Tuesday, July 6, 2010

3 cm

The 3-cm (10-GHz) amateur band is gaining popularity at a very creditable rate. The primary equipment used for these 10-GHz activities is the Gunnplexer. The Gunnplexer has a Gunn diode located in its 10-GHz cavity , which is directly mated with its waveguide and horn-antenna system. The complete 10-GHz unit functions as a "front end" for a lower frequency unit that acts as an i-f stage. A small portion of the transmitted signal from each Gunnplexer is used as the receiver's local oscillator .

A further clarification of this technique is shown in Fig. 1-4. The two communicating Gunnplexers are frequency separated by the amount of the desired i-f, which is 146 MHz in this example. Both Gunnplexer transmitters remain on continuously, thus providing a local oscillator for mixing with the 10-GHz signal from the other unit. The ultimate result is a 146-MHz signal appearing at the i-f port of each Gunnplexer.

These 3-cm communications systems have proven their abilities over paths of 100 miles (160 km), and several European amateurs have communicated over 500 km (310 miles) on 10 GHz. An attractive plaque , sponsored by Microwave Associates of Massachusetts, awaits the first 3-cm pioneers to break the 1000-km (621 mile) range on this unique band. Gunnplexer communication networks are ideally suited for data communication links and multichannel TV relays, and as such could truly mark the direction for future .developments in amateur communications.

Fig. 1-4. A basic Gunnplexer communications system for 10 GHz. Each Gunnplexer oscillator provides energy for transmitted signal and couples a small amount of that energy into a mixer for heterody ning the received signa l down to an i·f range. The two transmitter signals are separated by the frequency of the chosen i-f.