Clear Channel – Antenna Design and Testing

Clear Channel is a network of powerful AM radio stations that provides coverage for the entire USA. Developed as part of the Emergency Broadcast System, it was designed for alerting the entire population in the event of a nuclear attack. (The familiar monthly system tests seen on broadcast TV stations.) This existing infrastructure is owned and operated by the US Government and all broadcasters are required to comply according to the terms of their licenses.

The AM network is composed of a number of high power (50KW) stations that operate between 550KHz and 1600KHz which due to its low frequency, travels hundreds of miles. For example, 640 KFI Los Angeles, 680 KNBR San Francisco, and 1070 KNX Los Angeles stations cover the entire state of California.

Now coordinated by FEMA, the Emergency Alert System is a vast sophisticated system that now includes TV stations, Cellular and Paging Operators, Cable TV Providers, and others.

My contention is that although this system was designed for national emergencies, regional blackouts qualify as emergencies as well.

The BIG ideas about utilizing the AM Clear Channel Stations:

- It covers the entire US with a common radio station interface.
- The infrastructure is already in place.
- It can target individual regions or localities.
- The remote control receivers are very inexpensive.
- It does not require new technology to be created.
- It is extremely reliable and has been tested over time.

For the “Smart Grid” the primary application of this system is Load Shedding of high draw appliances specifically air conditioners.

The device to be remotely controlled is very simple as shown below. Upon receipt of a DTMF string, it disconnects the supply of power to load. The device needs no external antenna and uses the power line which works quite well at low frequencies. The estimated cost to build is $5. It is envisioned that these could be user-installed or built into air conditioners at the factory. Only a single design would be required and be applicable for nationwide deployment.

Over-The-Air Signalling Format

The signaling format for Load Shedding is envisioned to be based upon DTMF. (Dual Tone Multiple Frequency) Developed by the Bell System, it was adopted by the US Signal Corps as being highly robust in noisy environments and compatible with voice-grade, twisted-pair telephone circuits which are ubiquitous. (Although consumer “Touch Tone” phones have a key matrix of (3) columns by (4) rows, military phones have an additional column for reserved functions.)

Implementing a regional addressing scheme for Load Shedding could be straightforward if based upon the existing format of Country Code, Area Code and Exchange Code.

For example, a single broadcast from WBZ could turn off all the air conditioners in the 617 Area Code impacting approximately 1.2 million customers.

617 OFF Command:

617 ON Command:

Each command is only 320 mS long, and during an actual Brown-Out to Black-Out emergency would not require any pre-warning announcement for minimal latency.