Mistertower,
Thanks for the feedback on the digital test at Barstow. I’m disappointed to hear of the unsatisfactory results. This certainly has not been our experience in either VHF or UHF, and in particular VHF simplex applications over long distances. From your description, it sounds like they’re testing in a simplex mode, without the benefit of a repeater. I’m in Palmdale, 90 miles from Barstow, and I can hear yard communications via a repeater that must be on high ground near the yard, such as Flash 2. I have not heard any digital communications so that may support my conclusion that they’re operating in a simplex mode and comparing results with an analog repeater system.
I sent an email to one of the BNSF telecom engineers in Kansas City asking for some specific information on their test results. If he responds, it will be interesting to learn what’s going on.
Contrary to the opinion of UP dispatcher STA, propagation is not a function of modulation mode so comparing cellular/digital with railroad type land mobile ROW system is like comparing apples and oranges. Digital will work quite nicely in a ROW environment with a design similar to analog. The only downside we’ve observed over very long multipath conditions is the digital stream is corrupted by the difference in propagation delay of multiple reflected paths, typically at more than twice the distance of railroad radio site spacing. Under the same propagation conditions, an analog signal will become distorted, but is usually readable.
In any case, a reply from the BNSF telecom engineer might shed some light on the deficiencies in Barstow.
Thanks again for your reply.