FAQ
TL;DR: Up to 100 m of RG-6 satellite-grade coax keeps full DOCSIS speed; “use a typical SAT antenna cable” [Elektroda, kasprzyk, post #6207187] Check modem levels (-15 to +15 dBmV) before relocating.
Why it matters: The right cable and signal level prevent random disconnects when you move a cable-TV internet modem outdoors.
Quick Facts
• RG-6 Cu-core coax price: ~PLN 1.5 per m [Elektroda, shadow125, post #6206996]
• Safe modem downstream: ‑15 to +15 dBmV [CableLabs, 2021].
• Upstream should stay < 58 dBmV for stability [Elektroda, kasprzyk, post #6252063]
• Shielded twisted-pair (FTP) works for Ethernet, not cable-TV internet [Elektroda, shadow125, post #6206996]
• Outdoor run length limit: ≈100 m before amp needed [Elektroda, kasprzyk, post #6207187]
What kind of cable should I use to move a Vectra cable-modem to another room?
Use RG-6 or other satellite-grade 75 Ω coax with a solid copper center to minimize loss. F-type connectors and weatherproof boots ensure a tight RF seal [Elektroda, kasprzyk, post #6207187]
Does the coax type affect my internet speed?
Speed stays unchanged if receive power remains between ‑15 and +15 dBmV. Poor cable raises attenuation, pushing levels below ‑15 dBmV and causing dropouts, not slower nominal speed [CableLabs, 2021; Elektroda, kasprzyk, #6210020].
How far can I run the coax without an amplifier?
With good RG-6 you can run about 100 m before downstream power usually falls >3 dB and risks going below spec [Elektroda, kasprzyk, post #6207187] Edge-case: thin RG-59 may halve that distance.
Will shielded twisted pair (FTP) work for this application?
No. FTP is for Ethernet. Vectra uses RF over 75 Ω coax; twisted pair will not carry the DOCSIS signal [Elektroda, shadow125, post #6206996]
How do I check my Motorola cable-modem signal levels?
- Connect a PC directly to the modem.
- Browse to http://192.168.100.1 before the Online LED turns solid.
- Read Receive (downstream) and Transmit (upstream) power values [Elektroda, kasprzyk, post #6208243]
What Receive Power Level should I aim for?
Target 0 dBmV; the acceptable window is ‑15 to +15 dBmV. Values below ‑15 dBmV double packet loss odds [CableLabs, 2021].
My Receive jumps by 6 dB—cause for concern?
Small swings (±6 dB) are normal and often temperature-related. Continuous swings >10 dB hint at damaged splitters or moisture-filled cable [Elektroda, kasprzyk, post #6249867]
Can I boost the signal myself with a home amplifier?
You need a return-path amplifier such as AMIGO M 865 P30. It lifts downstream but upstream may still max out at 58 dBmV, so consult the ISP first [Elektroda, kasprzyk, post #6251056]
Do coax Tees or splitters degrade internet levels?
Yes. Each 2-way splitter adds about 3.5 dB loss. A faulty splitter was blamed when Receive dropped from 3 dBmV to ‑7 dBmV after cable changes [Elektroda, sebaele22, post #6860165]
Will better copper-core coax always improve my signal?
Usually, but if connectors are poorly crimped or water-logged, signal may still worsen—as seen when copper replacement led to a 10 dB drop [Elektroda, 6860165]
Does signal level change my download speed tier?
Speed profile comes from DOCSIS provisioning. Signal out of spec causes retries or modem reboots, not a different tier [Elektroda, kasprzyk, post #6252063]
What’s the risk if upstream power exceeds 58 dBmV?
The modem may fail to reach the CMTS, leading to intermittent upload or total offline status; manufacturers flag >61 dBmV as critical [Arris, 2020].
