Scenario:

LCD HDTV has only 1 coax input.

Signals to be fed:
- OTA HD signal via coax. Antenna has preamp attached.
- ANALOG (yes NTSC) cable signal via coax. I do NOT have a digital cable box.


Plan:

Idea was to invert a 2-way coax splitter and feed both signals into the TV via one coax cable. This approach works fine when either coax cable is connected individually to the inverted 2-way splitter. The ANALOG cable signal is not that bad considering there is no booster and its being channeled through 75-100' of in-house cable and via 3 coax splitters. To me and the homeowner the cable picture quality looks quite good on this older HDTV LCD!


Problem:

When BOTH the ANALOG cable coax and the OTA coax cables are connected to the inverted 2-way splitter, the cable signal becomes extremely snowy. Some channels are better than others; some are barely viewable b/c of the noise. The minute we unplug the OTA coax cable from the inverted 2-way splitter, the cable signal becomes clear again.


Assumption:

I realise ANALOG NTSC signal reception is susceptible to noise and interference. My assumption is that b/c the OTA signal is being pre-amped, perhaps there is a lot of noise being fed into the inverted 2-way splitter from the OTA coax feed and thus polluting the ANALOG cable signal exiting the same output. The TV's single coax input is, after all, receiving both an analog + digital signal from the OTA feed AND the ANALOG cable signal simultaneously. The actual SELECTION is made by the TV's remote by choosing either "cable" or "antenna" in the menu.


POSSIBLE SOLUTIONS:

- Getting a digital cable box (NOT AT THIS TIME)
- Grounding the inverted 2-way splitter so as to isolate/cancel out possible noise pollution via the OTA coax feed: TRIED THIS; NO EFFECT.
- Finding a "better" or different device/setup to combine both coax cables/signals instead of inverting a 2-way splitter???

Any suggestions, or is this simply not in the cards?

EDIT: We are going to try unplugging the AC cord for the OTA preamp and see if that clears up the ANALOG cable signal with the OTA coax cable still attached to the inverted 2-way splitter. If that does the trick/is the culprit, then we'll have to get some sort of key-fob AC outlet going which the homeowner can easily toggle the pre-amp on/off when watching cable.

Not sure what you are up to, OTA analogue is gone, are you trying to insert cable analog signals and what chns, freq. would be appreciated.

If this is the case, a lot of issues can occur, levels, co-chn and interference.

There are ways around it, but more info needed.

Problem identified - its the antenna preamp. When we unplug the ac cord to the pre-amp, the cable signal looks fine. The antenna preamp being used is some no name unit which does not have a grounded AC cord. Am wondering if perhaps a higher end antenna preamp might have a grounded ac cord.

Nueatit there are two signals coming in via two coax/RG6 cables: OTA from antenna (digital) and basic cable. The cable is ANALOG b/c the RG6 comes into the house and gets screwed directly into the coax input on the TV. There is no digital/HD tuner box for the cable. So we have two different signals via two RG6 cables but only one coax input on the TV. So we're using a 2-way splitter backwards to feed the OTA and cable into the TV via a single RG6 wire.

And you're the recipient of my 20,000th post! I've always loved antennas and antenna systems. Thanks for this opportunity.

If I understand what you're saying, the problem goes away not because there's a problem with the preamp, but because when you unplug the preamp it does not let any signal through which is the same as disconnecting the OTA, which you've already found solves the problem.

The problem occurs when HD and analog stations are on the same frequencies. In the US and Canada, 2 - 13 are the same on all TVs, and channels above that are on different frequencies and may or may not overlap depending on whether they are OTA or cable channels. Look up a table of OTA frequencies and cable channel frequencies to see which ones overlap.

When you're tuned in cable 13 and connect the OTA, if there's a digital channel on 13 it will ruin the cable signal. The only way to get both of these signals into the TV is to use a switch, going from one to the other. That gets dicey if your TV requires you to learn the channels it will allow you to tune in before you can go to them, because you can't learn both sets of channels at the same time.

Go to tvfool or www.antennaweb.org to find out which channel frequencies are used for broadcast stations in your area. Many OTA stations are not on the channel frequencies that match their channel numbers as a result of the way we transitioned from analog channels to digital channels.

Best of luck!

Thanks Ernie. I guess Nueatit eluded to the same thing (frequencies). The TV for its part does NOT force you to re-learn the channels; you toggle between cable "on/off" and the cable channels once scanned are stored when you select "on" and all the OTA channels are locked in after scanning when selecting "off". But I see the problem with both ota and cable signals being sent into the TV simultaneously regardless of what side the TV wants to select...

I dug up a fairly new Noma outdoor AC outlet switch with nifty key fob from my place which I've never used. Problem is unless the plug being inserted into the noma swtich is grounded (3 prong), the device will not relay power. Shame, b/c we could have just plugged the antenna pre-amp into that and used the key fob to turn the preamp on remotely when wanting to watch ota and leaving it off so the cable channels display clean. Am thinking of looking at a pre-amp replacement with a grounded AC cord (if it exists) but for the cost the person I'm doing this for might as well look into a digital tuner box which isn't something they wanted to invest in (these are old folks I'm talking about).

So another option you suggested was looking into a coax "switch"? Will see what that's all about. Cheers.

There used to be small A/B switches for coax signals. (Radio shack)
2 cables in 1 out, and either buttons or a switch to let you select which signal you want to watch.

Trying to combine (using a splitter in reverse) OTA and cable will typically result in issues.

Just checked, there are a bunch of different models on ebay.

Lots of fun AND very time consuming, done a lot of this earlier on, with ATSC coming along life got easier. I would not go into A/B switches etc.

Suggest if only one or two TV involved

Opt #1 If tv(s) have composite in video, just use an old VCR and its tuner for NTSC and use HD tv to switch video source

OR

Opt #2 Buy inexpensive ATSC/NTSC tuner box with HDMI output, use HD tv to switch video source.

The rest is just playing around, and keeping the signal rf level usable from VHF to upper UHF is a challenge.

Nueatit that is brilliant! Somebody (if not me) has an old VCR kicking around and we can use that unit's tuner just as you said. The LCD TV in question does have composite A/V inputs.

Digital tuner box was an option I was aware of but people in question don't want to spend money buying/renting one, plus rogers cable provider recently changed ("upgraded") the guide interface on the nextbox turner they have in another room & tv in their house and they hate it; the display font for channels, volume, guide, etc is tiny and these people can't even see it. They HATE it. I think this VCR tuner solution will work just fine. its another remote in the mix, but I'll figure out a smooth approach for them. Thanks.

Good to be off help, most TV remotes also allow for VCR function especially the simple ones, shoiuld be able to control VCR & HD TV from one remote.