The 136 kHz band represents the lowest frequency amateur radio or amateur radio band. Although not allocated to all countries, this band is proving to be very popular with experimenters who are interested in LF band operating and the unique challenges it presents in ham radio.
The 136 kHz amateur radio band has only been available for radio amateurs in the past few years. With more countries releasing the band for ham radio use the level of activity is beginning to rise.
In view of its place at the very low end of the frequency spectrum, the 136 kHz allocation presents a unique challenge both in terms of operating and the technology that it used. Morse is generally used because it occupies very little bandwidth; several tens of Morse transmissions can be accommodated in this small band, whereas it is only wide enough for a single voice transmission. Many radio amateurs use very slow Morse combined with exceedingly narrow filter bandwidths and digital signal processing techniques. Also data transmissions are used, although the data rate that is used is again slow to reduce the bandwidth and also enable the signals to be received and deciphered despite their low level.
Full-sized antennas for these frequencies would be very large so radio hams use much smaller antennas. This presents new challenges for amateurs who use these frequencies.
|Frequency allocation:||135.7 - 137.8 kHz|
As this band is also allocated to other services in many countries 136 kHz is allocated on a secondary basis to ham radio users with the proviso that they do not cause interference to other services. Additionally the power levels are often limited. A typical power limit for the 136 kHz band is that used in the UK which limits the power to 1 Watt ERP (Effective Radiated Power). This for of power measurement is used because a full sized antenna at this frequency would be excessively large for virtually all ham radio users, and the small antennas normally used on 136 kHz have a very low level of efficiency because of their size. Accordingly the level of effective radiated power level is used.
While activity levels are still low on 136 kHz LF amateur radio band when compared to the very popular bands, interest is growing in this ham radio allocation and operating on these frequencies is particularly rewarding.