Most fta users probably give little if any thought as to how much power is needed to operate the switches that are installed in most fta systems. I think almost everyone knows that a ku satellite dish motor, and the lnb need power to operate, but the switch or switches may need the same amount of power that the lnb or motor does.

Earlier this year, I put together a digital meter that shows the voltage and milliamps that were being used by the antenna system or part of the antenna system. Use of Ohm's Law (Volts X Amps = Power in Watts) allows for the calculation of power being used by the antenna system or a particular part of the antenna system. This simple meter can be used for many different things in a fta system, but I will focus mainly on switches and the power they need to operate for this thread.

Here is a picture of my digital meter, shown connected to the back of an Octagon SX88 fta receiver .
[Only registered and activated users can see links. ]

The parts needed to construct this digital meter are a length of coax with two connectors installed, and the meter, which can be found here:
[Only registered and activated users can see links. ]

Most fta receivers have around 450 milliamps maximum current rating. This is the amount of power the receiver can produce for long periods of time. It is very easy for switches to use or consume about 25 percent of the receiver power output. Here are some examples:

1. Ecoda 22 KHz switch, 14 milliamps.
[Only registered and activated users can see links. ]

2. 3X4 Multi-Switch, 67.7 milliamps
[Only registered and activated users can see links. ]

3. 4 Position Diseqc switch, 26.2 milliamps
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3X4 Multi-Switch, Ecoda 22KHz switch, and 4 Position diseqc switch, 108 milliamps.
[Only registered and activated users can see links. ]


Adding a lot of switches may take away or rob the lnb or ku motor of the power these parts need to operate properly! A typical consumer fta lnb may need 60-200 milliamps of power to operate correctly. A ku motor may use up to 350 milliamps of power at peak or at start-up, and then may need 150-200 milliamps to move the dish. Add all of this up and you will see that it is easy to exceed 450 milliamps.

Most of the fta receivers that I have tested will produce more than 450 milliamps for a short period of time.

A receiver tends to run hotter when it is required to produce more power for the lnb port.

A 22 KHz switch will provide power to both sides of the switch at all times!
So if you have two lnbs that draw 200 milliamps per lnb, the receiver will need to produce at least 400 milliamps when these two lnbs are connected to a fta receiver using a 22KHz switch!

It is a good idea to understand how much power your antenna system needs to operate, and how much power your receiver is capable of producing. I think the amount of power that switches need to operate is mostly overlooked, or is not completely understood. EB