I am using a HMC510LP5/510LP5E VCO for an RF output of 4.5GHz. The VCO has three RF outputs namely RFout, RFout/2 and RFout/4. I want to take a RFout/2 output. While designing I have kept the unused RFout pin and RFout/4 pin OPEN. The datasheet says that the output level of the VCO should be between 8dBm to 14dBm. But I am getting a output level of -5dBm. Can anyone tell me the reason behind the low output level? Is it because I kept the unused RF output pins open?