| ARES - Linn County, Iowa |
Rockwell Collins operates a Doppler Weather Radar from their development laboratory at Collins Road and C Avenue NE in Cedar Rapids. During times of potentially severe weather, ARES members operate the radar and broadcast the displayed video using Amateur Fast-Scan Television (ATV). The Linn County Emergency Operations Center is equipped to receive this ATV picture to assist in their Storm Watch activities.
You are certainly welcome to try. The signal is broadcast with an omni-directional antenna with that purpose in mind. If you live within a few miles of the transmitter, it should be easy. If you live farther away, you may need higher gain beam antennas with low-loss coax. All you can do is try.
There are several ATV downconverters advertised in the Amateur Radio magazines. The receiver used at the EOC is from PC Electronics.
This is a long shot. The ATV signal is well below broadcast TV channel 14. Some, but not many, conventional TVs will tune far enough below channel 14 to receive the signal. Unless your TV has a manual tuning knob for UHF, or you have a hand-held TV that tunes by slewing through channels, you are probably out of luck. Even if you have one of these, it may not tune down far enough to work.
This is probably your best bet. Most people now own a "cable ready" TV or VCR. The ATV signal is transmitted in the UHF Amateur band on 426.250 MHz. This turns out to be between cable channel 57 and 58 if you program your receiver to receive cable TV. T We may also be transmitting on our alternate frequency of 423.?? MHz, so also check around cable channel 61. Since the signal is between channels, you may need to turn off your "AFC" or turn on your "game" switch to allow you to tune in the signal.
First, you should use a vertically polarized antenna. Depending on how far away you are from the transmitter, you may need an Amateur UHF beam antenna, low loss coax, and perhaps even a preamplifier at the antenna. The transmitter has a peak power of 80 watts, but the signal is 6 MHz wide. This is like trying to receive a normal FM voice signal (5 kHz deviation) transmitting a power of 0.15 watts. It all depends on your location. We have amateurs (that live on hills) receiving a good picture in Central City and Springville.
This is not always obvious. There are a lot of special modes and displays that the radar operator can bring up to better analyze the characteristics of a storm. It is best to keep your TV's audio turned up and listen to the comments of the radar operator. We try to comment on the things we are doing to educate others to interpret the display. If you would like more help on interpreting specific radar screens, contact one of the radar operators.
Listen to the 146.745 repeater. We try to announce when the radar is up. Another trick is to tune a scanner to the audio sub-carrier frequency of 430.75 or 430.7625 MHz. If you hear a dead carrier, the radar is up. This signal will turn into highly distorted audio when the radar operator is making comments (as the deviation of TV audio is far greater than normal 5 kHz deviation FM voice audio).