I had a hard time sleeping last night and so I got up to play on the radio at about 5AM. I didn't want to make a lot of noise so I was operating PSK31.
Unfortunately I sat there for some time and wasn't able to work anyone. Then at 0917 UTC I was calling CQ and got a response from W7NX on Oahu, 4326.2 miles away. Not the longest distance I've hit yet, but I've only made Europe once, and that was IK4ALM in Italy at 4817.3 miles.
W7NX said I was transmitting a tone off to the side of my signal and sent me a picture of his waterfall:
OK, so that's weird. I guess I wll have to investigate. Because I'm antenna-poor, I've been running 100 watts, which is probably overdriving the antenna (it's rated at 100 watts, but that and five bucks will get you a latte at Starbucks). W79X said
You can see that there is a straight line that represents a constant frequency tone. Your BPSK31 signal is at a lower frequency so I was able to copy you, but you can see how the tone is pumping my AGC making my noise floor drop as soon as your transmitter turns on. Your BPSK signal is not as strong as the tone.
I’ve been trying to think of a likely cause but nothing comes immediately to mind.
I don't know if running too much power would cause something like this or not. It sure looks like the FT-450D is transmitting a carrier about 1kc above the data signal, though.
AFTERWORD, October 2014:
I've been running digital modes for quite some time now, and looking back at this post, I want to frickin' facepalm and headdesk myself. 100 watts on PSK31. What a moron. Sigh.