Cable and low voltage / Signal tool
See where the signal goes.
Model a coax path in both directions, estimate device levels, and identify the segment or passive contributing the most loss.
Beyond one calculation
Use the same signal checks on every service call.
Build a reusable signal-quality or installation-QC inspection for yourself or your team.
Worked example
One path, two frequency-dependent losses.
Start with +8 dBmV downstream at 750 MHz and a 36 dBmV network-side upstream reference at 30 MHz. A 100-foot Belden 9116 Series 6 run contributes 5.65 dB at 750 MHz and about 1.09 dB at 30 MHz after interpolation.
Add a 3.5 dB passive and two connectors at a 0.1 dB design allowance each. The estimated device levels are approximately −1.35 dBmV downstream and 40.79 dBmV upstream transmit. The separate totals make the frequency assumption visible.
Method and data
Published points, explicit interpolation.
Built-in tables are tied to exact products rather than generic RG labels. The initial dataset includes the Belden 9116 Series 6 attenuation table, the CommScope 5781 RG6 specification, and the CommScope 2287V RG11 specification.
Exact published frequency points are used directly. Frequencies between points use linear interpolation in dB per 100 feet. Frequencies outside a selected product's table are rejected; custom entries are available for other verified cable data.
This is a path-loss estimate, not a replacement for a meter or full RF analysis. It does not model temperature correction, return loss, standing waves, damaged shielding, ingress, tilt, amplifier response, active-device alignment, or per-port frequency response unless those effects are entered as losses.
Formula and attenuation dataset version 0.1 · Cable-network SME review required before public launch
Common questions.
The frequency basis, data range, and interpretation windows stay visible so a field reviewer can challenge every assumption.
How is expected downstream level calculated?
The calculator finds cable attenuation at the selected downstream frequency, scales each value by segment length, and adds passive-device insertion loss and the optional connector allowance. That total path loss is subtracted from the starting downstream level.
How is estimated upstream transmit calculated?
The calculator finds cable attenuation at the selected upstream frequency and adds the same entered passive and connector losses. That upstream path loss is added to the network-side reference level to estimate the transmit requirement at the device.
Why are downstream and upstream frequencies separate?
Coax attenuation increases with frequency. Reusing a downstream-frequency loss for the return path can materially overstate upstream cable loss, so this calculator evaluates each direction independently across the same physical path.
How are frequencies between manufacturer table points handled?
The calculator uses straight-line interpolation between the two adjacent published attenuation points. It shows each table's supported range and rejects any frequency below or above that range rather than silently extrapolating.
Are RG6 and RG11 loss values interchangeable between products?
No. The built-in options identify exact Belden and CommScope products because construction and published loss can differ even within the same general series. Use custom attenuation when the installed cable does not match a built-in table.
Are the displayed signal windows DOCSIS pass/fail limits?
No. They are editable testing defaults used only to label a result as preferred, caution, or review. Replace them with the operating criteria, equipment limits, design targets, and escalation rules for the network being tested.