Increasing Cable TV signal strength

[amdx]

Hi All,
I'm on a boat, about 170ft from the utility post.
Recently our cable company switched to the wonderful world of
Digital TV. I got the new digital converter and had no picture.
I took the box back and got a second box, still no picture. So now I
suspect a weak signal and confirm that it is the cable length. The cable
company came out and gave me a better cable than I had installed. At
this point I have a picture but it is intermittent. The signal at the
utility post has 3 outputs and had a four way splitter, I suggested the
cable guy put in two 2 way splitters and give me the stronger (first) tap.
That got my signal to work almost all the time. I'd like to get the
signal to work 100% of the time.
I don't has access to electricity at the utility post, so an amp is
out. Although I could try an amp at the cable box end. Is that reasonable?
I would run two cables if there was a way to make it increase signal
strength.
Getting anymore from the cable company is not an option.
Any ideas to get a better signal?
Mikek


PS.

When the signal fails it seems channel 41 is ok and above 42 it breaks up.
Curious to know if there is an unusual frequency jump between those two
digital channels.

 

[Ian Jackson]

Hi All,
I'm on a boat, about 170ft from the utility post.
Recently our cable company switched to the wonderful world of
Digital TV. I got the new digital converter and had no picture.
I took the box back and got a second box, still no picture. So now I
suspect a weak signal and confirm that it is the cable length. The
cable company came out and gave me a better cable than I had installed.
At this point I have a picture but it is intermittent. The signal at
the utility post has 3 outputs and had a four way splitter, I suggested
the cable guy put in two 2 way splitters and give me the stronger
(first) tap.
That got my signal to work almost all the time. I'd like to get the
signal to work 100% of the time.
I don't has access to electricity at the utility post, so an amp is
out. Although I could try an amp at the cable box end. Is that
reasonable?
I would run two cables if there was a way to make it increase signal
strength.
Getting anymore from the cable company is not an option.
Any ideas to get a better signal?
Mikek


PS.

When the signal fails it seems channel 41 is ok and above 42 it breaks up.
Curious to know if there is an unusual frequency jump between those two
digital channels.

Despite your long 170ft drop cable, were you getting good analogue
signals before the change to digital? If so, it could be that something
is not right. Normally, even if you have had only fairly mediocre
analogues, the digitals are good.

Otherwise....
It sounds like your signals are just too weak. As things are, and if you
can, the obvious fix would be to overcome the substantial loss of the
170ft drop cable by fitting an amplifier at or near the utility post
(not at your end), and power it with low voltage via the coax from your
end (ie similar to a line-powered masthead antenna amplifier). However,
you would need to consult with the cable company to see if they were OK
with letting you do this. It could be that they might be able advise you
on the most suitable amplifier to use. It's not rocket science, but you
have to be a little careful not to break any of their rules and
generally do anything they don't approve of.

 

[mike]

Hi All,
I'm on a boat, about 170ft from the utility post.
Recently our cable company switched to the wonderful world of
Digital TV. I got the new digital converter and had no picture.
I took the box back and got a second box, still no picture. So now I
suspect a weak signal and confirm that it is the cable length. The cable
company came out and gave me a better cable than I had installed. At
this point I have a picture but it is intermittent. The signal at the
utility post has 3 outputs and had a four way splitter, I suggested the
cable guy put in two 2 way splitters and give me the stronger (first) tap.
That got my signal to work almost all the time. I'd like to get the
signal to work 100% of the time.
I don't has access to electricity at the utility post, so an amp is out.
Although I could try an amp at the cable box end. Is that reasonable?
I would run two cables if there was a way to make it increase signal
strength.
Getting anymore from the cable company is not an option.
Any ideas to get a better signal?
Mikek


PS.

When the signal fails it seems channel 41 is ok and above 42 it breaks up.
Curious to know if there is an unusual frequency jump between those two
digital channels.

Are you sure it's a signal strength problem?
The cable guy should have been able to measure the signal at your cable box.
Are the people using the other taps having problems?
If you're on a boat, you might be at the end of the cable run.
In that case, you might be able to get them to crank up the gain in their
distribution amp.
Power at the pole is not a problem. You can get amps that are powered
through the signal cable to your cable box. Getting them to let you
install it
is another matter.
You can get MUCH better wire, for a price.

Signal strength is not the only problem with digital TV.
Reflections in the system can confuse the decoder. Are there
any unterminated cables on the other taps?

I have OTA antenna digital TV. Plenty of signal, but reflections
cause significant drop outs on some channels. More signal won't fix
that. In fact, I have a variable attenuator to REDUCE signal strength.
I tweak the signal level for fewest dropouts.


Might be electrical noise coupled in thru the ground system.

Bottom line is that you pay the cable company for TV reception.
It's their responsibility to provide you with a watchable signal.
You shouldn't have to tell them what to do. They should just FIX it!!

 

[amdx]

Despite your long 170ft drop cable, were you getting good analogue
signals before the change to digital? If so, it could be that something
is not right. Normally, even if you have had only fairly mediocre
analogues, the digitals are good.

But, analog can be snowy but very watchable, digital an be pixalated
and stuttering without no sound or often no picture at all.

Otherwise....
It sounds like your signals are just too weak. As things are, and if you
can, the obvious fix would be to overcome the substantial loss of the
170ft drop cable by fitting an amplifier at or near the utility post
(not at your end), and power it with low voltage via the coax from your
end (ie similar to a line-powered masthead antenna amplifier). However,
you would need to consult with the cable company to see if they were OK
with letting you do this. It could be that they might be able advise you
on the most suitable amplifier to use. It's not rocket science, but you
have to be a little careful not to break any of their rules and
generally do anything they don't approve of.

I had not thought about a coax powered amp, Thanks.
Mikek

 

[amdx]

That's about 10dB loss at midband for RG6.


That was just a 3dB boost.

But that 3bd did get me a more consistent picture.

 

[Ian Jackson]

But, analog can be snowy but very watchable, digital an be pixalated
and stuttering without no sound or often no picture at all.

You are quite correct. However, digital is generally capable of working
to lower signal levels than analogue. It's amazing how rubbishy digital
signals can be, yet still give perfect pictures - but don't expect
miracles!

I had not thought about a coax powered amp, Thanks.
Mikek

I see that several others have also suggested a coax-powered amplifier.
[If the cable company can't give you more signal level, it's the only
solution.] As suggested, they should be able to provide a suitable
amplifier and power unit - or at least advise you what to use.

 

[amdx]

Adding an amp at the cable box isn't all that likely to work... you
can try it, but don't get your hopes up. Unless the amp has a
significantly lower "noise figure" than the RF front end in the cable
box, all you'll be doing is adding noise... the desired signal will be
stronger, but the noise will be stronger yet.

Something you could do, is add a single-port RF amplifier right at the
utility post splitter, where your tap comes off of the feed. You can
buy amplifiers of this sort which are designed to receive "phantom
power" through the coax cable... you'd install a "power injector" at
your boat, which feeds a DC voltage up the coax to the amplifier.
This is probably your best bet:

- It would amplify the signal before it's attenuated by the 170-foot
cable run.

- It won't require a power supply at the post... just at your
boat, where you already have power.

- It shouldn't interfere with the other taps on the
splitter, even when the amplifier is not receiving power from your boat.

You'd be looking for an "antenna mast" type of preamplifier. The
Channel Master 0068DSB or 7777, Winegard AP-8700 or AP-8275 or
HDP-269, AntennaCraft 10G212, or one of the Blonder Tongue Galaxy III
models might do the job for you. You'll probably want a "75 ohm in,
75 ohm out" model, which would connect directly to the 75-ohm coax.

Hey thanks for the part numbers, I'll look into these.
Mikek

 

[amdx]

see URL:
<http://www.dbsinstall.com/broadcast/vhf_uhf_freq_list.asp>

That's helpful. however, I do receive channels up to 484!
Dang, just noticed "Lesbo Euro Trash: Big Boobs" is on 502, but, it's
pay per view.

41 is 324 - 330MHz and 42 is 330-336 MHz
cables attenuate more at higher frequency.

I thought there might be a bigger jump between 41 and 42
because when 42 was pixelating 41 was always perfect.

By ALL means, if you're going to add an amplifier, add it at the
source location, not at the receiver location
Cheap, but good, ones are available from microcircuits. Can you buy a
line driver from your CATV company?

I suspect the 'better' cable is only marginally better. What is the
EXACT cable you're using? what is its attenuation per foot per MHz?
You can buy extremely low loss coax, but you may have to send in your
first born. Go to a local NRTL [EMC Test Lab] and see if they can
(are willing to) order a length for you.

I think I'll try the amp, before spending for better cable.

I think I just found a work around, The station I wanted, 42
is repeated on 428 in HD and it doesn't pixelate when 42 does.
The pixelating problem is rare, only a spall percentage of the time,
but very annoying. Ah, the wonderful world if Digital TV.
Mikek

 

[amdx]

Are you sure it's a signal strength problem?

Yes, it is the loss in the cable.

The cable guy should have been able to measure the signal at your cable
box.
Are the people using the other taps having problems?

No other problems, I'm just way down the dock from them.

If you're on a boat, you might be at the end of the cable run.
In that case, you might be able to get them to crank up the gain in their
distribution amp.

Next time they are around I'll ask.

Power at the pole is not a problem. You can get amps that are powered
through the signal cable to your cable box. Getting them to let you
install it
is another matter.
You can get MUCH better wire, for a price.

Signal strength is not the only problem with digital TV.
Reflections in the system can confuse the decoder. Are there
any unterminated cables on the other taps?

Yes that is possible, There are transients in and out so sometimes the
taps are used and sometimes not. I suppose I could make a bunch of 75
ohm terminations, and put on a new one every time it's needed.
However I never noticed a correlation between boats in and boats out.

I have OTA antenna digital TV. Plenty of signal, but reflections
cause significant drop outs on some channels. More signal won't fix
that. In fact, I have a variable attenuator to REDUCE signal strength.
I tweak the signal level for fewest dropouts.


Might be electrical noise coupled in thru the ground system.

Bottom line is that you pay the cable company for TV reception.
It's their responsibility to provide you with a watchable signal.
You shouldn't have to tell them what to do. They should just FIX it!!

Ya, but no. It's in a marina and the marina has a deal with the cable
company.
At this point there is talk about putting up an antenna.
The marina has ten cable boxes for transients that need to be plugged in
and connected (I guess keep them updated). So it has become a hassle for
the marina handle the boxes. I just want to lay low and not rock the boat.

 

[Sal]

Hi All,
I'm on a boat, about 170ft from the utility post.
Recently our cable company switched to the wonderful world of
Digital TV.

Getting anymore from the cable company is not an option.

I take respectful exception to that last sentence. My digital cable box is
about 130 cable-feet from the pole. My signal is tapped enroute for digital
telephone, tapped enroute for Internet and then split (by me) so I can feed
analog signals via a disttribution amp serving bedrooms, kitchen and shack.
I get enough from the pole tap to do the job.

Somebody is treating you badly -- maybe the cable company, maybe the marina.
Yes, the approach for you to buy and install an inline, remote-power amp at
the pole is entirely valid, technically. However, that's not in keeping
with reasonable expectations. You needn't roll over so easily. It's
supposed to work.

What -- Are you worried you might offend somebody? That "somebody" seems
quite okay with kicking you in the ankle. Or elsewhere.

"Sal"

 

[Joerg]

Hi All,
I'm on a boat, about 170ft from the utility post.
Recently our cable company switched to the wonderful world of
Digital TV. I got the new digital converter and had no picture.
I took the box back and got a second box, still no picture. So now I
suspect a weak signal and confirm that it is the cable length. The cable
company came out and gave me a better cable than I had installed. At
this point I have a picture but it is intermittent. The signal at the
utility post has 3 outputs and had a four way splitter, I suggested the
cable guy put in two 2 way splitters and give me the stronger (first) tap.
That got my signal to work almost all the time. I'd like to get the
signal to work 100% of the time.

Looks like the cable guys screwed up.

a. They should be putting enough signal on that cable to overcome the loss.

b. They should be able to measure the amplitude of pilot signals at your
end of the cable and tell you how much above minimums they are.

I don't has access to electricity at the utility post, so an amp is
out. Although I could try an amp at the cable box end. Is that reasonable?
I would run two cables if there was a way to make it increase signal
strength.
Getting anymore from the cable company is not an option.
Any ideas to get a better signal?
Mikek


PS.

When the signal fails it seems channel 41 is ok and above 42 it breaks up.
Curious to know if there is an unusual frequency jump between those two
digital channels.

If all else fails you may need an amp. What Fred means with drop amp is
usually called a "mast preamplifier", like this:

http://www.amazon.com/Uhf-Vhf-Anten...EQ/ref=sr_1_20?ie=UTF8&qid=1328748729&sr=8-20

I don't know this particular one but essentially it should be
weather-proof. It gets its DC voltage via the coax, from a wall wart
that would plug in at your boat. So no need to run a power supply cable
up there.

Don't go for too much gain. This dreaded DTV falls apart rather easily
on the slightest distortion or cross-modulation. Not sure if the above
amp can handle that. You might need a more expensive one. Michael
Terrell might know which ones are good. What matters is dynamic range.

Also, make sure you have a perfect 75ohms match at your end. The cable
box from the cable company should provide that. if you have Internet
and/or phone through them as well check that connection so it doesn't
cause reflections. On a boat at sea stuff can corrode quickly.

Oh, and don't dare to watch that boobs channel while your wife's on the
boat

 

[amdx]

Ok, 200ft of coax. Presumably RG6a/u.


You have been assimilated. Resistance is futile.


Something is wrong. The nominal signal from the cable drop is suppose
to be 0dBm. If there's a splitter involved, they like to crank it up
to about 10dBm. Your 200ft of RG6a/u will drop the signal from
between 4dB at the low end, to about 6dB at the high end. Your set
top box is suppose to operate with a 10dB margin. If you would kindly
disclose the maker and model, it might be possible to find the specs.
Typically, you'll have at least 10dB margin. Even with 200ft of coax,
you should have 4 to 6dB margin.

Now remember the problem is quite intermittent, but seems to be
happening almost daily for short periods.

Drag your cable box and TV over to the splitter and try it on the
incoming drop. If that works, move to the ports on the splitter. Make
sure that the unused ports are terminated properly. If that doesn't
work, call your unfriendly cable company and ask them why they don't
have sufficient level to operate your set top box without the 200ft
cable. If it does work, find a 200ft RG6a/u cable that isn't
saturated with water. Try to get some compressing fittings instead of
the crappy crimp type.

There should be no water in the cable, it's only a couple of months
old and both ends have crimp on connectors and are located in a box or boat.

Your unspecified cable set top box may also have some user accessible
diagnostics which include per channel signal levels. You may want to
check those.

It does have diagnostics, I'm not sure if it is each channel though.
But I can get some info out of the box. I'll be there Friday and I'll
get that info and the model of the cable set top box.

I'm not familiar with Knology, but I suspect they do the same thing as
Comcast. With Comcast, the lower 72 channels are still analog in my
area. If so, you can probably plug your TV directly into the cable,
set the TV for cable frequencies, not broadcast, and see if that still
plays.

I'm using Comcast at the boat. We are lucky here (I think) in that
we have a choice of two cable companies.

Hint: Troubleshoot by substitution.

Drivel: I spent about an hour troubleshooting my TV distribution
system, only to find a brand new Type F "barrel" connector, with no
center connections. That which is most obviously correct, beyond any
need of checking, is usually the problem.

Drivel is good.

 

[amdx]

Some better numbers for RG6a/u:
Freq Atten
MHz -dB
10 0.8
50 1.4
100 2.9
200 4.3
400 6.4
1000 11.0

The CATV band is approximately 50 to 800MHz. With 200ft of cable, you
should see 2.8 to 16dB of loss. While there may be problem at the
high channels, all the lower channels should work.

Any idea where channel 428 would be in that frequency range?
That's a duplicate of 4,2 but in HD, and it works when 42 doesn't.

The 4 way splitter has a loss of about -7dB.

Just a point. I may not have made it clear. I had the tech put in two
2way splitters and connect me to the first one. Hoping to gain 3db.
(or 4) and it did make a difference.

 

[amdx]

Looks like the cable guys screwed up.

a. They should be putting enough signal on that cable to overcome the loss.

b. They should be able to measure the amplitude of pilot signals at your
end of the cable and tell you how much above minimums they are.




If all else fails you may need an amp. What Fred means with drop amp is
usually called a "mast preamplifier", like this:

http://www.amazon.com/Uhf-Vhf-Anten...EQ/ref=sr_1_20?ie=UTF8&qid=1328748729&sr=8-20

I don't know this particular one but essentially it should be
weather-proof. It gets its DC voltage via the coax, from a wall wart
that would plug in at your boat. So no need to run a power supply cable
up there.

Don't go for too much gain. This dreaded DTV falls apart rather easily
on the slightest distortion or cross-modulation. Not sure if the above
amp can handle that. You might need a more expensive one. Michael
Terrell might know which ones are good. What matters is dynamic range.

Also, make sure you have a perfect 75ohms match at your end. The cable
box from the cable company should provide that. if you have Internet
and/or phone through them as well check that connection so it doesn't
cause reflections. On a boat at sea stuff can corrode quickly.

Oh, and don't dare to watch that boobs channel while your wife's on the
boat

Been trying to think of something funny to say about that...
Best I got is, she would say, "mine look better than those!

 

[Joerg]

Any idea where channel 428 would be in that frequency range?
That's a duplicate of 4,2 but in HD, and it works when 42 doesn't.

I believe that's entirely up to the cable company, you'd have to ask an
engineer there.

http://en.wikipedia.org/wiki/Digital_cable

Quote "For example, a cable company might call channel 5-1 "channel 732"
and channel 5-2 "channel 733"".

Just a point. I may not have made it clear. I had the tech put in two
2way splitters and connect me to the first one. Hoping to gain 3db.
(or 4) and it did make a difference.

Where does the other leg of that splitter go to? And is that end
properly terminated?

[...]

 

[Michael Coslo]

I take respectful exception to that last sentence. My digital cable box is
about 130 cable-feet from the pole. My signal is tapped enroute for digital
telephone, tapped enroute for Internet and then split (by me) so I can feed
analog signals via a disttribution amp serving bedrooms, kitchen and shack.
I get enough from the pole tap to do the job.

I respectfully agree! 8^)

I don't know exactly how it's done now, but when I worked in the Cable
industry many moons ago, we had a lot of adjustment we could make. Even
more, we had variable by frequency attenuators so we could ensure that a
flat signal showed up. There was a lot of signal at the amplifiers, and
if we really needed more oomph, we could put in a distribution amp.
Another amp was really rare.

Somebody is treating you badly -- maybe the cable company, maybe the marina.
Yes, the approach for you to buy and install an inline, remote-power amp at
the pole is entirely valid, technically. However, that's not in keeping
with reasonable expectations. You needn't roll over so easily. It's
supposed to work.

What -- Are you worried you might offend somebody? That "somebody" seems
quite okay with kicking you in the ankle. Or elsewhere.

Yeah, there is something wrong there. For as much as people hate
Comcast, when I had cable internet put in, they replaced all the cable
from the pole to the house, and a lot inside the house. I did talk them
out of replacing the new cable I had put in, but insisted on putting new
connectors on them. The measured all the levels and set them high enough
that I'd be able to add more televisions if I liked.


Time to call the cable company and tell them you want your MTV.


- 73 de Mike N3LI -

 

[Sal]

Time to call the cable company and tell them you want your MTV.

No way to know from here, but they may not be able to add another amp.

While I was looking for something else, I lurched into this page:

<http://www.cisco.com/en/US/products/hw/cable/ps2217/products_white_paper0900aecd800fc94c.shtml>

While its intended audience is Internet modem designers, the noise
discussions are informative with regard to other signals, too.

My point: When you try stringing too many amps in line, the signal-to-noise
ratio (SNR) eventually becomes unacceptable. (Remember the acceptable SNRs
cited for 256 QAM and 64 QAM.)

"Sal"

 

[Sal]

My point: When you try stringing too many amps in line, the
signal-to-noise ratio (SNR) eventually becomes unacceptable. (Remember
the acceptable SNRs cited for 256 QAM and 64 QAM.)

"Sal"

Sorry. I should have said carrier to noise ratio (CNR), not SNR. SNR
applies to post-detection signals. i joined the digital world late in life.

"Sal"

 

[Ian Jackson]

Something is wrong. The nominal signal from the cable drop is suppose
to be 0dBm. If there's a splitter involved, they like to crank it up
to about 10dBm.

Careful! Don't get your dBm mixed up with your dBmV. There's around 48dB
difference! 0dBm is a massive 48dBmV. That would certainly make most
set-top boxes wake up and pay attention!

 

[amdx]

Any idea where channel 428 would be in that frequency range?
That's a duplicate of 4,2 but in HD, and it works when 42 doesn't.

I believe that's entirely up to the cable company, you'd have to ask an
engineer there.

http://en.wikipedia.org/wiki/Digital_cable

Quote "For example, a cable company might call channel 5-1 "channel 732"
and channel 5-2 "channel 733"".

Just a point. I may not have made it clear. I had the tech put in two
2way splitters and connect me to the first one. Hoping to gain 3db.
(or 4) and it did make a difference.

Where does the other leg of that splitter go to? And is that end
properly terminated?

[...]

They go to two other outlets, that are used for transient boaters.
sometimes they are used and sometimes they sit unterminated.
I have not seen my problem better or worse when boats are in or out.
But I have several 75 ohm F connector terminations. It's worth a try.
Mikek