I have built my second QCX (40m model) in a D-Link AP box.
Also using a 4-cell pack without problems so far, considering that a 4-cell pack doesn’t stay at 16.8V very long, and I didn’t bridge the “idiot” diode.
But I did put the 7805 on a large heatsink, it gets quite hot otherwise.
And I glued an IC heatsink to the three BS170’s with superglue.
In the picture : the 4 cell Li-Ion battery fits in an audio cassette case.
Using an external speaker at the time.
“Clothespeg” paddle (the history of that paddle is here ).
The antenna on the kitchen table is a portable “Patterson” loop, which got me RBN spots all over EU.
In the extra space I later added a small LF amplifier board and flat speaker (from a laptop). Here a look inside (the pushbuttons are mounted on the lid).
I used a Tiny SWR board in an external Endfed tuner (Fuchs type), so that I can use it with several different rigs (the TinySWR is bottom left in the picture).
More pics and details on request.
73, Luc - ON7DQ