[time-nuts] AM Broadcast stations as a frequency reference...

paul swed paulswedb at gmail.com
Thu Oct 13 17:07:08 EDT 2011


Burt
I see that those are all LA stations. Curious if anyone knows of central or
eastern US stations that would be gps locked.
Thanks

On Thu, Oct 13, 2011 at 1:13 PM, Charles P. Steinmetz <
charles_steinmetz at lavabit.com> wrote:

> Burt wrote:
>
>  There are some AM broadcast stations in the U.S. that are GPS referenced.
>>
>> Supposedly being GPS locked would allow receivers that are GPS locked to
>> lock up faster and stay locked better.  So far I don't know of a single IBOC
>> receiver that has the capability of being GPS referenced
>>
>> while it would be simple enough to GPS lock/reference an AM broadcast
>> transmitter, this may not always be desirable.  Having two co-channeled
>> stations precisely on or very near the same frequency, even though they may
>> be thousands of miles apart, can have serious fade issues.  If they are
>> exactly on the same frequency they can cause deep nulls in their coverage
>> depending on the relative signal strengths.
>>
>
> I believe the argument that was advanced for better reception through
> GPS-locking had to do with improving nighttime skywave reception.  So the
> argument went, locking the carriers of co-frequency stations would prevent
> fast fading (beating).  Instead, you would get only long fades due to
> atmospheric changes.  I'm not sure how much of an advantage that would be,
> in practice, but it shouldn't mess up local coverage (which is all the FCC
> cares about).
>
> Best regards,
>
> Charles
>
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