Michigan’s total area is something around 97,990 square-miles, which includes approximately 38,575 square-miles of the Great Lakes and 1,305 square-miles of inland lakes leaving about 58,110 square-miles of land.

Of the above, the Upper Peninsula contains about 16,452 square-miles of land leaving about 41,658 square-miles of land in the Lower Peninsula to install ham repeaters on. The approximate widest dimensions of the Lower Peninsula are 195 miles wide by 277 miles high. The Lower Peninsula also has hills 1,705 feet above sea level around Cadillac, ranging down to a level of 571 feet around Lake Erie. Such elevations can give a “radio tower view” of up to 75 miles, i.e., 2M radio signals will easily extend 60 to 75 mile distances in Michigan but frequently occurring band enhancements will extend this distance three or four times.

The 2-meter ham band spectrum for amateur radio repeaters in Lower Michigan ranges from 145.11 to 145.49 MHz and from 146.02 to 147.38 MHz. That is a total of 1.74 MHz available spectrum for 2M repeaters.

The Michigan Area Repeater Council (MARC) band plan for 2M repeaters in Lower Michigan is on a spacing of 20 kHz; so there can be 20 repeater channels between 145.11 and 145.49 MHz, and 39 repeater channels between 146.02 and 147.38 MHz providing a total of 59 standard repeater channels (plus one Shared Non-Protected Repeater or SNPR channel) in the 2M band.

The 59 repeater channels are coordinated on a 120-mile separation basis in the state, and a 100-mile separation basis to adjoining states and Canada (although some have been grandfathered closer). Using factors of 195/120 times 277/120 times the ratio of real-land acreage to max-dimension acreage (.77), times the number of available channels (59), reveals an approximate total number of repeaters possible in lower Michigan of 170 give or take a few.

The Michigan Area Repeater Council (MARC) record of 20 August 2008 indicates that there are 159 analog 2M repeaters coordinated in Michigan’s Lower Peninsula; also there are 13 provisional coordination assignments for D-STAR repeaters on 10 kHz splinter channels. These provisional assignments are presently based on a 50-mile separation to adjacent 10 kHz analog repeaters with no apparent “other considerations” made, i.e., D-STAR TX power, HAAT, etc., although quite possibly a propagation analysis is being used but not indicated.

Some hams have stated:
1) D-Star repeaters cannot be on the same frequencies as analog repeaters.
2) People do not want to hear D-STAR noise on an analog repeater channel.
3) Since D-STAR only has a 6.25 kHz bandwidth, it can go in a 10 kHz band plan on 2M.
4) You can put three D-STAR repeaters in a 20 kHz analog channel space.
5) There are benefits in spacing D-STAR repeaters 10 kHz away from analog repeaters.
6) D-STAR is the only way to go!

Actually, all the above statements need to be discussed further in order to fully understand why they may not be true. The arguments could probably fill a book! Let’s discuss some of them.

1. D-Star repeaters cannot be on the same frequencies as analog repeaters.

The simple statement has broad implications. Is it because there is a single technical reason or, a dislike for hearing the sounds made by D-STAR repeaters on analog channels or, more or less interference related and to whom or by whom? Quite possibly the statement was made because in Michigan, there supposedly are no (or very few) analog 2M channels available to put D-STAR repeaters on to, but that doesn’t mean there couldn’t be more, especially if there were committee activity and cooperative planning among the repeater owner/trustees. Technically, there is no reason why D-STAR repeaters could not exist on the same channel with an analog repeater as long as proper considerations were made in insuring compatible signal level profiles, which might affect potential interference with one another. It’s mainly driven by receive signal levels from the other repeater user’s transmitters (which are driven by TX power, distance, equipment, and band conditions). NOTE: The same things have to be considered in coordinating D-STAR repeaters on the 10 kHz splinter channels. As far as hearing a D-STAR repeater on an analog channel, it’s the same as hearing a distant analog repeater on-channel. It’s not classified as interference and simply turning PL decode ON will usually mitigate the problem (providing that the distant repeater has a different PL frequency).

2. People do not want to hear D-STAR noise on an analog repeater channel.

That’s a matter of personal opinion but it makes sense that if there is no intelligence to copy, then it is distracting noise and it should be eliminated. And it can be eliminated, just turn ON PL decode for the repeater that you desire to hear and the weak D-STAR noise will go away. D-STAR repeaters do not need or use a PL. If the analog repeater doesn’t transmit PL, urge the repeater group/owner that it be installed. There may be an actual advantage for PL decode working better to protect against D-STAR noise on-channel, than for protecting against a 10 kHz splinter D-STAR channel because of some recent off-channel interference observations. The interfering D-STAR signal on the splinter channel “cut-out” the desired on-channel signal, i.e., it squelched it out even with PL decode ON (that’s interference). Also, in the end, it may be simpler to deal with changing PL tones than changing frequencies.

3. Since D-STAR only has a 6.25 kHz bandwidth, it can go in a 10 kHz band plan on 2M.
It is true that D-STAR has a 6.25 kHz bandwidth, but there is a lot of power outside that 6.25 kHz bandwidth; enough to make it show up 10 kHz away in the typical analog FM receivers used today. A single D-Star repeater may be placed where there was an analog repeater in any existing band plan. It just has to be addressed with coordination standards. Unfortunately, in this situation, one cannot take advantage of the spectrum-reducing capabilities of D-Star unless contiguous spectrum can be created. The truth is that the narrow bandwidth can only be taken advantage of in an ALL D-STAR operation, which no one has created yet; therefore it must fit with existing analog repeaters in an existing band plan. Given the current heavy usage of the 2-Meter band, careful planning and coordination will be required to achieve some contiguous spectrum where only D-STAR repeaters would exist. If that could be achieved, a panacea would result. The present experiment of wedging the D-STAR repeaters into the 2M band on the splinter channels may not be the optimum method because reality must prevail in maintaining compatibility with analog repeater operations.
Carson's rule is often used to estimate the occupied bandwidth of an FM signal; it defines the bandwidth as twice the sum of the peak deviation and the highest modulating frequency. For example, Carson's rule would suggest that the occupied bandwidth for analog FM repeaters using speech (400Hz - 3kHz) with a peak deviation of 5kHz would be 16kHz which is one reason why Michigan opted for the 20 kHz band plan in 1984.
The Utah VHF Society has done some excellent real hardware tests in February 2008 to determine acceptable 2M band plan recommendations for analog and D-STAR repeaters. See: http://utahvhfs.org/dstar_channel_spacing.html. Based on the test data as well as frequency and spectral analysis, following are their concluded recommendations:
D-STAR-to-D-STAR channel spacing: 12.5 kHz minimum
D-STAR to Analog channel spacing: 15 kHz minimum

They also said: Remember: These are minimum spacing recommendations. Depending on the specific situation, there may need to be other considerations based on the necessity to protect existing systems. In follow-up, here is a statement in an email I recently received from the Utah VHF Society Frequency Coordinator John Lloyd, K7JL: We at the Utah VHF Society looked at D-Star very carefully and performed several on air surveys and test bench evaluations and have concluded that 10 KHz separation between repeaters was way too close for adjacent channel operations.
4. You can put three D-STAR repeaters in a 20 kHz analog channel.
Yes you can but what is next to the channel? Is it the band edge, a D-STAR repeater, or an analog repeater frequency? Using the narrow band capability of D-STAR requires change, which requires planning, cooperation and work. It may take time, a very long time, for various reasons. In some areas, it seems feasible that something can be done albeit on a limited basis. Eventually, some contiguous frequencies might be found expressly for only D-STAR repeaters. In Michigan’s Lower Peninsula, there is a provisional experimental activity occurring now to see how best to fit D-STAR repeaters in by placing them on 10 kHz splinter channels with a minimum 50-mile co-channel separation. It by no means is a final solution and by the words in paragraph 3 above, will probably have to eventually change, but to what?
5. There are benefits in spacing D-STAR repeaters 10 kHz away from analog repeaters.
The comment raises some questions. Is there less interference to D-STAR or less interference to the analog repeater? Is it because the analog listeners won’t hear the D-STAR noise? Is it easier to coordinate them into the band plan? Certainly the details in the Utah VHF Society Report don’t support the statement and some of the recent test observations in southeast Michigan prove that it’s risky at best and subject to potential long-term changes. It also is, or will be, putting a potential burden on existing analog repeater users and D-STAR repeater owners until a final resolution is had.
6. D-STAR is the only way to go!
There is nothing further from the truth! It is certainly one of the quickest and conveniently available systems to use digital communications technology and connect to the world-wide Internet with nice bells and whistles, etc., but it IS NOT and WILL NOT be the only way to go digital in the future! Just ask some of the knowledgeable hams who are playing with APCO-25 and other coding methods. They too, will have future obstacles and constraints to contend with and will have to be placed into the Lower Michigan 2M band plan. NOTE: There is an existing provision to include APCO-25 repeaters; basically it’s the same as for D-STAR.
So where is all this Michigan D-STAR activity going? The answer is, it’s growing, it’s expanding, and more groups are seemingly getting Grant money to buy the expensive equipment. It’s a “buy and play” world in digital ham radio.

Bill WD8MKG in Holton had the first D-STAR repeater in Michigan in latter 2006 operating on 147.32 (his analog repeater frequency). Presently, the Holton D-STAR repeater is operating on 145.36 MHz.

Last year, there were only one or two 2M D-STAR repeaters operating in Michigan.

In April 2008, a Michigan Region One Homeland Security grant provided funding to purchase D-Star repeaters, antennas, feed line, duplexers, gateway hardware, and radios for deployment in the 9 counties with the Region One borders. Those counties are:
Clinton County KD8IEI
Eaton County
Gratiot County KD8IEK
Hillsdale County KD8IFO
Ingham County KD8IEG
Jackson County
Lenawee County N8TTH
Livingston County W8LIV
Shiawassee County

In August 2008, there were thirteen D-STAR repeaters with provisional coordination’s listed in the Lower Michigan 2M repeater database, with more probably waiting in the wings.

If D-STAR continues to grow in the 2M band next year as in the past year, a more capable and permanent plan will have to be born in Michigan, which means repeater owners and trustees will have to become more involved in assisting the MARC in their endeavors and goals. There either will have to be more area in square-miles acquired by the State of Michigan or more frequencies must be made available for D-STAR repeaters. Which do you think is more realistic?

Would anyone care to predict the fill-in date for that coming announcement from the FCC that says, “In (month - year) all analog ham repeaters will stop transmitting and only digital repeaters will be in operation. You can redeem a $40 coupon for a digital converter box at your friendly ham store.”

This information article is intended to inform those interested hams and repeater owner/trustees of some of the things happening with 2M D-STAR repeaters in Michigan. Hams communicate and there should be plenty of subject matter in this article to talk about. Comments are welcome and if I can be of further assistance to anyone please contact me at abra@i2k.com, or send them directly to the MARC at: mail@miarc.com.

73, Ray W8HVG