Frequency Stackers
Many people have a situation where they have a HD Directv satellite receiver with only a single cable run to the area where the satellite receiver is located. Then they decide they would like to get a DVR with dual tuners and the requirement comes up for two feeds to the DVR for the dual tuner operation.
The initial solution is to run another cable, but sometimes this is next to, if not, impossible. Many people, including myself in the past, will tell you there is only the choice of running a second cable to the receiver, but actually there is another way. Because of the cost it is definitely a last resort method, but nonetheless a way. The simple explanation of this system is there is a stacker box at the dish and a Dstacker (de-stacker) at the Directv receiver.
Description Of Operation
The normal frequency range of the signal between the dish and the receiver is between 950 and 1450 Mhz. The OTA frequency range is between 50 and 800 Mhz so the two can both be sent over the same RG6 coax by the use of a diplexer a specialized splitter/combiner for satellite signals. As is covered in detail in my essay on Connecting Multiple Directv Receivers there are actually two different banks of signal from the dish for SD, odd and even polarities (some text refer to this as horizontal and vertical polarities), and four different banks of signal from the dish for HD. Both the odd and even signals are in the same frequency band of 950 to 1450 Mhz so the receiver sends a signal to the LNB to tell the LNB which signal, odd or even, to send down the coax.With those prerequisite issues behind us, what the frequency stacker does is to take one of the frequency bands and shift it above the standard band so it can be sent down a common coax. The Dstacker does the opposite and shifts the upper band back down to its original band. Another benefit of the system is once the bands are stacked the signal can be distributed like a CATV system using 2 Ghz splitters over a daisy chained single RG6 coax if SD satellite signals are all that are involved. This makes this system very popular for retrofitting apartments and condominiums that had been wired for cable or a CATV antenna. The Sonora SS212 system, for example, will shift the even polarity signals up to 1525 to 2025 which results in the following signals on the coax when a diplexer is used for OTA: 50-800 Mhz OTA; 950-1450 Mhz odd polarity channels; and 1525-2025 Mhz even polarity channels. That pretty well uses up the bandwidth of a RG6 cable. HD satellite from the 3 LNB dish can require up to 4 bands so the HD stacker systems are more limited in their wiring flexibility. More on that later.
Basic SD Stacker System
First we will discuss the basic SD stacker system. One such system would use the Sorona uS575-T stacker with D575d and D575 Dstackers as shown here:
(From 9thtee.com - used without permission)
Note to use the splitter it also requires an amplifier to overcome the splitter losses and a power injector to power the amplifier and uS575. What is very nice about this is the signals can be distributed in the same manner as a CATV or cable system. This allows a retrofit of installations where it is next to impossible to add additional coax runs. It will not work for HD satellite however.
Stacker for HD system
While somewhat limited compared to the SD system, the HD version of the stacker system allows for the four different bands that is potentially required for HD signals by allowing the receiver to tell the stacker which 2 bands are to be placed on the coax. Because of this the splitter method of distribution is not possible as it would require the placement of all four bands on the single coax which would exceed the bandwidth of standard RG6. There are such systems, but they are not recommended for retrofit use due to the need of using extra high quality coax and very careful installation of the cable, neither of which can be assured with a retrofit installation.The HD version of the stacker is primarily used for installations where there is a single coax run from the dish or multiplexer to the HD receiver and the user wants to change the HD receiver to a HD DVR such as a TiVo. Under those circumstances a stacker
(From www.solidsignal.com - used without permission)
To the left is a cabling diagram of such a stacker/Dstacker system. Notice it requires two feeds from the phase III dish. Alternately you can feed the stacker with 2 feeds from a HD multiswitch, should you have one in your current system. This stacker requires a power supply, so it would need to be located near a power outlet, but there are others that use either a power injector or are powered from the receivers. If you are interested in this system it is available from www.solidsignal.com here: http://www.solidsignal.com/prod_display.asp?PROD=SS212
To be clear this system as shown is required for each TiVo receiver and so if more than one TiVo is required it will take one of these systems for each TiVo.
Also suppose you have a HD TiVo with two feeds and you want to add a SD or HD receiver for PIP use. The solution would be to use one of the feeds for this system and the other feed for the additional receiver.
While not an inexpensive solution for the equipment compared to the cost of coax, sometimes when it is impossible to run additional coax cables, frequency stackers will provide a solution over a single coax.
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