| This block layout best describes a conventional way of hooking up your UHF/VHF local broadcast antenna signal and your Satellite Receiver using a channel 3 or 4 signal combiner - going through a distribution amplifier to a 2 or 4 way splitter. Note that all tv's (or vcr's ) need to be hooked up to all outputs for best results. All tv's have equal amount of signal. Choose the channel combiner you want for satellite output settings ( 3 or 4 ) The distribution amplifier needs to be 15 dbm approximately |
| This above example can be used for large format Cband or Dss - Dish Network type formats where the combiner is used to combine the satellite signal as well as the local broadcast signals so that the output at the splitter is equal levels at the four way splitter output. |
| The problem does exist with the above configuration that if a
local broadcast carrier on channel 3 or 4 is too strong ( at local levels ) then a
herringbone pattern is developed. Example your satellite is set for channel 3 and
you have a channel 4 local signal that is quite strong then this co-channel interference
will arise. First make sure that the local antenna is the problem with the satellite channel by disconnecting the antenna input while checking the satellite picture. If there is a major difference then reconnect and adjust the small set screw ( channel combiner) on the antenna side to reduce the overall local signal. If this helps your done. Make sure that the locals channels are ok first. If there is a a slight improvement, then you need to apply a separate amplifier at the rf output of the satellite receiver ( before combiner) ...10db or less will usually not overdrive the channel combiner. If the picture is totally distorted then you will need to pad the output of the amplifier with a 3db in line signal reducer or add a second 3db pad if necessary. The outcome is that you want an acceptable picture on your satellite channel as well as a normal local broadcast adjacent channels. Usually the satellite channel takes precedence. See Layout below.
The above example is what I would recommend, however there is another approach to the problem...
UHF Modulator SubstitutionBy using a uhf modulator set for channel 14 you can eliminate the adjacent channel interference and move the signal to the uhf frequencies. The only consideration is to make sure that you amplify the signal since there is considerable loss through conventional splitters. If your house is wired with a four way splitter use the above layout and substitute the satellite amplifier for the UHF Audio Video Modulator. For a digital alternative substitute the uhf modulator with a Digital Video Modulator and use the rca inputs rather than the rf output (see back of satellite receiver ) See illustration below
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| Antenna systems are quite complex and their are differences in signal levels from more splitters and long line runs. 3db loss per 100' of RG-6 coax. Good clean connectors are essential and always use coax extenders indoors if possible. This is the first place to look if you are experiencing problems with just one line ( or room ) on your antenna system. |
