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I am not sure if this is the correct site for this question, so let me know if it needs to be moved.

Through the coax network I have set up in my house I can't seem to propagate antenna signals for any channel above 21. I am a little clueless as to what my main issue is, so here are the steps I took:

The previous owner of my house dry-walled everything, so I have no idea what's hidden in the walls/ceilings. I have successfully determined that in 3 rooms of my house I have 2 coax outlets each. One outlet in each room runs to the output of a 3-out splitter in my basement that was historically connected to cable TV. The other outlet runs to 1 of 3 random locations outside of my house, annoyingly.

I have since discontinued my old cable service (I was tuning using the QAM tuners of the TVs as set-top-boxes annoy me).

I have a reasonably good, 4-bay antenna in an upper room (Room 1) in my house. It gets a good number of channels, a fairly thick sprinkling between channel 2 through 62. I wanted to try routing the signal from that antenna to my other 2 TVs. So... I temporarily disconnected my antenna from the TV, and instead plugged the antenna into the wall outlet. I routed the Room 1 cable to the input of the splitter, which splits the antenna to Rooms 2 and 3. The following bad diagram explains what I did.

See bad diagram below: What I Did

The result of this in Room 2 and 3 is that all the channels above 20 are cut completely, but I get no losses of any of the channels from 2 to 20.

The splitter should not be purposely stripping any channels, as it is the same splitter that was being used with analog and digital QAM cable TV, and I don't believe there is any directional filtering on my [Room 1 to Splitter] cable run.

Could cable run length alone be perfectly cutting channels above 20, but none of the channels below?

EDIT

Here are some specifics. Before going through the wall I have channel 20 (506MHz) and channel 30 (566MHz). After the wall I still have 20, but not 30. So, I would say (as do the comments) that it is frequency related, as I get no channels above 506-ish MHz.

Having said that, could it be that 30 and 32 are just weak channels for me, and 56, 62 are being especially attenuated by my cabling? Would a signal booster do anything for me?

Could my wall cabling possibly be limiting the frequency like this? VHF cuts off at 215-ish MHz, so I would expect that if I had the wrong type of coax I would not have channel 20.

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    It might be frequency related. Low-numbered channels used to be VHF and high numbered channels were UHF. If you are using the wrong type of coax (75 ohm) or wrong type of connectors, you might have this type of problem.
    – RedGrittyBrick
    Jul 6, 2016 at 13:23
  • @RedGrittyBrick I get channels 14 through 20, which are all UHF. I specifically get channel 20 (506MHz) and specifically do not get 30 (566MHz). Could I possibly have a coax that's good for 506MHz and not good for 566MHz? When I was using it for digital QAM I was using the same splitter and cables for channel 120 (700+ MHz). Also, this house is 15 years old, and very unlikely to have been cabled specifically for the VHF band, but I suppose it's possible, how do I find out?
    – Gorchestopher H
    Jul 6, 2016 at 13:37
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    added this as a comment after re-reading the question instead of answer - This really sounds like a splitter that is not rated for the frequency range you are trying to use. I've had similar problems with cable modems (which just use specific channels to transmit data) where they won't work in one room of a house and it has always ended up being a "bad" splitter. Sometimes actually bad, other times just the wrong one.
    – kinar
    Jul 6, 2016 at 13:56
  • @kinar The splitter in question is rated for 5MHz to 2400MHz. Channel 62 doesn't get near to escape that. A cable modem was also being split to (after Room 1 was disconnected) which was working without issue, but that typically uses lower bands anyway.
    – Gorchestopher H
    Jul 6, 2016 at 14:06
  • @GorchestopherH do you have a model number of the splitter by chance? Is it a single 1 input 3 output splitter? Do you have an extra splitter (a simple 1in/2out would work or even just a coupler to bypass the splitter) on hand that you could use for troubleshooting? How far are the rooms in question from the splitter?
    – kinar
    Jul 6, 2016 at 14:20

2 Answers 2

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You might try replacing the splitters. I had one outside a condo failing in such a way that it caused low frequency signals (<50 MHz) to be severely attenuated but higher frequency signals passed quite well. The result was that analog U.S. television channels 2 through 4 were garbage, 5 and 6 were snowy, and the cable modem worked very poorly. In this case, I think the splitters were degraded by flooding (high river levels submerged them for a couple days).

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    Thanks for the response. I did replace the splitters. The solution ended up being the addition of a signal booster.
    – Gorchestopher H
    Nov 28, 2016 at 16:51
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The attenuation of the signal does go up as the frequency goes up, as you have witnessed. Try a signal amp where at the antenna end, and verify the splitter you are using is rated for the correct frequency. You could also try a new run of cable as a test.

Not also that a two way splitter will loose 3.5db average on each output. A three way splitter internally "re-splits" one of the 2 way outputs, and causes another 3.5db loss on it's two outputs, so you have a 7db loss on each output.

I'm guess the amp will work, or a two way splitter.

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  • Thanks. As mentioned above, 2-way splitter did nothing but the signal booster helped. One thing to note is that with un-terminated output you don't get the "average loss".
    – Gorchestopher H
    Aug 22, 2016 at 21:25

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