Amateur 23cm
Understanding the Amateur 23cm Band
If a Ham Radio operator gets bored of talking to their local friends on standard VHF radios, they move up to the big leagues: the 23cm Band (1240 - 1300 MHz). This is where radio becomes true microwave engineering, requiring massive satellite dishes, extreme precision, and the ability to bounce signals off the actual Moon.
The Shift to Microwaves
At 1.2 GHz, the radio wave is physically 23 centimeters long. This completely changes the physics of how the radio behaves.
- A simple wire antenna no longer works. To capture a signal, you must build massive, complex metal grids (Yagi antennas) or physical parabolic satellite dishes.
- The radio wave acts like a flashlight beam. It travels in a perfect straight line and will violently bounce off mountains, airplanes, and rain clouds.
- Because the frequency is so high, standard cheap coaxial cable absorbs all the power. Operators must use incredibly thick, expensive, low-loss Heliax 'Hardline' cables to prevent their signal from dying before it reaches the antenna.
Moonbounce (EME)
The ultimate flex in the 23cm band is Earth-Moon-Earth (EME) communication. An operator in Texas aims a massive dish at the Moon and blasts 1,000 Watts of raw microwave power into space. The radio wave takes 2.5 seconds to travel through the vacuum of space, violently smash into the rocky surface of the Moon, and bounce back. An operator in Japan aims their dish at the Moon, captures the microscopic, billionth-of-a-Watt reflection, and successfully decodes the message.
Key Equations
The Amateur 23cm Band is an internationally allocated microwave frequency range (spanning roughly 1240 MHz to 1300 MHz) granted to licensed Amateur Radio operators by...
Key specifications:
23 cm | 1240 MHz | 1300 MHz
Power: P(dBm) = 10log(PmW), 0dBm = 1mW
Comparison
| Aspect | Amateur 23cm Spec | Typical Range | Impact | Design Note |
|---|---|---|---|---|
| Primary function | The Amateur 23cm Band is an internationa... | Application-dep. | Critical | Verify in sim |
| Operating range | Positioned in the L-Band, it represents... | Application-dep. | Critical | Verify in sim |
| Performance | Because 23cm waves are strictly line-of-... | Application-dep. | Critical | Verify in sim |
| Integration | Instead, the 23cm band forces amateurs t... | Application-dep. | Critical | Verify in sim |
| Trade-off | Understanding the Amateur 23cm Band If a... | Application-dep. | Critical | Verify in sim |
Frequently Asked Questions
Is the 23cm band in danger of being taken away?
Yes, heavily. The L-Band is incredibly valuable real estate for the military and global aviation (specifically GPS and the Galileo navigation systems). Because the 23cm band sits dangerously close to these massive, trillion-dollar satellite systems, governments (like the ITU) are constantly attempting to shrink or heavily restrict the amateur 23cm band to prevent accidental interference.
Can you use 23cm for video?
Absolutely. Because the 23cm band is incredibly wide (60 MHz of total bandwidth), it is legally wide enough to transmit full, high-definition television signals. Amateur operators frequently use this band to transmit 'Amateur TV' (ATV), blasting live, unencrypted video feeds to other hams across the city using massive dish antennas.
Why do 23cm radios look like plumbing pipes?
Because of 'Cavity Filters'. At 1.2 GHz, standard electronic filters (made of tiny capacitors on a green circuit board) become useless. The only way to perfectly filter out chaotic radar noise is to build a filter out of physical brass or copper plumbing pipes. The radio wave enters the pipe, resonates perfectly at 1.2 GHz, and exits clean. The radio literally looks like a piece of industrial plumbing.