RG501Q-EU incorrectly measures the signal on two antennas when the band works on 1x1 SISO

[Tirkiz]

When the base station switches to energy saving mode at night, where it turns off MIMO on certain bands (only 1x1 SISO works), this modem measures a 10-30 dBm signal drop on two connected external antennas (Iskra P-60 MIMO).

For example on B3 during the day when MIMO is working the signal is -74 dBm and at night when SISO is working it measures up to -105 dBm.
Due to poor signal at night, if cell lock is set, the modem fails back to 3G (which will soon be a problem as many ISPs shut down the 3G network). If the cell lock is not set, the modem switches to another direction at night on the same base station where B3 MIMO works and measures about -85 dBm, and in the morning it returns to my direction when MIMO is turned on and measures -75 dBm.

Tried all SMA combinations for connecting two antennas and measured a weaker signal on all of them when connected to the SISO band.

For comparison, the signal on my mobile phone, Huawei B535 and ZTE MF289F which are connected to the same two external antennas, on the same base station and cells during the day and night measure the same or only 1 dB weaker signal when the B3 SISO is working.

When all four antennas are connected to the RG501Q-EU modem (tested with 4 omni antennas), then at night it measures the same signal as during the day or a signal drop of only 1 dB at B3.

B3 band is an example, this also happens on B1 and B7 where MIMO works during the day and SISO at night.

Current modem firmware: RG501QEUAAR12A09M4G_04.200.04.200

I see that a new firmware RG501QEUAAR12A10M4G_04.200.04.200 is available for this modem.

Does the new firmware contain a fix for this?

Do you test modems with only two antennas connected to base stations that turn off MIMO at night, i.e. only SISO works?

I thank you

[silvia]

Dear @Tirkiz
Why did you only contact two antennas?
Here is the antenna mapping for reference. How did you measure the signal? Via tool or AT command? It has newer firmware, you can try.

[Tirkiz]

@silvia Apologies for the late reply.

In Croatia, all ISPs have 2x2 MIMO on their base stations, so there is no need to buy 4 antennas. Only on the coast and rarely in the summer do they turn on the 4x4 MIMO mode.
The device in which this modem is used is Teltonika RUTX50.

I am currently without it for two months because the firmware upgrade for this modem went wrong (RG501QEUAAR12A10M4G_04.200.04.200) so the device is currently on RMA service, so the attached data is old until the device is returned to me.

The antennas I use are Iskra P-60 MIMO (two antennas), distance 34 cm (amplification of B3 band for upload), distance from the base station 3 km, clear optical visibility.

Antenna set P-60 5G 7003800 MIMO

All SMA combinations have been tried and only the first two left SMA ports (ANT0 and ANT1) give the best results, on the others either there is no signal or the modem behaves strangely in the sense that the Internet barks a lot or does not work even though the WAN status says that it is properly connected to the network and the signal is good.

I put together a PHP CURL cronjob script to save signal data from the modem via AT commands to a mySQL database. The script runs every minute. I have all the data about the signal, MIMO info and aggregations at any time, going back a year that I have owned this device with this modem.

The firmware of the modem is RG501QEUAAR12A09M4G_04.200.04.200

AT commands for the primary cell:
AT+QENG="servingcell"

AT commands for aggregations:
AT+QCAINFO

AT command for MIMO info:
AT+QNWCFG="lte_mimo_info"

When the base station broadcasts the bands in 2x2 MIMO mode during the day, these antennas give a peak RSRP signal of about -73 dBm.

When the base station at night and switches some bands to 1x1 SISO mode, this modem sees it as a signal drop of 10-30 dBm, as when.

When I test the signal measurement with 4 omni antennas connected, it measures a signal drop of only 1 dBm at night on the SISO bands, which clearly proves that the modem correctly measures the signal strength when all 4 antennas are connected.

I contacted my ISP where even they thought that their base station reduces the signal at night, but after a month of various testing and setting up measuring probes, we came to the conclusion that this modem incorrectly measures the signal strength when the bands work in SISO mode.
The ISP said it sent you a query on how your modem measures the signal level.

I also did a day and night comparison on my cell phone because it is connected to the same B3 cell and my cell phone (Samsung Galaxy A22 5G) measures a signal drop of 1 dBm at night on the same cell. While your modem, when only two antennas are connected to it, measures a signal drop of 10-30 dBm, which is not an accurate value.

[silvia]

Dear @Tirkiz
From your observation, only with 2 antennas, it drops 10-30 dBm, right?
Please share which antennas you connect and band combinations via AT+QENG=“servingcell”.