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Known for its NASA Mission and Countdown coverage on the K4GCC 146.940 2-Meter FM repeater, this non-profit amateur radio club operates an ATV (Amateur TeleVision) repeater. With the call sign K4ATV, it is located in Cocoa, Florida (near State Road 520 & Clearlake Road intersection) and operates with 439.25 MHz input, and 427.25 MHz output, on cable channels 60 and 58 respectively. It outputs NASA TV Video/Audio, sequencing bulletin boards of current amateur radio news and information, including a daily updated list of planned launches and color test patterns in quad format or full screen. A 1.2 GHz. band feed is also an input. Viewers can select video and audio source from a menu using DTMF tones on 144.340 MHz.
The signal can be demodulated by standard NTSC analog TV receivers. For TV's not cable ready, downconverters are used to shift the signal to TV Channel 3 output to a TV set. For cable-ready sets, the repeater's video carrier output of 427.25 MHz is the same as Cable TV's channel 58. A cable-ready TV receiver, tuned to cable channel 58, with a gain antenna connected to its input (vertically polarized), can receive the repeater in central Brevard with broadcast station signal levels. Individual amateur TV stations transmitting on 439.25 MHz, can be received using cable channel 60.
Several manufacturers produce transmitter-downconverter units and these units, with a camera, low-loss coax and 6-12 db gain antenna, permit 20 mile range operation. Mobile units are operational in Brevard County, and the county's Emergency Management officials have equipped the Emergency Operations Center (EOC) in Rockledge with an ATV transmit and receiving station with video and audio into or from the EOC's video monitors, cameras, and microphones.
The LISATS repeater uses broadband UHF antennas (vertically polarized). Received and transmitted signals are routed through 7-pole bandpass filters. The received signal goes to a GAsFet input stage in a downconverter. The downconverter output signal, at TV channel 3 or 4, is input to a demodulator (receiver) which routes video and audio to the repeater controller, which contains the modal switching. The controller senses NTSC horizontal sync pulses in the received video and keys up the transmitter. The controller provides DTMF-controlled switching of 10 video and 4 audio sources. Video is reconditioned to NTSC configuration.
The NASA TV downlink is provided by a digital free-to-air satellite receiver from a 10 ft. dish. Bulletin board screens are the output of a PC transmitted in on 1277 MHz. ID test patterns and logo are sent every ten minutes. A control receiver on 144.340 MHz permits DTMF control by radio. A video overlay circuit keeps the word LISATS on all screens.
A cable TV modulator drives a linear amplifier to 50 watts.
A 10 dbd collinear antenna radiates the signal from 265 feet on the Ezycom, Inc. tower site near SR520 and Clearlake Road. The repeater ID's in video and CW, every ten minutes for 20 seconds. Evenings find ATV'ers showing equipment, computer graphics or video tapes. The repeater transmits NASA missions continuously (usually) until the mission is completed. Recently published expendable launches are also covered whether from satellite signal rebroadcast or from LISATS mobile amateurs. The FCC and NASA authorized these transmissions to provide another outlet for space science education,
The LISATS K4ATV/R ATV Video repeater can be controlled by the following DTMF (Touch Tone) codes transmitted on 144.340 MHz in the central Brevard area (Control operators monitor 144.340 frequently):
Repeater Command List
|February 6, 2007|
|The following DTMF tones are sent on 144.34 MHz simplex. They are monitored using Audio 3. Audio inputs can be mixed (listen to up to all 4 inputs at the same time).|
|Continuous On Mode|
|Select 434 MHz Video In||1|
|Select NASA TV Video In||2|
|Select 1277 MHz Video In||3|
|Quad Screen Video In||4|
|Select Color Bars Video In||5|
|Follow commands below with * to turn ON, # to turn OFF.|
|Select 434 MHz Audio In||*A1 (on) | #A1 (off)|
|Select NASA TV Audio In||*A2 (on) | #A2 (off)|
|144.34MHz Audio is on all the time||*A3 (on) | #A3 (off)|
|Select 146.940 MHz K4GCC Audio In||*A4 (on) | #A4 (off)|
The "A" referred to above is the topmost of the ABCD keys on a 16 Key touch-tone pad. Not all keypads have this column of keys.|
| Follow Commands below with * to turn ON, # to turn OFF
Note: Audio is switched with Video.
|Select Video input that keys Transmitter||01 through 04|
|Operates with Video 1 priority highest|
|Beacon Mode (is enabled)|
|The repeater will transmit the Video ID (K4ATV with color bars) and audio Morse Code of the call sign. After 20 seconds the repeater turns off. This repeats every 10 minutes. Therefore a video and audio signal is available for users to check reception, make antenna adjustments, etc.|
Net Control Protocol