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8. Troubleshooting

  • Polarization incorrect

    Install the unit with the correct horizontal or vertical polarization: The arrow mark (placed just next to the Status LED) indicates the unit RX polarization. When the arrow is perpendicular to the earth, the unit receives a signal in vertical polarization. When the arrow is parallel to the earth, the unit receives a signal in horizontal polarization. The connectors must point downward at an angle.

  • The link cannot be established

    Start with the most “resilient” configuration. This configuration depends on the type of unit. We recommend using the narrowest available bandwidth (e.g. 3.5 MHz), the lowest modulation level (QPSK) and maximum available output power. TX and RX channels must be the same as the RX and TX channels in the remote unit. When the connection has been established and the antennas have been directed, proceed with operation parameters.

    Units operating in licensed bands (RAy2-10, RAy2-11) are mounted with the same RX polarization (the polarization indication arrows show the same polarization on both units).

    Units working in the bands equipped with RAy2-17 and RAy2-24 units must be mounted with opposite polarization; one with RX horizontal polarization (horizontal arrow) and the second with RX vertical polarization (vertical arrow).

  • Access to the Local unit is blocked

    Access to the Local unit may be accidentally blocked, for instance by disabling HTTPS access. If you can access the Remote unit over HTTPS, type its address in your web browser’s address field. The link will transfer the packet over the Local unit with blocked service access all the way to the Remote unit, which will give you access to the control menus of both units. Warning, the Remote unit will report as Local.

  • Distinguishing Local-Remote

    A unit accessed via service access always reports as Local. If you connect through another (peer) unit and radio channel, a certain amount of caution is necessary. For example, do not reduce the transmission power so that the link interrupts accidentally. Errors of this type should be fixed by the rollback function within approx. 1 minute.

    Resolution can be done by comparing the length of ping on Local and Remote. Pinging the unit behind the radio channel is slower. The difference is more pronounced in the case of a long packet and the low speed of the radio channel.

  • Access security

    For better protection against unauthorised access to configuration you should only allow as few kinds of access as possible. The most secure type is SSH with key – leave only SSH active with “only key” choice.

  • RSS

    To configure the link and monitor its state, several menus display the RSS signal strength. Please keep in mind, that Ray2 is not a measuring instrument, hence the precision of the RSS reading is limited. Though, in most situations the RSS reading accuracy is better than ± 2dB, the absolute RSS value should not be used for accurate comparisons e.g. between two links.

  • Problem with https certificate

    See the Appendix E, Https certificate

  • Overexcited receiver

    A natural property of each radio receiver is to compress the signal in one of the functional blocks, typically in a second receiving mixer. A downside of this property is the distortion of the input signal (decrease in the signal to noise ratio, i.e. the distortion measured as SNR).

    In extreme cases, this can lead to the disintegration of the radio link due to reduced signal to noise ratio (distortion). Extreme limits for guaranteed availability of the RAy2 connections are:

    • -30 dB for all channel bandwidths and fixed modulation 256QAM

    • -10 dB for all channel bandwidths and fixed modulation QPSK

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