Ten feet from a 22kW transmitter? Wow, that is brutal!
In general, downtown Chicago is one of the worst RF environments of any
city I have ever been in. This is especially the case in the West Loop
area (which has long been the stomping ground for car radio
manufacturers to put their tuners to the test). We have had to do a lot
of equipment mods to our location production audio gear over the years
to contend with it, and with the move to DTV, it has just gotten worse.
Re: SCR dimmers. There are a few companies that make chokes and
band-pass filer that help with the chopped waveform problems. I use some
on the X-10 dimmers I have at home. There are also some high-end dimers
from companies like Lutron that have built-in filtering. We have used
these in a number of commercial installations.
My favorite, however, is still the old Superior Electric auto-formers,
which is what I use whenever I can. Just replace the brushes every 5
years or so, and you're ready to rock for another 5 years, which is more
than I can say for most SCR dimmers (even the commercial ones).
Scott D. Smith CAS
Chicago Audio Works, Inc.
On 6/19/2014 2:22 PM, Paul Stamler wrote:
> On 6/19/2014 10:49 AM, Tom Fine wrote:
>> If there is dimmer hash in a home system, shouldn't the power
>> transformer eliminate the problem by only passing low frequencies
>> (60hz)? If not, I'm sure someone makes a non-ridicu-priced isolation
>> transformer with a band-pass. I don't have any dimmers or anything else
>> that rides on the power lines in my house. However, the place is full of
>> RF from wifi, cellphones, radio and TV, etc. Never had any problems with
>> RF or hash. Regarding dimmers, if you like listening to music, consider
>> whether you really need dimmers. I view them as a useless cheezy fashion
>> trend from the 70s. Just use the lightbulbs you need to do the job.
>> Granted, it's harder in the age of non-incandescent lights, but it's
> I agree, dimmers are dreadful. But some people have them.
> The bad news is that some of the crud gets broadcast out into the
> ether rather than into the power lines. So it can get picked up by
> cables and piped into the inputs of equipmwnt -- and phono systems,
> alas, don't use balanced connections. If they did, life would be
> simpler. As it is, ferrite beads are useful for keeping the crus out
> of the audio circuits.
> The dimmers might be in the house or apartment next door and still
> create interference.
> One of my biggest challenges was building a phono preamp for my
> parents' apartment on Chicago's near north side. There was dimmer crud
> from adjoining apartments, but the worst problem was the antenna farm
> on the Hancock Building, 0.75 miles away. Taxi radios were
> occasionally an issue too, though not as much.
> Worst was a pair of phono preamps that lived 10 feet from a 22kW FM
> transmitter. That was a challenge.