A Discussion on Narrow-Band Digital Implementation Planning for the 2M Band

1. A Discussion on Narrow-Band Digital Implementation Planning for the 2M Band Ray “Abe” Abraczinskas, W8HVG

2. INTRODUCTION • This is an idea document; not a plan! • It’s a “seed” to plant in an already growing garden • Could be cultivated some more • Not to imply that the garden isn’t being cultivated!

3. 2M BAND PLAN

4. 2M BAND PLAN continued

5. 2M BAND PLAN continued

6. MARC DOG Resolution #11 • Excellent future-thinking experiment • MARC is to be congratulated • Is it the final solution? • Are there other things to consider in honing it? • The subject needs to be discussed and analyzed further in order to:

7. Hone the Solution 1. Involve the MARC constituency (and the surrounding areas) 2. Discuss, identify, and quantify problems and constraints between analog and N.B. digital repeaters (quantify any testing) 3. Determine if DOG Resolution #11 can become a permanent plan (pros & cons) 4. Summarize what other states/areas are doing (what is and is not working?)

8. Hone the Solution continued 5. Determine what if any elements can be incorporated long-term (the benefits) 6. Work towards removing the “provisional coordination constraints,” i.e., have something more stable (ultimate goal) 7. Determine what frequencies can be designated for narrow-band digital repeaters and narrow-band simplex in Lower Michigan (and surrounding areas)

9. BACKGROUND • In December 2006, MARC made a provision called Resolution #11 under the Development Operational Guidelines (DOG) (later modified thru June 2007) to coordinate narrow-band digital voice/data repeaters in Lower Michigan • Is it the final solution or are there other elements to improve it, or replace it? • The MARC Board may already know the answers but these have not been revealed to the MARC constituency

10. BACKGROUND continued • It would seem appropriate that an “activity” is needed for a “period of time” to address the question in a “process” to be “defined and acted upon by a cadre of supportive hams” to assist MARC in obtaining an answer • This activity could augment the on-going DOG Resolution #11 experiments and be expanded upon in answering “the question” to the MARC membership and the surrounding areas

11. BACKGROUND continued • D-STAR and APCO P25 operation in Michigan over the past 20-months has probably yielded valuable experience to a limited number of hams - and that’s great! • Where willing and able, those knowledgeable hams would be a valuable asset in continuing leading and/or assisting in the above discussions and determinations

12. BACKGROUND continued • At this stage of DOG Resolution #11 provisional experiments, there must be many more interested and supportive hams in the MARC constituency that would be willing to assist in addressing the question and seeking answers (several I know are willing to try along with myself)

13. BASIC GOALS TO ADDRESS • Get expanded involvement of 2M repeater owners/trustees aiding the MARC (explore and promote involvement which could aid buy-in by the entire MARC constituency * • MARC brief the status to interested constituency hams (educate) • Clear up the “paper repeater” issue to get the real picture (focus) * • Identify singly owned multiple repeaters covering same areas. *

14. BASIC GOALS TO ADDRESS • Identify repeaters in the same area with overlapping coverage * • Identify repeaters with “little activity” * • Identify the non-coordinated repeaters operating in Lower Michigan * • Explore and identify repeaters willing to implement narrow-band digital operation in place of analog *

15. BASIC GOALS TO ADDRESS • Explore, draft, and negotiate agreements to make provisions * • Based on the above results explore finding contiguous spectrum holes for dedicated narrow-band digital use in the current 20 kHz band plan (say, two or three adjacent 20 kHz channels) *

16. BASIC GOALS TO ADDRESS • Explore the advantages of a 15 kHz band plan for contiguous spectrum (even a partial if necessary) • Compare the on-channel to adjacent channel implementation schemes (pros & cons of each) • Strategize the band edges for potential narrow-band digital implementation benefits and feasibility *

17. BASIC GOALS TO ADDRESS • Strategize set frequencies for narrow-band digital repeaters and narrow-band digital simplex operation • Analyze the results, iterate, and implement useable elements * • Produce a summary document/report that describes and/or justifies the total result (post on-line for the benefit of others) * * Items that I believe others and I can contribute to

18. POSSIBILITIES • Do we need 20+ simplex frequencies in Michigan? Can the bottom or top five be formalized into a band plan of “narrow-band digital only channels” that would yield nine 10 kHz N.B. digital repeater channels (high-in, low-out) with a 1 MHz offset in Michigan (and surrounding areas)?

19. POSSIBILITIES continued • Scrutinize the digital packet channels to see if all are required (poll the packet gurus). Could some be utilized for narrow-band digital simplex and even become a contiguous narrow-band digital spectrum for both N.B. digital simplex and N.B. digital repeater inputs?

20. POSSIBILITIES continued • If 10 kHz channel operation is positively useable, splintering the packet channels (144.910 to 145.090) could yield nine N.B. digital repeater channels (low-in, high-out with 600 kHz offset) and possibly eventually augment the existing packet net capabilities in the future. N.B. digital would seem to be less traumatic to digipeaters. Has the DOG Resolution #11 experiment tested any packet splinter channel interference effects?

21. POSSIBILITIES continued • Could the Miscellaneous Experimental Mode channels (145.50 to 145.80 MHz) become formalized “digital experimental mode channels” or at least some of them for simplex N.B. digital? 145.61 and 145.67 are being used for D-STAR simplex now. Could the FCC be petitioned to allow narrow-band digital repeaters in this spectrum?

22. POSSIBILITIES continued • Invert the D-STAR repeater channels on the splinter frequencies to gain 600 kHz isolation (vs 10 kHz) in analog user receivers. Has the DOG Resolution #11 experiment tested this scheme? This has apparently worked OK on the analog channels in Michigan for years with surrounding states because of their 15 kHz vs 20 kHz band plan effects

23. CONCLUSION • Given the above, it seems feasible to have an estimated 18-plus new N.B. digital voice and data repeater channels and several N.B. digital simplex channels in the Michigan 20 kHz band plan on a permanent basis compatible with analog repeaters without the potential of causing interference, and without a risk of having to change frequency, all with the added benefit of using existing “standard coordination procedures” (and possibly provide the same capabilities for the surrounding states)

24. CONCLUSION continued • Can a process addressing the above GOALS substantiate the 18-plus narrow-band digital repeaters and several narrow-band digital simplex channels estimate? • Does the MARC want to do it?

25. THE END • Comments? • Questions? • Discussion?

26. A “SPLINTER” EXAMPLE • The 147.29 D-STAR transmitter could affect a user’s receiver for two analog repeaters on 147.28 & 147.30 in the yellow areas. • A D-STAR base station in the yellow areas could desense HT users of both analog repeaters. • Inverting the D-STAR repeater may require more distance separation but should eliminate ALL user interference potential. 147.29 147.28 147.30