HF pagers

From HFUnderground

Revision as of 18:14, 5 January 2024

List of known pager paging data link data systems using digital modes remote control radio control in the 26-28 MHz CB or 11-meter frequency range.

See also the Remote Control FCC Part 95 Class C Page - Remote Control Radio Service (RCRS), FCC Rules Part 95, Personal Radio Services, Subpart C—Radio Control Radio Service 95.701-95.899, previously 95.201-95.225

History and Background Information

The original five RC frequencies can trace their roots back to the origins of the CB radio service - when the band was first allocated as 26.96 MHz to 27.23 MHz (23 channel CB) the FCC band plan included five model control/data channels 35 kHz from the band edges with 50 kHz spacing between each RC channel. 26.995 MHz is 35 kHz above the bottom of the band (26.960 MHz) and 50 kHz away from the next R/C channel (27.045 MHz). 27.195 MHz is 35 kHz below the original edge of the band (27.230 MHz) as well. The 50 kHz spacing was in line with the capability of remote control systems in the 1950s. 27.255 MHz was originally used for paging and kept that use even after being designated as CB channel 23. Since 27.255 MHz is 60 kHz away from the 27.195 MHz frequency, higher transmit power was (and still is) permitted.

In the United States, Part 95 of the FCC rules allow use of the six 26 MHz/27 MHz RC frequencies for high power control, supervision, data link, telemetry networks and "attention getting" devices. Mean (average) power limit is 4 watts on 26.995 MHz, 27.045 MHz, 27.095 MHz, 27.145 MHz, 27.195 MHz and 25 watts on 27.255 MHz. The majority of high power systems use 27.255 MHz - however some do transmit 4 watts on 26.995 MHz. Many of these devices are in use in the United States and elsewhere. Common uses include farming, agribusiness telemetry and remote control, lightning detection systems (with remote sensors and/or remote alarms/sirens) and numerous other applications. Harris Radio (under the brand name PRIVATEPAGE) produced a local area paging system that operates on 27.255 MHz, RadioShack sold two similar versions, one advertised as having a 7 watt transmitter, the other advertised as having a 4 watt transmitter.

26.995, 27.045, 27.095, 27.145 and 27.195 MHz are all RC exclusive frequencies and voice transmissions are not allowed. However, these frequencies are often used as a "secret channel", "A channel" or "alpha channel" by CBers and freeband operators. Modified CB and 10 meter radios with a +10 kHz switch (or +10kc switch) allow access to the A channels. 27.255 MHz is CB channel 23 and data transmissions must co-exist with voice traffic on the same frequency. This likely explains the 25 watt power limit on 27.255 compared to the 4 watt power limit on the original 5 R/C channels.

There is also extensive Part 15 usage of these frequencies for low-power R/C model control. Higher power levels are used by professional grade systems. Most higher-end remote control/radio control devices use the 72 MHz and 75 MHz frequencies (where 0.75 watts is the maximum power output) or the unlicensed 2.4 GHz band. However, there remains considerable use of 26-27 MHz for data link, remote sensor monitoring and other similar purposes due to the high power available for unlicensed users and excellent propagation characteristics for point-to-point data networks. Some vendors are now offering systems that operate on the 5 VHF MURS frequencies for telemetry, telecommand and data link purposes (although these are covered under the Part 95 rules as well, they are not part of the RCRS under FCC Part 95).

Frequency List

Note: This list is a dynamic list and will never be complete. Many of these systems - especially the paging systems and telemetry or data link systems, act as de facto 11 meter beacons and de facto high frequency beacons. Included FSK data signals and pager signals - 25 to 30 MHz, included 29.7 MHz to 30 MHz portion above the 10 meter ham radio allocation 28 to 29.7 MHz but below the official beginning of VHF at 30.000 MHz