Thursday, June 28, 2012

Frequency Coordination

This the only place in Part 97 that discusses the duties and authority of a frequency coordinator.

§ 97.3 Definitions.
(a) The definitions of terms used in part 97 are:
(22) Frequency coordinator. An entity, recognized in a local or regional area by amateur operators whose stations are eligible to be auxiliary or repeater stations, that recommends transmit/receive channels and associated operating and technical parameters for such stations in order to avoid or minimize potential interference.
Please note that it doesn't say it requires any recommendation of the FCC, the ARRL, or existing frequency coordinators, etc. So it doesn't say that there can't be more than one frequency coordinator in a local or regional area.

Here is something interesting I ran across in some recent ARRL Executive Meeting Minutes:

4.1. Mr. Imlay reviewed material he had circulated to the committee prior to the meeting with regard to a repeater coordinator dispute in Wyoming. He explained that while the longstanding policy of both the ARRL and the National Frequency Coordinators’ Council (NFCC) is that there should be only one recognized frequency coordinator for a band in a given geographic area, FCC rules and policies do not rule out the possibility of there being more than one. In Wyoming there are two coordination entities, each of which can claim recognition by amateur operators in the state. While the ARRL is not directly involved in frequency coordination, there is a Memorandum of Understanding between the ARRL and the NFCC and ARRL policy is to accept only information supplied by NFCC-certified coordinators for publication in the Repeater Directory. NFCC has experienced a period of inactivity, which has caused the current accuracy of its list of certified coordinators to be called into question. However, new NFCC officers have just been elected.

What bothers me is that most of the VHF-UHF bands are inundated with mostly inactive repeaters.

Where in Part 97 does it say that a frequency coordinator should be in charge of parceling out exclusive (both geographic and frequency) usage of 144 - 148 MHz (etc)?

It doesn't make any sense at all to be attempting to more finely regulate that all of the potential "repeater channels" on 2m, 70cm, for all of an area, are not actively in use.

Frequency coordination made sense 20 years ago when there was intense demand for repeaters and there weren't easy ways to do coordination without a slow, manual, group effort.

Back then the Frequency Coordinators newsletter was a good source to share/disseminate technical information regarding building a repeater.  Since then websites like repeater builder have taken over that aspect.

The technical justification for coordination has also greatly diminished.  The days of custom ground crystals and waiting weeks for their arrival went away when PLL gear took over the market.  Changing frequency isn't as big of a deal anymore.

It is interesting to note that repeater coordination has only been around since 1985? (per docket 85-22). It was prompted a number of repeaters causing interference to one another.

Now there's little, and falling usage of voice repeaters, and coordination can easily be accomplished with a wiki page listing who is responsible for a particular system that's operating on a particular frequency at a particular location.

Modern sites like Repeater Book allows you to update your own listing.  And that is the bottom line to most repeater owners.  Being listing with minimal fuss.

I and others had the unfortunate experience of the coordination body complaining that some aspect of the repeater isn't up to their standards. Perhaps it was a short distance move, or some other minimal system change. The communication had no merit as there was no other official station complaint. They just want to be the repeater police, and justify their existence.

I think that for the most part, a frequency coordination body has little service to ham radio these days. It seems most just likes making paper work for themselves.

I think their continued existence actually, actively Harms Amateur Radio by propagating a mistaken impression that repeaters on the air should be "rationed".  Yet in reality, their job is to accommodate.

When the repeaters are idle the majority of the time, the chance of interference is low, which begs the question why bother with it at all?

Since a receive tone is a requirement of coordination, you really seldom notice if you are prone to interference which may be affecting your fringe areas.

It should be easy for an individual, club, or group to put up more equipment to make better use of Amateur Radio spectrum. Instead, the coordination policies and procedures make it difficult to do so, and people walk away discouraged and disgusted from even trying to put up interesting systems on the air.

The problem is frequency coordinators have broken the bands into channels most fairly narrow in width, with conventional input and outputs. I think this image/model discourages potential other use, that may not fit the convention.

Take a look at CDMA Spread Spectrum, in the implementation of Cellular Telephony. We had tons of buzz about this in 80's-90's but it never went anywhere in ham radio. How could it? It's totally incompatible with the way we slice up the bands.

And even with conventional channels plans, there is room for determent. Shouldn't we try to accommodate a multitude of different experiences?

Lets say there are 5 available pairs in a given area. Three are already filled by conventional analog repeaters. There are two requests for pairs for D-Star. One request for a P25 (APCO 25) mixed-mode repeater, and one for DMR. How does or should these be doled out? Does the policy say the first requested, is the first filled? Does this help the hobby move forward, and provide opportunities to area hams for multiple mode exposures/experiences?

I think anyone who wants to put a system on the air - packet, D-Star, WiFi, P25, whatever, should simply monitor the band in question, find the quietest spot in the "repeater section" of the band in the geographic area you plan to construct the system, and put it on the air. Likely you won't interfere with anything. On the off chance that you interfere with a system that's actually used for more than ID'ing itself, then relocate. You'll find a place in short order.

In the past there have been FCC reports on interference situations.  They looked at the total history of both sides and at technical levels. The FCC takes all of this on a case-by-case basis. They do not automatically side with a coordination body. They take the total situation into account. billcross1.pdf

What you can take away from this is that the FCC regards repeater coordination as a volunteer thing taken on by the amateur community. They don't appoint  them, and regard repeater coordination as a self-enforcement or self-regulation issue. That talk by Bill Cross is a reaffirmation of policies they developed nearly 10 years ago. It also states that the FCC does not officially recognize any coordinating body.

When the repeaters are idle the majority of the time, the chance of interference is low, which begs the question why bother with it at all? Most of who participate really only primarily concern themselves with being listed. A way to advertise their systems.

Frequency coordination needs sweeping changes and to move forward. One of the purposes of a frequency coordinator is to recommend standard operating procedures.

The ARRL recently revised their outdated microwave bandplans. Now it's time for regional coordination bodies to adopt these, and put some thought into their coordination policies not only for microwave, but VHF and UHF as well.

(It's no wonder the NFCC has been dangling by a thread for years.)

It has been suggested: To start a 5-year phase-in plan for 6.25kHz channel centers and mandatory 2.5 kHz narrowband FM deviation on analog.

I also think we should have more shared non protected repeater pairs available on each band. While I am not a fan of more repeaters, I am also not a fan of unnecessary rules and other deturants that might prevent someone from experimenting. If someone wants the experience of trying to build their own repeater, and / or how a particular location plays, let them. Even if no one really uses it. Amateur radio is a playground for learning.

Thought should be given to creating digital repeater segments within each band. Just like we have sub-bands for ATV and packet, perhaps we should be doing this with digital repeaters? Hitting the scan button on an analog rig, and having it screech, and beep on a digital repeater right next to an analog one is less than desirable. Due to "crowding," this would have to be a process of clearing / reserving segments via a process of attrition over time.

I'd like to suggest repeater coordination newsletters should be a clearing house for sharing technical info from time-to-time. Again, ham radio should be about learning.

If you are still believing "tradition must continue,"  read on.

Local frequency coordination bodies guard their frequency database carefully.  They attach a copyright to the data (at least the format of it - legally speaking).  They sell the list to the ARRL for the ARRL's directory for a substantial annual fee. Both are copyrighted, so anyone else publishing repeater data either has to get their own (a daunting task), or illegally use copyrighted data (though some argue the validity of the copyright for the actual data). However, the irony is many coordination bodies put their data on the web for personal use.

You pay or donate to a frequency coordinator, and provide them with your data, that they copyright and sell.  I am sorry, but ham radio has always been a collaboration of people working together and sharing information freely, so this irks me as bad as the AMBE patented algorithms.

It's time to relax the rules, while the band activity is low, and allow a gestation period.

Tuesday, June 12, 2012


Bob Witte, K0NR wrote an interesting column for CQ-VHF's Spring 2012 magazine issue.

It's titled "TRBO Hits the Amateur Bands."

Its about Digital Mobile Radio (DMR) sometimes called MOTOTRBO.

He points out that its a new digital standard that is gaining traction on the VHF and UHF amateur radio bands. He reports there are over 90 DMR repeaters up and running in the U.S with more planned.

DMR originated as a European Telecommunications Standards Institute (ETSI) standard.

The DMR Association is the industry body promoting adoption of the standard and includes these companies as members: Harris, Hytcra, Icom, JVC, Kenwood, Motorola, Tait Communications, Vertex Standard, and Zetron.

DMR takes a novel approach to spectral efficiency. The bandwidth of the radio signal is nominally 12.5 kHz with two signals sharing the channel via Time Division Multiple Access (TDMA). Simply put, two mobiles working through a DMR repeater share the channel by cycling their transmitters on and off in a synchronized manner. This is similar to how some cellular-phone systems handle multiple phones operating on the same channel. The cellular-phone base station controls the synchronization of the various phones so they do not interfere with each other. Similarly, with DMR the repeater has to synchronize the two mobiles using the same 12.5-kHz wide channel.

"A DMR installation looks a lot like a normal repeater system but with the benefit of two channels built in."

For those totally unfamiliar with TDMA, I recommending checking out my older blog titled "Understanding Digital," where I reference some Hak5 videos on Pulse Code Modulation. And the following week, Time Division Multiplexing (TDMA).

These sort videos give a good tutorial on how this works.

But if you really need the nitty-gritty, the TDMA time slots are 30 msec in duration.
In the 30 msec slot, the transmitter is required to ramp up to full power in 1.5 msec, send data for 27 msec, then power down in 1.5 msec.

For further good reading and information, I suggest reading K0NR's article. I believe this is the first printed ham article on DMR.