High Input Gain

If the antenna LNA gain exceeds the cable loss by more than +40 dB (OEM7.03 or earlier) or +55 dB (OEM7.04 or later), the RF signal must be attenuated before reaching the receiver, as shown in Figure: In-Line Attenuator.

In-Line Attenuator

1	Most GNSS antenna LNAs safely operate with +5.0 VDC input voltage
2	The in-line attenuator must allow DC power to continue to the antenna.
3	The net gain at the RF input should not exceed:	+40 dB (OEM7.03 or earlier) +55 dB (OEM7.04 or later)

Attenuation Requirement

In this example, we will select an in-line attenuator that reduces the signal by the amount necessary to result in an overall gain of +30 dB, as shown in the formula below. Be sure to take into account the loss created by any additional equipment being used with the attenuator. Install the attenuator as close to the receiver as possible to avoid adding extra noise to the GNSS signal.

ATTENUATION = GAIN_ANTENNA – LOSS_CABLE – LOSS_OTHER – 30 dB

For example, if the selected antenna LNA provides +70 dB gain and the cable has a loss of -10 dB, a -30 dB attenuator can be added.