RMILEC NB20 Pt. 2: Binding and EMI Scan

RMILEC's T4047NB20 from Foxtechfpv.com

Long range 20 channel UHF radio system

Binding and EMI Scan

In this article we will go through the binding process and look at a few of the features of Rmilec's newest offering for long range radio control. This system has the ability to act as a relay, taking the 2.4 GHz signal from your transmitter and sending out a high powered uhf signal to the Rmilec receiver in your model. For an overview of the system check out our prevous article here: T4047NB20 Overview 

Setting up the system is quite easy. Below is a picture of how your 2.4 GHz receiver hooks into the NB20 signal acquisition module using standard PWM output. I have used a Frsky V8R7 SP receiver. The big green plug is 12 volts input to power everything. To the right of that are red and black leads that will go to a hot pin and a negative pin on an open channel on your receiver providing it with power. Next we have a yellow lead going from the signal pin on receiver channel 1 to the corresponding channel 1 pin on the signal acquisition module. The same thing goes for the following three pins. They are channel 2, 3 and 4 from your receiver.

The purple lead on the right connects receiver channel five to the pin labled IP on the signal acquisition module, which puts the transmitter module into idle mode and stops the NB20 from transmitting. 

Binding the NB20 receiver is easy. Pushing the bind button while powering up the receiver will put it into bind mode. You can see I have servos pluged into channels 1 and 2 at the bottom left of the NB20 receiver. 5 volts from a BEC goes to an open channel for power.

After you have put the receiver into bind mode hold down the button labled PB1 on the NB20 transmitter module while powering it on. Hold down button PB1 until the transmitter starts beeping.

Binding is complete. During the bind process the receiver does a scan for electromagnetic interference or EMI that might be caused by other onboard electronics and chooses the best channels to use for the strongest signal. For this reason it is best to do the binding with the receiver installed in a model and with all of the onboard equipment powered on. 

If we want to bind an additional receiver to the NB20 transmitter we must use the receiver copy function or the NB20 will scan for and choose new frequencies causing it to no longer communicate with the first receiver. To copy a receiver just put the new receiver into bind mode like before and now hold button PB2 on the transmitter while powering it on. The DONE led will light up on the receiver when the data copying is complete.

The performance of this system, like all other systems, is directly affected by received signal quality and outside interference. Rmilec have added an EMI scan function that can be done separate from the binding/EMI scan. This is a helpful tool when installing your receiver or other electronics that can cause interference. Power on the receiver while holding down the EMI scan button to enter EMI scan mode. The row of 5 leds on the face of the receiver will cycle up and down. We tested it by placing different HD cameras (which are a known source of EMI) near the receiver antennas.

It worked very well. We were clearly able to see that the proximity of the antennas to the HD cameras had an affect on the number of leds that would light up. In EMI scan mode the more leds that light up the more interference your receiver is getting. This could be an invaluble tool when setting up a new model.

The NB20 can transmit up to 20 channels and using the signal acquisition module you can send signal from 2 different RC transmitters to the NB20 receiver. The pictures below show how we hooked up two Frsky receivers to the signal acquisition module. Installing the second receiver is the same as installing the first. 5 volts from the signal acquisition module powers the receiver. The other leads are from the signal pins of each channel on the receiver.

The way we have it setup the first receiver opperates channels 1-5 and the second receiver is controlling channels 11-14. This is an ideal solution for aerial video platforms where one operator has flight controls and the other has control of the camera functions. It could also be used for just taking a passenger along on a flight, giving them the ability to sight see while the pilot maneuvers the model. 

Since we have two NB20 receivers we wanted to try one last thing that people have been speculating about. Controlling two models at the same time. We copied the info from receiver A to receiver B so that they are using the same set of frequencies. Then we pluged servos into channel 1 and 2 on receiver A. Next we pluged servos into channels 11 and 12 on receiver B. We powered the system up and voila! It works! Two different opperators controlling two different receivers using just one NB20 transmitter module.

It works well on the test bench, hopefully it works well in the air. We are looking forward to doing some long range formation flights.

So far, so good. The Rmilec NB20 was easy to setup and use. We are excited to put it to use soon in the air.

Remember to check your local rules and regulations before using this system. In most countries a license is required to opperate on these frequencies. An attenuator can be used between the transmitter module and the antenna to reduce the output power if needed.

Thanks to the people at Foxtechfpv.com and RMILEC for sending us this for testing.

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