A box to put it all in

I always like to try to make a nice job of the aesthetics on my home-brew projects. Not for me the old battered aluminium box with holes in the wrong places from earlier projects. It seems to me that if I am spending several hundred pounds on the innards then it is not doing the project justice to then scrimp on the case.

To determine the best sort of case assembly I first looked at the largest components it will have to house. The amplifier module is 250mm (L) x 125mm (W) x 100mm(H) and the power supply is much the same size, though not quite so tall. Between them these two units dictate the size of cabinet. 

A 3U 19 inch rack unit is 425mm (W) x 127mm (H) and comes in various depths - the standard depth closest to the project requirements is 335mm (D). RS Components do a nice range of self contained 19" rack cases and in the end I selected an RS PRO unit, stock number 188-1319.

The amplifier module and the PSU will go side by side, leaving about 70mm of width for ancillary stuff such as control circuitry, processor, etc. Whilst the case will be fairly full, it won't be difficult to work on and its shape makes for a neat logical layout.

Both the amplifier module and the PSU require forced air cooling, so there will be axial fans front and rear, making for some quite large holes to be cut in the two panels. It is notoriously hard to make a good job of these by hand but I shall have a go and if it turns out to be unsatisfactory then I have option B up my sleeve - getting CAD-CAM designed panels made up to my specification. Not cheap, so hopefully it won't come to that. We shall see.

Internally I will mount everything on a removable base plate and fit screens between the amplifier module and the rest of the case. This is partly just good RF engineering practice and partly to help create an effective airflow over the amplifier module's heat sink and components. More on this later.

Externally, I am planning to have no panel controls, opting instead to have a separate control head, so the amplifier can be away from the operating position. There should be nothing on the front panel and just mains power input, RF input & output, PTT in and external control head connections on the rear panel. I've little doubt that there will be much more to say about this in due course.