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Discussion Starter · #1 ·
(I originally posted this on the Home Theater PC forum but I think this one may be more suited for my issue. )


I invested in a decent VHF/UHF/FM (HDTV-ready) antenna from Radio Shack to receive OTA digital signals for my ADTV card in my HTPC. I mounted it in my attic. Now..currently at the location of my HDTV I only have one cable drop which currently carries standard cable.


My original plan was to install another RG6 at the same location so that the HTPC gets the OTA signal and the TV remains connected via cable but after several failed attempts at making the drop from my attic (unfortunately not using fish tape) I have given up.


Questions:

1) Does anyone know if I may be able to combine the antenna and cable signals into just the one drop w/o causing interference? If so, would a simple splitter/combiner be ok to use?


2) Terk has a diplexer which allows a Satellite signal and a Cable/Antenna signal to be combined then separated w/o interference when used in pairs but the Satellite "port" does not work for Cable or antenna. Is there a non-satellite diplexer available anywhere or is there a way to make the Terk diplexer work with only the cable and antenna?


3) Can anyone suggest another solution to getting the antenna feed to this location w/o damaging sheet rock, etc?


Thanks.
 

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sjpdavis,


Sorry I do not know the solution to your question. But I have a question for you. :) I am living in apartment, I wonder if your antenna is small enough as an indoor antenna? What is the model number and how much? How is the performance with or without the antenna. Do you think a preamp would help or made it worst?


Thanks.
 

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Discussion Starter · #4 ·
bfoster:


This was my thought from the start but do you know if there is a diplexer that will work similar to the Terk but not be restricted to Satellite and Cable/Ant?


aleet2600:


The model I purchased from RS is the VU-110 which is quite large (VHF range of 110 miles) and I mounted it in my attic. For 2001-02 RS replaced this model with the VU-90 which currently is listed at $39.99. However, since the 110 was discontinued I got it for $29.99. Certainly a great deal since the 110 had greater range. Anyway, both are HD-capable.


I think that either of these are a bit too large for an apartment unless you live on the top floor and can externally mount it. Otherwise you're probably better off looking into one of the indoor amplified models.


As for the performance, that's still up in the air. I won't be able to make a determination until I'm able to run a cable down to my accessDTV card.
 

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Lowe's or Home Depot have a molding that goes over wire that is ran down a wall. if you have a door with door trim and follow it up the wall with the molding you would only have a few inches above the door trim to reach the ceiling. Colors can be matche dto many wall colors unless you have custom colors. Have your wife take a look at it and see if you could live with it. :D
 

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In real simple terms, not to get technical, sat. uses channels 100 - 999, where cable uses channels 1 - 99, and OTA uses channels 2 - 69.

A diplexor is a filter that will allow low channels 0 - 99 and sat channels 100 - 999 to be filter combined on one cable.


Does that clear some of your confusion?
 

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If your broadcast DTV signals are UHF, you can combine them.


If you put a Channel Plus LP-380 on the cable line, you can distribute cable channels 2-50 and 95-99, plus the entire UHF band on a single coax.


With a Channel Plus LP-470, you can watch cable channels 2-64 and 95-99, and still have clear reception of UHF channels 18 and up.


With a Channel Plus LP-600, you can watch cable channels 1-86 and 95-99, along with UHF channels 40 and up. With the latter three filters, a few of your cable channels above 64 may be degraded by broadcast TV overlap.


Make sure you put a UHF/VHF separator/combiner (typical part number UVSJ) on the broadcast antenna line to filter off VHF and midband signals.
 

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I stand corrected.

I was focused on the diplexor, and not the overall problem.

AntAltMike is correct.

Cable frequencies are below UHF frequencies, and sat frequencies are above UHF.


Question:

Why is there a space between or lower of cable channel 95?

The channel plus seems to give up to channel 50, 64, 86 respectivily.

Is this a function of the cable carrier?
 

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Actually some cable channels overlap UHF broadcast frequencies.


Cable channel 65 = UHF Broadcast channel 14, and so on, until cable ch. 125 = UHF Broadcast ch. 69.


There is a gap at cable chs. 95-99. Cable ch. 94 = Broadcast ch. 43 and then cable ch. 100 = Broadcast channel 44.


Cable chs. 95-99 are actually squeezed in between cable chs. 6 & 14. (They share the same spectrum as Aviation and FM Broadcast frequencies 90 MHz - 120 MHz.)


Of course, cable chs. 2-13 = Broadcast chs. 2=13.


If your cable company does not use channels above 64 (excepting 95-99) then you won't have problems with UHF Broadcast overlap.


But if they are using 64, 65, 67, etc., then you must be mindful of overlap with UHF 14, 15, 16, etc.
 

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You also must be mindful of additional cable services, cable modem,digital cable etc... which are also generally between 550 and 750 MHz.


You also have to be VERY carefull about cable signals getting to the antenna and serving as a broadcast medium. The FCC is very stringent about cable leakage. The broadband nature of cable, and the fact that it is a closed system allows the cable cos to use all frequencies. Any cable signal getting to an antenna could potentially interefere with the licensed users of that bandwidth, including Public Safety, FAA and Ham Operators.


The filters mentioned earlier are intended to add locally modulated channels to your existing cable, such as security cameras.


It can be filtered properly if in your particular case you have no overlap, but what happens when the cable co re-alighns things? IMO it would be much easier to run a second cable. Also be advised that the cable company would be REQUIRED by the FCC to disconnect your service if their signals are leaking from your residence beyond a certain level.


Brian
 

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Is there a way to test for leakage? I have a cable modem diplexed with my sat signal, and have a UHF antenna hooked up to the same DTC100.


mlr
 

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Cable technicians think of leakage as "egress" where signals flow outwards from their system.


Equal and opposite is "ingress" where broadcast signals from outside flow into their systems.


Sometimes you can gauge leakage by watching cable channels sharing FCC licensed broadcast frequencies for signs of interference like herringbones or cross sync.


For example, cable ch. 95 could show interference from strong local FM stations between 90-96 MHz, ch. 96 from 96-102 MHz and ch. 97 from 102-108 MHz.


Also, cable chs. 19 & 20 often show intermittant intereference from two-ways and paging systems using 150-162 MHz.


Locally the cable company carries Telemundo on cable ch. 67 and if you see crossed-sync interference from local OTA UHF ch. 16 in the background that would indicate "ingress."


And whatever condition causes the ingress would likewise cause egress, hence "leakage."


We join cable chs. 2-67 together with OTA chs. 20-69 for a master antenna system at our station using a simple 2-way splitter and a 503 MHz low pass filter on the CATV side and a 503 MHz high pass filter on the OTA side to be sure our receiving antennae don't act as transmitting antenna for CATV signals.


(The LPF on cable also keeps cable's scrambled/digital signals above 503 MHz from interfering with OTA signals on our master system.)
 

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In addition to George's method, by looking at ingress on chs 18, 19 & 20, you can also use a programable police scanner and tune it to the audio frequency of a television channel to look for leakage.


George also has the key if want to combine them when you NO overlap, a LP and a HP filter. A UHF/VHF antenna balun may or may not have the necessary filtering to accomplish the same thing.


Brian
 

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Quote:
Along a similar thread can FM and UHF digital broadcasts be combined on a single coaxial cable?
Without filtering I would be concerned about the two antennas picking up out of band signals and creating multipath problems. Unless you are trying to pick up very distant FMs I would bet that you could just put an FM splitter on the UHF antenna lead and fead that to your FM receiver with acceptable results. I would definetly use an FM splitter to prevent front end overload on the FM receiver.


Brian
 

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Quote:
Originally posted by bfoster



I would bet that you could just put an FM splitter on the UHF antenna lead and feed that to your FM receiver with acceptable results.

Brian
I'll take that bet. The FM/TV type splitters that are designed to separate FM from broadcast TV only reject out-of-band signals by anywhere from 10 to 25dB, depending on the product. I'm certain that UHF/VHF splitters, typically carrying the part number UVSJ and selling for just a couple of dollars have greater out-of-band rejection, probably in the neighborhood of 40dB.


Mr. Raulston might be best served by taking the VHF output from the UVSJ that is intended for his FM tuner and passing it through the FM port of the FM/TV splitter, so it would work as a bandpass filter to then weaken the VHF, but unless he is right under a channel 5 or 6 transmitting tower, I wouldn't expect that additional filtering to be necessary


I will going to a customer's premises this afternoon, and will measure the out-of-band rejection on a UVSJ while I am there and report back
 

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The reason I want to combine UHF digital and FM signals is that I have an omnidirectional FM antenna in the attic that is fed all the way to the basement of this 100 year old house where the entertainment center, HT etc is located and fed to the rest of the house. I have recently installed a fringe area UHF antenna to pick up soon to be available HDTV broadcasts OTA.


I would like to avoid the hastle of running another cable which will take the better part of a weekend and upset the wife.


Larry
 
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