'm I going to do with it?"

Reading the FULL licence document I realised that we can run a 70MHz personal beacon "subject to your interpretion of the jargon". Well that was going to be the new purpose of the RFzero.

Still the output is very low and I still needed a way of increasing it alittle. I searched the internet for some time looking at "70Mhz", "QRP amplifiers" as key words into my search list. I finally came across a circuit that M0DTS made for his 71MHz DATV transmitter that gives him 10watts output, which is too much for a personal beacon but looking closely at the design it consists of two stages.

The first stage is a RD06HVF1 where he is using it to give 1watt on DATV. This power level is what I'm after so I decided to order the device and set out building the board.

M0DTS 70MHz RD06 Amplifier

 

As like most of my homebrew designs, the amplifier is built on copper clad board as I can place/move components as needed and with the Saturday post landing on my doormat, a package containing the RD06HVF1 and the amplifier was finally finished!

 

With it all connected up and running off my 12v bench power supply that is limited to 1amp just to do a quick test the amplifier is working fine and I'm able to vary the output from nothing to 3watts via the 2k2 pot. This is the power levels I was after and suprised no one has developed a PCB or kit as I sure something like this would sell!

I only placed a small heatsink while I was testing the amplifier and I found anything over 250mW that small heatsink it got warm quickly, so this will definitely need bolted to a larger heatsink even though the plan for me is anything from 500mW to 1watt output. 

Please check out Rob (M0DTS) website for details on the amp plus loads of other interesting ham related  projects. 

Now all that is left is to rebox the Rfzero with the new amplifier!