Welcome to DBSTalk
- Start new topics and reply to others
- Subscribe to topics and forums to get email updates
- Get your own profile page and make new friends
- Send personal messages to other members.
2 SWM16 with SWM-E2
Posted 30 March 2013 - 09:20 PM
The document doesn't state that the LNB draws a constant 200ma from the 18v lines, but it does imply that. If it does so, it is likely utilizing constant current diodes, which would always draw the current they are designed for, never more, never less, independent of voltage. This would allow it to limit the draw on any one coax to a set value. It would then use a linear regulator to step down to whatever voltage it requires to power itself, since one would expect that introducing as little noise as possible is one of the primary design goals of an LNB.
The document describes a 16v minimum on the 18v lines but does not list a minimum for for the 13v lines. If Sonora's document is correct about the 13v lines drawing only 50ma, they probably aren't used for power, but for signaling only. When the 18v lines fall below 16v presumably there isn't enough power at the linear regulator's input to produce the output power required for the device's operation.
Posted 30 March 2013 - 09:43 PM
Given that the SL5 must work with only one coax and using only 13 volts, Sonora's testing isn't correct "for all cases".
If Sonora's document is correct about the 13v lines drawing only 50ma, they probably aren't used for power, but for signaling only. When the 18v lines fall below 16v presumably there isn't enough power at the linear regulator's input to produce the output power required for the device's operation.
This is sort of Sonora's problem with their testing/spec sheets.
Posted 31 March 2013 - 12:31 AM
I don't know enough about how it works to guess whether it would need less power if there is only one output active. It seems reasonable, but I have no real idea. The document discusses a single LNB 95* dish and says "LNB current is typically less than 200ma", so I guess those aren't current limited like the SL5. If someone had a few multimeters lying around to hook up to the lines running to an SL5, they could do a little testing and figure out what it draws under what circumstances, and what the minimum and maximum total draw is. Not that it really matters to anyone but the terminally curious such as ourselves.
Sure would be nice if there was a technical manual available for LNBs and switches, so it wouldn't be down to a bunch of speculation and guessing