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Antenna Separation and Receiver Desense.

Discussion in 'General Discussion' started by Typhoon Charlie, Oct 9, 2016.

  1. Typhoon Charlie

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    I have been researching this for some time, I have asked Yuneec and have not found anyone to give me an answer. I have been a ham radio operator for 30 years, and have installed many VHF and UHF repeaters. A repeater is just a transmitter and a receiver on the same band, with a frequency separation of 600KZ . This arrangement requires what is called a duplexer installed at the receiver. The duplexer is an isolator that keeps the transmitter frequency from desensitizing the receiver. This allows the use of one antenna for both TX and RX. If a duplexer is not used, and 2 separate antennas are used, then the antennas need to have a certain amount of vertical or horizontal separation. Now for my point. Yunnec uses a receiver for the control signal from the ST-16 inside the Typhoon H at a frequency of 2.4 Ghz. At the same time they use a transmitter for the telemetry down link at 2.4 Ghz. From what I have seen inside the H, there is just a TX/RX board and no other device acting as a duplexer. We know from experience that having a GoPro with the WiFi on on a copter using 2.4 RC radio is a recipe for disaster, or flying near a strong WiFi signal can produce the same affect. So, how is Yuneec getting away with having a receiver and a transmitter on the same band and not causing fly aways . Or are they. The research I have done tells me that a TX on the 2.4 band must have 16 ft of horizontal separation in order to not desensitize the receiver. If any one out there with more knowledge and maybe a spectrum analyzer could explain this, I would love to hear it.
     
  2. Steve Carr

    Steve Carr Moderator
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    Good question TC. I've been of the opinion the TX and RX are on different antennas on the ST16 and the H. Although they are both 2.4Ghz they are on different channels which eliminates the interference. If it was higher power it would probably cause an issue. I'm a novice here so I'm likely simplifying a more complex system.
     
  3. Typhoon Charlie

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    Yes they are low power, and different channels I'm sure. However, I believe there has to be some sort off desensing going on. Take in consideration that as the H gets further away from the ST16 the control signal gets weaker, but the signal from the telemetry stays the same to the receiver.