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Re: Cable Modems on HAM bands?



99 percent of the modems are in the 5-42 MHz band in the US. The 5-65 MHz is
not a newer/old issue it is a north america / europe issue. The cable splits
are:

40/52 or 42/54 for north america
65/86 for europe
55/70 for japan

These can change +/- a couple of MHz.

Pieter

----- Original Message -----
From: "Jon Ogden" <na9d-2@speakeasy.net>
To: "Bob Bruninga" <bruninga@usna.edu>; <amsat-bb@AMSAT.Org>
Sent: Tuesday, May 20, 2003 10:17 AM
Subject: Re: [amsat-bb] Cable Modems on HAM bands?


> on 5/15/03 3:43 PM, Bob Bruninga wrote:
>
> >
> > Any experts want to fill in the modem details and the bandwidths and
> > frequencies?
>
> Bob,
>
> I'm not sure if someone has filled this in or not, but I talked briefly to
> the guy across the hall from me that I work with.  In his previous career
he
> worked for the "Circle M Ranch" designing CATV head end equipment.  He
still
> calls on the CATV groups at "Circle M" as well.
>
> Anyhow, the current systems work with the following frequencies:
>
> From modem to head end (uplink): 5 to 65 MHz
> From head end to modem (downlink): 85 to 860 MHz
>
> Older systems used 5 to 40 MHz for the uplink and 50 to 750 for the
> downlink.
>
> The data channels end up fitting into a standard 6 MHz TV channel.  What
> channels are used for data is determined by the CATV operator based on
what
> they use for TV, etc.  The data channels are assigned to the unused slots.
> Each local trunk may be assigned one or more channels for data depending
on
> the users in that area.  When you use the cable modem, you share that
> channel with the other users in your area.  This is why things slow down
as
> more and more people get on and use the system.  The head end equipment
will
> determine what channel your modem operates on.
>
> Based on some of the comments my co-worker made, the modems won't do squat
> w/o the head end equipment which is very complex and costly.  It's a
similar
> relationship to the cell phone and cell base station/switch.
>
> I hope this helps, but I doubt that cable modems would be very useful for
> the idea you suggested.  Probably easier to design a whole new system
> yourself.
>
> 73,
>
> Jon
> NA9D
>
>
> -------------------------------------
> Jon Ogden
> NA9D (ex: KE9NA)
>
> Citizen of the People's Democratic Republik of Illinois
>
> Life Member: ARRL, NRA
> Member:  AMSAT, DXCC
>
> http://www.qsl.net/na9d   <- Updated on 1/22/03!!!
>
> "A life lived in fear is a life half lived."
>
>
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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>
----
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