NARCC Update

The past several months have seen a rekindled interest in "Refarming" a portion of the 2-meter band in an effort to add additional channels. "Refarming" may not be the correct term although that is what the effort has been referred to in recent months. The focus of this effort lies is changing channel spacing of the 145-146 mHz portion of the band, sometimes referred to as the sub-band, to bring it in line with the 146-147 mHz portion. If you have spent much time on 2 meters you already know that repeaters between 146 and 147 are separated by 15 kHz whereas those below 146 are spaced at 20 kHz.

To the proponents of the refarming project, reducing the spacing between channels would permit the addition of 6 or 7 additional channels and in this crowded part of the state that would not necessarily be a bad thing.

The opponents of this effort say they are opposed because 15 kHz spacing is too close and normal FM radios can't work properly this close together. One might wonder how his can be since they seem to work just fine in the original part of the band, 146 to 147 mHz. The reality is, they don't work that well and really don't conform to what commercial operators would consider "standards". As an example, the W6CO repeater on 147.180 mHz, located on Mt. St Helena has a coverage area of well over 100 miles in diameter. Another repeater, Located just 35 miles away on Mt Vaca operates 15 kHz above the 147.180 repeater and causes interference to some users within that 100 mile circle. Both repeaters transmit a sub-audible tone that permits tone coded squelch to mitigate the problem and this works well for most, but some users in the fringe areas, Novato as an example, hear both signals and as a result have trouble understanding the audio when both repeaters are transmitting. If you recall the formula for calculating the bandwidth requirements of an FM signal you will find that a transmitter using 5 kHz of deviation and being modulated by a 3kHz audio signal will occupy 16 kHz. There are some obvious fixes to this problem: First, reduce the deviation to 4 kHz or less. Limit the audio modulation to less than 3 kHz and you will find 15 kHz spacing works a lot better. Secondly, reduce transmitter output power to keep the service area within a manageable range. Does any repeater in this congested area really need to cover a 100 mile circle?

The opponents also claim that "Special Interest Groups" are driving the effort to fix something that isn't broken. The SI groups referred to are, of course, the D-Star repeater operators who are having trouble finding homes for their 2-meter modules. D-Star users respond by saying "Look, it's not just D-Star. Digital radio is coming whether it is D-Star, Moto-Trbo, P-25 or homebrew. It's coming and we need to find a home for it." They point out that a digital signal such as D-Star occupies a much narrower bandwidth, perhaps only 6.25 kHz, and to plunk one down in the middle of a 20 kHz channel is a huge waste of spectrum. These folks are not calling it "Refarming" but rather "Spectrum Efficiency". They point out that 2 digital repeaters can occupy a single channel and not interfere with each other or adjacent channel repeaters.

The pros and cons as stated so far are pretty much based in fact. There are some other arguments which are often heard that are far more subjective. There are numerous Hams that feel that anytime the internet is involved in a radio network, that network is "poisoned" and they don't' want anything to do with it. Other examples of RF/internet systems are IRLP and Echolink and while D-star does take advantage of the internet to form linking, the net is not necessary for the repeater to work. It simply expands it's range from local to Worldwide.

Another group of opponents point out, incorrectly, that D-star is a proprietary format and is only produced by Icom. Many don't have any use for imported radio equipment, especially from Japan. They are often die-hard commercial equipment users, clinging steadfastly to their surplus Motorola or GE equipment. (interestingly, I find the same attitudes in motorcycling, with many refusing to own or even ride with someone on an imported motorcycle.)

The result of these divisions was seen at the NARCC meeting on July 11th. The board, in response to the general membership held a special meeting to adopt a plan to promote "Spectrum Efficiency". There were 3 original plans submitted prior to April of this year and since then 8 additional plans had been submitted. One of the plans (plan-7) was to do nothing. This may sound strange but in any project involving multiple alternatives, "do-nothing" should always be the first alternative.

Minutes after the meeting started Norm Lucas, WB6RVR made a motion to consider Plan-7 before all others. This made perfect sense, since if the membership decided to "do nothing" then debating and voting on the other 10 plans would be unnecessary. the motion was seconded and carried by a pretty fair margin.

A second motion by Norm was to direct the board to not attempt any additional activity on "refarming" for 3 years. This motion was also seconded and carried.

Digital radio proponents came away from the meeting somewhat perplexed. They will now be required to find homes for their digital systems in the same way analog system owners must do and when they find a space will be tying up much more spectrum than necessary. On the positive side, if the frequency is carefully chosen, in some cases two systems can occupy the same 20 kHz channel if the systems below and above that channel are located far enough away geographically.

One thing seems to be clear: Digital radio is indeed coming. D-Star alone now has more than 10,000 registered users and more than 460 repeater systems worldwide. There are a few Moto-Trbo and P-25 systems and just today I heard a homebrew system from the UK on REF014