Winter 2008 Issue

FM

D-Star Creates Band Planning Challenge

By Bob Witte, KØNR

 

In the Summer 2007 issue of CQ VHF, I mentioned the challenge that frequency-coordinating bodies are facing with regard to coordinating digital voice (e.g., D-Star) repeater systems. The emergence of D-Star is putting pressure on the frequency-coordinating bodies to find a place in the spectrum. This challenge has caused significant debate within the ham community, and some frequency-coordinating bodies have now taken action.

Frequency Coordination

Frequency coordination is a critical function for effective use of repeaters on the amateur radio bands, because repeaters are inherently fixed in frequency and usually fixed in location. Frequency coordination is a process that minimizes repeater-to-repeater interference by carefully planning separation in frequency and geography. This is a voluntary function, but has the strength of the FCC behind it. When it comes to interference issues, the FCC is crystal clear that coordinated repeaters take priority over ones that are not coordinated. Overall, it is a great example of how the Amateur Radio Service can self-regulate, with a little help from the FCC.

In many parts of the U.S. designated repeater pairs in the 2-meter band are all allocated—that is, the portion of the band designated for repeaters has a repeater coordinated on each channel. When a new request is made for a repeater coordination, there is no available frequency pair that can be used without causing undo interference to existing repeaters. The 2-meter band in the U.S. is only 4 MHz wide and serves a wide variety of interests—moonbounce, meteor scatter, weak-signal CW/SSB, FM simplex, FM repeaters, and satellite. The 70-cm band in the U.S. is 420 MHz to 450 MHz, which offers a much wider slice of radio spectrum. Still, the designated FM repeater portion of the band is also fully allocated in many areas.

Frequency coordination is a difficult and often thankless job. Potential repeater owners often come to the frequency coordinator with unrealistic expectations. They frequently do not understand the principles of spectrum management; they find an “open” frequency and want to plop a repeater on it. The frequency coordinator needs to make decisions that protect the interests of established repeaters while making room for newcomers. When the band gets full, this becomes a difficult to impossible task.

To determine your local frequency coordinating body, see the National Frequency Coordinators’ Council website listed in the References section at the end of this article.

There is quite a buzz surrounding D-Star, fueled by ICOM’s marketing efforts and the desire of many hams to experiment with new technology. Frequency coordinators are getting requests for D-Star repeater coordination, often for a “standard D-Star stack” of 2-meter, 70-cm, and 23-cm repeaters (see Table 1). (The ICOM D-Star system is set up to use one controller for up to four bands. A common configuration is to deploy D-Star on all three available bands: 2 meters, 70 cm, and 23 cm.)

Challenging the Rules

When faced with a problem (no repeater pairs on 2 meters), some hams start to “innovate” by carefully interpreting the FCC rules and regulations. It is an interesting process, as most of FCC Part 97 was written decades ago with a particular technical context in mind. The FCC rules are intended to last over time, but sometimes they have to be “re-interpreted” to remain relevant, or sometimes people just want to read their own agenda in the existing rules.
 

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