[Elecraft] Samlex SEC-1223 12VDC Switching P/S - RFI Reduction

[Marcus Busch [DL1EKC]]

Hi Tom,

just would like to thank You very much for Your (and Nigel's) very 
valuable information You have put on Your web site.

I stumbled on the birdies on 160/80 some time ago on a fieldday and was 
thinking about looking into the circuits one day. But the birdies are just 
S3-5 here.

Just to add a few notes:

I added a hard DC connection from the negative output to chassis/ground. 
This was done because modern 12 V rigs do not have any chassis ground 
connection when using symmetrical antennas (dipoles) and those ground 
isolated PS. This makes the rig chassis and coax braid eventually floating 
on unknown voltages. I observed this on several field setups, especially 
when using vertical antennas. The protective ground of Your mains may not 
be a good RF grounding, though. But it prevents static charge up of Your 
chassis (and the "connected" operator) via the coax braid.

I also added a surge arrestor to the 13.8 V output of the PS. One day on 
the field there was a thunderstorm around, but it was still some miles 
distant. But a surge came via the mains line killing not the Samlex PS but 
the TR switch in my K2! Fieldday over. The only destroyed part was the 
1500 V rated ZVN4424A! Ouch.

After christmas I will add the ferrite beads ...

Have a good time.

VY 73 de Marcus, DL1EKC