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
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|