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Streetlight

join:2005-11-07
Colorado Springs, CO
reply to whamel

Re: [Signals] Modem signals better when split twice on highdB le

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.
--
There is nothing more deceptive than an obvious fact.

Sherlock Holmes in
The Boscombe Valley Mystery
A. C. Doyle
Strand Magazine, October 1891


EG
The wings of love
Premium
join:2006-11-18
Union, NJ
kudos:10
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.


whamel
billhamel .net
Premium
join:2002-05-09
Hinsdale, IL
kudos:10
Reviews:
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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...
--
Bill - Hattiesburg, MS - »www.billhamel.net