sporkme
drop the crantini and move it, sister
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join:2000-07-01
Morristown, NJ
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| reply to AMD Phreak
Re: Min Distance from VHF Antenna
said by AMD Phreak  :Go as far as you can, but more importantly run STP to the radios, that is if they are on the tower. Curious, what's the spectrum that ethernet uses (100MB FE)? Any harmonics from nearby transmitters to look out for (meaning, do any "common" VHF bands perhaps disrupt ethernet with one of their harmonics)? |
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lutful
Premium
join:2005-06-16
Ottawa, ON
| said by sporkme :Curious, what's the spectrum that ethernet uses (100MB FE)? Fast Ethernet transmission uses 125Mbps "raw" data rate which is carried in a 62.5Mhz "MLT-3" waveform.
There is not much VHF coming out of properly twisted portions of the cable - most noise is coupled in the small untwisted section near the connectors. |
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wispman
join:2004-12-21
USA | reply to sporkme
One time I had an ethernet cable I put in at an install that ran across a desk and it went right by a police scanner. The scanner "keyed up" and was locked on something like 150-160mhz. |
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sporkme
drop the crantini and move it, sister
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join:2000-07-01
Morristown, NJ
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| reply to lutful
said by lutful :said by sporkme :Curious, what's the spectrum that ethernet uses (100MB FE)? Fast Ethernet transmission uses 125Mbps "raw" data rate which is carried in a 62.5Mhz "MLT-3" waveform. So you're saying that ethernet is centered at 62.5 MHz or goes from "0"-62.5MHz?
said by lutful :There is not much VHF coming out of properly twisted portions of the cable - most noise is coupled in the small untwisted section near the connectors. I was thinking more about RF from other sources getting into the ethernet cable and providing a hard to diagnose failure or near-failure.
So anything with a strong harmonic that lands somewhere below 100MHz could be bad news, right? Technically, ethernet is RF, correct? |
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lutful
Premium
join:2005-06-16
Ottawa, ON
| Here are various Ethernet baseband spectrum. Properly twisted CAT5 cable has 50-100dB VHF rejection. |
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