Lifeline TV
Lifeline TV service essentially provides channels 2-13 plus 98 and the FM band. The service is provided by adding two filters that remove expanded TV channels, allowing lifeline channels to pass:
- A band-reject filter that rejects channels 14-21 (120-174 MHz), and
- A low-pass filter that rejects all channels above Ch. 24 (216) MHz. (Ch, 98 is visible because it is actually located between Channels 6 and 14).
Filters are imperfect devices because some channels fall into "transition bands" that can neither be described as "pass" or "reject." Reception of transition-band channels will be variable, depending on the signal strength, the TV receiver and whether the transition is from pass-to-reject or reject-to-pass. In the former case, low-frequency parts of the TV signal may be visible but not the high-frequency parts, so color and sound information may be lost. In the latter case, the loss of video carrier may result in unstable reception. Also, channels at the extreme end of a pass band will be somewhat attenuated.
A quick look at a typical lifeline filter appears below. Note that the channel numbering was assigned in the order that they were defined historically rather than with increasing frequency. As one goes up in frequency, cable channels are numbered 2-6 (low band), 95-99 and 14-22 (mid-band), 7-13 (high band), 23-94 (super band), and then 100 and up. Broadcast channels above Channels 2-13 are numbered completely differently, which is why your TV, TiVo, or VCR must be put in "Cable" mode to receive channels nunmbered higher than Channel 13 correctly.
| Channels | Frequencies | Filter Response |
|---|---|---|
2 - 6 |
54 - 88 MHz |
Pass |
95-97 |
88 - 108 MHz (FM Band) |
Pass |
98 |
108 - 114 MHz |
Pass |
99 |
114-120 MHz |
Transition. Signal may appear weak, colors will fade or will disappear. Sound may disappear. |
14-21 |
120-172 MHz |
Reject |
22 |
172-178 MHz |
Transition. Possible instability signal due to reduction of video carrier. |
6-13 |
178-216 MHz |
Pass |
23 |
216-222 MHz |
Transition. Signal may appear weak, colors will fade or will disappear. Sound may disappear. |
24-94 |
222-648 MHz |
Reject |
100 up |
648 Mhz up |
Reject |
Some older lifeline filters may have slightly different results, showing channel 22 but not showing channel 98. If you experience this problem, call our support line and we will update your lifeline service.