Archived from groups: alt.video.satellite.mpeg-dvb (
More info?)
On Mon, 28 Jun 2004 17:21:08 -0600, "CWCunningham"
<charlesw-at-blackfoot.net> wrote:
<snip>
>I guess I should have been more clear, it's not a diseqc switch, but a multi
>switch (I don't really quite understand). I have browsed through catalogues that
>imply that there are versions that work for FTA, but some are DSS/FTA and some
>are "DSS/para todo (or something)" only. I guess the question is whether DSS
>switches use diseqc commands.
>
>These are definitely multi output since the whole point is to attach multiple
>receivers to multiple lnb's.
>
>Is there a difference between diseqc 1.2 switching and 22khz switching?
A DSS 4 or 5 input multi-switch is a combination 14(sometimes called 13)/18
Volt and 22Khz switch. There are 2 sets of 2 inputs that can be routed to
each of the outputs. If a receiver connected to one of the outputs puts up
a 22kHz tone, the switch will select one of the 2 sets of inputs. In the
absence of the 22kHz tone, the other set of inputs is selected. Then
depending on whether the receiver has put up 14 or 18 volts of LNB power,
one of those 2 inputs will be selected. Normally you will have LNB-1 (0
kHz) (Vertical (14V)/Horizontal(18V)) and LNB-2 (22kHz)
(Vertical(14V)/Horizontal(18V). In a conventional Corotor II C/Ku setup,
you use the 22kHz to select the band and the 14/18 is ignored since
polarity would be controlled by some other means. You need to split the C
and Ku feeds so that you can send a signal to both the 14V and 18V inputs
since most DVB receivers default to trying to select polarity with the
14/18V LNB power. This usage gives you the equivalent of a multi-output
22kHz switch. If you have LNBF's instead of servo controlled polarity, you
need to have 2 C and 2 Ku LNBF outputs since the multiswitch sends constant
14 volts out 2 of the inputs and constant 18 volts out the other two. The
switch is designed switch between 2 dual LNBF's.
The only difference between a 4 input and 5 input DSS multiswitch is that
the fifth input is selected when there is NO LNB power applied to an
output. This selects the terrestrial input.
Yes there is a difference between diseqc and 22kHz. 22kHz switching uses a
continuous 22kHz tone that is either on or off. Diseqc uses modulated 22kHz
(don't know the details) to control switches, positioners, and other
devices.
--
John Gilman
zoundz@xxxReMoVexxxnewscene.com
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