[hpsdr] HPSDR EMI Issues

[FRANCIS CARCIA]

Hi everyone,
From a humble emi guy
I read there  are a number of issues with signals leaking out of modules and strong RF getting in.
I figured this day would come. I think we should have used threaded BNC connectors on all modules
to provide a good shield tremination to chassis and an isolation barrier. Now any noise on a module ground flows out the coax shield because the board is floating in space. Also strong signals on the coax cables flow directly on to module local grounds. This is the reason for the grounding system of accessory boards you add to a PC.
I was going to replace my connectors but the PC hole pattern is different than the threaded connectors I have.
I have not looked into purchasing threaded connectors with the same hole pattern. This would also provide better support for modules. 
An option would be to add a ground lug on the pandora cover plates and attach it to module grounds near each coax connector. A copper flange could be soldered to each connector and then bolted to the pandora back plates.
Snap on beads on coax cables and computer interface should help with VHF emissions
Alex issues, I would find a ribbon cable snap on bead and hope it provids the isolation you need. I suspect RF is getting into the logic over the interface cables. A bead on the VSWR cable is also in order. Maybe the VSWR cable could tolerate some bypass caps. I wonder if a shield plate would fit between both alex boards to provide more isolation.  The 12volt  lead into pandora could also take a bead. I power my system with 115VAC using an IEC connector with internal filter from an old computer power supply. 
All the mating surfaces on pandora should be free of paint. A film of no-ox would also improve the bond between untreated aluminum joints. Frank WA1GFZ 
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