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3-centimeter band

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3-centimeter band
Frequency range10.0–10.5 GHz in all three ITU regions
WavelengthAbout 3 cm
GroupSHF (microwave)
US licenseTechnician and above, full privileges
Operating
Weak-signal calling frequency (US)10368.100 MHz
Narrowband center (IARU Region 1)10368.200 MHz
Satellite segment10.45–10.50 GHz
QO-100 narrowband downlink10489.5–10490.0 MHz
Sharing
StatusSecondary
Shared withRadar; also fixed and mobile services in Regions 1 and 3

The 3-centimeter band is the amateur allocation from 10.0 to 10.5 GHz, usually called "10 GHz" or "10368" after its narrowband calling area. It is the most popular of the microwave bands and, for many hams, the first one they try. The band edges are the same in all three ITU regions,[1] small dishes give very high gain, and cheap satellite-TV parts work at these frequencies. The band also carries the downlink of the geostationary satellite QO-100, and it is the classic band for rain scatter.

Allocations and sharing

Amateurs are secondary users of the whole band worldwide, and the amateur-satellite service shares 10.45–10.50 GHz.[2] In the US, Part 97 requires amateurs to avoid interfering with, and to accept interference from, government radiolocation;[3] in ITU Regions 1 and 3 they must also protect fixed and mobile stations of other countries.[3] National rules can be narrower. In the UK, for example, parts of the band are not available to amateurs.[4] The IARU Region 1 plan provides a second narrowband area at 10450–10452 MHz for countries where the usual one is unavailable.[5] See IARU regions for how the regional plans are divided.

What you'll find on the band

  • Weak signal. SSB, CW and digital modes meet around 10368.100 MHz in North America[6] and 10368.200 MHz in IARU Region 1, with beacons a little higher.[5] Moonbounce is also active on the band.
  • Satellites. QO-100's narrowband transponder retransmits signals from its 13-centimeter uplink on 10489.5–10490.0 MHz,[7] and its wideband transponder, used for digital television, transmits just above.[8] An ordinary satellite-TV low-noise block downconverter (LNB), often modified for better frequency stability, can receive both.[4] QO-100 covers Europe, Africa, the Middle East, much of Asia and the eastern edge of South America, but not North America.[9]
  • Wideband. Segments are set aside for amateur television and high-speed data.[6] The ARRL band plan still reserves 10200–10300 MHz for "Gunnplexers", simple wideband FM units built around Gunn-diode oscillators.[6]

Propagation

Line-of-sight paths from hilltops are the core of 10 GHz operating, and tropospheric ducting, especially over water, can extend them to hundreds of miles. The band is particularly good for rain scatter.[10] Both stations aim their dishes at a heavy rain cell, which scatters signals between them; scattering is roughly ten times stronger than at 5.7 GHz.[11] Signals arrive with a rough, rasping sound caused by Doppler spreading, and CW is the easiest mode to copy.[11] Aircraft scatter and EME add further possibilities.

Equipment

Most stations use a transverter driven by a 2-meter or 70-centimeter radio and mounted at the dish, since feed line loss at 10 GHz is severe; some use waveguide for the last connection. A dish 2 feet (60 cm) across gives more than 30 dBi of gain with a beam only a few degrees wide. Frequency stability matters: an oscillator error of one part per million puts a signal about 10 kHz off, so stations lock to a GPS-disciplined reference. Among commercial radios, Icom's IC-905 reaches 10 GHz through an optional transverter with half a watt of output.[12]

Contests drive much of the activity. The ARRL 10 GHz and Up Contest runs over a weekend in August and another in September,[13] and national societies elsewhere hold their own microwave contests.

If you live within QO-100's footprint, a satellite-TV dish and LNB feeding a software-defined radio receiver will pick up the satellite's beacons and traffic, an inexpensive first look at 10 GHz before building a transmitter.

See also

References

  1. ↑ 47 CFR 97.301, eCFR.
  2. ↑ Frequency allocations, SHF band, ITU Radio Regulations, ITU Radio Club.
  3. ↑ 3.0 3.1 47 CFR 97.303, eCFR.
  4. ↑ 4.0 4.1 5.7 and 10 GHz band plans, RSGB.
  5. ↑ 5.0 5.1 IARU Region 1 SHF band plan, IARU Region 1.
  6. ↑ 6.0 6.1 6.2 ARRL band plan, ARRL.
  7. ↑ QO-100 NB Transponder Bandplan and Operating Guidelines, AMSAT-DL.
  8. ↑ QO-100 WB Transponder Bandplan and Operating Guidelines, AMSAT-DL, February 2021.
  9. ↑ Es'hail 2 / QO-100, AMSAT-UK.
  10. ↑ The Microwave Bands, RSGB.
  11. ↑ 11.0 11.1 Rain Scatter Propagation, RSGB.
  12. ↑ IC-905, Icom America.
  13. ↑ 10 GHz & Up, ARRL.
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