On Mon, 05 Feb 2007 22:58:28 GMT, David Spain <nospam@127.0.0.1>
wrote:

>While we're on the subject:
>
>> Don Bradner wrote:
>> The bandwidth cost of a 4020 (to Hughes or the VAR) is roughly three
>> times what a 7000 runs.
>>>
>>> Since you can get a used 7000 pretty cheaply, and it will upload at
>>> 2-3 times the speed (downloads around the same) for less per month,
>>> why would you consider a 4020?
>
>Can you elaborate on this one a bit for me? At face value the two statements
>seem contradictory.

The download side (where most bandwidth usage is) is the issue. The
4000 is only capable of BPSK, Binary Phase Shift Keying, where there
is one bit (2 states) of data possible for each symbol (cycle).

The 7000 uses QPSK (Quaternary), which is 2 bits of data (4 states)
per symbol.

The 7000S uses OPSK (Octal), also called 8PSK, which is 3 bits of data
(8 states) per symbol.

Satellite transponders are paid for by symbols, so the more data you
can load on a symbol, the less it costs the provider.
Don Bradner
donb (not don) at arcatapet.com
Posting today by Satellite from
Quartzsite, AZ