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ARRL Microwave Band Planning Committee Releases Draft Band Plans

05/15/2012

The ARRL UHF-Microwave Band Plan Committee has released for comment its draft band plan for 13 cm (2.3/2.4 GHz) and welcomes comments on it. The amended draft band plan for 902-928 MHz (33 cm) has also been released.

13 cm

This is the third of four draft band plans released for comment. The Committee appreciates the initial suggestions and reports of the current and proposed activities on the band. If you have specific comments as to the Draft ARRL 13 cm Band Plan, please submit them via e-mail no later than June 4, 2012. For a copy of the Draft ARRL 13 cm Band Plan, please see the graphic below.

33 cm

Based on numerous comments, both supporting and expressing concerns about the initial Draft ARRL 33 cm Band Plan, the Committee noted that there is enormous regional variation in both current uses of the band and the noise environment created by in-band and adjacent commercial users and Part 15 devices. The latter is changing -- and, for the most part, growing -- in real time, leaving much of the band virtually unusable for some purposes.

Most commenters acknowledged that the background noise levels increase as the frequency increases from the bottom of the band, making the bottom one or two MHz the most desirable segment for listening, whether by weak-signal operators or by topographically advantaged repeaters that receive from wide geographic areas. The Committee noted that, of the top seven states in terms of number of 33 cm repeaters, all but one include in their plans repeater inputs 100 kHz or less from the popular 902.100 SSB calling frequency, yet it did not receive any reports of those existing allocations adversely affecting weak-signal users.

Although some commenters suggested, in essence, “Adopt my region’s plan as the national plan,” the plan most often mentioned by these commenters would clearly not work in other heavily populated areas of the country. Some places have clusters of active weak-signal users and only a handful of repeaters on the band. Others have more widely scattered weak-signal users but many repeaters -- more than 150 in one state alone -- with a correspondingly large base of users. During both the initial solicitation of user input and the draft plan comment period, the Committee received no comments indicating that any existing regional plan was not working or had disenfranchised a subset of band users. To the contrary, commenters making any reference to their respective regional plans reported that they were working well and would not like to see them changed. This includes weak-signal users in regions where most of the bottom 500 kHz is open to repeater inputs.

Some commenters expressed the concern that publication of a national band plan different from their own would ruin the band or cause them to abandon their 33 cm activities. It is important to remember that no frequency coordinator or similar regional group is under any obligation to make any change to its plan to bring it in line with a national plan. The national plan serves primarily as a set of recommendations, particularly for areas of the country where band use is starting to grow and regional coordination is only now becoming important. A national plan is not intended to -- and cannot possibly -- replace a well-designed and effectively functioning local plan. This has always been the case and it remains so. Accordingly, the Committee has revised the Draft ARRL 33 cm Band Plan to reflect more regional options as to mode and application, particularly as between FM and SSB/CW near the bottom of the band.

While most commenters expressed support for a 25 MHz repeater split, a minority suggested that such a split was due merely to lack of effort expended to make more difficult modifications to commonly available commercial equipment. While ease of conversion is certainly a factor in the popularity of 25 MHz repeater splits (more than 90 percent of the 500+ 33 cm repeaters in the US use it, despite no recognition of such a split in the previous ARRL band plan), the aforementioned difficulty in receiving outside the bottom of the band is also a big influence in choice of repeater frequencies. Nonetheless, the Committee has amended the draft band plan to provide for alternate repeater splits as a regional option.

The Committee had originally proposed 927.100 MHz as a simplex calling frequency, since it is 25 MHz up from a widely used SSB calling frequency. A brief survey of published regional plans shows at least six simplex “calling frequencies,” so it appears there is no national standard; however, most of those who did comment on this aspect suggested that 927.500 was more commonly used for this purpose, and recommended that it be retained as such. Since it is the most commonly mentioned frequency, the revised draft plan shows 927.500 MHz, with an option for a regionally selected alternative. Unlike 146.520 MHz -- which is monitored by amateurs while driving, camping and hiking -- there is no pressing need for an FM calling frequency on 33 cm that is uniform throughout the country.

If you have specific comments as to the revised Draft ARRL 33 cm Band Plan other than how it would affect a regional plan (because it won’t, unless the amateur community there wants it to), please submit via e-mail them no later than May 31, 2012. For a copy of the Draft ARRL 33 cm Band Plan, please see the graphic below.

Status of Remaining Tasks

Drafting of a revised plan for the 23 cm band will be completed after the Committee and ARRL staff have had an opportunity to research and evaluate recent and planned deployments of replacement air-navigation radar systems. These systems operate in and around our amateur 23 cm frequencies, where we are secondary users.



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