Cable TV signal merging with antenna signal.

[micky]

Cable TV signal merging with antenna signal.

Would an antenna amp be uni-directional and keep a cable TV signal from
getting to the antenna even if there were a multiplexer or splitter
connecting the two signals, used to merge the two signal for a TV?

Don't many people merge their cable and antenna signals like this?



A while back we discussed feeding a TV from a cable box and an antenna,
and from two antennas of different design.

Someone tells me that the cable signal will go through the multiplexer
-- or maybe he said splitter -- to the antenna, and that would violate
FCC rules.

I said that I didnt' think the little signal that comes out of a cable
or satellite box would be strong enough to radiate interference even to
the next door neighbor (antenna or not).

He said the FCC thinks otherwise and that it published
https://www.fcc.gov/guides/cable-signal-leakage which includes:
"Cable signal leaks occur when the RF signals transmitted within a cable
system are not properly contained within the cable plant. Cable signal
leaks can be caused by loose connectors, damaged plant and cracked or
unterminated cables."

and then it talks about how homeowners either have to let the cable guy
come in and look for the leakage or risk getting their cable
disconnected.

A) What does it mean "plant"? That seems like a strange word to use,
and like it refers to the cable company and doesn't include a customer's
house.

B) Woudln't an antenna amp be uni-directional and keep the cable signal
from getting to the antenna?

C) Don't many people merge their cable and antenna signals like this?

Thanks.

 

NOBODY combines antenna and cable like that because the FCC doesn't like it but mainly because it doesn't work. Any signals on the same frequency will interfere and neither will be usable. It gets complicated because except for the channels numbered 2-13, the frequencies are _not_ the same between antenna and cable and with switched digital service on cable, the frequency for a given channel number may change day to day on the cable company. Many cable signals are scrambled and need the cable card to sort it out and are modulated QAM while Over The Air (OTA) are modulated 8VSB. The DATA (the TV signal riding on the carrier) is ATSC but tuning them in even if on the same frequency is different. You'll probably need to look up what the initialisms are all about.

ALSO to keep you confused, the OTA transmit frequency may NOT be the actual channel number. For example, in LA Channel 2 KCBS WAS analog an channel 2 until June 2009. Their digital channel was on channel 60 from 1998 until 2009. After the analog shutdown KCBS moved to channel 43. Data in the signal tells your TV to report that it is watching channel 2 even though it's on channel 43 (and when it was on channel 60)

I have one computer that is sourced by both my antenna and the cable company but they are separate tuner cards. The antenna card is a dual tuner Hauppauge 2250 and the cable unit is a Ceton InfiniTV6 cable card 6 tuner. They both function together seemlessly. That PC has a total of 8 tuners. The PC is connected to the TV by DVI-D / HDMI with the audio connected analog.

A 'Plant' would be cable company equipment.

B No

C No

 

[amdx]

On 10/9/2015 7:12 PM, micky wrote:

Cable TV signal merging with antenna signal.

Would an antenna amp be uni-directional and keep a cable TV signal from
getting to the antenna even if there were a multiplexer or splitter
connecting the two signals, used to merge the two signal for a TV?

Don't many people merge their cable and antenna signals like this?

I've just been through this wishing my TV had to antenna inputs,
for antenna and cable, switchable by remote. It doesn't. So I hooked up
a 3 position RF switch to switch between antenna and cable. It didn't
work, when the antenna cable was attached to the switch the signal on
the TV quit. Tried different inputs and a different 3 position switch,
nothing worked. I then found a 2 position switch, when I installed the 2
position switch, it worked fine. I can only assume the 3 position
switches did not have enough isolation between positions.
The better solution for me is to use an 'OTA converter box' wired
with an HDMI cable. Then just switch to different HDMI inputs with the
remote.
Mikek

 

[micky]

In sci.electronics.repair, on Sat, 10 Oct 2015 17:21:13 -0700 (PDT),
stratus46@yahoo.com wrote:

Thanks for your answer.

NOBODY combines antenna and cable like that because the FCC doesn't like it but mainly because it doesn't work.

Before we get distracted by the other stuff, I should have given more
emphasis to the other half of the question. Ignoring for a moment the
fact that it won't work, would the antenna amplifier keep the cable
signal from going up to the antenna and radiating from there?

If not, why not? That was the big bone of contention between me and
anotehr guy, but though he maintains it, he's not able to explain it.

Any signals on the same frequency will interfere and neither will be usable. It gets complicated because except for the channels numbered 2-13, the frequencies are _not_ the same between antenna and cable and with switched digital service on cable, the frequency for a given channel number may change day to day on the cable company. Many cable signals are scrambled and need the cable card to sort it out and are modulated QAM while Over The Air (OTA) are modulated 8VSB. The DATA (the TV signal riding on the carrier) is ATSC but tuning them in even if on the same frequency is different. You'll probably need to look up what the initialisms are all about.

ALSO to keep you confused, the OTA transmit frequency may NOT be the actual channel number. For example, in LA

I knew about that.

Channel 2 KCBS WAS analog an channel 2 until June 2009. Their digital channel was on channel 60 from 1998 until 2009. After the analog shutdown KCBS moved to channel 43. Data in the signal tells your TV to report that it is watching channel 2 even though it's on channel 43 (and when it was on channel 60)

I have one computer that is sourced by both my antenna and the cable company but they are separate tuner cards. The antenna card is a dual tuner Hauppauge 2250 and the cable unit is a Ceton InfiniTV6 cable card 6 tuner. They both function together seemlessly. That PC has a total of 8 tuners. The PC is connected to the TV by DVI-D / HDMI with the audio connected analog.

Sounds great.

A 'Plant' would be cable company equipment.

B No

C No

 

Ignoring for a moment the

fact that it won't work, would the antenna amplifier keep the cable
signal from going up to the antenna and radiating from there?

If not, why not? That was the big bone of contention between me and
anotehr guy, but though he maintains it, he's not able to explain it.

yes for the most part

If the amplifer has say 10 dB of gain in the forward direction, it MUST have at least 10 dB loss in the reverse direction, otherwise it would be an oscillator.

So if you you had a 20 or 30 dB gain amp in line with your antenna any signals trying to go through the amp in the reverse direction would be ATTENUATED by at least 20 to 30 dB. This may or may not be enough attenuation to prevent a problem depending on how strong the signals are to start with.

Tthe safe way to do it is with a switch. Or use a modulator that is operating on an UNUSED frequency so even if it does radiate, it won't bother anyone.

Mark

 

[Ron D.]

On Sunday, October 11, 2015 at 9:30:07 AM UTC-4, amdx wrote:

On 10/9/2015 7:12 PM, micky wrote:
Cable TV signal merging with antenna signal.

Would an antenna amp be uni-directional and keep a cable TV signal from
getting to the antenna even if there were a multiplexer or splitter
connecting the two signals, used to merge the two signal for a TV?

Don't many people merge their cable and antenna signals like this?

I've just been through this wishing my TV had to antenna inputs,
for antenna and cable, switchable by remote. It doesn't. So I hooked up
a 3 position RF switch to switch between antenna and cable. It didn't
work, when the antenna cable was attached to the switch the signal on
the TV quit. Tried different inputs and a different 3 position switch,
nothing worked. I then found a 2 position switch, when I installed the 2
position switch, it worked fine. I can only assume the 3 position
switches did not have enough isolation between positions.
The better solution for me is to use an 'OTA converter box' wired
with an HDMI cable. Then just switch to different HDMI inputs with the
remote.
Mikek

amdx;

You maybe needed a 75 ohm terminator on the unused input for some reason.