[BC] 10 kHz/9 kHz switch in auto radios

[Kevin Tekel]

Dan Strassberg wrote:
> In American Samoa and other places outside of the Western Hemisphere
> that are US protectorates or whatever, the remaining AMs are moving to
> frequencies that are divisible by 90 kHz (540, 630, 720...). These are
> the frequencies that are compatible both with the frequencies receivable
> on the radios in US cars (which represent most of what's on the road
> there) and with the 9-kHz-spacing Asian AM-channel-allocation scheme.

In the late '70s and early '80s, when there was talk of changing the
Western Hemisphere to the 9 kHz AM channel spacing plan, some digital-
tuning receivers tuned simultaneously in 9 and 10 kHz steps.  This
eliminated the channel spacing problem, but sometimes when seeking this
kind of tuner would stop on an incorrect frequency, for example stopping
on 711 kHz when the local station is actually on 710 kHz.  However this
was actually a benefit because just like on a regular analog tuning,
the slight off-tuning helped to open up the treble response.  In fact on
my Sangean shortwave radio the bandwidth was so narrow that I deliberately
off-tuned by 2 or 3 kHz (it tuned in 1 kHz steps) to squeak some treble
out of it.

Anyway, other tuners of that same era tuned in 3 kHz steps on AM, which
meant that no matter what frequency a station was on -- regardless of the
channel spacing in local use -- the receiver would never be more than 1
kHz away from the correct frequency.  Today, many multi-band radios tune
in
3 kHz steps on the Longwave band (150-280 kHz), due to the non-matching
channel allocations in Europe, Africa, and Asia.

p.s. Speaking of clash between U.S. and European standards, when I was in
the Bahamas years ago, they drove on the left side of the road and sold
leaded gasoline.... but American cars were commonly used as taxicabs.  So
for them, the driver would be sitting on the "wrong" side of the car, but
they drove like that anyway, and also filled up their "Unleaded Gasoline
Only" cars with leaded fuel.  There were also a few AM Stereo stations on
the islands, who took advantage of the fact that many of these "foreign"
U.S.-built cars came with C-Quam-capable receivers.



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