[sdiy] Preventing Radio Ham Interference

[Oakley Sound]

Hi all,

My next door neighbour, a keen radio ham, has erected a new 144MHz 
directional beam antenna. Unfortunately, for both of us, when it's 
pointing towards my house and transmitting, it interferes with my audio 
set-up in both my living room and my little music area. I get on very 
well with my neighbour and we've briefly worked together on this so we 
know what particular combination of output power, frequency and antenna 
choice causes the problem. This antenna mast is around 5m away from the 
wall where my audio gear is situated. When he uses his other non 
directional antennas there is no problem.

Anything more than 20W and the RF signal has an affect. Generally, with 
my more modern gear it is not a problem, but my vintage gear (eg. my 
hi-fi and older synths) are badly affected. More annoyingly, it's also 
the modular and my ten year old Event active monitors.

When transmission is ongoing I hear what seems to be a loud buzz at 
100Hz and harmonics. It's as if the mains is being gated into the audio 
pathway during transmission. The higher the RF output power the louder 
the buzz. The Event monitors pick up the noise even with the audio 
cables unplugged and the mains additionally filtered. Bizarrely it also 
makes the modular and my old SY-1 go out tune but I can't detect any 
drop in power supply voltage so I think it's directly affecting the VCO 
circuitry.

I think I may have solved it with ferrites on the loudspeaker cables on 
the hi-fi but the music area is still a problem.

At the other end of my house I haven't got an issue but moving all my 
gear there isn't really practical - although I'm thinking about it.

Any ideas? Would some sort of earthed wire mesh fitted to the wall 
directly between him and me create a suitable RF shadow?

Tony

www.oakleysound.com