Phase 2 ~ Thinking Inside the Box
While it may be exciting to have your rig operate "al fresco", with it sprawled out all over the work bench ultimately one day you will want to move it and that is when having everything all neat and tidy comes into play.
In 2009 I built a Tri-Band SSB transceiver made mostly from components that traced their roots back to a Heathkit HW-101. Essentially I made a QRP solid state version of the HW-101. Here is what it looked like sprawled out all over the workbench.
It was only after I had it to this stage and working that I thought about how to get this into a box. It was a real challenge and the final box was a half cubic foot. 12x12X6! My point I should have thought about the box before I built the radio and the final product looked like this:
The same applies to the Bitx40. Earlier I suggested the use of two enclosures one of which is a very nice metal box that is about 7X5X4 and the other is a chassis that is 6X10X2. Both will work but the box will take a bit more noodling to get all to fit inside. There is also another factor here. The Bitx40 as supplied will put out about 5 watts. One of the "hacks" is to feed the final RF output device from 24 volts while the rest of the radio is fed with a nominal 12 Volts. This ups the Pout to about 20 watts but will require a substantially larger heat sink!
The Bitx40 rig comes with an un insulated heat sink that will handle the 5 watts so you are good there. But suppose you want the higher power then what is the solution? The answer is to use the case itself with an added appropriate insulator kit. Thus how you initially install the board in the case will/may impact the higher power version. With all of the metal surface of the case it should do a pretty good job at handling the heat sinking requirements. BUT you have to think about that before you start drilling holes or cutting metal.
Another factor is shielding. At 5 watts and using the AD9850 DDS (Direct Digital Synthesizer) or the Si5351 PLL (Phase Locked Loop Clock Generator) may not be an issue. But with 20 watts running around inside the box may require internal shielding. Thus you must think about how to do that up front.
In my build I used the chassis as it was available and I have several external RF linear amplifiers so my decision process bypassed any thought of a 20 watt version and I just moved on.
So when contemplating any project you really do have to think inside the box and what long term decisions must be considered before drilling that first hole or making the first metal cut.