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Understanding LNB's - Info and Switching Requirements
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Why can’t I run 2 receivers from a single LNB dish?
A single LNB is designed to handle the control signal from one receiver
only where a dual can handle the control signal from 2 receivers also
The signals coming from satellites (applies to 110, 119, 148, 83, 91,
61.5, etc ) are polarized (Left-Hand-Circular - LHCP and
Right-Hand-Circular- RHCP)...roughly a 50/50 split...half of the
channels are LHCP, half of the channels are RHCP.
Each individual LNB can go one way other the other, LHCP or RHCP, but
not both at the same time. The polarization is selected by changing the
voltage to the LNB, if ~18VDC is sent (from the receiver), then the LNB
looks at the LHCP signals...if ~13VDC is sent then the LNB looks at the
RHCP signals.
With one receiver (IRD), when you change the channels, the receiver
changes the voltage as appropriate. If you have two boxes talking to
the same LNB, and one is trying to watch an RHCP signal and the other
is trying to watch a LHCP signal, then the LNB is going to switch to
LHCP (higher voltage wins).
If you have a "DUAL LNB" there are actually two LNB'S under the cup,
with two external connections for the RG/6 coax. Each receiver talks to
its own LNB, commanding the LNB to switch according to the channel that
each of the receivers is tuned to. If you have more than two receivers,
then a multiswitch is necessary for the same reason mentioned above.
To use a standard two-in, four-out multiswitch (a "2X4"), you MUST have a dual LNB...that's rule #1, and it's in concrete.
The multiswitch is a group of switches, either mechanical (relays) or electronic (silicon...like a transistor).
In a situation where some of the receivers are watching programming
sent on a RHCP signal and others are watching programming sent on a
LHCP signal, the multiswitch energizes the LNB'S such that one is
"tuned" one way, and the other is set the opposite.
The multiswitch then feeds the correctly polarized signal to the
receiver (it knows who wants what because of the voltage level sent by
the receiver).
Within each block of polarized signals, there is a range of frequencies
available to be selected...just like TV or radio...the signals are
always there, you tune to the frequency within the block that you want
to listen to.
The multiswitch has sent the LHCP or RHCP block of frequencies, now the
receiver can select the correct frequency within that block that's
appropriate for the channel you want to watch.
More-often-than-not, the multiswitch will keep one LNB at LHCP and one at RHCP for faster channel switching if it can.
SO, again, splitting a signal from a single LNB doesn't work in a
normal setup because the receiver presenting the higher voltage level
will always win at the LNB.
Many splitters all drop, divide, or block the voltage to the LNB and
you only get half the channels available (Scan for "Only getting the
ODD transponders".
There’s a lot of problems out there - a *tload of 'them, and most are
from people trying to use splitters, or have bad cable (drops too much
voltage, can't get to 18VDC), or crummy connectors, or flaky grounding
blocks.
Sometimes trying to use a splitter can smoke one or both receivers
(depends on the splitter, and how it's hooked up). There are some
splitters on the market that lead you to believe that they are for
splitting one dish to two receivers...it isn’t so. Printing a satellite
on the face of the splitter does not impart enough of the correct magic
into the splitter to get it to work in this fashion (splitting dish to
multiple receivers). Now...to (hopefully) cut off the few that'll try
to correct me on that point: there are some special splitters that WILL
split one LNB to two receivers BUT it's still a bad idea, you have to
know EXACTLY what to buy, and know EXACTLY how to connect it...and it
STILL a bad idea...Dual LNB'S are not that expensive, MULTISWITCHES are
not that expensive. Do it right or get cable TV (IMHO).
--------------------------------------------------------------------------
Why am I no longer receiving my satellite signal?
These are the most common reasons for losing signal: - Has the dish
been moved? -Any tree growth? (branches or leaves) - Are you
experiencing any damaging weather? (rain, hail or heavy winds, or Snow,
or thunder storms,Etc.) Check out … the Latest Dish Covers .
--------------------------------------------------------------------------
UNDERSTAND DISH PRO STACKED TECHNOLOGY
DishPro LNBFs are a new technology that is only supported in the newest
receivers from Dish Network (Models 301, 501, 508, and 721). DishPro
LNBFs and switches allow for longer runs up to 200 feet from receivers
to the dish. DishPro installations are easier as there are fewer cables
to run from the dish to the switch(es) for more than 2 receivers as
well as simpler installations if more than 4 satellite feeds are needed
(especially important now that 721s and 921s need 2 satellite feeds per
receiver)
Quick lesson: all DBS providers have up to 32 frequencies to use per
orbital slot. The Frequencies are opposite polarities either even or
odd.
Legacy LNBFs and switches can only transmit one polarity at a time down
the feed cable to your receiver. Legacy switches and LNBFs use a
voltage signal from your receiver to change the polarity of the LNBF it
is connected to, 13 volts is odd, 18 volts is even.
Since voltage will drop as the length of the cable gets longer, at some
point the attenuation of the cable will drop the voltage from the
receiver below 18 volts so that the LNBF can't switch to the even
polarity even though the signal from the receiver is 18 volts, the LNBF
is only able to use the 13 volt or odd polarity.
DishPro is different as it will stack or transmit both even and odd
signals down the same wire, by shifting the frequencies up so both
polarities can travel the same feed to the receiver or switch. Since
this is the case the LNBF doesn't need the receiver voltage to switch
back and forth.
A switch is necessary to be able to connect one stacked 119° feed and
one stacked 110° feed to each receiver. The only way a legacy receiver
will work with this arrangement of LNBFs and Dish Pro switches is with
a DishPro adapter that can down convert the stacked frequencies to the
standard odd or even only frequencies. Each legacy receiver has to use
this adapter which must be installed within 10 feet of the receiver.
FTA testing requires to change all Horizontal polarity to Vertical due
to the fact that Dish Pro uses stacked technology (band-stacking scheme
- the IF frequency of the horizontal block is shifted upwards to
vertical)
They will need to be edited for example (just go to
Menu-Installation-Tp/edit and set all to V) then subtract all horiz.
transps. frecuencies from 25600. enter result as your new transp freq.
(IE. on sat 119 transp 6 is 12297h. doing the subtraction, you get
13303. So change transp 6 to 13303).
This is needed because dishpro lnbs use an oscilator that runs at
25600mhz. this is mixed with the horizontal transp freqs and new freqs
are generated.
--------------------------------------------------------------------------
What is an LNB, or is it LNBF?
LNB(F) stands for Low Noise Block downconverter with integrated
(Feedhorn). Either acronym may be used in the small dish world. It is
the final stage of the antenna, and the first stage of the receiver. It
comes in single and dual units. A dual LNB is just like two singles in
the same case. Each half is independant of the other. Inside is the
detector and downconverter electronics, along with circuitry designed
to switch the LNB from right hand circularly polarized to its opposite.
Adjacent transponders on the satellite use opposite polaritization to
prevent adjacent channel interferance. The widely used Twin and Quad
each have 2 dual LNBs along with an integrated switch.
For those who care to know, a "block converter" is simply a device that
converts a block of radio frequencies (in this case the 12.2-12.7GHz
DBS satellite signals) to a different frequency (in this case
950-1450MHz) useable by the receiver. 12GHz signals wouldn't survive
through 10 feet of RG-6, never mind 100! The lower frequencies are much
easier to work with.
To bore everyone further, LNB is not technically "short" for LNBF,
since LNBs CAN come without feedhorns, like on most C-band (big)
dishes, where the C-band (or Ku band or both) LNB bolts to the feedhorn
on the dish. All DBS LNBs I've ever seen have the feedhorn built-in, so
the "F" is essentially unnecessary, just like the "A" (all LNBs have
amplifiers, yet we don't call them "LNABs"!)
In the "old days" the low-noise amplifier and downconverters were
separate units, so the amplifier was called an "LNA", which then
plugged into the downconverter with a really thick chunk of short RG-11
cable, before feeding into the house on RG-59 (typically.)
Eventually the LNA and converter merged into one unit, which back then
was either called an LNB or LNC depending on whether you thought "Block
converter" or "Converter" deserved an initial. LNB finally stuck.
Satellite "old-timers" still often call LNBs LNAs, the same way our
grandfathers still refer to refrigerators as "ice boxes."
--------------------------------------------------------------------------------
Why can’t I run 2 receivers from a single LNB dish?
A single LNB is designed to handle the control signal from one receiver
only where a dual can handle the control signal from 2 receivers also
The signals coming from satellites (applies to 110, 119, 148, 83, 91,
61.5, etc ) are polarized (Left-Hand-Circular - LHCP and
Right-Hand-Circular- RHCP)...roughly a 50/50 split...half of the
channels are LHCP, half of the channels are RHCP.
Each individual LNB can go one way other the other, LHCP or RHCP, but
not both at the same time. The polarization is selected by changing the
voltage to the LNB, if ~18VDC is sent (from the receiver), then the LNB
looks at the LHCP signals...if ~13VDC is sent then the LNB looks at the
RHCP signals.
With one receiver (IRD), when you change the channels, the receiver
changes the voltage as appropriate. If you have two boxes talking to
the same LNB, and one is trying to watch an RHCP signal and the other
is trying to watch a LHCP signal, then the LNB is going to switch to
LHCP (higher voltage wins).
If you have a "DUAL LNB" there are actually two LNB'S under the cup,
with two external connections for the RG/6 coax. Each receiver talks to
its own LNB, commanding the LNB to switch according to the channel that
each of the receivers is tuned to. If you have more than two receivers,
then a multiswitch is necessary for the same reason mentioned above.
To use a standard two-in, four-out multiswitch (a "2X4"), you MUST have a dual LNB...that's rule #1, and it's in concrete.
The multiswitch is a group of switches, either mechanical (relays) or electronic (silicon...like a transistor).
In a situation where some of the receivers are watching programming
sent on a RHCP signal and others are watching programming sent on a
LHCP signal, the multiswitch energizes the LNB'S such that one is
"tuned" one way, and the other is set the opposite.
The multiswitch then feeds the correctly polarized signal to the
receiver (it knows who wants what because of the voltage level sent by
the receiver).
Within each block of polarized signals, there is a range of frequencies
available to be selected...just like TV or radio...the signals are
always there, you tune to the frequency within the block that you want
to listen to.
The multiswitch has sent the LHCP or RHCP block of frequencies, now the
receiver can select the correct frequency within that block that's
appropriate for the channel you want to watch.
More-often-than-not, the multiswitch will keep one LNB at LHCP and one at RHCP for faster channel switching if it can.
SO, again, splitting a signal from a single LNB doesn't work in a
normal setup because the receiver presenting the higher voltage level
will always win at the LNB.
Many splitters all drop, divide, or block the voltage to the LNB and
you only get half the channels available (Scan for "Only getting the
ODD transponders".
There’s a lot of problems out there - a *tload of 'them, and most are
from people trying to use splitters, or have bad cable (drops too much
voltage, can't get to 18VDC), or crummy connectors, or flaky grounding
blocks.
Sometimes trying to use a splitter can smoke one or both receivers
(depends on the splitter, and how it's hooked up). There are some
splitters on the market that lead you to believe that they are for
splitting one dish to two receivers...it isn’t so. Printing a satellite
on the face of the splitter does not impart enough of the correct magic
into the splitter to get it to work in this fashion (splitting dish to
multiple receivers). Now...to (hopefully) cut off the few that'll try
to correct me on that point: there are some special splitters that WILL
split one LNB to two receivers BUT it's still a bad idea, you have to
know EXACTLY what to buy, and know EXACTLY how to connect it...and it
STILL a bad idea...Dual LNB'S are not that expensive, MULTISWITCHES are
not that expensive. Do it right or get cable TV (IMHO).
--------------------------------------------------------------------------
Why am I no longer receiving my satellite signal?
These are the most common reasons for losing signal: - Has the dish
been moved? -Any tree growth? (branches or leaves) - Are you
experiencing any damaging weather? (rain, hail or heavy winds, or Snow,
or thunder storms,Etc.) Check out … the Latest Dish Covers .
--------------------------------------------------------------------------
UNDERSTAND DISH PRO STACKED TECHNOLOGY
DishPro LNBFs are a new technology that is only supported in the newest
receivers from Dish Network (Models 301, 501, 508, and 721). DishPro
LNBFs and switches allow for longer runs up to 200 feet from receivers
to the dish. DishPro installations are easier as there are fewer cables
to run from the dish to the switch(es) for more than 2 receivers as
well as simpler installations if more than 4 satellite feeds are needed
(especially important now that 721s and 921s need 2 satellite feeds per
receiver)
Quick lesson: all DBS providers have up to 32 frequencies to use per
orbital slot. The Frequencies are opposite polarities either even or
odd.
Legacy LNBFs and switches can only transmit one polarity at a time down
the feed cable to your receiver. Legacy switches and LNBFs use a
voltage signal from your receiver to change the polarity of the LNBF it
is connected to, 13 volts is odd, 18 volts is even.
Since voltage will drop as the length of the cable gets longer, at some
point the attenuation of the cable will drop the voltage from the
receiver below 18 volts so that the LNBF can't switch to the even
polarity even though the signal from the receiver is 18 volts, the LNBF
is only able to use the 13 volt or odd polarity.
DishPro is different as it will stack or transmit both even and odd
signals down the same wire, by shifting the frequencies up so both
polarities can travel the same feed to the receiver or switch. Since
this is the case the LNBF doesn't need the receiver voltage to switch
back and forth.
A switch is necessary to be able to connect one stacked 119° feed and
one stacked 110° feed to each receiver. The only way a legacy receiver
will work with this arrangement of LNBFs and Dish Pro switches is with
a DishPro adapter that can down convert the stacked frequencies to the
standard odd or even only frequencies. Each legacy receiver has to use
this adapter which must be installed within 10 feet of the receiver.
FTA testing requires to change all Horizontal polarity to Vertical due
to the fact that Dish Pro uses stacked technology (band-stacking scheme
- the IF frequency of the horizontal block is shifted upwards to
vertical)
They will need to be edited for example (just go to
Menu-Installation-Tp/edit and set all to V) then subtract all horiz.
transps. frecuencies from 25600. enter result as your new transp freq.
(IE. on sat 119 transp 6 is 12297h. doing the subtraction, you get
13303. So change transp 6 to 13303).
This is needed because dishpro lnbs use an oscilator that runs at
25600mhz. this is mixed with the horizontal transp freqs and new freqs
are generated.
--------------------------------------------------------------------------
What is an LNB, or is it LNBF?
LNB(F) stands for Low Noise Block downconverter with integrated
(Feedhorn). Either acronym may be used in the small dish world. It is
the final stage of the antenna, and the first stage of the receiver. It
comes in single and dual units. A dual LNB is just like two singles in
the same case. Each half is independant of the other. Inside is the
detector and downconverter electronics, along with circuitry designed
to switch the LNB from right hand circularly polarized to its opposite.
Adjacent transponders on the satellite use opposite polaritization to
prevent adjacent channel interferance. The widely used Twin and Quad
each have 2 dual LNBs along with an integrated switch.
For those who care to know, a "block converter" is simply a device that
converts a block of radio frequencies (in this case the 12.2-12.7GHz
DBS satellite signals) to a different frequency (in this case
950-1450MHz) useable by the receiver. 12GHz signals wouldn't survive
through 10 feet of RG-6, never mind 100! The lower frequencies are much
easier to work with.
To bore everyone further, LNB is not technically "short" for LNBF,
since LNBs CAN come without feedhorns, like on most C-band (big)
dishes, where the C-band (or Ku band or both) LNB bolts to the feedhorn
on the dish. All DBS LNBs I've ever seen have the feedhorn built-in, so
the "F" is essentially unnecessary, just like the "A" (all LNBs have
amplifiers, yet we don't call them "LNABs"!)
In the "old days" the low-noise amplifier and downconverters were
separate units, so the amplifier was called an "LNA", which then
plugged into the downconverter with a really thick chunk of short RG-11
cable, before feeding into the house on RG-59 (typically.)
Eventually the LNA and converter merged into one unit, which back then
was either called an LNB or LNC depending on whether you thought "Block
converter" or "Converter" deserved an initial. LNB finally stuck.
Satellite "old-timers" still often call LNBs LNAs, the same way our
grandfathers still refer to refrigerators as "ice boxes."
