Its an AP story - take it with the big fat grain of salt that all their stuff deserves. Whatever the technical issues are, it's sure to be blown way out of proportion by the AP. The more sensational the reporter makes it sound, the better his annual evaluation will sound!

As to "multipath interference" in the mountains, that's a new one on me. For radio waves to reach the same point from more than one path, there must be some sort of reflective object(s) between the transmitter and receiver. And the earth itself is not very reflective at VHF frequencies. Unless of course, the surface rock nearby has a very high metallic content. Besides, digital radios (and TVs) are much better at rejecting all sorts of interferences and noise, including multi-path.

What may sound like multipath, is when multiple base stations are located too closely in a winding canyon, to fill in the radio gaps caused by the non-reflective - non line of sight nature of canyon walls. Trying to properly place base stations in such a circumstance to fill in all the radio gaps is a freakin nightmare, so they often end up with multiple coverage areas. Though with FM, the strongest signal should win out and completely block out the other interfering TX; what can happen instead is a sound similar to the "picket fencing" so often associated with multi-path. Digital radio is clearly superior in that realm too.

What makes digital not so good, is when they skimp on the "sample rate". To be digitized, the sound pressure wave must be sampled at several points during each cycle of the wave, each point having its own numerical value; which is then sent over the radio in a digital stream. To faithfully and accurately reproduce the sound, it must have been sampled at a rate many times higher than the maximum frequency of the sound.

This works spectacularly when the sample rate is very high , such as in a ".WAV" CD file. But with cell phones in particular, and also cheaper digital systems of any sort, the minimalist approach is often used. With a sample rate as low as two to four times the maximum frequency, all sorts "overtones" and distortions are generated. The closer the max sound frequency is to the sample rate, the worse it gets.

I suppose we could hope the railroads will care about voice clarity, and not be cheapskates. But as I will be retiring very soon, it won't matter to me much. Unless of course, I want to keep my ear into it and listen in (once railroading is in your blood - you can't get it out)

But what will then concern me is the future availability of scanners capable of decoding the digital format that the A.A.R. is recommending, and several Class 1 railroads have been purchasing. Moreover, since they have already been purchasing radios capable of digital, they obviously expect to convert to it well within the lifespan of those radios. What do we have then, at most 3 years left to enjoy our current analog radios. If I already need a new scanner (mine refuses to program the new channel frequencies); should I get another analog one that will program for narrow channels - risking its quick obsolescence to the digital; or should I just wait for digital scanners to come out.

The question then becomes, will they (digital scanners) even be produced at all! No one at the radio scanner sites I have asked at so far; seems to definitively know the answer.

OPB