You may not be able to do anything, being you live so close to the tower. You might call the station and ask to talk to a tech. Explain your problem to him, he might be able to filter it out. Be nice, It is your problem not the stations.
Are your speaker cables long? The speaker cables act like an antenna.If they are try to set your speakers closer to your amp with shorter cables. Go buy some cheap speaker cable for a test. Do any of your neighbors experience the same problem? For get trying to use any 120v line filters,it is not coming in through the ac power line.
I hope this helps, Jim