 whamelPremium
join:2002-05-09
Hattiesburg, MS
 ·Comcast
| reply to Streetlight
Re: [Signals] Modem signals better when split twice on highdB le If you notice, the second (bottom) picture where I used the -3.5dB leg, the DOCSIS 1.X freq 29.5MHz increased 3dBmV. I know for a fact I use that frequency. I have another modem UBEE DDM3513 that is provisioned on the same line in my apt (I have 2 internet connections) and it it says I config. page says I use that upstream frequency. Weirdly enough, after re-wiring and installing a new passive 3-way splitter, the downstream frequency switched from channel 1 to channel 4 which means I go from 669MHz to 663MHz.
Can't seem to figure it out because I know certain areas are provisioned on a certain frequency to avoid "crowding" and loss of speed and signal quality. In Hattiesburg, MS we have 4 downstream channels available to us and only 2 upstream.
I have just noticed that while I was in Chicago, (my mothers home in the burbs) her modem had 8 downstream channels and 4 upstream. But that forward-path attenuator sounds like a good option.
Thanks for the suggestion.
-Bill
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Bill - Hattiesburg, MS - »www.billhamel.net |
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| whamel, and EG
Oops, I didn't notice the 2nd QAM signal had gone up in your changed setup. Not sure, then, why the higher upstream frequency was attenuated and not the lower.
I found the manufacturer's spec sheet for these things and it seems that there is some small attenuation back for frequencies below 65 MHz of 1 to 1.5 or 2.0 dBmV, but at higher frequencies they have the labeled attenuation. That is, a 6 dBmV one will attenuate 6 to 7 dBmV at 88 MHz and higher. Generally, that would be OK for internet frequencies - upstreams are 25-36 MHz, downstreams are 580-606 MHz on my modem - but maybe not the higher frequencies used for cable TV since there's no data for >860 MHz. This suggests that these things should be plugged in to the cable input of the modem and definitely not at the input to a splitter that my connect eventually to a cable box.
I found a UK blog that shows these attenuators attenuate both up and down streams:
»www.cableforum.co.uk/board/12/16···int.html
These results leave me with some questions about how well these things work.
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There is nothing more deceptive than an obvious fact.
Sherlock Holmes in
The Boscombe Valley Mystery
A. C. Doyle
Strand Magazine, October 1891 |
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 EGThe wings of lovePremium
join:2006-11-18
Union, NJ
kudos:9 | Too much is being read in to this IMO... The forward path only attenuators that I have perform fine and DO NOT attenuate the return path.. Perhaps they introduce 0.1 dB of attenuation in to the return path which is insignificant. |
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whamelPremium
join:2002-05-09
Hattiesburg, MS Reviews:
·Comcast
| reply to Streetlight
said by Streetlight:whamel, and EG
Oops, I didn't notice the 2nd QAM signal had gone up in your changed setup. Not sure, then, why the higher upstream frequency was attenuated and not the lower....
I found a UK blog that shows these attenuators attenuate both up and down streams:
»www.cableforum.co.uk/board/12/16···int.html
These results leave me with some questions about how well these things work.
I found attenuator "conditioners" that worked on both up and down stream. Was very confused about those. I will have to find the website again...
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Bill - Hattiesburg, MS - »www.billhamel.net |
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