Tuesday, August 28, 2012

Getting Crossed Up is a Good Thing...

Over in the APN Facebook Open Group, a wonderful question came up which inspired this article about being cross... or actually crossbanded.

Every ham knows operating UHF & VHF allows wonderful point to point, close range communications, however, effective signal range can be another matter. With handheld radios transmitting with only a few paltry watts, and frequencies which travel line of sight, and often subject to scattering by obstacles like buildings, terrain or vegetation, the distances which UHF & VHF radios can get a signal out, can often be too limited. For the most part, most activity on the upper bands involve using signal boosting repeater operations, where each individual point is actually communicating to a powerful repeater, instead of the intended receive point directly.
It's a system that works like gangbusters. Repeaters allow UHF/VHF communications far past normal ranges...it's THE thing to do. But what of the lowly handheld which, for one reason or another, can hear the repeater, but just doesn't have the stuff to get a signal to the repeater? That's when you need to get cross... as in Crossband Repeat.

Crossband capable Icom IC-2820H
One of the neat features some mobile UHF/VHF dual-band radios offer, is the ability to simultaneously receive on one band, and transmit on another band... to crossband repeat. That neat feature adds the ability to boost a weak signal...like from your little handheld...and give it the power it needs to be heard several miles away at the big repeater, or to any receive point far beyond the range of the handheld. Besides a crossband capable mobile or base radio, you need a handheld radio with dual-band capability...usually 2 meter and 70 centimeter (440 Mhz.), and able to operate "split", or able to transmit on one frequency & receive on another, (most dual-band handheld radios do). The method of setting up a crossband radio would depend on the individual model radio, but in essence the crossbanding radio is usually set up to receive a 70cm discrete frequency...say 444.600MHz... and transmit on the target 2 meter repeater frequency, or the discrete 2 meter simplex frequency your receiving party is monitoring. Then you would transmit to your crossband radio on the 70cm frequency, and split receive the repeaters 2 meter transmit frequency, or whatever frequency your receiving party is operating on. The following diagrams may help visualize this method...
Neat-o Diagram made by yours truely!
It's easy to see that crossbanding can extend greatly the operating range of a small handheld radio, allowing greater ability to operate in less than optimal conditions, as well as enabling you far greater capability to set up remote net operations free of additional outside support... perfectly suited for emergency ops. If you like to learn more about crossbanding, here's a great article on the Worldwide Radio Forum, which may help you further.
So the next time you can't get your signal into the local repeater, don't get cross... just get crossbanded!        '73 from KI4HEE

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