Mutara

Connect a radio

With a radio, your node is an RF node. Without a radio, it is an internet hub. You can add a radio at any time.

What you need #

  • A USB radio interface with a CM108 or CM119 sound chip, or an AIOC. Mutara reads the carrier (COS) and keys the radio (PTT) through the USB interface.
  • A radio that connects to the interface.
  • Or a radio module on a USB serial port, such as the SR110U or the SA818. Mutara sets its channel.

Note: A node has one radio. With several nodes in one install, only the first node can have a radio.

Use a USB radio interface #

  1. Connect the USB interface to the node.
  2. In Settings, under On the air, click Radio.
  3. Turn on Use a radio.
  4. In Interface, select your interface. If there is only one, keep the automatic choice.
  5. In Carrier detect, select how the radio tells the node that it receives a signal.
  6. Click Save and restart.

Result: The node restarts. On the dashboard, On this node shows the radio.

The Carrier detect choices
ChoiceWhen to use it
COS input, active high (most fobs, AIOC)Most USB interfaces and the AIOC.
COS input, active lowAn interface that pulls the COS pin low on a signal.
VOX (audio level)An interface with no COS wire. The audio level opens the receiver.
OffNo carrier detect.

If your radio decodes CTCSS on a separate pin, set CTCSS detect too. Then the node hears only signals with the correct tone.

Select the radio mode #

The radio mode tells the node how to use the transmitter. Set it in Settings, on the Station page.

Radio modeWhat it does
Simplex, quietNo courtesy tone and no hang time.
Simplex nodeCourtesy tone and hang time, like a hotspot.
Duplex repeaterThe node repeats the local users on the radio.

Links to other nodes are always full duplex. An admin can also change the radio mode in Node tools on the dashboard, until the next restart.

Set the audio levels #

Good levels make your node easy to hear on the network. Use the Radio levels part of Node tools on the dashboard. You must be an admin.

  1. On the dashboard, open Node tools.
  2. Key up on a radio, and speak as you do on the air.
  3. Read the level of the last transmission in Radio levels.
  4. If the level is not good, click Set receive gain from last.
  5. Do the test again.

Result: The average level is from −32 to −21 dBFS, best near −25. The peaks are below −6 dBFS.

The Receive level and Transmit level sliders set the sound card, from 0 to 999. The Receive gain and Transmit gain add digital gain, from −20 to +20 dB. Use the sound card level first.

To level all received audio, turn on Auto level (AGC) on the Radio page. It levels the audio to about −25 dBFS and adds at most 12 dB.

Test with parrot mode

  1. In Node tools, turn on Parrot mode.
  2. Key up on your radio and speak for a few seconds.
  3. Unkey.
  4. Listen to the node play your audio back on the radio.
  5. Turn off Parrot mode when you finish.

The activity log shows the average level of each transmission, with a reading such as Good or Too loud.

Set the audio band #

The radio filters work at 48 kHz. A soft low-pass sets the top of the receive audio. A band-pass sets the transmit audio. Listeners on the dashboard and in the apps hear the receive band. AllStar links and the digital modes get 8 kHz audio, as before.

  1. In Settings, under On the air, click Radio.
  2. Open More settings.
  3. Under Filters, select the Receive audio band: To 5 kHz (medium), To 3.4 kHz (narrow) or To 7 kHz (wide).
  4. Select the Transmit audio band: 300 Hz to 5 kHz or 300 Hz to 3 kHz.
  5. Click Save and restart.

Result: The node restarts with the new filters.

  • The default for both is 5 kHz. Most radios need no change.
  • A wider receive band carries more energy from the same signal. If received audio is too loud after an update, lower Receive gain a little.
  • A narrower receive band removes more hiss from a weak signal.
  • If the transmit deviation or the occupied bandwidth is too high, select 300 Hz to 3 kHz.

Caution: Check the deviation of your transmitter after you change the transmit band or the transmit level.

Use a radio module #

A radio module, such as the SR110U, is a small radio with a USB serial port. Mutara writes the frequency, the tones and the other settings to it.

  1. Connect the module to the node.
  2. In Settings, on the Radio page, turn on Use a radio module.
  3. Click Find module.
  4. Select the ports to check.
  5. Click Check chosen ports.
  6. When the module answers, click Use this port.
The Radio module section in Settings. Find module checked one USB serial port. The port shows SR_FRS module, version 110U-V223, and a Use this port button. A built-in serial port below it is not checked.
The module answered on a USB serial port.
  1. In Band, select VHF or UHF.
  2. Type the Receive frequency (MHz), for example 446.0000.
  3. Keep Transmit frequency (MHz) empty for simplex.
  4. Set the tones and the channel width.
  5. Click Write to module.
  6. Click Save and restart.

Result: Each command shows its result. The module is on the new channel.

The Radio module section in Settings after Write to module. The SR_FRS module, version 110U-V223, has the settings. Each command shows its result: channel 438.4000 MHz, volume 8, microphone 6, power saving off and VOX off, all with the reply 0.
The result of Write to module.

Note: The module cannot report its settings. Mutara keeps them and writes them to the module. Turn on Write the settings at each start if the module loses its settings after a power cut.

Caution: Transmit only on frequencies that your license permits.

Stop the radio audio for a time #

An admin can stop the radio audio and keep the links up. Use it, for example, when the frequency is busy with a net.

  1. On the dashboard, open Node tools.
  2. In Radio audio gate, select RX only, TX only or Off.
  3. Select the time, from 10 minutes to Until I change it.

Result: The dashboard shows the gate. After the time, or after a restart, the node uses its settings again.