I received this email reply to my letter regarding intererence from CODAR in
New Jersey:

Michael,

I apologize about the interference. What frequencies encompass the 60
meter band?
We (Rutgers University) operate several sites along the New Jersey coast.
There are many other groups, most academics, who run other sites all over
the world. There are many users of the data outside the academic community,
including the Coast Guard, NOAA, and K-12 education

All the systems operate at low power (~ 40 watts). Since there are many
sites around the world, the operators are making efforts to get primary
bands for the system. I have already spoken with several SW listeners and
asked what frequencies we should try and avoid. I was told to try and stay
below 4.7 MHz.

We are trying to do this. Unfortunately, the FCC is restricting the
frequencies we can use and has asked that we move some of our sites to 4.8
MHz. The primary bands will allow us to stay at the lower frequencies
without having the FCC ask us to move.

I am not sure if our sites are causing your particular interference , but
please be aware that the CODAR community is taking steps to get primary
bands that will not interfere with others. It is difficult, as you know,
because of all the different users that occupy these bands.

Please do not hesitate to ask any questions that you may have. I hope that
this information has helped.

Regards,
Josh

http://marine.rutgers.edu/mrs/codar.html

He replied very promptly and was very polite as well as you can see. I think
they would be responsive to polite letters explaining our concerns as
shortwave listeners within the constraints of the FCC.