[Elecraft] OT 20M Moving QRM (Video)

[Fred Jensen]

Weigh it.  Most small wall warts are also very light.  I've got a couple 
of heavy larger ones in the junk box and the difference is hard to miss. 
  The cable from it is the radiator of course, a BC band radio tuned to 
a clear spot [preferably at the high end] will usually show a distinct 
increase in noise as you move it up the cable.

I was choking a 4 A feed to the wireless equipment and used a couple of 
3 1/2" OD [or so] toroids that N6XI gave me.  Consulting the K9YC 
recipe, I wound 12 turns of Radio Shack red-black pair on one, and as 
many turns as I could get in one layer on the other, wired them in 
series and then stacked them using zip ties.  My theory was that the one 
with lots of turns would get the 160-80 m stuff and the 12 turns would 
get 40-30-20.  They went right at the Chinese RPOJ power supply in the 
24 VDC cable.  I don't know the mix but I think probably 34 or 43, I 
think they were part of a group buy by the contest club.

My experience with the small clamp-ons has been poor, unless you get 
several turns of the cable through it, and even then I don't think 
there's enough permeability in the magnetic circuit to do much.  It's 
pretty hard to find linear wall warts these days.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the Cal QSO Party 1-2 Oct 2016
- www.cqp.org


On 3/3/2016 2:53 PM, David Christ wrote:
> Is there any way to easily determine if a wall wart is a SMPS?  Most
> probably are but are there any that are not?
>
> David K0LUM