[sdiy] Preventing Radio Ham Interference

Oakley Sound oakleylist at btinternet.com
Tue Nov 29 10:55:46 CET 2016

Wow. Thank you for all the replies and help. I got several PMs too and 
even a phone call.

To answer a few questions:

I have done the ferrite clamps and they seem to work on the hi-fi when 
added to the speaker and main cables. But I have yet to test this when 
he is outputting at full power.

20W causes a noticeable buzz on the Event monitors in my music area even 
with the audio cables unplugged and ferrites on the mains cable. At 60W 
then the buzz is so loud it's unusable and VCOs go out of tune. 60W is 
the maximum power output of his rig. I've no idea how much ERP is being 

I've not asked him to see what happens when the antenna is pointed in 
any other direction. But when he was doing the tests it was around 45 
degrees away from pointing directly at my house wall. Getting him to 
test it with a dummy load sounds a good idea - although it should be 
noted that the same rig driving a different but omnidirectional antenna 
causes no problems.

We do share the same power and phase. The substation (step down 
transformer) is up a pole just outside my back garden and I'm the 
closest in the village to it. When pointing at my house his antenna is 
also pointing straight at the overhead power lines that feed my house.

I will look into adding some capacitance across the bridge rectifier 
diodes of the modular power supply.

His hi-fi is unaffected by it although it's more modern and the beam was 
not pointed across his house at the time of testing.

His antenna is probably about as high as it can go on a single 
unsupported pole. We're both in bungalows and the antenna is about as 
high as the apex of his roof.

With the exception of the modular and the Event monitors everything that 
is affected is old and was built before the letters EMC meant anything. 
The Events are also liable to picking up mobile phone interference so I 
think it may be worthwhile getting some more 'rad hard' replacements for 

I may try some grounded chicken wire to create a shield but from various 
answers it seems that this may have little if no effect unless I go for 
the full cage which is impractical. However, that idea I had of buying 
an old shipping container and converting it to a home studio is starting 
to become more and more attractive.


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