how to test an lnb

[billhiggs]

Is there an easy way to test an LNB, besides the obvious?
its kinda hard to line a dish if you are not sure the LNB is good

Thanks

Bill

[Benney]

Thanks goes to jorgek

C/P
There is no real easy way to test an lnb other than to try a known good replacement or eliminate it as the problem.

But if you know how to use a multimeter you can at least determine if power is actually getting to the LNB. The LNB requires one of 2 voltages depending on whether the STB is tuned to a Horizontal channel or a Vertical channel transponder signal.
13vdc for a Vertical channel and 18vdc for a Horizontal one.
Assuming your STB is okay, either 13vdc or 18vdc will be at the antenna coax connector at the back of the STB. The switch on the front of the STB does not kill the lnb volts at the connector. That is why you must totally power down the STB when disconnecting or connecting the coax, switches or lnbs.

Shut power to STB with switch at back of set. Disconnect dish coax. Turn power back on. Connect multimeter, red (positive lead) to center of antenna connector and black (negative lead) to outside of connector. Be careful not to short out the connector. You will read about 13vdc for a VERTICAL channel and about 18vdc for a HORIZONTAL channel. You can do the same test at the lnb end by disconnecting lnb and do the voltage test at the connector. Also turn off main power switch. The voltage readings at the connector end will be lower depending on the number of switches and length and type of coax. This is a good way to determine if the LNB is getting voltage. At the same time you will see the effects that cable length and switches have on the voltage reaching the LNB.

Test equipment, Fluke 8020a multimeter (lab grade).
Here are the voltage readings on my VS Ultra 2000 V1 at the connector on back of set with coax disconnected;

Test 1, Power on:
18.25 vdc for Horizontal channel
13.80 vdc for Vertical channel
1.30 vdc with switch at front of set OFF. ( STB is in standby)

Test 2, Voltage measured at lnb end of 80 feet of RG6 quad coax, heavy duty 4x1 Chieta switch (half way down), 2 barrel connectors in line and LNB disconnected: All other coax connectors are quality compression type.

18.21 vdc for Horizontal channel
13.78 vdc for Vertical channel.

It’s a simple test that should help trouble shoot if the problem is with the LNB or the rest of the equipment.

[billhiggs]

Thanks

Bill


C/P
There is no real easy way to test an lnb other than to try a known good replacement or eliminate it as the problem.

But if you know how to use a multimeter you can at least determine if power is actually getting to the LNB. The LNB requires one of 2 voltages depending on whether the STB is tuned to a Horizontal channel or a Vertical channel transponder signal.
13vdc for a Vertical channel and 18vdc for a Horizontal one.
Assuming your STB is okay, either 13vdc or 18vdc will be at the antenna coax connector at the back of the STB. The switch on the front of the STB does not kill the lnb volts at the connector. That is why you must totally power down the STB when disconnecting or connecting the coax, switches or lnbs.

Shut power to STB with switch at back of set. Disconnect dish coax. Turn power back on. Connect multimeter, red (positive lead) to center of antenna connector and black (negative lead) to outside of connector. Be careful not to short out the connector. You will read about 13vdc for a VERTICAL channel and about 18vdc for a HORIZONTAL channel. You can do the same test at the lnb end by disconnecting lnb and do the voltage test at the connector. Also turn off main power switch. The voltage readings at the connector end will be lower depending on the number of switches and length and type of coax. This is a good way to determine if the LNB is getting voltage. At the same time you will see the effects that cable length and switches have on the voltage reaching the LNB.

Test equipment, Fluke 8020a multimeter (lab grade).
Here are the voltage readings on my VS Ultra 2000 V1 at the connector on back of set with coax disconnected;

Test 1, Power on:
18.25 vdc for Horizontal channel
13.80 vdc for Vertical channel
1.30 vdc with switch at front of set OFF. ( STB is in standby)

Test 2, Voltage measured at lnb end of 80 feet of RG6 quad coax, heavy duty 4x1 Chieta switch (half way down), 2 barrel connectors in line and LNB disconnected: All other coax connectors are quality compression type.

18.21 vdc for Horizontal channel
13.78 vdc for Vertical channel.

It’s a simple test that should help trouble shoot if the problem is with the LNB or the rest of the equipment.[/QUOTE]

[jvvh5897]

You could try to pick up the LO leakage from the LNB. You can build a circuit that picks it up and rectifies it to a DC indication. Or if you have a receiver that picks up the LO frequency look for a spike at the LO freq. Or hook up an LNB that might get the signal to something that a receiver that you have can pick up.

But the obvious is the easy way.

[Terryl]

The only real way to test an LNB is to use a 12 GHz RF generator, a 12 GHz test antenna, a LNB test interface and a spectrum analyzer.

I use a highly modified Dish 301 receiver, it is modified to track the DC voltage and current used by the LNB, the modifications let me measure the actual DC voltage and current used by the LNB when receiving actual transponders and sending the IF down to the receiver.

Example:

A DP single satellite LNB needs @ 175 mA of DC current at 18 to 20 volts DC to just run without a signal from a satellite, add a signal from a satellite, with about 30 transponders on the IF signal going to the receiver, and your DC current draw could go up about 75 to 100 mA. (example only, these are approximate measurements)

You can not correctly measure the DC current and DC voltage on the coax going to the LNB with an active signal, not without some very special equipment, with out the special equipment the LNB will shut down as you will cause an imbalance on the systems RF and control signals.

So with this all said, the only way to test if the LNB is working or not is to substitute with a known good LNB of the same type and manufacture.