Loss and Gain Calculations

DHFC networks are inherently directional, which is a node-centric approach to design. A node is an emitter of the forward signal, which sends a signal downstream to subscribers, and the return signal is sent from the subscriber back to the node.

A node has pre-determined output levels that are defined in the DHFC Catalog.

Loss and gain can be calculated on the following RF components:

Tap
Conditioning tap
Cable
Directional coupler
Amplifier
Inline equalizer
Inline equalizer (LEQ/RC)
Splice
Splitter
Power inserter
Attenuator plugin

NOTE: Calculations are available on the Output tab and Tap Ports tab, whereas the Input tab has no calculations. You can select a component (based on the list above), click Output, and view the expanders. When you select an expander, you can view the calculation.

In the following example the signal strength output is 53.88 dBmV at 1000 MHz:

To calculate the forward loss at 53.88 dBmV for this component and for each individual component downstream, the loss is calculated from that component. Calculating signal loss depends on the device and the configuration provided in the Catalogue. The spec information in the Catalogue denotes the type of each component.

NOTE: Unbalanced outputs aren’t supported, so the output values are always identical.

For the example component above, the Catalogue spec indicates that the length of the cable is ~237 ft. Given that cable loss is calculated in loss per 100 ft., 237 ft. divided by 100 results in a signal loss on this cable of approximately 4 dB.

While tap calculations are fairly straightforward (only signal loss from the device is taken into account), directional couplers are slightly more complicated in that the loss calculation is dependent upon which leg is selected. Directional couplers have a through leg and a down leg, which are noted In the Catalogue, and in this example you can see the forward leg and down leg of the coupler:

The through leg produces the hot leg, which is represented by a hot dot on the device in the map:

Through leg and hot leg are synonymous, and typically there is less signal loss on the hot leg than the down leg. The through leg is the closest to the input signal for this particular device. The down leg consistently experiences greater signal loss than the through leg.

In the following image you can see that this directional coupler has ~2 dB of signal loss on the forward leg:

On the down leg, you can see a significantly higher signal loss at ~12 dB.