# Technical Support

## Program an Indirect Power Channel

A telemetry channel can be setup to give an indirect power reading. In this mode the channel does not give a reading based on its telemetry input but instead calculates a reading based on the two channels before it. Those two channels must read the plate voltage and plate current respectively.

For example, to calculate an indirect power reading on channel 03, channel 01 must read the plate voltage and channel 02 must read the plate current.

The settings for the indirect power reading are stored in the same memory locations that normally assign a unit word, scale and decimal to the channel. Special calculations are required to generate the correct settings.

This page simulates the behavior of the indirect power operation of the RFC-1/B with reasonable accuracy. Since it is a simulation there are cases where it does not respond exactly like the actual processor. The discrepancies are minimal.

### Calculation

The telemetry value for the indirect power channel is calculated from the equation: POWER = (VOLTAGE * CURRENT * EFFICIENCY * SCALE)/10,000,000

- VOLTAGE is the plate voltage in volts
- CURRENT is the plate current in amps
- EFFICIENCY is the system efficiency
- SCALE is a multiplier used to adjust the result into the correct scale

### Efficiency

Efficiency values greater than 100% can be used to compute effective radiated power (ERP) as opposed to transmitter output power (TPO). This value can also be adjusted so that the power calculation results in a percentage of authorized power.

#### Example

If an antenna has a gain of 6.5, the feedline has an efficiency of 75% and the transmitter has an efficiency of 72%, the overall efficiency (input power-to-ERP) is 6.5 * 0.75 * 0.72 = 3.51.

In this example, to compute the actual ERP the efficiency value should be 351%–the decimal is dropped. If transmitter power output (TPO) is to be computed, the efficiency should be programmed to 72%.

The efficiency value can also be adjusted so the computed reading is a percentage of authorized power. In that case, the efficiency resulting from the above formula should be multiplied by 100 and then divided by the normal transmitter output power in kilowatts. The goal is for the reading to be "100.0" at 100% of authorized power.

## Instructions

Use the selections below to program an indirect power channel. All items must be completed.

The values and adresses will be calculated and displayed. Click the "Show Instructions" button to display step-by-step programming instructions.