If you know the frequency transmitted by those towers, you can tune a receiver to listen for broadcasts. A field strength meter that is sensitive in the frequency range will also detect the RF emissions.
GWEN operates between 150 KHz and 175 KHz. Many GWEN sites are being converted to host NDGPS which is a national terrestrial differential GPS transmitters (maintained by the Coast Guard) and operating at 300 KHz. The GWEN packet radio network has an anticipated service life of about 15 years. It provides a redundant communication path in case the MilStar and other satellite systems fail in a nuclear war.
It appears there is an active process of decommissioning GWEN sites and converting to NDGPS. Idaho Falls will get an NDGPS tower this year.
AT&T Phone Bill Errors
WEAU TV 13 ^ | May 13, 2004 | Mandy Grosser
Posted on 05/14/2004 12:02:33 AM CDT by quietolong
AT&T Phone Bill Errors
May 13, 2004
Mandy Grosser
State officials are investigating after more than 12,000 Wisconsin telephone customers had about $5 in erroneous fees added to each of their monthly bills by AT&T earlier this year.
The company says it improperly billed just under $4 in charges, plus additional fees and taxes, on the phone bills.
http://www.freerepublic.com/focus/f-news/1135274/posts