[CentOS] live audio feed via telephone link

Thu Mar 26 16:23:31 UTC 2009
Scott Silva <ssilva at sgvwater.com>

on 3-25-2009 5:00 PM Frank Cox spake the following:
> On Wed, 25 Mar 2009 16:32:07 -0700
> Scott Silva wrote:
>> If the radi station has phone lines, they should be able to get something like
>> a T1 or fractional part. Much more reliable and more bandwidth.
> I don't think it's available there.  Even the next-nearest town has only
> dial-up Internet.  The nearest location that has real dedicated Internet
> service available at all is the location that I'm looking to move the signal out
> to.
>  > Or look into a  microwave or satellite link. 
> As always, cost is THE factor.  I have no idea how much a 24-hour satellite
> link would cost but I suspect it might be more than a phone line.  Based on my
> (very limited) experience with tv satellite dishes around here, they don't seem
> to perform very well when it's -50 degrees outside and blowing snow.  Some
> years back I had to go out and try to beat ice off of a dish a few times in
> those conditions and didn't really enjoy it all that much.
>> I don't think you will be able to compress a
>> radio signal enough to fit over a dial line without a lot of loss. You would
>> need several lines multiplexed together for a decent sounding broadcast.
> Well, that's what I'm looking into.  I remember listening to streaming audio
> over a 14.4 modem way-back-when which wasn't great quality but modems have
> gotten a lot faster than that since, too.  I don't know enough about it (yet)
> to be aware of exactly what can be accomplished.
>> There are many point to point links that will cover 40 miles (65 km).
>> I don't know how far you have to go.
> That's another thought.  The station's antenna is on top of a hill but for
> protection from the elements and whatnot, the studio is down in a
> valley (i.e. a hole). They currently use a microwave link to send the signal up
> the hill from the studio, so I'm not sure how feasible that would be to get a
> point-to-point solution going, but it's worth looking into. Do you have any
> recommendations for hardware that might work?  I just checked, and Google Maps
> tells me that the distance is 52.3km.
If the station is in a hole, you would need to pipe the signal through relays,
possibly up to the antenna site and then on to the next point. Motorola makes
some long range PTP radios that reach as far as 124 miles (200km), as does
Proxim (not sure of their maximum range). Motorola is the leader in this area,
and they are worldwide. This site has some options;

If they already have a microwave link to the antenna site, it shouldn't be
that hard to repeat that signal to another site. They could put a microwave
repeater at the antenna site and move the receiver that is now there to the
third site.
> I've been talking to the station manager for quite a while about doing
> something to get their signal online, but the stumbling block has always been
> how to get the signal out where you can get an Internet connection.  I just had
> this dedicated phone line idea last week; if it (or something else) will work,
> then I'll be able to provide him with a set of costs that he can take to
> his board of directors, and we'll see what happens after that.  The phone
> company is working on a proposal for me so I'm now trying to get the rest of it
> figured out.
A pure digital 56k link should be just as easy as a modem link if the wiring
is sound. If the wire is marginal, even a modem won't keep a full 56K link
going. Besides, most modems don't do 56K from modem to modem unless they are
synchronous. 56k dialup from modem to modem usually doesn't go over 33.6k. You
only get the 56k if there is only one analog to digital conversion, which you
would only get by dialing into a T1 concentrator at the ISP. I suppose you
could do something over a plain 4 wire link from site to site. There used to
be modems that ran over those years ago, and maybe they are still available.
You would need a leased 2pair wire run from one point to the other.

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