Alan Melia

Hi Conrad I am wondering if you are attacking the right source. Just because it is still there on a clean external DC power supply does not mean that there is no SMPSU internally providing various rail voltages from the clean supply.

I have had screen interference on LF but it did not extend to anywhere near 70cms .....the fundamental was 700Hz or thereabouts, and it was rock stable on a waterfall, not the drifting you report. Drifting lines with mains modulation has nearly always been traced to an SMPSU where I have encountered it.....a free running switching oscillator. What does seem clear is that it is not radiated from the supply lead ......which might be an easy fix.

The best way to cure RFI is to attack it at source rather than trying to screen it out. What technology is the monitor screen?? the RSGB EMC helpdesk man (Ken) is an ex TV engineer and has had a lot of success getting some errant TVs replaced.

Good Luck with it
Alan (G3NYK)
RSGB EMC Committee member

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