[RFI] Monitor interferes with transmit audio

[Ian White, G3SEK]

Pete Smith wrote:
>
>It does seem as if some low-frequency RF from the monitor is getting 
>into the DXD, but it's hard to see how.  The DXD's case is all steel 
>and with no obvious gaps in the shielding.  Aside from throwing away 
>the monitor (a noisy brute in the HF bands too) or moving the DXD 
>(which would disrupt a good station layout), I'm stumped.
>
Sounds like magnetic pickup. Monitors put out very strong magnetic 
fields.

The audio circuit is literally a circuit - a loop, including the ground 
return path, and external magnetic fields will induce currents 
proportional to the enclosed area of that loop.

Also, does the DXD include 1:1 audio transformers (intended to break 
possible ground loops)? If so, even a small amount of flux leakage could 
couple with the strong magnetic field from the monitor.


-- 
73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)
                            Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek