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[linux] Callsign coding (was Take a Stand)

Martin Ewing martin at aa6e.net
Wed Oct 13 15:46:22 UTC 2004


This might be good if the only consideration is to
save address space (bits) for normal callsigns.  But
36 symbols are not enough. People use "/" and "-" and
maybe others.

The trouble is that a "callsign" has no well defined
syntax.  We find things like FG7/WA1ABC and even
worse.  I suppose the roman (english) alphabet is
standard, but which special characters and what
maximum length to allow are not clear to me.  Is there
an ITU standard? Probably not, except for prefixes.

For very best address efficiency, you'd want a unique
binary identifier, and 24 to 26 bits should be enough
for all the hams in the solar system.  But you need a
registry database (like DNS) somewhere to convert to
human readable callsigns.

Given that IPv6 has lots of bits, maybe we don't need
to be so careful.  Or, we could even use a variable
length field, ASCII-coded. (Takes more work to parse,
but CPUs are cheap.)

So nothing is easy!

73, Martin, AA6E

--- "Bob Hansen, N2GDE" <n2gde at tapr.org> wrote:

> Think of the callsign as a base-36 number.
> For 7 places of 36 symbols (0-9, A-Z) you have:
> 36 to the 7th power or about 78 billion
> combinations.
> To encode this in binary, you need at least 37 bits:
> 2 to the 37th power is about 137 billion.
> This is where Darryl got 37 bits.
> 
> Of course, as N4HY suggests, most of those
> combinations are not valid for
> callsigns and an elegant hashing method may be
> possible.
> 
> -Bob H.
> N2GDE
> 
> 
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