Safety of using the device without all antennas installed

NETWORKING SOLUTIONS
1

Hello.

I have several devices that I use in my daily work, e.g. RUTX12, RUT955, RUT950, etc. In the past, I was taught that all radio devices should ALWAYS work with an antenna connected because its absence can cause wave reflection in the connector and heating of the radio transmitter elements, ultimately leading to its damage. Normally, when the antenna is properly matched, this energy is dissipated by it. However, I wonder if this is still required in modern, multi-antenna designs such as RUTX12?
Maybe it is enough to only use antennas whose functions are enabled in the device?

For example, if in WebGUI we disable all functions except for the mobile network and LAN ports, we do not have to install WiFi or BT antennas? All the more so not installing a GPS antenna should not be a problem, after all, here we only receive the signal and do not transmit anything, so no energy will be additionally dissipated in the form of heat…

I ask because some time ago my long-used RUT950 broke down, which was working without WiFi antennas because this function was disabled in WebGUI and I wonder if this could have damaged it…

Someone may say that this is a rare problem and it is enough to check that all unnecessary functions are disabled in the device settings and then we only install antennas for the functions used, BUT what happens when the OS is just loading, because e.g. the device has a reboot set to no ping with some host and does it often for some time? When the device starts up, are these previously disabled options not active and can lead to weakening of the radio modules or even their damage?

I really hope for a detailed and technical explanation of this issue because maybe technology has advanced so much that all kinds of transmitters/modems verify at startup whether the antenna is connected and in the event of its absence they protect themselves from damage?

In my case, a common problem is also the lack of free space to mount the device with all the antennas, so if it were possible to use it safely only with the number of antennas used it would be worth its weight in gold :slight_smile:

Thank you in advance for your help and a clear answer.

2

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5

Hello,

Apologies for the late reply.

Antennas or a 50-ohm termination resistor should always be connected to the device’s SMA ports. However, if you have disabled a function (e.g., Wi-Fi), then the antennas or resistors may not be needed.

Additionally, I want to mention that simply disabling the SSID is not enough to fully stop Wi-Fi functionality. To completely disable Wi-Fi, you should navigate to Network → Wireless → Radio in the WebUI and Disable Radios. This will fully disable the Wi-Fi, and the antennas may no longer be required.

Hope this helps!

Best regards,

6

Hello.

Thank you very much for your answer.

However, I have some more specific questions:

  • will the lack of antennas during device startup not cause gradual damage to the transmitter, because as I understand it, disabling WiFi disables the module only after loading the operating system, drivers, services and configuration files, and this takes a while?
  • is it possible to disable GSM/LTE modules in the same way?
  • what resistance of terminators are needed for GSM/LTE ports (because for WiFi it is already the mentioned 50 Ohm)?
  • can the BT module also be completely disabled?
  • what resistance of terminator is needed for the BT port?
  • is some kind of terminator also required for the GPS module and if so, what resistance, because it is probably just a receiver that does not transmit anything, so maybe the terminator is not needed even with the GPS module enabled?

Thank you in advance for your comprehensive answer.
Best regards.
P

7

Hello,

Regarding the startup, it is better to have the antennas connected to the device.

For the resistors, 50 ohms should be used for all antenna ports.

To disable mobile, please refer to this link.

For Bluetooth, it should be disabled via the WebUI: Services → Bluetooth → General Settings.

For GPS, it should be disabled if the GPS antenna is not attached to the router.

Best regards,

8

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