Passing LNB

[Young Jim]

G'day.

Have just acquired a Topfield 4000Fi and have a simple technical question it will probably save a lot of grief putting to you guys rather than trying to get an answer from Topfield.

I notice that on the back it has an LNB out connection, for connecting a second receiver. My question is (not referred to in the manual): Does the LNB power on the second receiver have to be turned off, can they both be left on or can the LNB power on the first receiver in the chain be turned off with the LNB powered by the second reciever, so that even if the first receiver in the chain is powered down the second will still receive a signal through it?

Many thanks

[simmo]

Welcome to Vetrundotcom Jim.
There is usually no DC path on the lnb or loop out.
Therefore, it doesn't matter what you do with the lnb power control of the second RX'er. I would suggest leaving it on, on both boxes.
The only disadvantage of using this loop, is that the second decoder will only get channels on the same polarity as the first decoder.
Hope this helps.

[Young Jim]

Thanks for that, Simmo.

Am I then correct in thinking that if I power-down the Topfield it will power down the LNB, thus cutting off the signal to the second receiver? So the Topfield will have to be left 'on' all the time?

Thanks.

[simmo]

Yes mate, that's correct.
(or get a dual op lnb!)

[wtyt2]

Yes mate, that's correct.
(or get a dual op lnb!)


Or get yourself a splitter. :p

[simmo]

Actually, on this subject, I was talking to a mate the other night, and he reckons that he has put a diseqc positioner on the loop out of his decoder, and it still moves the dish...
I didn't think this would work!? If it does, then a looped decoder should move the dish too eh? Any comments/experiences???

[Ocean]

Some tuners use a capacitor to drive the loop out port directly from the LNB in port, but I would have expected this capacitor to be a fairly low (RF) value - maybe it's big enough to pass the DiSEqC commands back the other way ?

Other tuners use an SMD transistor buffer arrangement.

[simmo]

hmmmm