In the olden days, the circuits within your receiver were not all that linear - they generated a lot of intermodulation (IMD) products. This is what everyone was concerned with from about the mid 1970s to about the 90s... "IMD dynamic range", often just called "dynamic range". Defined, it is the range from the minimum discernable signal (MDS - the smallest signal your receiver can pull out of the thermal noise background) to the largest signal your receiver can process without creating IMD products that act like real signals (i.e, the IMD "junk" begins to rise above the noise floor at this high signal level). Back in the day, the difference between the two was smaller than it is now... receivers were plenty sensitive (nice, low MDS), but the IMD junk started causing problems at a not-very-high signal level. Today's receivers are something like 20 to 50 dB (about 3 to 8 S-units!) less sensitive to this. This is good - it means you hear less stuff that isn't really there, and loud nearby signals don't stomp on your receiver and make it go deaf when TC2W is responding to your call. These days we have synthesized receivers... the oscillators are all generated by digital circuits rather than LC circuits. It has apparently been quite a lot of trouble to get these to be as quiet as a simple LC oscillator. The term you see is "phase noise", specified at a certain offset from the oscillator center freq... like "-120 dBc at 100 kHz", or whatever. That little bit of noise 100 kHz off your oscillator's freq mixes with any signal that happens to be there and produces results that you hear. I suspect this is the problem you are having. Ok... that was my best shot at a quick explanation... how did I do Zedders?