[RFI] SO2R 2nd Harmonic Interference

[qrv at kd4e.com]

I've used an IOTA PS with IQ/4 battery manager across a large deep-cycle
battery for years.

Dead quiet, gear runs off clean battery power, and has power for a while
when the grid goes down.

Best of all worlds.

YMMV ... 73, KD4E

> I have been trying to solve an interference problem for quite a while 
> here at my QTH. Symptom is that when I transmit on 40M CW, even at QRP 
> power levels using bandpass filters and transmitting stubs, the second 
> harmonic on 20M is a wide signal, covering 30-40 KHz. As per advice 
> given by Frank W3LPL regarding RF flooding, I started searching for an 
> electrical device (probably charger/wall wart).
> 
> I eliminated my own home as the source by testing with battery power and 
> all circuit breakers turned off. Through more testing, I found that even 
> at 100 milliwatt output on 40M, I still got the 20M wide band hash, but 
> only when I pointed my 40M antenna at my neighbors house.
> 
> Today, I got together with the neighbor and he let me snoop around with 
> a portable Rx. Voila! Culprit is a cheap little trickle charger.
> 
> DBT Auto Electrical Products PTE LTD Part no. 021-0123
> "Household automotive battery charger" 120V input and 12V output at 750 mA
> 
> Question: Is there a battery charger that any of you can recommend? I 
> tried wrapping the 12V leads of the current charger roughly 10 x through 
> a large toroid and there was little if any reduction in interference.
> 
> 73 Randy K0EU