About the 1296 MHz Band ….
Like 28 MHz, the 23 cms band is a transitional band between VHF-UHF and microwaves. This is a popular band that forms the mainstay for many microwave operators, and a band that gives many their first real taste of the GHz spectrum.
In many ways the band is similar in nature to the lower VHF-UHF bands, but there are many propagation modes that place it squarely into microwave territory.
23 cms is also a band where some manufacturers still offer band modules for their transceivers, the Icom IC-9100 is a notable recent entry to the market with a 23 cms module available as an add on . Newcomers to 23cms should also not overlook the acquisition of older, yet still highly capable, multiband multimode transceivers, such as the Kenwood TS790 and Yaesu FT736R, which still offer an excellent high performance entry method to the band although these modules are now becoming quite scarce and therefore appropriately priced!
Of course, like its lower band neighbours, the band offers a good choice of FM simplex, repeater and digital modes. The wide bandwidth at 23 cms also offers access to one of the first main bands for Amateur Television (*some countries having an ATV allocation at 70 cms). Amateur satellites also use this band for uplinks/downlinks.
The mainstay modes for long distance communication remains SSB/CW, and of course in line with most modern weak signal working, digital modes such as JT65 have become common place. JT4 has also been a newcomer to the digital scene and the latest release of WSJT (WSJT-X) from K1JT offer multimode digital capability in an updated package.
23 cms is rather unique in that it allows operators who do not wish to build equipment, access to the band via built commercial equipment, but also for the amateur who is willing and able to build their own gear, there a wide choice of kits on offer, from transverters, preamps, amplifiers and more complex equipment for frequency control etc.
The band offers many constructors their first taste of construction at microwaves, which is very different than that at HF-UHF.
Like many of the VHF-SHF bands, 23cms has benefited greatly from the introduction of modern RF devices which have allowed the construction of sub dB noise figure receivers with relative ease. Some constructors have broken through the 0.2 dB figure and are heading forever lower!
High power LDMOS devices originally designed for the mobile phone industry have percolated into the amateur market and high power Solid state amplifiers of 600W and greater are now available with relative ease.
Of course 23 cms has also benefited from modern Yagi design techniques and the days of those old loop yagi designs are long gone with the introduction of modern long Yagis, such as the DL6WU designs. Due to the small wavelength, a high gain yagi array can be easily built using home construction techniques or purchased commercially.
The mobile phone industry is not the only new technology that has benefited 23 cms. The use of C Band Satellite services in the late 1990s encouraged the spread of small 3-5M dishes across many countries and amateurs were not slow in pressing these into amateur service. Using modern receivers, low loss cables designed for cellular services , compact solid state power amplifiers and a C band dish, many amateurs are active on EME from relatively simple, yet highly capable stations. This has been supported by developments in circular polarised feeds such as the Septum feed, and the availability of high performance preamps from people like G4DDK which as spurred many small, low power, EME stations onto the band.
As mentioned earlier, 23 cms retains many of the propagation characteristics of the lower VHF-UHF bands. Tropospheric ducting is a prevalent mode and small scale regular openings occur frequently during the passage of weather fronts. Most VHF-SHF amateurs turn into amateur meteorologists!
But it is some of the more interesting modes such as aircraft scatter and rainscatter that places it worlds apart from the lower bands.
Rainscatter refers to the scattering of signals from hydrometeors in the troposphere such as ice particles, rain droplets, even snow. This scattering at this lowest microwave band usually occurs in the heaviest of thunderstorms and can lead to long distance contacts being made at distances up to 1000 Km.
Aircraft can also act as a reflective medium, which is not surprising as this is how RADAR works. Amateurs however are not looking to locate the aircraft for navigation purposes, but for communications, as the reflections allow contacts to be made over much longer distances than normally possible, generally at ranges of up to 750-900 kms.
Surprisingly modes such as Aurora are still effective at 23 cms and there have been a number of well publicized auroral contacts at 23 cms. It is fair to say however that this mode is not a mainstay mode for this band and has usually been limited to the Nordic countries. Passive satellite scatter has also occurred in this band.
Overall the 23 cms is a very exciting band and modern RF devices and design techniques allow many amateurs to exploit this band to its fullest.