Multi-Rock II VFO

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The Multi-Rock II is an addition to the RAT5 receiver. It is a programmable DDS frequency generator designed to use as a VFO with the RAT5 receiver and FAT5 transmitter. It can also be used as a signal generator to test equipment. It used PIC processsor chip and already assembled DDS generator.  With the success of my RAT5 receiver, I decided to have a go at building this kit and build it so that it matches the RAT5. The kit is fairly straightforward to build, if you follow the instructions, but you have to be careful with the soldering as the tracks are very small. There are two separate boards to build and they are fixed together using solder-in pins.

This is a nice project to build, I have not built anything like this before. When I first switched on to try the MR2 I followed the set up instructions, these are a little complicated as it means pressing the control buttons in sequence. I had a bit of a hicup at first as the frequency control didn’t change frequency! After spending a while checking and measuring I discovered a microscopic short between two tracks. I managed to clear the short with a craft knife. Once cleared, I realised that there was a fault in the PIC chip, it was stuck on channel 2. With some help from Eric GW8LJJ he kindly sent me another PIC chip. This solved the problem!

Now all I need is a case. I looked at the supplier that I used for the RAT5 receiver and they make one which is a perfect fit for the MR2. It needs modifying slightly to ensure that nothing touches the case.


The RAT5 receiver needed modifying to accept the input from the MR2, which was easy enough to do. I also added a switch so that I could change from the external MR2 VFO to the internal VFO.


The MR2 works great with the RAT5 receiver, I have programmed a few channels so that I can just switch to a fixed frequency on Topband or use the VFO to tune the whole band.

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