Hello, i have acquired three M138 for testing, powered/registered two but only had a single successful transmission from ~3 days testing. I have looking into the pass-checkers and there were several windows, some over an hour.
The only packet I’ve been able to transmit was when the antenna was mounted on a tripod (~1.5m from the ground). Background RSSI stayed around -98, although a lot of times it also reported RSSI and SAT ID (which i believe means that an swarm satellite is in range?)
Could the problem related to poor reception where i am? (Sao Paulo - Brazil)?
I saw on the swarm website that they have a similar antenna to be mounted on vehicles, Since they are based of the M138 shouldn’t the antenna placed on the car roof work?
I really appreciate any advices. Currently I’m using OrbComm (attached to heavy machinery roofs) and I’m looking for cheaper alternatives.
Regarding the swarm email support, took ~1 week to get a email response from them, is this always the case? because it was a big red flag for me.
For the remainder, was the antenna always mounted on a vehicle? Or have you been unsuccessful with the tripod too?
On day 1 the antenna “A” was on the tripod and “B” on car roof. A has sent 6 messages which were in the buffer in one go, but didn’t send anything after it for the rest of the day. On day 2 I’ve switched them (B tripod, A car) but didn’t work, day 3 switched again and got the same result. Didn’t try again after these three days.
RSSI and SAT ID does indeed indicate the modem is receiving a signal from a satellite. Do you still see those with the antenna on the vehicle?
It did show the RSSI and SAT ID. although i don’t know what is the ideal values for RSSI (background stayed within -95 to -98 on car and tripod).
[edit] i’m adding a picture of the test (tripod/car), and another form a small display showing most info the m138 provides, such as rssi, background rssi, rssi, sat id, geolocation/datetime, , internal voltage (stayed at 3.2v all the time) and temperature. its been built using the examples of swarm github.
I don’t have a full explanation for you. But the following might help?
The Molex GNSS antenna needs to be in “free space”, away from any “ground planes”. It does not perform well when close to anything metallic or conductive. I once made the mistake of sticking the antenna to a LiPo battery pack. It took me a long time to work out what I had done wrong. For vehicles, I would recommend using a standard GNSS antenna - perhaps one that includes a magnetic mount?
In your car photo, it looks like you only have three wires between the ‘Arduino’ board and the Swarm modem? Are they TX, RX and GND? I guess you are providing power for the modem via USB? Maybe consider providing power from the Arduino board, to minimise the cable lengths and avoid any large ground loops?
Sorry for the long delay, i gave up, Either i bougth three defective units, or the hardware is garbage. I tried every single thing i could think of and even hired an guy specialist in RF to see if i was making some mistake. we reviewed the manual and FAQs multiple times, and nothing would make it work
powered the modem with an 5V 3A psu
Tried remote locations (not a single tree, building or anything nearby)
Tried over 15 transmissions on 6 different locations within Brazil.
Tried the other modules (bought three, none worked), another antenna, and so on. The subscription was OK and paid.
Antennas were powered up for 3+ days straight without a single uplink transmission (several uplink windows on swarm pass checker)
I do see RSSI, Background RSSI, and SAT ID when there is coverage, but the message doenst leave the TX buffer, never. no matter what we did. Even tried to buy a plastic tripod with no change.
Also been unable to receive anything. Unfortunately this wont be useful for our company, and i cant recommend this kit to anyone. does NOT work and is not reliable in my region
Apologies for the delay. I may have an explanation for the modem transmission failures:
Other users have reported strange behaviour if the M138 modem is not properly inserted into the M.2 connector. Please try loosening the screws by one turn, push the modem into the M.2 connector as far as the screws will allow, then re-tighten the screws. Does this help?
