Rangecast FAQ
[FAQ-1014] Error Message: NO AUDIO PORT (Code 26)

Page Type: SYMPTOM


The 'No Audio Port' error occurs when the Rangecast software is in communication with the radio scanner (over the com/data port), but is unable to find an audio input to the PC that appears to have this scanner's audio output. Therefore, Rangecast cannot capture the audio content from transmissions received on this scanner. The most common causes include a problem with the Windows audio or USB system, or a loose connection on an audio cable or to a sound card within the interface box.


Differences in Rangecast hardware:

OLD Rangecast installations used a USB box to interface up to 4 scanners to the PC. The box provides an enclosure to protect 8 interconnections between USB cables, audio sound cards, and audio cables. Any of these can become disconnected due to vibration or stress and will cause malfunctions. Opening the box and checking that everything is connected is sometimes necessary.

NEW Rangecast installations use individual Rangecast RCX interface units mounted directly on the back of each scanner. The connections to the radio are secure. A single USB cable provides audio and data connections to the PC. Disconnecting that cable breaks all communications, causing a RADIO MISSING message instead of a NO AUDIO PORT message.


1. Check Windows volume setting for each audio input. Windows provides a master volume setting for each audio input. If the volume is set too low, then the Rangecast software will not be able to clearly hear the scanner when automatically detecting the scanner's audio port. This can result in an error message (NO AUDIO PORT) indicating that the scanner's audio cannot be detected. Therefore, a good first step is to check the Windows volume setting for each audio input, to ensure that none of the inputs is set too low.

Launch the Windows Sound console (there is usually a Sound icon on the desktop; if not present, this application can be reached via the Windows Control Panel.) Go to the Recording tab. For each audio input, click on the input, then go the Levels tab, and check the level. On Windows 7, the level should usually be above 50; on Windows 10, it should usually be 100.

If the level is too low, raise the level, and relaunch Rangecast to see if the software can then detect the audio input.

2. Reboot the PC. Some problems related to either the driver, or the Windows audio system, may be cleared by a reboot.

If the problem is not resolved when Rangecast launches, continue below. The following steps must be done while physically present at the PC.

3. At the PC, power down the computer, unplug the PC from all power sources (wall or UPS), wait at least 30 seconds, then restart the computer. Some problems related to the Windows USB system, or the interface hardware, may be cleared by this process. (Unplugging the PC is necessary because some PCs maintain power to the USB subsystem even if the PC has been shut down and the power switch turned off, so physically disconnecting power is actually needed to force a full reset.)

4. There are two kinds of interface boxes in use. A newer unit (called RCX) mounts on the back of the scanner, with one USB cable leading to the PC. An older unit is a black box that sits beside the PC, supports four scanners, and has two USB cables leading to the PC.

If the affected scanner uses the older style box, there will be two wires leading from the interface box to the scanner. One of these (an audio cable) should be plugged into the green jack on the rear panel of the scanner (except for the model 536 scanners, in this case the cable should be plugged into the speaker output.) Check that the cable is connected to the correct jack, and securely plugged into that jack (not loose.)

5. If the affected scanner uses the older style box, if you wish, you may open the box and see if any internal connections are loose. On occasion, with this model of interface box, vibration has loosened a sound card from an internally mounted USB hub.

6. If the problem is still not resolved, there may be defective hardware in the interface box, consider replacing the hardware.


Here is how a Sender finds its correct audio line.

A typical feedsite may have four scanners. Each has an audio connection to the PC. The audio connection may a standard audio cable to an USB audio sound card. In newer installations an "RCX" box with an internal USB sound chip is mounted on the back of a scanner, plugged directly into the scanners audio jack. The PC receives the audio over a USB connection. In either case, a Sender commands its assigned scanner to play alternating NOISE and QUIET periods and listens to each line to find the matching pattern. When detected, it begins normal Rangecast service.

(1) Note that the Sender must be able to "hear" audio from the scanner for this to be possible. If it cannot hear the noise/quiet pattern, then it cannot find its audio audio line. In that case the Sender will display a NO AUDIO PORT message and turn an indicator red. It will try again periodically.

(2) Note also that a NO AUDIO PORT message confirms that the Sender is in data communication with its scanner. This usefully confirms a number of good things; that the Sender is working, that the proper scanner is present and responding normally, that the data connection works. The issue is specifically an audio problem.




Rangecast FAQ - ID 1014 - last updated 15 June 2018     Images shown - [block]