Garry C. Hess invented the delay spread calculation described in
TSB-88. Modern propagation prediction software used by Harris and
Motorola employ this method along with monte carlo simulation to
depict TDI regions in multiple site simulcast. Regarding a
specific acceptable TDI value, the results are affected by number
of overlapping signals three or more require tightening up the
delay spread. Also narrow band signals are more susceptible, have
worse (higher) capture ratios.
Really interesting thread so far.Tim I was getting those figures from an article I read here -
"Analog FM systems on 25 kHz channels typically can withstand two relatively strong, equal amplitude signals with up to 150 microseconds relative delay before speech is unintelligible, according to Garry C. Hess in Land-Mobile Radio System Engineering"
I have used radio mobile quite a lot. It might be time to ascertain my coverage. The only gripe I have with Radio Mobile is that it overestimates at low band VHF by default. UHF coverages are pretty accurate in my opinion. I've also used Splat, and still use Splat to overlay onto Google Earth.
Do you change the strong signal margin on one site in Radio Mobile to 0dB/20dB for the 10dB difference, then plot the two together?
Hayden
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