Currently, the receiver splitter is passively split into two. I can tolerate 3dB attenuation, so I'm using it as is, but when I connect a direct receiver I made to the splitter terminal, the carrier of the direct receiver leaks to the ANT terminal, so when I monitor the waveform with the other receiver, it appears at the carrier point at 20 to 30dB. I can't tell if this is the carrier leakage of the received radio wave (the other party's radio wave), or if I transmit, I can't check the carrier leakage of my own radio wave. So, a local station said that they connected the same direct receiver to the splitter, but it didn't show up on the waveform monitor. When I checked, I found that they were using active distribution (military splitter) instead of passive distribution, so I had to somehow switch from passive distribution to active distribution, and I considered various options. This is the configuration diagram of the current two-distribution configuration. 　 Carrier leak from RX2 leaks into RX1 and appears on the waveform monitor. Therefore, we would like to operate it as shown in the figure below. 　 Since the distributor is configured as an active one, insertion loss can be set to 0 dB without sacrificing it. The required items are distortion at strong input / frequency characteristics (30 MHz in the HF band) / NF value. These must be satisfied. I found an interesting IC (6 dB video amplifier 50 MHz band) at Akizuki, so I checked to see if I could use it. There was no discussion about NF, but everything else was OK. However, if we assume that the video output is 1 Vpp and S/N = -90 dB, this noise is equivalent to S = 5 (-93 dBm) at the ANT terminal level, and noise rises from S = 0. In the first place, in this level of consideration, concrete numerical measurements cannot be made unless a proper shield loop is set up, so it is judged by the receiver's S meter, the amount of noise on the waveform monitor, and the amount of audible noise from the receiver. So I tried using a discrete (FET push-pull). It wasn't exactly +6dB, but the distortion, frequency response and NF were all good, so I decided that this would work, and stored it in a shielded case, divided it into three, made the ANT terminal a dummy, and checked the power of the active circuit by turning it OFF and ON. When I ran a current of about 50mA, the NF was also clear, so I raised my hands up high. So, what was the problem? The carrier leak from the direct receiver, which is my main purpose, should not appear on the waveform monitor. When I turned on the direct receiver, 15 to 20dB appeared. I set up an output buffer, but the NF was sacrificed. I was worried that this would not work, but then I found that there was a good device in the op-amp system recently, so I thought I would check it out, and when I actually experimented, it was amazing. The device output was low impedance and consolidated into one device, so I should be able to achieve my first purpose. What I was concerned about was the NF, which was almost no different from the FET push-pull. This seems like it might work, so I'll make a prototype inside a shielded case and check the data for each item. [Prototype active splitter] 　 Circuit diagram It is possible to distribute to two with one device, but when using it as a normal distributor, it is more efficient to distribute to two from one device. In my case, I needed to eliminate leakage from other receivers, so I configured it to be one distribution/one device. 　　　　　　　　　　　　　　　　 ① At strong input, S = 9+60dB (-13dBm) splitter input and output data Insertion loss = -0.2dB, no IMD issues, input = output 　 ② Frequency characteristics At 30MHz, it is -1.4dB based on 3MHz, so there is no problem. 　　　　　　　　　　　　　　　　　　　　　　　　　 ③NF (Noise Fix) The ANT terminal is a dummy connection (open is fine), and the noise characteristics of the distributor output when the power to the active distributor is turned OFF/ON. When the power is turned ON, there is a sign of an increase of 1-2 dB. There is no clear increase of about 20 dB like with the video distributor, so the rest is to check using a receiver. 　 When the power of the active distributor is turned OFF and ON, the audio noise on the receiver's waveform monitor and the S meter are compared (ANT terminal = dummy). The audio noise appears to have risen by 1 to 2 dB, just as in the RF comparison above. However, although it does seem that the noise tone has changed slightly when switching, there is almost no change, and there is no change at all on the S meter. The actual unit is originally connected to ANT, and it is absolutely very FB. 　　　　　　　　　　　When the distributor power is OFF　　　　　　　　　　　When distributor power is ON 　 ④ Carrier leak data from direct receiver First, with the current Passive2 splitter connection, the carrier point on the waveform monitor comes out about 38 dB from the noise floor. The ANT terminal was measured as a dummy, and if you connect the ANT, the noise will float, so it will be about 20 dB. However, it comes out more clearly on the transmission air monitor. 　 Finally, we confirmed that there was no carrier leakage in the prototype active splitter, and when the power of the direct receiver was turned on, nothing at all was coming out of the noise floor at the carrier point.