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Discussion Starter · #1 ·
I am currently working on fixing my Dad's Antenna in his attic. It is a 20+ year old antenna but it is VHF/UHF (a big mother too...about 80-100 inches long). He is 38 miles from the transmitter towers and he can pull in Analong VHF signals very good, but UHF are pretty weak during the day and somewhat better at night. I have the antenna pointed in the right direction, but there are some small hills between him and the transmitter station. Would the CM 7777 help out in his case? If so, how do you install it. Also, he has direct TV that is running along his RG6 cable that shares the antenna line and has some special "switches" that separate the signal before going into the Direct TV box. I had never seen this type of setup before (not a fan of Direct TV), but will the 7777 interfere with the Direct TV signal? And one last thing, should he use one of the powered switch boxes in the house as well?


Thanks,


Dave
 

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Please be more specific with topic titles.
 

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Dave..

Combining DirecTV with OTA is called "Diplexing." Since the two services don't share any parts of the radio spectrum they can be combined (something the multiswitch in the attic is probably doing) and separated back out (by a diplexor) near the TV.


If you have hills between you and the transmitters and you're getting fuzzy UHF signals, your best bet is to go higher. Get out of the attic. You can TRY an antenna pre-amp or even a bigger antenna, but the attic is costing you 8 - 12 db.


If you try the pre-amp route, the pre-amp goes as close to the antenna as you can get it. The power supply can go anywhere, but has to be in the line before it gets combined into the DirecTV lines. But keep a receipt in case it doesn't help.


If you'd like to test it all out beforehand, carry a small TV into the attic and look at the UHF stations. If they're still snowy a few feet from the antenna, then the pre-amp won't help.


Doc
 

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In other words, the power inserter, which takes AC line voltage and converts it into 18VDC to power the preamp, would have to be placed in the attic, because most diplexers block the DC on the VHF/UHF antenna port. Is there AC power available in the attic? If the attic has just a single lightbulb but no outlet, you can screw a outlet adaptor with a pullstring switch for the light into the light socket and use that for your outlet, leaving the wall switch always on and using the pullstring to control the light.


Channelmaster and Terk furnish diplexers that pass DC to both ports, but that may present a couple of problems. One is that some satellite receivers do not output enough current to power both an LNB and a VHF/UHF preamp. In my experience,Sony receivers are not well suited to that application. The other is that sometimes the satellite receiver wil be outputting 13 volts and other times 18 volts. I don't know if the Channelmaster prework well at 13 volts. You'd have to call Channelmaster to get the definitive word on whether their preamps can work at 13 volts. I wouldn't rely on a dealer's opinion on that.
 

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Discussion Starter · #5 ·
Thanks for the help guys. I will try out the amp and yes there is power in the attic so that won't be a problem. Also, sorry about the non specific title.


Dave
 

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Dave, Click EDIT to change the topic title :)


I would avoid adding a preamp to a "diplexed" DirecTV+OTA coax. Running a separate coax for the OTA antenna will likely give you less problems and make diagnosing trouble a *lot* easier.


If you're only interested in UHF channels, a dedicated UHF antenna like the CM 4221 or CM 4228 (+ CM 7775 preamp, if needed) might work better for you.


If these aren't available locally, check with Solid Signal or Warren Electronics online.
 

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Discussion Starter · #7 ·
arxaw,

Unfortunately, there is no way to easily rewire everything. The Satalite signal is being carried into the house on the prewired RG-6 cables. The OTA Antenna also uses the same wire. I plan on trying the amp before it goes into the diplexor in the attic since there is power in the attic that I can hook in to. If it doesn't work, then I'll just return the amp to Lowes.


Dave
 

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Discussion Starter · #8 ·
1 more question though. Is it possible just to use a UHF Antenna and splice it into the line running from the existing antenna? The other TV's in the house use the VHF band for local channels, but the HDTV only needs the UHF band. I read somewhere that a dedicated UHF antenna gets better reception than a combines UHF/VHF unit. Is this true? If so, do i just use some type of coupler to combine the two signals?


Thanks,


Dave
 
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