I've been trying in vain to coordinate a frequency pair for my D-Star repeater. (I will have a lengthy rant about the effectiveness of the local coordination body in another upcoming thread.) Since I'm not getting any help, I'm going to have to pick my own frequencies, put the repeater up uncoordinated, and do my best not to interfere with the coordinated repeaters.
I want to make sure I understand the bandwidth characteristics of D-STAR before I finalize my pair. For reference, I've studied this page, which has some very good information on real tests that they've performed on the bandwidth usage of D-STAR as compared to a typical analog signal: The Utah VHF Society - D-Star channel spacing recommendations
Here's an interesting spec analyzer plot showing D-STAR on the left and analog on the right:
In the summary table on that page, they show that the typical -30db bandwidth for D-STAR is about 11khz and -55db bandwidth at about 14khz. They go on to recommend a minimum channel spacing of 12.5khz for D-STAR segments of a coordinated repeater plan, although they said that you could get away with 10khz if it wasn't for random frequency stability issues present in most transceivers.
In Southern CA, the 70cm band is channelized into 20khz segments for repeaters like this: 445.020, 445.040, 445.060, etc. If I understand the spec plot above as well as the analysis on the referenced page, I think I should be able to squeeze a D-STAR repeater between two distant analog repeaters on a frequency like 445.030, right? If my TX
-30db bandwidth is about 11khz, my D-STAR repeater would take up roughly from 445.0255 to 445.0355, right? If I'm reading their chart right, the -30db bandwidth of a typical analog signal is 17-18khz. So, if I squeeze my station between them, it looks to me like I'm more likely to receive interference from other repeaters than cause interference. Am
I looking at this correctly? The machines I have in mind of squeezing between are so far in the distance, I don't think it will be a problem even if I was right on top of their frequency, however I'm obviously trying to be careful if I have to do this uncoordinated.