In article ,
Mark Roberts wrote:
Scott Dorsey had written:
| Mark Roberts wrote:
|
| If AM IBOC is such hot stuff, why is it restricted to daytime hours only?
|
| Because the group delay that is the result of the uneven ionosphere prevents
| it from being decoded properly when the signal is received on skip, and the
| amount of stuff coming over the horizon on skip prevents it from being
| properly received when it's being received on groundwave at night.

I didn't quite expect an answer to a rhetorical question -- but it does
point to a very fundamental flaw in the scheme.

Sorry, I can't seem to find Bob Orban's reply to this. But I agree with
Bob that the encoding scheme is very robust about dealing with group delay
issues. Even so, I have found the actual skip performance poor to the
point of unusability.

Bob, do you have a citation on any actual measurements of this stuff?
Ionosonde data is easy to get, so it should be really easy to build a
simulation of ionospheric distortions in matlab or something, even if you
just take into account group delay and multiple reflections. Has anyone
actually done any simulations on the current encoder to see how it survives
under various simulated skip conditions? I'd be curious to see which of
the various skip characteristics is the most serious issue.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."