[Hallicrafters] I bet you knew this already.

[Roy Morgan]

On Dec 8, 2008, at 7:27 PM, Jack Dunigan wrote:

> ... a terrible buzz obliterates all signals ... switch off the  
> light, the radio works normally.... a tubular quartz bulb and a  
> dimmer switch.

1) junk the "green" flourescent lamp and use a normal incandescent  
one.  (Note: Some quarz halogen incandescent lamps have a diode in  
them to run the filament on half cycles only. These might cause noise  
but I've not seen it happen.)

2) Is the tubular quartz bulb lamp have the dimmer in the lamp?  If so  
junk it.  If the dimmer is in the wall, buy a Lutron dimmer and  
install it.  "The Lutron Nova series ($25 price range) has excellent  
filtering built in."


>  Is there an easy way to filter this out?

Yes, you can get inductors and bypass caps and install them in the  
fixtures if you want to.

Or:

 From my notes:

"...Lutron Lamp Debuzzer Coil  LDC-10-TCP in another attempt to  
eliminate this radiated hash. Low and behold the $110 investment  
worked fantastically!  Now what I want to know is how to build such an  
animal for a lot less than $110!   All there is to this is a box about  
the size of a smaller ballast transformer with two wires. It goes in  
series between the dimmer and the light load. They have very specific  
amperage ratings , 400-600 watts, 600-1200 watt, and 1200-1920 watts  
depending upon the needed load range.  It sure is great to now have  
the XYL upstairs watching TV with a dimmed light and I can listen to  
the DX BC band on the 390!  There has to be a cheaper solution for the  
rest of my dimmed light circuits.

More:

  http://www.lutron.com/applicationnotes/360484.pdf

It is probably a pair of high-Q coils, such as a toroid, in series with
each line that will handle the AC current, combined with filter
capacitors across the line and to ground.
...
Also check out this:
http://www.ethanwiner.com/dimmers.html
...
... here's one more idea:  Get the ARRL
RFI Handbook.  Apparently it has circuit designs.   See
http://lists.contesting.com/archives/html/RFI/2000-09/msg00015.html

From:
http://www.arrl.org/tis/info/touchlamp.html

"The Lutron NOVA series uses toroidal chokes that provide a  
significant level of RFI suppression.
I bought a Lutron model N-600, which will handle up to 600 watts of  
incandescent lighting. Temporarily installed in my radio shack, a  
generic light dimmer produced an S9+ reading at 230 kHz (an arbitrary  
noisy frequency). The N-600 produced a reading of S3, a difference of  
about 40 dB. Admittedly, this is not zero, but installing the N-600  
some distance away provided a reduction in RFI that is very  
gratifying. Indeed, I new hear new noise sources, heretofore  
undetectable through the dimmer din.

You're not likely to find these dimmers at your local discount store,  
and they are not inexpensive. Check for the availability of these  
dimmers at a lighting fixture store and expect to pay about $25 apiece  
for them. "


Roy

Roy Morgan
k1lky at earthlink.net
529 Cobb St.
Groton NY, 13073




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