[BC] Can traditional AM and IBOC co-exist?

[Phil Alexander]

On 10 Jul 2005 at 19:09, Kevin Tekel wrote:


> 2. The Expanded Band is skywave land.  I've gotten strong skywave DX in
> the Expanded Band even during broad, sunny daylight.

The daytime skywave is a function of D-layer depletion as a result of
sunspot activity. However, x-banders also tend to work with shorter
towers rather than the 180 to 210 degree towers typical of Class A
stations. This increases vertical radiation, hence short skip skywave
in the 200-300 mile region appears more common in the X-band because
nearly all stations are non-DA with quarter wave towers. As solar
activity cycles, there will be more, then less, then no daytime
skywave over a seven year cycle, however there is also an eleven year
cycle and when both of them reach zenith or nadir at the same time
the effects are more pronounced.

Thus, the problems of skywave for X-band are only slightly poorer than
for the low end of the standard band when taken over a period of several
years. The daytime skywave which you mention is a completely different
thing than nighttime skywave bouncing off the F2-layer, and really not
a valid reason for special consideration in the X-band. Also, it is
probable, based on preliminary data and theory, that there will be 
less co-channel interference to digital signals as a result of
redundancy, DSP and QAM itself.


Phil Alexander, CSRE, AMD
Broadcast Engineering Services and Technology 
(a Div. of Advanced Parts Corporation) 
Ph. (317) 335-2065   FAX (317) 335-9037





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