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Tuesday, 3 January 2012

Change rockmite (not 20m) 30m PA

Original unmolested.

Going to have a bit of fun with a rockmite kit I have unfinished.

I think it is 20m but might be for 30m I have the SCAF filter boards with it too.

I'm going to play about with the pa and see what is possible.

Then time to play with what a PP3 battery can do with a rockmite.

I'll update this post or create a new one with the results.

It was a 30m kit... Q6 (PA) was already soldered in but I'll chop it out, add some turned sockets (and something for bias if using a FET) and try some PA fun and games. In the meantime I also added a VXO mod (Xtal freq 10.116), I'll include schematic details later but pictures here...

 Note I added shrink wrap to the multiturn resistor connections.
 Yes I really have glued two pads to the top of the AF chip :-)

I bought a whole box of random pots and multiturn pots at GQRP Rishworth 2011 and this is a 20k 10 turn Bourns pot.
The VXO mod is from KE2SP. The details are on the rockmite yahoo group but here they are as well.

These two images are the board before and after modification.

The MV1662 varicap... don't discard it they are like hens teeth. The 5V1 zener you should save and use again another time. The pads on the AF sound chip do not have to be round I have used two 5mm pads but small square off cuts of pcb also work.
The 220K resistor, you can just add a 120K in series with the 100K that is already there.

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