Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Default coax splitter replacement

I am having persistent problems with coaxial cable connectivity with my
cable modem.

It has to go through a splitter. I thought I got the best when I bought a
broadband splitter fro Radio Shack for $20.00, but it is no better than the
cheap model I have on it now.

Typically I disconnect the cable, coat the wire with DeOxit and it works
again for a little while. Then in a few days it goes offline again.

I want to solder the son of a bitch and be finished with it for good. I can
solder all the center wires together, but what do I do about the shields?
(the screw-on conductor part). How do I connect all the shields together?

I don't think there's anything out there, but I thought I'd ask. My
solution is to cut the damned Radio Shack splitter apart with a Dremel tool
and go from there. I can strip the coax center wires back 3" and see if I
can stick them through far enough to solder them together.

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On Sun, 10 Jun 2012 18:59:42 -0400, "Jon"
wrote:

I am having persistent problems with coaxial cable connectivity with my
cable modem.


Make and model of cable modem? Most cable modems have internal
diagnostics that will provide you with the line levels. If the levels
are too low or vary, you will have problems.

It has to go through a splitter.


True. For cable TV, the bandwidth has to go down to 5 MHz. The upper
end is determined by the highest frequency used by your cable
provider, which you also didn't bother mentioning. 1000MHz is usually
sufficient unless you're piggy backing satellite TV, which requires
2000MHz.

I thought I got the best when I bought a
broadband splitter fro Radio Shack for $20.00, but it is no better than the
cheap model I have on it now.


I guess it's too much trouble to disclose the model number. If you
can't manage that, perhaps the number of ports on the splitter would
be helpful.
http://www.radioshack.com/family/index.jsp?categoryId=2032195
Incidentally, you overpaid. I pay about $2/ea for 2-1000MHz 2 port
splitters.

Typically I disconnect the cable, coat the wire with DeOxit and it works
again for a little while. Then in a few days it goes offline again.


It's unlikely to be the splitter, especially since your previous
splitter showed similar problems. Much more likely are crappy crimps
on the F connectors and RG-59a/u junk cable instead of RG-6a/u. If
the connector looks and feels like it's about to fall apart, it
probably has already done so internally.

I want to solder the son of a bitch and be finished with it for good.


Solder to what?

I can
solder all the center wires together, but what do I do about the shields?
(the screw-on conductor part). How do I connect all the shields together?


Don't bother. Inside your two unidentified splitters is a small
torroid transformer and a resistor. You need those between the center
pins. If you just connect everything in parallel, it won't work.

I don't think there's anything out there, but I thought I'd ask. My
solution is to cut the damned Radio Shack splitter apart with a Dremel tool
and go from there. I can strip the coax center wires back 3" and see if I
can stick them through far enough to solder them together.


Don't forget to wrap the whole thing in aluminum foil for shielding
and so that nobody will see the mess.

Hint: If your question is lacking numbers, you probably won't get a
usable answer.

Incidentally, you're header shows a peoplepc.com email address and an
Earthlink ISP, neither of which offer cable service. How did you
manage that?


--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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Default coax splitter replacement

In article ,
"Jon" wrote:

I am having persistent problems with coaxial cable connectivity with my
cable modem.

It has to go through a splitter. I thought I got the best when I bought a
broadband splitter fro Radio Shack for $20.00, but it is no better than the
cheap model I have on it now.

Typically I disconnect the cable, coat the wire with DeOxit and it works
again for a little while. Then in a few days it goes offline again.

I want to solder the son of a bitch and be finished with it for good. I can
solder all the center wires together, but what do I do about the shields?
(the screw-on conductor part). How do I connect all the shields together?

I don't think there's anything out there, but I thought I'd ask. My
solution is to cut the damned Radio Shack splitter apart with a Dremel tool
and go from there. I can strip the coax center wires back 3" and see if I
can stick them through far enough to solder them together.


F connectors are not bad *provided they are properly installed on the
proper type of cable*. I wouldn't be surprised if the problem isn't just
marginal signal levels. Like all things "digital", the system will
transition from working fine to not working at all with a level change
of half a dB or less. That can happen just from the backbone cable going
from full sun during the day to cooling off after dark. Especially if
your system was set up without a splitter, or a while ago, losses may
have increased over time.

Best solution is to get a cable company tech out to your house with a
tool to measure the level, including the splitter loss.

The tech can adjust the attenuator that connects your drop to the
backbone cable (it's probably on the pole), and things will be fine
again.

If you can do a test by taking that splitter out of the circuit, and the
CM works fine, then signal level is the culprit for sure.

Isaac
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Default coax splitter replacement

It appears that advice from The Lady from Philadelphia is again needed.

The Lady from Philadelphia uses the splitter supplied by Comcast. One of its
outputs connects directly to her Motorola modem, using a double-male
(hmmm...) barrel connector from MCM. The other output connects to a cable
that feeds her Vizio monitor. She has no problems.

If changing the splitter doesn't fix the problem, then the problem is
probably //not// with the splitter. (The Lady from Philadelphia does not
understand why this is not obvious.) Furthermore, it is not clear to her how
soldering the leads is going to fix //anything//. How does one //get// to
the leads, anyway? F connectors were not designed for soldering to their
innermost... parts.

The Lady from Philadelphia's gut feeling (pardon her vulgarity) is that your
modem has a bad F connector, making intermittent contact. She suggests that
you drop by the cable company and explain the problem. Of course, as you are
(likely) the modem's owner, the technically ignorant people behind the desk
will probably tell you that you need to buy a new modem. Perhaps a veiled
threat (of your choosing) will encourage them to loan you a spare, so you
can see what happens. Do not forget to have your account's MAC changed
before you leave, or your Internet cable connection will be deader than
Marley.

There is also the possibilty that the little bare wire sticking out of the
cable is, shall we say, too short to perform its required duties? Have you
experimented with a better-endowed cable?

The Lady from Philadelphia concludes by offering this rude (and unsolicited)
observation... TWENTY BUCKS FOR A BLEEPING SPLITTER? She hopes it was at
least gold-plated. The Lady from Philadelphia knows from personal experience
that expensive items from RodentShack (polite folk do not talk of r**s in
public) are not necessarily better than those from elsewhere, costing
one-fifth as much.


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On 6/10/2012 8:31 PM, Jeff Liebermann wrote:

Incidentally, your header shows a peoplepc.com email address and an
Earthlink ISP, neither of which offer cable service. How did you
manage that?



You subscribe through TW Cable or Brighthouse like I do. They
offered a choice of Road Runner, AOL or Earthlink when I signed the
contract. They used a directional coupler instead of a splitter when
they installed my cable modem. I can't get to it right now to tell you
how many dB drop right now.

Brighthouse currently uses S.A./Cisco Webstar modems in this area.
192.168.100.1 will display the current data.

(I hid the MAC Address)

Name CISCO DPC2100R2
Modem Serial Number 224656807
Cable Modem MAC Address xx:xx:xx:xx:xx:xx
Hardware Version 2.1
Software Version dpc2100rx-v202r1256-110513Uas-TWC
Receive Power Level -4.9 dBmV
Signal to Noise Ratio 37.7 dBmV
Transmit Power Level 41.5 dBmV
Cable Modem Status Operational


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Default coax splitter replacement

On Mon, 11 Jun 2012 11:47:02 -0400, "Michael A. Terrell"
wrote:

On 6/10/2012 8:31 PM, Jeff Liebermann wrote:

Incidentally, your header shows a peoplepc.com email address and an
Earthlink ISP, neither of which offer cable service. How did you
manage that?


You subscribe through TW Cable or Brighthouse like I do. They
offered a choice of Road Runner, AOL or Earthlink when I signed the
contract.


Thanks. I didn't know that. On the left coast, we have mostly
Comcast, which offers ummmm.... Comcast. Locally, AOL and Earthlink
both resell DSL. However, they can be purchased with a "bring your
own ISP" contract that will work with any means of connectivity.

They used a directional coupler instead of a splitter when
they installed my cable modem. I can't get to it right now to tell you
how many dB drop right now.


Locally, Comcast uses splitters. The only time I've seen directional
couplers used is when the line level is to high and the installer
wants to drop the receive level to the cable modem, while not
introducing any additional loss to the return path.

Brighthouse currently uses S.A./Cisco Webstar modems in this area.
192.168.100.1 will display the current data.


That's the most common IP address for cable modem diagnostics. The
same IP is used by Comcast modems. I haven't found it in the
CableLabs specs, but outgoing traffic to 192.168.100.1 is apparently
trapped by cable modem firmware, and redirected to the internal web
server, instead of going out to the internet.

If you have problems accessing the SNR values, try this work around:
http://kd6cae.livejournal.com/234572.html
http://www.broadbandreports.com/forum/r26111757-CISCO-DPC2100R2-signal-status-page

Name CISCO DPC2100R2
Modem Serial Number 224656807
Cable Modem MAC Address xx:xx:xx:xx:xx:xx
Hardware Version 2.1
Software Version dpc2100rx-v202r1256-110513Uas-TWC
Receive Power Level -4.9 dBmV
Signal to Noise Ratio 37.7 dBmV
Transmit Power Level 41.5 dBmV
Cable Modem Status Operational


Looks good.

For reference, the cable modem is designed to work with -15 to +15dBmV
receive power, but it's usually best to keep it between -8 and +8dBmV.
Upstream power should be at the lower end of 37 to 55dBmV. It's a
measure of upstream line loss. You're fine.

SNR (signal to noise ratio) isn't measured in dBmV. Did you edit the
above diagnostic output? It should be greater than 30dB SNR. I've
seen the SNR vary erratically as a result of ingress and crappy
connections, while the other numbers remain fairly constant. That's
my guess what is happening with the OP's setup.

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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In article ,
William Sommerwerck wrote:

There is also the possibilty that the little bare wire sticking out of the
cable is, shall we say, too short to perform its required duties? Have you
experimented with a better-endowed cable?


Noooooooooooooooooooo!

I've found out the hard way that having the center wire sticking out too
far from an F connector is a great way to destroy F jacks. A wire that
goes too far in will spread the two inside contacts. Tightening down
on the threaded part can apply a lot of force to the inside guts.


Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)

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Default coax splitter replacement

In article ,
William Sommerwerck wrote:

There is also the possibilty that the little bare wire sticking out of the
cable is, shall we say, too short to perform its required duties? Have you
experimented with a better-endowed cable?


Noooooooooooooooooooo!

I've found out the hard way that having the center wire sticking out too
far from an F connector is a great way to destroy F jacks. A wire that
goes too far in will spread the two inside contacts. Tightening down
on the threaded part can apply a lot of force to the inside guts.


Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)

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On 6/11/2012 1:14 PM, Jeff Liebermann wrote:
On Mon, 11 Jun 2012 11:47:02 -0400, "Michael A. Terrell"
wrote:

On 6/10/2012 8:31 PM, Jeff Liebermann wrote:

Incidentally, your header shows a peoplepc.com email address and an
Earthlink ISP, neither of which offer cable service. How did you
manage that?


You subscribe through TW Cable or Brighthouse like I do. They
offered a choice of Road Runner, AOL or Earthlink when I signed the
contract.


Thanks. I didn't know that. On the left coast, we have mostly
Comcast, which offers ummmm.... Comcast. Locally, AOL and Earthlink
both resell DSL. However, they can be purchased with a "bring your
own ISP" contract that will work with any means of connectivity.



They were forced to offer other choices, since AOL owns
TWC/Brighthouse and most of the RR fiber optic backbone. AOL was the
obvious choice, and since Earthlink was one of the largest ISPs they
only had to add one other service to satisfy the regulators. I'm not
sure that you can still get Earthlink from Brighthouse for new accounts.
I haven't seen it in their ads in some time.


They used a directional coupler instead of a splitter when
they installed my cable modem. I can't get to it right now to tell you
how many dB drop right now.


Locally, Comcast uses splitters. The only time I've seen directional
couplers used is when the line level is to high and the installer
wants to drop the receive level to the cable modem, while not
introducing any additional loss to the return path.

Brighthouse currently uses S.A./Cisco Webstar modems in this area.
192.168.100.1 will display the current data.


That's the most common IP address for cable modem diagnostics. The
same IP is used by Comcast modems. I haven't found it in the
CableLabs specs, but outgoing traffic to 192.168.100.1 is apparently
trapped by cable modem firmware, and redirected to the internal web
server, instead of going out to the internet.

If you have problems accessing the SNR values, try this work around:
http://kd6cae.livejournal.com/234572.html
http://www.broadbandreports.com/forum/r26111757-CISCO-DPC2100R2-signal-status-page

Name CISCO DPC2100R2
Modem Serial Number 224656807
Cable Modem MAC Address xx:xx:xx:xx:xx:xx
Hardware Version 2.1
Software Version dpc2100rx-v202r1256-110513Uas-TWC
Receive Power Level -4.9 dBmV
Signal to Noise Ratio 37.7 dBmV
Transmit Power Level 41.5 dBmV
Cable Modem Status Operational


Looks good.

For reference, the cable modem is designed to work with -15 to +15dBmV
receive power, but it's usually best to keep it between -8 and +8dBmV.
Upstream power should be at the lower end of 37 to 55dBmV. It's a
measure of upstream line loss. You're fine.

SNR (signal to noise ratio) isn't measured in dBmV. Did you edit the
above diagnostic output? It should be greater than 30dB SNR. I've
seen the SNR vary erratically as a result of ingress and crappy
connections, while the other numbers remain fairly constant. That's
my guess what is happening with the OP's setup.



I only edited the MAC Address, for security reasons.

Directional couplers provide better isolation from the garbage sent
upline by crappy TV tuners. I worked in CATV for years, and tested
hundreds of samples of 2 to 8 way splitters for return loss in our lab.

I'm used to using a Fireberd to measure the BER on digital
communication systems. FPQSK was real fun when we first added it to our
telemetry products. The units are those selected by SA, long before
Cisco bought that divison. At one time we built the SA Telemetry
receiver that they had cloned from our 1200 series.

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There is also the possibilty that the little bare wire sticking
out of the cable is, shall we say, too short to perform its
duties. Have you experimented with a better-endowed cable?


Noooooooooooooooooooo!
I've found out the hard way that having the center wire sticking out too
far from an F connector is a great way to destroy F jacks. A wire that
goes too far in will spread the two inside contacts. Tightening down
on the threaded part can apply a lot of force to the inside guts.


I won't disagree with you -- but the wire just might be a bit too short.

There is no way to lengthen the wire, so no harm can occur simply looking at
it...




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On Tue, 12 Jun 2012 04:49:35 -0400, "Michael A. Terrell"
wrote:


Name CISCO DPC2100R2
Modem Serial Number 224656807
Cable Modem MAC Address xx:xx:xx:xx:xx:xx
Hardware Version 2.1
Software Version dpc2100rx-v202r1256-110513Uas-TWC
Receive Power Level -4.9 dBmV
Signal to Noise Ratio 37.7 dBmV
Transmit Power Level 41.5 dBmV
Cable Modem Status Operational


I only edited the MAC Address, for security reasons.


Veddy strange. SNR usually isn't expressed to 3 significant figures
and should be in dBm, not in dBmV. The firmware scribblers seemed to
have goofed. Oh well.

Directional couplers provide better isolation from the garbage sent
upline by crappy TV tuners.


Huh? The FCC demands that anything connected to an antenna have very
low LO radiation. That transfers to the cable TV connection when the
F connector is attached to the cable instead of an OTA antenna.

This is kinda old, but covers the topic:
New Measurements and Predictions of UHF Television
Receiver Local Oscillator Radiation Interference
http://h-e.com/sites/h-e.com/files/tech_docs/rw_bts03.pdf
With 40dBmV (or about -9dBm @75 ohms) transmitted on the return path,
even a lousy LO radiation of maybe -40 to -60dBm in the return channel
isn't going to do much damage.

I'm used to using a Fireberd to measure the BER on digital
communication systems.


The Acterna (JDSU) Fireberd is a nifty gadget. I had an Acterna
HST-3000 but didn't have the CATV plug in or software. I did have a
BERT but it maxed out at T1 rates.

FPQSK was real fun when we first added it to our
telemetry products. The units are those selected by SA, long before
Cisco bought that divison. At one time we built the SA Telemetry
receiver that they had cloned from our 1200 series.


I think you mean FQPSK.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
#
http://www.LearnByDestroying.com AE6KS
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As others have posted, it is likely a marginal signal ... not due to
connections or splitters.

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On 6/12/2012 6:27 PM, Jeff Liebermann wrote:
On Tue, 12 Jun 2012 04:49:35 -0400, "Michael A. Terrell"
wrote:


Name CISCO DPC2100R2
Modem Serial Number 224656807
Cable Modem MAC Address xx:xx:xx:xx:xx:xx
Hardware Version 2.1
Software Version dpc2100rx-v202r1256-110513Uas-TWC
Receive Power Level -4.9 dBmV
Signal to Noise Ratio 37.7 dBmV
Transmit Power Level 41.5 dBmV
Cable Modem Status Operational


I only edited the MAC Address, for security reasons.


Veddy strange. SNR usually isn't expressed to 3 significant figures
and should be in dBm, not in dBmV. The firmware scribblers seemed to
have goofed. Oh well.


Some tests I did on Telemetry systems were to four places, and had
to match to within .01 dB in diversity sysems.

SA probably didn't bother to review the design, since it's rarely
seen by anyone. Most who would look have no clue what a Decibel is, or
that there are multiple references.

I was never impressed by SA designs. Their C band receivers were
noisier than even the cheapest Microdyne. They reverse engineered a
Microdyne receiver for their only Telemetry product, and lost the court
case for using a patented method. It was a slam dunk case. They bought
a couple receivers, and a year later they release their design. The
only real difference was they replaced the LED displays with a bad LCD
display. Most of the units we repaired had failing or dead displays,
and had to be modified to use a better panel.


I had trouble teaching some techs to use the 'relative' function on
a Fluke 8920 True RMS Voltmeter, and that you had to make sure you used
50 or 75 Ohm cables and terminators that matched a particular board or
module. We used them on the video amps, with up to 20 MHz video outputs.


Directional couplers provide better isolation from the garbage sent
upline by crappy TV tuners.


Huh? The FCC demands that anything connected to an antenna have very
low LO radiation. That transfers to the cable TV connection when the
F connector is attached to the cable instead of an OTA antenna.



You might be surprised at the crap that can come out of a damaged
tuner, or one with a damaged F connector. The backmatch was horrible on
some brands of splitters I tested. Some were over 20 dB off spec. It
seemed like the fancier the label or plating the cheaper the inside were
made. I peeled the back off of a lot of them to see that the soldering
was substandard, and in some cases, they missed some joints.

We blacklisted multiple sources. When you buy them 1000 at a time
and drop cable 50,000 feet at a time, it was worth the pre-screening.
Our plant was the only one in the corporation with a lab & repair shop
so we arranged the supplies fr all the locations.


This is kinda old, but covers the topic:
New Measurements and Predictions of UHF Television
Receiver Local Oscillator Radiation Interference
http://h-e.com/sites/h-e.com/files/tech_docs/rw_bts03.pdf
With 40dBmV (or about -9dBm @75 ohms) transmitted on the return path,
even a lousy LO radiation of maybe -40 to -60dBm in the return channel
isn't going to do much damage.

I'm used to using a Fireberd to measure the BER on digital
communication systems.


The Acterna (JDSU) Fireberd is a nifty gadget. I had an Acterna
HST-3000 but didn't have the CATV plug in or software. I did have a
BERT but it maxed out at T1 rates.



I wasn't working in CATV by that time. We used them to test error
rates for Telemetry systems.


FPQSK was real fun when we first added it to our
telemetry products. The units are those selected by SA, long before
Cisco bought that divison. At one time we built the SA Telemetry
receiver that they had cloned from our 1200 series.


I think you mean FQPSK.


Yes. We used it in the RCB2000/DCR2000 series, but that was over 10
years ago, and just before I became disabled. I'm lucky to sleep a few
hours a day anymore and miss technical typos.
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Jon wrote:
I am having persistent problems with coaxial cable connectivity with
my cable modem.

It has to go through a splitter. I thought I got the best when I
bought a broadband splitter fro Radio Shack for $20.00, but it is no
better than the cheap model I have on it now.


My cable company is happy to give me the quality cables and splitters that they
use, without additional charge.


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