Re: [IRCA] Synching-up

[r j carpenter <rcarpen@xxxxxxxxx>]

Carriers would only cancel when of similar amplitude - and the stations 
would not be listenable in those areas anyway because of the level of 
interference.  Of course this doesn't apply to synchronized stations 
with the same audio.

I don't understand the comment "bandwidth of satellite signals would be 
inadequate for phase locking".  The concepts of phase and time are 
similar. Ten-degree phase error at one megahertz is 1/36-th of a 
microsecond. I'd think an atomic frequency standard steered by GPS would 
be that good ... and not as expensive as it sounds.  Don't all UHF TV 
stations have them?  But we are talking about something too expensive to 
retrofit the desperate Mon&Pop AM that can't even afford new tubes.  I 
noted an AM in Chase City, VA, recently sold for $51K, about the price 
of mid-range Mercedes car.

As for applicability of very accurate frequency control, I'd think the 
Class C channels would benefit as much as any.  All of the stations 
suffer substantial cochannel QRM at night.

bob c.


Dan Strassberg wrote:
> Nick Hall-Patch questioned the likelihood that stations in other
> Western-Hemisphere nations would be willing to participate in the
> "synching-up" scheme.
> -----
> Thanks for the response, Nick: Until I started getting replies to my
> question, I had no idea about the connection between HD Radio and GPS. I
> also had no thought of getting Cubans. Mexicans, or other Western
> Hemishphere nations to buy into the scheme. I thought of it simply as a way
> of minimizing the SAH between (primarily) US Class Bs on Class A channels
> (and not all of them) and the dominant co-channel US Class As (though I
> guess that if the scheme had any merit, it might also be usable by US Class
> Ds operating on Canadian Class A channels). Based on one of the responses
> I've received, although frequency locking would be possible, the bandwidth
> of the satellite signals would be inadequate for phase locking. If that's
> so, it would be impossible to position the dead spots (where the signals
> would cancel) and keep them from "walking" around the listening area. Also,
> since the location of the dead spots would depend on the (quite variable)
> height of the reflective layer of the ionoshere, it would be impractical to
> attempt to position the dead spots.
> 
> I guess I can't call synching-up a non-starter, because it started 3/4 of a
> century ago, but it looks as if the satellite-based version is a
> non-starter. Still, I wouldn't know that if I hadn't asked. So thanks to all
> who responded.
> 
> --
> Dan Strassberg, dan.strassberg@xxxxxxx
> eFax 707-215-6367
> 
> 
> 
> 
> 
> 
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