The problem tends to be some form of inductive feedback related to the SWER systems etc with the power.

The fact that a PSU has a mains earth is no guarantee. Most of the ones I have built, or bought have metal cases to match the radios or are tied to the transformer. In most cases as we have SWER; The radio requires earthing to the PSU's earthing terminal

Be well aware that this earthing terminal, actually on the board of the commercial units, is grounded to the mains earthing cable via a 0.01mfd HV cap. This is a trap as previously mentioned. Beware of how the antenna primary is wired. It must not be mains grounded if it diectly contacts the DC circuit (eg. grounds to chassis)

Units with no regulators seem to be a lot less fussy.

Marc

Wow I didn't know SWER was common. I've never seen it used where I'm from in the USA.