[Elecraft] Local Noise Problem

[AB8XA]

Forgive me for participating in this OT thread fork, but my next house will have a code-approved sub-panel for overhead and sconce lighting that I'll pull off 120 VAC after inspection and feed with eight series-parallel 6V golf cart batteries for nominal 24 VDC. The overhead boxes will each be fed from two wall switches and support 24 VDC paddle fans with added runs to added LED overhead lights.  The sub-panel will also have a 30 amp circuit to my "shack," feeding a 24 VDC to 13.8 VDC converter for full nominal voltage to our 100 watt rig. There are many advantages to 24 VDC over 12 VDC in residential use.
--
Moe - AB8XA
ARRL LOTW, eQSL, Fists #13020, SKCC #7460, 
FPQRP #2617,  NAQCC #5352, QRP-ARCI #14326



On Apr 3, 2011, at 6:24 AM, David Cutter wrote:

> I'm looking forward to a time when all domestic lighting can be run from a 
> 12V supply at the main switchboard.  With led lights progressing as they 
> are, I can see no reason for continuing to build houses with high voltage ac 
> for lighting.  The wiring will be cheaper and safer and hopefully that will 
> be a driving force for change.  Indeed a lot of domestic equipment outside 
> the kitchen can also be run from 12V (I'm thinking of laptops, lcd tv, 
> audio, gaming, side lamps).  If governments can ban incandescent light bulbs 
> to save energy, then why not change the building regs to encompass new 
> lighting systems when they come into mass use.  One might beget the other.
> 
> This will concentrate noise producing power sources and make them easier to 
> treat, especially being adjacent the main earth/ground point into the house.
> 
> David
> G3UNA
> 
> 
> 
>> On 4/2/2011 6:21 AM, Jim McCook wrote:
>>> There is a very serious problem with the local noise source from low
>>> voltage lighting systems.  These are sold as pendants, single lights, or
>>> multiple lights on a support, such as a bar.  The retailer supplies them
>>> with a choice of two types of transformers, either a regular magnetic
>>> type (non interfering), or an "electronic" supply, which is a very noisy
>>> switching supply.  The latter is most popular because it's small enough
>>> to be contained within the smallest fixture.
>> 
>> SNIP
>> 
>>>  This is a
>>> noise source that could seriously affect our hobby when new construction
>>> begins en masse again.
>>> 
>> 
>> Absolutely on target, Jim. I inherited a half dozen of these little
>> monsters in the home I bought in California five years ago. There are
>> two major components of the probem -- first, that these types of devices
>> are exempt from Part 15, thanks to ARRL being asleep at the switch when
>> the exemption was made (perhaps so focused on BPL that they saw nothing
>> else), and to lobbying effort for "small government" that has
>> essentially gutted the FCC.  Second, a real 12V transformer big enough
>> to handle the load of these lights is at least 2-4X larger than the the
>> limited space available in the electrical back-box for the fixture. So
>> from a practical point of view, these switching power supplies are the
>> only option. Those sold by the electrical supply houses here in Santa
>> Cruz county, CA, are unbranded and carry no FCC labels.
>> 
>> One piece of good news -- most, if not all, of the noise is radiated as
>> a common mode signal on the AC power wiring, so  a good AC line filter
>> can make a big dent in the RFI.  I was able to fit a filter in the
>> backbox with one of these power supplies. It's also possible to suppress
>> the noise with a multi-turn toroid choke plus a line-voltage rated
>> capacitor across the line. There are two pieces on my website about this
>> -- one on RFI and Ham radio, and the other specificcally about these
>> filters -- how to use them and where to buy them.
>> 
>> http://audiosystemsgroup.com/publish.htm
>> 
>> 73, Jim Brown K9YC
>> 
>> 
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html