[sdiy] Preventing Radio Ham Interference

Jarno Verhoeven@ziggo.nl jarno.verhoeven at ziggo.nl
Mon Nov 28 19:06:54 CET 2016


If you want to do any kind of mesh or copper foil screening, I wonder if doing
just a single wall will make enough of a shadow.
And if you do want to do more walls, it is quite a job. All of the edges and
corners will need to be connected as well (granted 144Mhz isn't that short a
wave).
Quite a bit of cash involved as well, copper is not cheap.
Our MRI machines are in RF shielded cages as well (to keep our 20odd kW of RF
inside :-) ).
 
Can't he put the antenna higher?
 
I'd perhaps look into proper RF shielding for the studio and chokes for the
affected equipment in the rest of the house?
 
Regards,
 
Jarno.
 
 

> Op 28 november 2016 om 17:14 schreef Oakley Sound <oakleylist at btinternet.com>:
>
>
> 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
>
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