Wednesday, 19 June 2013

4m Transverter

The Larkspur mast is nearly refurbished, just one section left to repaint, so ive turned my attention to another project - a transverter for 4m. This is the G3XBM QRP design.

Its taken me quite some time to even get started with this, as the 42MHz crystals are not exactly cheap nor easy to come by. And once I had the crystal, I found I didnt have the series inductor. However, a kind chap at the vintage forum has supplied said part, and so on we go.

Working with 'Manhattan' construction, I have the Local Oscillator constructed. As is often the case, first time out it failed, and in my tired state trying to fault find last night at gone 23:00, I confused myself with the display on the spectrum analyser, and so the one time I did get it to oscillate, I thought it was just a false reading.

Having correctly started alignment this morning, I find it free runs at 27MHz. A quick check of the inductor shows it has far too many turns on than specified, so next task is to take a few off and get it free running around 42MHz, then the short can be taken off of the crystal.

Just started removing the excess turns, and have cracked the damn former off the base! Out with the cyanoacrylates...

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