In this case the 'transmitter' was the switching power supply in a USB cell phone charger plugged into an outlet in relatively close proximity to the antenna (other side of the wall of the house).
The charger plugged in by itself put off a little noise. With the USB cable plugged into it and stretched out across the floor, it put off a lot more noise (until I added a ferrite to it). Unplugging the charger or switching off the circuit breaker to that side of the house also would make the noise go away (for the most part... but there are a lot of random little cheap switching power supplies in the house that get picked up to some degree). I'm a little stumped about how the noise put off by these little things could be so strong as to blow past the mixer and get into the detector, unless it's just the close proximity to the antenna (probably 2-3 feet). There's little question that it was, though, given its lack of movement when changing QRG (and this was USB) and the fact that it went away by changing RX SHFT. Extra weird is that it seemed to be getting picked up by the ground connection (or maybe the cable shield). Nick On 9 February 2014 18:37, Matt Zilmer <mzil...@roadrunner.com> wrote: > Hi Nick, > > RX SHFT is normally used to cancel the effects of AM detection of very > strong signals that blow by the mixer and enter the detector - > overload. Since enabling RX SHFT cured this 60Hz+harmonics problem, > it seems likely that you were copying a strong signal with little or > no modulation. You may have been hearing the transmitter's power > supply ripple. > > Is your QTH near a broadcast station or military facility? I've come > across a similar problem once in a while when operating portable. > Usually, the signal comes out as station audio that can't be tuned > away from. A couple years ago, I had exactly the same symptoms (never > could explain the _what_ part) and RX SHFT was what I used to solve > it. It also works well on the OM down the street that operates with > all gain controls set to 11. :) > > 73, > matt W6NIA > > -- *N6OL* Saying something doesn't make it true. Belief in something doesn't make it real. And if you have to lie to support a position, that position is not worth supporting. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
