[Elecraft] Basement QRN

[Dave Andrus]

I don't know if anyone will find this interesting or not, but I found  
a noisy switcher powering the electric blanket in the master bedroom-- 
several rooms away from the shack, and on the opposite side of the  
house from my HF antennas.  It's a 4-year-old JC Penney model that  
advertises the fact that it's running only low-voltage DC through the  
blanket to avoid bathing you in an AC field.

You don't hear anything from it when you first turn it on, but as soon  
as it reaches the thermostat's set temperature, it begins to pulse on  
and off.  When in the "off" mode, the switcher is apparently  
experiencing a high EMF condition inside the switcher "brick" unit-- 
since it is not under the load of the resistive wiring then, and that  
high-voltage moment is when all the RF radiation happens.  It's mostly  
just a problem on 80 meters, since I can hear a definite peak in the  
distinctive broadband noise right around 4 MHz.

An interesting side note is that I can reliably turn the blanket  
electronics completely off by transmitting a few dits and dahs at  
anything greater than about 20 watts on 80 meters!  Great design,  
huh?  And, no, I haven't been able to "fix" it yet by wrapping all the  
cords in a bunch of ferrites.  I'm driven more by curiosity than  
anything else, but I'm going to open it up and make it RF-proof when I  
have time.

73,

Dave K7DAA
http://www.k7daa.com

On Mar 9, 2008, at 3:52 PM, Jerry Flanders wrote:

> You must have had a noisy switcher power supply for those low- 
> voltage halogens. The halogen bulb is simply another conventional  
> bulb with a filament and halogen gas is added to prevent the metal  
> filament from evaporating. 110 V halogens would probably have been FB.
>
> Jerry W4UK
>
> At 05:42 PM 3/9/2008, Denise&Werner wrote:
>> When I put my shack together I put in some halogen lighting from an  
>> overhead
>> shelf that looked pretty cool till I turned on the lights.
>>
>> Talk about noise. It was like a blanket . I switched off the lights  
>> and it
>> was gone.
>>
>> These were the low voltage halogens.
>>
>> By the way, I just ordered my K3 yesterday. I just couldn't stand  
>> to hear
>> about all the fun I was missing.
>>
>>
>>
>> Werner   N8BB
>>
>> _______________________________________________
>> Elecraft mailing list
>> Post to: Elecraft at mailman.qth.net
>> You must be a subscriber to post to the list.
>> Subscriber Info (Addr. Change, sub, unsub etc.):
>> http://mailman.qth.net/mailman/listinfo/elecraft
>>
>> Help: http://mailman.qth.net/subscribers.htm
>> Elecraft web page: http://www.elecraft.com
>
> _______________________________________________
> Elecraft mailing list
> Post to: Elecraft at mailman.qth.net
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com