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SB5120 & Comcast Woes mediumhappy 12-18-2006
Posted by Warren on December 24, 2006, 2:47 am
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> It isn't packet loss that causes the modem to pump out more --

That's an important thing to keep in mind. TCP/IP packets is just the data
that's carried over an RF signal on the coax. You could have 100% or 0%
packet loss, and it wouldn't have any affect upon how the RF signal levels
are negotiated.

In other words, the railroad tower operator doesn't care if the trains
have people in them or not, as long as they're arriving at and leaving the
stations at the correct time. The railroad tower operator doesn't even
know if the arriving train had any people on it when it left the last
station, so even if it was full when it left station one, if it arrives at
station number two on-time, it's a success even if the train is now empty.

Of course if the train doesn't arrive at all, the passengers can't arrive,
either. So a crappy RF signal could cause packet loss, but packet loss
doesn't have to be related to a crappy RF signal. And packet loss won't
have any affect on the RF signal levels.

--
Warren H.

==========
Disclaimer: My views reflect those of myself, and not my
employer, my friends, nor (as she often tells me) my wife.
Any resemblance to the views of anybody living or dead is
coincidental. No animals were hurt in the writing of this
response -- unless you count my dog who desperately wants
to go outside now.

Shop for networking gear:
http://www.holzemville.com/mall/linksys
http://www.holzemville.com/mall/netgear




home networking made easy, greater protection, less stress, introducing nm 5.0, 728x90
Posted by Timothy Daniels on December 24, 2006, 4:40 pm
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"Warren" wrote:
> Ed Nielsen wrote:
>> It isn't packet loss that causes the modem to pump out more --
>
> That's an important thing to keep in mind.


Yes - if someone had said that. I certainly didn't.


> Of course if the train doesn't arrive at all, the passengers can't arrive,
> either. So a crappy RF signal could cause packet loss, but packet loss
> doesn't have to be related to a crappy RF signal. And packet loss won't
> have any affect on the RF signal levels.


If by "crappy" you mean "weak", yes, as strong signals can also
be noisy and the noise can cause bits to be misinterpreted and
thus "lost", causing a bad checksum for the packet and a request
for a retransmission and thus a lowered data throughput, i.e. lower
bytes-per-second of good data. But whether any circuitry can
adjust the power to affect the signa-to-noise ratio as measured by
a high retransmission rate, I don't know.

*TimDaniels*

Posted by Timothy Daniels on December 24, 2006, 4:25 pm
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I never posed that it was packet loss that caused the modem
to increase its upstream signal level.

You say that it is the CMTS at the headend that tells the modem
to turn its signal level up or down. And when the splitter is substituted
for the barrel connetor, the output level of the modem is increased.
That suggests that the splitter itself is attenuating the upstream signal
from the modem to the CMTS, as nothing else has changed. It may
also be the splitter which is mangling the packets. I'll search around
for another splitter to see if that helps.

*TimDaniels*


"Ed Nielsen" wrote:
> It isn't packet loss that causes the modem to pump out more -- nor is it
> because the downstream has changed. [You could use a couple of diplex
> filters (not the satellite ones but similar in purpose) that separate
> the forward path from the return path, pad the downstream down as much
> as you want (or even amplify it) and you would see virtually no change
> in the transmit level of the cable modem.] It is merely that because of
> the reduced attenuation on the drop, the cable modem is hitting the CMTS
> too hot, so it is told to turn down.
>
> That suggests to me that there might be something (noise) getting into
> the drop between the cable modem and the splitter/barrel location. When
> you insert the splitter, you lower the signal level hitting the CMTS, so
> it tells the cable modem to increase its transmit level. The signal
> level from the splice location back to the lockbox remains pretty much
> the same whether the splitter is in there or not -- it is only in the
> portion of the drop from that location to the outlet that sees the
> increase/decrease in signal level as the modem's transmit level changes.
> Could that piece run parallel to some A.C. lines for awhile? There
> could be something that is induced onto and is riding on the shield
> until it finds a spot where it can leak onto the center conductor. Have
> you tried grounding the splitter? If there is something riding on the
> shield, that could give it somewhere to go where it will do no harm.
>
>
> CIAO!
>
> Ed N.
>
> Timothy Daniels wrote:
>> Yup, that all sounds right. :-) And it sounds like the cable modem
>> is receiving and transmitting the right signal levels. But why would
>> the packet loss increase when the barrel connector is substituted
>> for the splitter, thus causing the upstream signal level to rise from
>> +47dBmV to +49 dBmV as a result of the downstream signal level
>> dropping from +10 dBmv to +7 dBmV? I'd think that the louder
>> outgoing signal would better the signal-to-noise ratio. as seen by
>> the network.
>>
>> *TimDaniels*
>>
>>
>> "Ed Nielsen" wrote:
>>> That "reference level" (as you call it), like most numbers that have a
>>> (+) or a (-) before them is 0. DOCSIS says that cable modems have an
>>> input level window of -15 - +15dBmV, which simply means that as long
>>> as the input signal level is within that window, it will work. The
>>> output level window, as dictated by DOCSIS, is +8 - +58dBmV. Again,
>>> as long as the output level of the cable modem is within that window,
>>> it will work.
>>>
>>> The input level, of course, is determined by the plant/drop system.
>>> For example: There is a line extender (amplifier) at the pedestal
>>> that feeds your house. [Single family home with a white picket fence
>>> and a couple of elm trees in the front yard out in the suburbs. Can't
>>> forget the 2 dogs and a cat, a swing on the front porch, a vegetable
>>> garden, and a few fruit trees out back, etc.] The tap on the output
>>> of that L.E. is a 26 value tap, and the length of your drop is 100',
>>> and the DOCSIS frequency is 600MHz, and it is a QAM256 system. The
>>> L.E is running out at 44dBmV (no slope, the output is flat), which
>>> equates to 18dBmV coming out of the tap. 100 feet of RG 6 loses
>>> ~5dB@600MHz, so you a level of 13dBmV at the groundblock. In a QAM256
>>> system, the data carrier runs at 6dB below the nearest analog channel,
>>> so that 13dBmV becomes 7dBmV. Place a cable modem right at the
>>> groundblock, and it will see an input level of +7dBmV. Say you have a
>>> TV set in the family room and your computer is in a room 25' from the
>>> groundblock. A 2-way splitter loses ~3.9dB at 600MHz and the 25' drop
>>> to the cable modem loses 1.25dB. That 7dBmV at the groundblock then
>>> becomes (+7-3.9-1.25=) 1.85dBmV at the input of the cable modem.
>>> Suppose you have 4 TV sets. The input level at your cable modem would
>>> then be (7-7.9-1.25=) -2.15dBmV. Change the attenuation and the input
>>> level changes by the same amount. A 30dB wide input level, cable
>>> modems have.
>>>
>>> On the output side in the same scenario, the return amp in the L.E.
>>> wants to see ~10dBmV. The pathway from cable modem is the drop and
>>> the tap. Let's say that the upstream frequency is 22MHz. RG 6 loses
>>> ~1.25dB/100' at 22MHz. The pathway to that amp has the signal losing
>>> 1.25dB (drop) and 26dB (tap). 10 (required input level to the amp) +
>>> 26 (tap) + 1.25 (drop) would have the cable modem pumping out
>>> 37.25dBmV. One TV (2-way splitter) and the cable modem 25' from the
>>> groundblock would have it pumping out (10+26+1.253.6+.31=) 41.16.
>>> Four TVs would necessitate that the modem transmit at 44.56dBmV.
>>>
>>> The CMTS (Cable Modem Termination System (in the headend)) wants a
>>> signal level of 0dBmV at its input. No wide window like cable modems
>>> have -- it wants 0dBmV. If the attenuation at a cable modem changes,
>>> the CMTS tells the modem to increase or decrease its output level
>>> accordingly. If a cable modem runs so as to hit the CMTS with too hot
>>> of a signal, the CMTS tells it to turn itself down. Too little and it
>>> tells the modem to turn itself up. When you remove the splitter from
>>> your drop, you reduce the attenuation of your drop by 3.5dB, which
>>> means that there is 3.5dBmV more signal hitting the CMTS than
>>> previously, so the CMTS tells the modem to turn itself down. Put it
>>> back in and the modem is told to crank up the power to compensate for
>>> the increase in attenuation. That is why the transmit levels vary
>>> when you remove/insert the splitter.
>>>
>>> If noise gets into the line, whether it be in the drop or somewhere in
>>> the plant, the CMTS can't hear the cable modem as well as it needs to,
>>> so it tells the modem to "speak louder," same thing as you do when
>>> conversing with someone on the sidewalk and a loud car drives by.
>>> Noise can be ingress from a local broadcaster or impulse noise such as
>>> from a blow dryer or vacuum cleaner.
>>>
>>>
>>> CIAO!
>>>
>>> Ed N.
>>>
>>>
>>>
>>> Timothy Daniels wrote:
>>>> I think you got that backwards. First, the modem appears to be
>>>> reporting a positive offset - a level *above* some reference level,
>>>> not a negative offset from some reference. Thus, with the splitter
>>>> in the line, the downstream level drops in magnitude from 10 dBmV
>>>> to 9 dBmV (this morning, and during the day yesterday, the downs-
>>>> stream level with the splitter in the line is/was 7 dBmV). And the
>>>> upstream level rose to 49 dBmV from 47 dBmV with the splitter
>>>> (today it's at 50 dBmV with the splitter.)
>>>>
>>>> That's agrees with the model that the Transmit upstream level varies
>>>> counter to the downstream Received level, and it also suggests that
>>>> the upstream level is a positive value, not a value below a reference
>>>> level. Given that, it looks as if the high downstream level was set
>>>> too high for there not to be a splitter since the packet loss
>>>> *increases*
>>>> when I substitute a barrel connector for the splitter.
>>>>
>>>> This would make sense if the cable company always assumes that
>>>> there would be one or two TVs hung off the same line - a likely
>>>> scenario for the average unit in a condo building, but just not the
>>>> scenario in my condo unit.
>>>>
>>>> *TimDaniels*
>>>>
>>>>
>>>> "Ed Nielsen" wrote:
>>>>> Lower packet loss with the modem pumping out more suggests that
>>>>> there may be some noise (impulse, ingress) hopping onto your drop.
>>>>> Where did they pad your cable? Right at the modem? If you can get
>>>>> to the main splitter, try padding there. Don't worry about the
>>>>> input -- you have plenty of room there to do what you want. You can
>>>>> go down to ~-12dBmV before there would start to be any cause of
>>>>> concern. Heck, I used to run at ~-12/52 for about 4 years until
>>>>> some plant issues caused me to alter that. Now, I'm at +7/49, and I
>>>>> hate it. One of these days soon, I'll get around to swapping out my
>>>>> DC to fix it.
>>>>>
>>>>>
>>>>> CIAO!
>>>>>
>>>>> Ed N.
>>>>>
>>>>> Timothy Daniels wrote:
>>>>>> Without the 2:1 splitter, the downstream signal level rises to 10
>>>>>> dBmv
>>>>>> (from 9 dBmV) and the upstream signal level drops to 47 dBmV (from
>>>>>> 49 dBmV). The tracerts show a quadrupling (or more) of timeouts with
>>>>>> the splitter removed. It seems that the lower transmit level
>>>>>> hinders the
>>>>>> packets' survival rate, and that the splitter, in reducing the
>>>>>> receive level,
>>>>>> causes the modem to drop its transmit level and thus increases the
>>>>>> timeout incidence. Is that right?
>>>>>>
>>>>>> BTW, *I* put the splitter between the modem and the RR network
>>>>>> for analog cable TV reception of local stations. Whenever the techs
>>>>>> were here, the splitter had been replaced by a barrel connector
>>>>>> (don't ask). As far as TW is concerned, my only service from them
>>>>>> is RoadRunner. But no instruments measured levels within my condo
>>>>>> unit. The only measurements that they took directly were on the level
>>>>>> from the amp in the vault at the curb and on the output from the
>>>>>> building's
>>>>>> amp that resulted from their padding down the signal coming from the
>>>>>> curb amp. The only measurements that they took specific to my modem
>>>>>> were the remote readings reported to them from by cell phone from the
>>>>>> central office. They said that it gave them more information than
>>>>>> what
>>>>>> I got from the modem's webpage and, presumably, what they could learn
>>>>>> by tapping into the line between the wall outlet and my modem. So
>>>>>> it's
>>>>>> strange that the timeouts are so much less frequent when I put my 2:1
>>>>>> splitter in the line - it is not what they thought the usual
>>>>>> configuration was.
>>>>>>
>>>>>> *TimDaniels*

Posted by Ed Nielsen on December 25, 2006, 10:20 am
If you were  Registered and logged in, you could reply and use other advanced thread options
Sorry -- I had misread something you had written. Warren had given a
good analogy of that, though.

Technically, a splitter is a power divider. In fact, as you probably
already know, in the commercial world that is what they are called.
When the voltage is cut in half (half of the voltage goes down each leg
of a 2-way splitter), there is a 3dB reduction in signal strength.
Actually, it's 3.01. Throw in a little more for imperfect materials
used in the manufacturing process and we have ~3.5. That number varies
slightly with different manufacturers and it also varies a little with
frequency. As the frequency increases, so does the loss through the
splitter. The insertion loss through a 2-way splitter is typically from
~3.3dB (5MHz) to ~4.2dB (1GHz). A 4-way loses ~6.7dB (5MHz) to ~8dB (1GHz).

It is possible that a splitter could cause disruption amongst the
packets. Make sure that the one you have in there has a high return
loss on all ports. Also, of course, solder-backed (no epoxy).

HAVE A VERY MERRY CHRISTMAS!


CIAO!

Ed N.

Timothy Daniels wrote:
> I never posed that it was packet loss that caused the modem
> to increase its upstream signal level.
>
> You say that it is the CMTS at the headend that tells the modem
> to turn its signal level up or down. And when the splitter is substituted
> for the barrel connetor, the output level of the modem is increased.
> That suggests that the splitter itself is attenuating the upstream signal
> from the modem to the CMTS, as nothing else has changed. It may
> also be the splitter which is mangling the packets. I'll search around
> for another splitter to see if that helps.
>
> *TimDaniels*
>
>
> "Ed Nielsen" wrote:
>> It isn't packet loss that causes the modem to pump out more -- nor is
>> it because the downstream has changed. [You could use a couple of
>> diplex filters (not the satellite ones but similar in purpose) that
>> separate the forward path from the return path, pad the downstream
>> down as much as you want (or even amplify it) and you would see
>> virtually no change in the transmit level of the cable modem.] It is
>> merely that because of the reduced attenuation on the drop, the cable
>> modem is hitting the CMTS too hot, so it is told to turn down.
>>
>> That suggests to me that there might be something (noise) getting into
>> the drop between the cable modem and the splitter/barrel location.
>> When you insert the splitter, you lower the signal level hitting the
>> CMTS, so it tells the cable modem to increase its transmit level. The
>> signal level from the splice location back to the lockbox remains
>> pretty much the same whether the splitter is in there or not -- it is
>> only in the portion of the drop from that location to the outlet that
>> sees the increase/decrease in signal level as the modem's transmit
>> level changes. Could that piece run parallel to some A.C. lines for
>> awhile? There could be something that is induced onto and is riding
>> on the shield until it finds a spot where it can leak onto the center
>> conductor. Have you tried grounding the splitter? If there is
>> something riding on the shield, that could give it somewhere to go
>> where it will do no harm.
>>
>>
>> CIAO!
>>
>> Ed N.
>>
>> Timothy Daniels wrote:
>>> Yup, that all sounds right. :-) And it sounds like the cable modem
>>> is receiving and transmitting the right signal levels. But why would
>>> the packet loss increase when the barrel connector is substituted
>>> for the splitter, thus causing the upstream signal level to rise from
>>> +47dBmV to +49 dBmV as a result of the downstream signal level
>>> dropping from +10 dBmv to +7 dBmV? I'd think that the louder
>>> outgoing signal would better the signal-to-noise ratio. as seen by
>>> the network.
>>>
>>> *TimDaniels*
>>>
>>>
>>> "Ed Nielsen" wrote:
>>>> That "reference level" (as you call it), like most numbers that have
>>>> a (+) or a (-) before them is 0. DOCSIS says that cable modems have
>>>> an input level window of -15 - +15dBmV, which simply means that as
>>>> long as the input signal level is within that window, it will work.
>>>> The output level window, as dictated by DOCSIS, is +8 - +58dBmV.
>>>> Again, as long as the output level of the cable modem is within that
>>>> window, it will work.
>>>>
>>>> The input level, of course, is determined by the plant/drop system.
>>>> For example: There is a line extender (amplifier) at the pedestal
>>>> that feeds your house. [Single family home with a white picket
>>>> fence and a couple of elm trees in the front yard out in the
>>>> suburbs. Can't forget the 2 dogs and a cat, a swing on the front
>>>> porch, a vegetable garden, and a few fruit trees out back, etc.]
>>>> The tap on the output of that L.E. is a 26 value tap, and the length
>>>> of your drop is 100', and the DOCSIS frequency is 600MHz, and it is
>>>> a QAM256 system. The L.E is running out at 44dBmV (no slope, the
>>>> output is flat), which equates to 18dBmV coming out of the tap. 100
>>>> feet of RG 6 loses ~5dB@600MHz, so you a level of 13dBmV at the
>>>> groundblock. In a QAM256 system, the data carrier runs at 6dB below
>>>> the nearest analog channel, so that 13dBmV becomes 7dBmV. Place a
>>>> cable modem right at the groundblock, and it will see an input level
>>>> of +7dBmV. Say you have a TV set in the family room and your
>>>> computer is in a room 25' from the groundblock. A 2-way splitter
>>>> loses ~3.9dB at 600MHz and the 25' drop to the cable modem loses
>>>> 1.25dB. That 7dBmV at the groundblock then becomes (+7-3.9-1.25=)
>>>> 1.85dBmV at the input of the cable modem. Suppose you have 4 TV
>>>> sets. The input level at your cable modem would then be
>>>> (7-7.9-1.25=) -2.15dBmV. Change the attenuation and the input level
>>>> changes by the same amount. A 30dB wide input level, cable modems
>>>> have.
>>>>
>>>> On the output side in the same scenario, the return amp in the L.E.
>>>> wants to see ~10dBmV. The pathway from cable modem is the drop and
>>>> the tap. Let's say that the upstream frequency is 22MHz. RG 6
>>>> loses ~1.25dB/100' at 22MHz. The pathway to that amp has the signal
>>>> losing 1.25dB (drop) and 26dB (tap). 10 (required input level to
>>>> the amp) + 26 (tap) + 1.25 (drop) would have the cable modem pumping
>>>> out 37.25dBmV. One TV (2-way splitter) and the cable modem 25' from
>>>> the groundblock would have it pumping out (10+26+1.253.6+.31=)
>>>> 41.16. Four TVs would necessitate that the modem transmit at
>>>> 44.56dBmV.
>>>>
>>>> The CMTS (Cable Modem Termination System (in the headend)) wants a
>>>> signal level of 0dBmV at its input. No wide window like cable
>>>> modems have -- it wants 0dBmV. If the attenuation at a cable modem
>>>> changes, the CMTS tells the modem to increase or decrease its output
>>>> level accordingly. If a cable modem runs so as to hit the CMTS with
>>>> too hot of a signal, the CMTS tells it to turn itself down. Too
>>>> little and it tells the modem to turn itself up. When you remove
>>>> the splitter from your drop, you reduce the attenuation of your drop
>>>> by 3.5dB, which means that there is 3.5dBmV more signal hitting the
>>>> CMTS than previously, so the CMTS tells the modem to turn itself
>>>> down. Put it back in and the modem is told to crank up the power to
>>>> compensate for the increase in attenuation. That is why the
>>>> transmit levels vary when you remove/insert the splitter.
>>>>
>>>> If noise gets into the line, whether it be in the drop or somewhere
>>>> in the plant, the CMTS can't hear the cable modem as well as it
>>>> needs to, so it tells the modem to "speak louder," same thing as you
>>>> do when conversing with someone on the sidewalk and a loud car
>>>> drives by. Noise can be ingress from a local broadcaster or impulse
>>>> noise such as from a blow dryer or vacuum cleaner.
>>>>
>>>>
>>>> CIAO!
>>>>
>>>> Ed N.
>>>>
>>>>
>>>>
>>>> Timothy Daniels wrote:
>>>>> I think you got that backwards. First, the modem appears to be
>>>>> reporting a positive offset - a level *above* some reference level,
>>>>> not a negative offset from some reference. Thus, with the splitter
>>>>> in the line, the downstream level drops in magnitude from 10 dBmV
>>>>> to 9 dBmV (this morning, and during the day yesterday, the downs-
>>>>> stream level with the splitter in the line is/was 7 dBmV). And the
>>>>> upstream level rose to 49 dBmV from 47 dBmV with the splitter
>>>>> (today it's at 50 dBmV with the splitter.)
>>>>>
>>>>> That's agrees with the model that the Transmit upstream level varies
>>>>> counter to the downstream Received level, and it also suggests that
>>>>> the upstream level is a positive value, not a value below a reference
>>>>> level. Given that, it looks as if the high downstream level was set
>>>>> too high for there not to be a splitter since the packet loss
>>>>> *increases*
>>>>> when I substitute a barrel connector for the splitter.
>>>>>
>>>>> This would make sense if the cable company always assumes that
>>>>> there would be one or two TVs hung off the same line - a likely
>>>>> scenario for the average unit in a condo building, but just not the
>>>>> scenario in my condo unit.
>>>>>
>>>>> *TimDaniels*
>>>>>
>>>>>
>>>>> "Ed Nielsen" wrote:
>>>>>> Lower packet loss with the modem pumping out more suggests that
>>>>>> there may be some noise (impulse, ingress) hopping onto your
>>>>>> drop. Where did they pad your cable? Right at the modem? If you
>>>>>> can get to the main splitter, try padding there. Don't worry
>>>>>> about the input -- you have plenty of room there to do what you
>>>>>> want. You can go down to ~-12dBmV before there would start to be
>>>>>> any cause of concern. Heck, I used to run at ~-12/52 for about 4
>>>>>> years until some plant issues caused me to alter that. Now, I'm
>>>>>> at +7/49, and I hate it. One of these days soon, I'll get around
>>>>>> to swapping out my DC to fix it.
>>>>>>
>>>>>>
>>>>>> CIAO!
>>>>>>
>>>>>> Ed N.
>>>>>>
>>>>>> Timothy Daniels wrote:
>>>>>>> Without the 2:1 splitter, the downstream signal level rises to
>>>>>>> 10 dBmv
>>>>>>> (from 9 dBmV) and the upstream signal level drops to 47 dBmV (from
>>>>>>> 49 dBmV). The tracerts show a quadrupling (or more) of timeouts
>>>>>>> with
>>>>>>> the splitter removed. It seems that the lower transmit level
>>>>>>> hinders the
>>>>>>> packets' survival rate, and that the splitter, in reducing the
>>>>>>> receive level,
>>>>>>> causes the modem to drop its transmit level and thus increases the
>>>>>>> timeout incidence. Is that right?
>>>>>>>
>>>>>>> BTW, *I* put the splitter between the modem and the RR network
>>>>>>> for analog cable TV reception of local stations. Whenever the techs
>>>>>>> were here, the splitter had been replaced by a barrel connector
>>>>>>> (don't ask). As far as TW is concerned, my only service from them
>>>>>>> is RoadRunner. But no instruments measured levels within my condo
>>>>>>> unit. The only measurements that they took directly were on the
>>>>>>> level
>>>>>>> from the amp in the vault at the curb and on the output from the
>>>>>>> building's
>>>>>>> amp that resulted from their padding down the signal coming from the
>>>>>>> curb amp. The only measurements that they took specific to my modem
>>>>>>> were the remote readings reported to them from by cell phone from
>>>>>>> the
>>>>>>> central office. They said that it gave them more information
>>>>>>> than what
>>>>>>> I got from the modem's webpage and, presumably, what they could
>>>>>>> learn
>>>>>>> by tapping into the line between the wall outlet and my modem.
>>>>>>> So it's
>>>>>>> strange that the timeouts are so much less frequent when I put my
>>>>>>> 2:1
>>>>>>> splitter in the line - it is not what they thought the usual
>>>>>>> configuration was.
>>>>>>>
>>>>>>> *TimDaniels*

Posted by Timothy Daniels on December 26, 2006, 9:23 pm
If you were  Registered and logged in, you could reply and use other advanced thread options
Now the splitter seems to make no difference in packet loss (as measured
by "ping -t"), except to drop the downstream signal level to the modem
to 6-7 dBmV and to cause the modem to raise its signal level to 50 dBmV.
The splitter is a TVC unit that's rated for use to 1 GHz, and it's solder sealed.
On pings to yahoo, google, and mit, packet loss is reported as 2-3% (although
I observe twice that) and to rr.com it's reported around 10%. There seems
to be no pattern, now.

*TimDaniels*

"Ed Nielsen" wrote:
> Sorry -- I had misread something you had written. Warren had given a
> good analogy of that, though.
>
> Technically, a splitter is a power divider. In fact, as you probably
> already know, in the commercial world that is what they are called.
> When the voltage is cut in half (half of the voltage goes down each leg
> of a 2-way splitter), there is a 3dB reduction in signal strength.
> Actually, it's 3.01. Throw in a little more for imperfect materials
> used in the manufacturing process and we have ~3.5. That number varies
> slightly with different manufacturers and it also varies a little with
> frequency. As the frequency increases, so does the loss through the
> splitter. The insertion loss through a 2-way splitter is typically from
> ~3.3dB (5MHz) to ~4.2dB (1GHz). A 4-way loses ~6.7dB (5MHz) to ~8dB (1GHz).
>
> It is possible that a splitter could cause disruption amongst the
> packets. Make sure that the one you have in there has a high return
> loss on all ports. Also, of course, solder-backed (no epoxy).
>
> HAVE A VERY MERRY CHRISTMAS!
>
>
> CIAO!
>
> Ed N.
>
> Timothy Daniels wrote:<