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There was not enough room for an internal speaker in the uBITX HF Transceiver. There was not much point in fitting a small low profile speaker as the frequency response would probably have been pretty poor with all the space filled inside.

As a nod to the usual lineups of the FT and TS series transceivers with decent size speakers, I made a nice matching external speaker. The speaker was a small, but smart and reasonable power handling 50mm 5W type, with silver cone without the centre coil cover. 

Spray painting the panels

The bottom half with the speaker fitted. I tried covering the top and sides to see where the cabinet was resonant, it seemed up at 400Hz or something like that, making the audio sound a bit like someone talking into a bin. That was no good, so a port would be necessary to move the resonant point down a lot. A sawed off 25ml syringe seemed the perfect size and length.

Gluing it in place. Now you can see the state of my desk... eek.

The glue was almost set, so I spray painted the port tube in place.

Complete! The sides were soldered on, then glue was run along every edge inside to seal the case. Then the top was placed on, the audio checked to ensure resonant point was low enough - it was - so then the top was glued on to finalise it. The tone is similar to a standard size ported bookshelf speaker so it's great for radio audio and music too. Bass is reproduced very well considering its size. Quick entry of dimensions into an online calculator indicate the port is resonant at approx 100Hz, which seems to match with what it sounds like.

Ah - lineup! Hmmm, a tuner and QRO amp might be needed...

Category: Homebrew electronics
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