Monday, March 21, 2011

Hunt for QRM!


Since moving permanently to our country home I have been plagued with very strong S9+ QRM (man made electrical interference) on the HF bands. I've not noticed it before because I previously only operated 2m VHF FM. 

I've been very concerned about this noise since it was making HF operation unbearable with this horrific static. I was worried that the source of the interference may have been coming from a nearby faulty line transformer or perhaps even my neighbor's micro hydro generator! I didn't rate my chances of resolving the problem in either scenario. Who cares that their chinese voltage regulator is spewing RF garbage right? 

Well in a moment of desperation, this evening I decided to start investigating the source. I used my handy Yaesu VX-5 to track down the culprit. To my relief the noise disappeared as I moved away from the house. OK, something inside is generating this horrible noise. Since it was already dark, hitting the main circuit-breaker was not an option without incurring the wrath of my wife and son ;-) so I began eliminating fridges and electrical gadgets one-by-one.

Eventually I found the evil pollutant - a crappy AC/DC adaptor from Taiwan that was providing power to an equally badly shielded GSM box that provides a cellphone circuit to the house alarm system.

What a difference! I can now hear faint signals on all bands! No more QRM :-)


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