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Frequently Asked Questions


What comes with the Swarm M138 Modem?

Each M138 Modem includes a GPS patch antenna, a U.FL to SMA cable, and a Swarm 1/4 wave VHF antenna that is tuned to Swarm’s operating frequencies.

When is the activation date for my device(s)?

A device’s activation date is the first of the month following when ≥50 messages are sent. For example, if you send the first ≥50 messages on Feb 17th, the activation date will be March 1st and your data plan will annually renew each March 1st. Please see Terms & Conditions for further details.

How long will my transmission messages remain on the M138 Modem?

Data messages will remain on the modem for 48 hours by default after which they will expire if not transmitted. The 48 hour expiry time can be configured as needed by following the instructions in the Product Manual.

How many data packets can be queued on the Swarm Modem?

The Swarm Modem can queue a maximum of 1000 outgoing messages and 1000 incoming messages. Each type of message is stored in separate files. Customers have the flexibility to break up each larger packet into smaller packets as needed.

Can I delete messages from the Modem’s queue?

Messages that are queued on the Swarm Modem can be read, counted, and deleted using the $MT command. Complete usage instructions can be found in the Product Manual available on the Documentation page.

Can messages automatically be bundled into 192-byte size packets and be transmitted automatically when a satellite is in range?

The Swarm Modem does not manage data “bundling”. Each message is treated as a single packet and is transmitted as such within the system. A designer can choose to bundle messages outside of the Swarm Modem and optimize for package usage if desired.

What type of connectivity does the Swarm Modem support?

The Swarm Modem communicates via a standard 3.3V CMOS serial UART interface, or a PC interface with a USB-to-serial converter.

Does Swarm currently support LoRa?

Swarm Modems do not currently support LoRa.

Where can I find more information regarding power requirements for the Swarm Modem?

More information regarding power requirements for the Swarm Modem can be found in Section 4.3 of the Product Manual.

Does the Swarm Modem support communication using RS232/485/etc?

The Swarm Modem only communicates via a standard 3.3V CMOS serial UART interface, or a PC interface with a USB-to-serial converter. Please include any necessary signal conversion circuitry if you would like to use another communications protocol in your device.

Can we load our own firmware onto the Swarm Modem?

No, the Swarm Modem does not allow for any user code to be loaded onto it.

How long does a GPS fix take from a cold-start?

GPS cold start (From power off, or more than 4 hours from last fix) takes ~30 seconds depending on your installation location.

How long does a GPS fix take from a hot-start?

GPS hot start takes 5-10 seconds if the last GPS fix was < 4 hours ago, and if the Swarm Modem has been powered on, or in sleep, since then.

Does the Swarm Modem need to wait for a ‘time lock’ when woken from sleep, or is there a need to wait for G2 2D GPS lock?

After any cold boot (power up, and not from sleep), the Modem will not accept a “$TD” command until time is set by the GPS. Once this happens, then the device is ready to communicate until the next cold boot (Power cycle) even across SLEEP wake-ups. This is because the RTC is set with the GPS time, and the RTC time survives sleep.

Do you support Assisted GPS (A-GPS)?

Swarm does not support Assisted GPS.

Can I send a command to the Swarm Modem to retrieve GPS information?

GPS information can be extracted from the embedded GPS module by using the appropriate commands as shown in our Product Manual.

When will my Modem transmit a message?

A Swarm Modem will attempt to transmit messages to a satellite after a satellite beacon is received during a satellite pass over Modem’s location. To know when the next satellite pass will be occurring over your device’s location, please use the Swarm Satellite Pass Checker. This video also describes the functionality of the Pass Checker in more detail.

How do I know if my Modem is communicating with your satellites?

Any Swarm Modem with queued transmission packets will attempt to transmit after receiving a satellite beacon. Satellite beacon packets are shown on the serial output of the Modem in the format $RT RSSI=<rssi_sat>,SNR=<snr>,FDEV=<fdev>,TS=<time>,DI=<sat_id>*xx

Satellite $RT unsolicited messages are printed independently of the background RSSI values as long as the query rate for $RT measurements is not 0.


What is included in the Swarm Evaluation kit?

Each Evaluation Kit includes:

  • FeatherS2 – ESP32 board + OLED for quick development, testing, and IoT product creation
  • Turn-key with 9W solar panel
  • Rechargeable 9000 mAh battery
  • IP67 waterproof enclosure
  • Aluminum tripod
  • Satellite antenna
  • GPS antenna
  • WiFi, USB-C, and serial inputs

When is the activation date for my device(s)?

A device’s activation date is the first of the month following when ≥50 messages are sent. For example, if you send the first ≥50 messages on Feb 17th, the activation date will be March 1st and your data plan will annually renew each March 1st. Please see Terms & Conditions for further details.

How can I power my Evaluation Kit?

The Evaluation Kit can be powered with any of the options listed below:

  • Lithium Ion 18650 batteries installed in their respective holders behind the PCBA. These batteries can be recharged using the solar panel which is included with your Evaluation Kit.
  • An external power supply connected to input terminal J13. The voltage input should be set to a value between 18 and 24 VDC. Please ensure that the power supply is able to provide the necessary current to the Evaluation Kit. This option will also charge the batteries installed in the kit.
  • A USB-C cable connected to the USB-C adapter on the Evaluation Kit. This option will also charge the batteries installed in the Kit.

Do I need to change any jumpers on the Evaluation Kit to use different types of power inputs?

No, there is no change of jumpers required to use any of the options listed above.

Why can I not send a message from the Hive to my Eval Kit?

The Evaluation Kit is designed for uplink communication only. You can send messages using the Evaluation Kit to the Hive, but not the other way around. Downlink communication is reserved for commercial applications.

How do I communicate directly with the Swarm Modem?

Please move jumper J7 (Located next to the stacked Feather/OLED) to the “USB” configuration. You can then connect a USB-C cable to the kit and power it on using the power switch. You will need to use a terminal program such as PuTTY or ZOC connected to the appropriate COM port using the following settings: 115200 baud rate, 8N1, disabled RTS/CTS signal, and flow control OFF.

Does the Evaluation Kit have Bluetooth connectivity?

No, the Evaluation Kit does not support Bluetooth connectivity natively.


Does Swarm support 2-way communication?

Yes, Swarm does support 2-way communication for commercial applications only.

How much data does your subscription support on a monthly basis?

Swarm’s baseline subscription supports 750 data packets a month per device (up to 144 kB per device per month per device).

What is the maximum payload allowed per data packet?

Swarm provides a maximum of 192 available bytes (out of a 250 byte packet, which includes a wrapper) per data packet.

Is there a limit to the number of messages I can send to my Swarm Modem from Hive?

Users can allocate up to 60 packets (of the monthly 750) per data plan for downlink, with a maximum of 10 downlink messages per day. Please see Terms & Conditions for further details.

How secure is the Swarm network?

Swarm devices are authenticated on the network by the satellites and ground stations. Each device has a unique device ID that is only known by Swarm and the customer.

Does Swarm provide any kind of data encryption?

Yes, Swarm implements end-to-end AES256-GCM encryption for data sent over the Swarm network.

Can the device ID for Modems be changed?

No, the Modem’s device ID cannot be changed, modified, or tampered with in any way. The device ID is set during production by Swarm.

Can Swarm satellite modems be jammed?

Swarm uses a narrow band carrier (about 40 kHz wide), and a chirped spread spectrum approach. This helps improve Swarm device immunity to noise and common forms of jamming.


What can I do to improve my RSSI values?

Please ensure that the device is powered from a clean power supply with minimal high frequency noise. Having the device placed outdoors with a clear view of the sky away from a city environment will also improve RF performance. The antenna of the device should not be making contact with, or placed near, any other conducting surfaces. The Swarm 1/4 wave antenna should be placed at least 1m above the ground or any solid surfaces. A counterpoise can also be used to improve RF stability.

What antenna can I use with the Swarm Modem?

Swarm currently offers 1/4 wave antennas that have undergone extensive testing. All antennas sent by Swarm are tuned in house. Our team is constantly working on smaller antenna form factors that will operate reliably in most field conditions. All information regarding antennas can be found in the RF Interfaces Section of the Product Manual.

Can we use our own antennas?

A VHF antenna specifically tuned to Swarm’s commercial frequencies is required to use our systems. A hardware designer can develop their own antenna if they choose to. We include a 1/4 wave antenna with each Swarm Modem.

Does the Swarm Modem require a VHF/GPS antenna?

The Swarm Modem requires its own external GPS and VHF antenna (both are included in the price per unit). Any GPS antenna (active or passive) can be used. We recommend this GPS Antenna.

What is a ground plane, and why is it required?

Ground planes are electrically conductive surfaces that are connected to the ground conductor of the antenna and serve as a reflecting surface for radio waves. Ground planes are required for use with Swarm’s 1/4 wave antenna.

You can use your own ground plane which should be tested before deployment. Another ground plane option is a counterpoise (we use an 18″ long, 18 gauge wire hanging downwards, commonly known as a “Tiger Tail” with amateur radio enthusiasts).

What would an ideal ground plane look like?

An ideal ground plane for the Swarm ¼ wave antenna would be a flat metal sheet with a minimum radius of 55 cm. To date, Swarm has reliably communicated with its satellites using a ¼ wave antenna mounted on top of a ground plane as small as 30x30x0.3 cm.

How do you connect an antenna to the Swarm Modem?

The Swarm Modem has a U.FL connector which can be connected to an SMA connector. The 1/4 wave antenna can be threaded onto the SMA connector. There is also a U.FL connector on the Swarm Modem for the GPS antenna.

How far from the ground should the 1/4 wave antenna be mounted?

The 1/4 wave antenna should be mounted at least 1m above the ground, or any solid surfaces.

What is a counterpoise?

In electronics and radio communication, a counterpoise is a network of suspended horizontal wires or cables, used as a substitute for an earth connection in a radio antenna system. In the case of the Swarm 1/4 wave antenna, you can use a ~18” long wire connected to the ground element of the antenna and hanging vertically downwards.


How do I differentiate between data packets from multiple devices?

Packets sent through the Swarm network have unique device IDs which indicate the device that the packet originated from.

What is an Organization ID?

An Organization ID (or OrgID) is a unique number assigned to each Hive Organization. You can find your OrgID by logging into Hive, and then navigating to My Profile.

What is an Application ID?

An Application ID (or AppID) is used to filter user messages. You can assign transmission packets a unique AppID so that the messages can then be filtered when they are retrieved from the Swarm Hive. An example of this would be using AppID 1000 for sensor data, AppID 2000 for location data, and AppID 3000 for status messages. Users have access to AppIDs between 0 and 64999. AppIDs 65000 to 65535 are reserved for internal use only. The default AppID for any message packet is 0. To learn more about how to assign an AppID to a message packet, please refer to the $TD – Transmit Data section of the Product Manual.

How do I retrieve data from the Hive?

You can retrieve data from the Hive by either using the REST API, or by using delivery webhooks. To learn more about how to use the REST API and webhooks, please refer to the API documentation after logging into your Hive account. There is also a Python script example for the REST API that can be downloaded by clicking here.

How long is data stored in the Hive?

Swarm stores data in the Hive for 30 days. After 30 days, any data left on the Hive will be deleted. Customers are expected to move their data upon transmission/reception.

Why can I not see my message packets on Hive?

Message packets that were received more than 30 days ago are no longer visible in the Hive. If you are using the REST API, or delivery webhooks, then the messages may be marked as acknowledged. Swarm will not automatically acknowledge transmission packets received in the Hive. It is highly recommended to mark message packets as acknowledged once they have been retrieved and logged into your backend application.