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. (Note this error does not mean that the audio port does not exist, but that the audio port cannot be located by software. This could be due to the port being missing, or an audio cable being disconnected, or a volume level problem resulting in no audio reaching the PC.)



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.

OLD Rangecast installations used a USB "Black 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.


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. See the instructions for Low Volume

[FAQ-1223] Error message: LOW VOLUME (Code 46)

The LOW VOLUME warning means that, when the scanner is set to a test condition where it receives static, the observed audio level is less than 40% of full volume. If the input levels are too low, the audio recordings may have lower quality. Also, the Rangecast software may not be able to reliably detect that the audio port is associated with a particular scanner, rendering the scanner either consistently or intermittently inoperative.

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.) For more detail

[FAQ-1084] Power cycle the USB system

On occasion, some element of the USB system (in either the PC or external hardware) may freeze (probably in firmware), and become unresponsive until it is power cycled. Simply turning a PC off/on may not clear the issue, since many PCs keep minimal power applied to some circuits. To ensure a clean power cycle of the USB hardware, physically disconnect the PC power cable for at least 30 seconds (with Windows safely shut down.)

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.

If you are one of our early customers, you may be using what we call our "Black Box Hub" (see image above.) This single hub unit provides an audio cable and a serial cable for each of up to four scanners. The box then converts the audio and data to USB and two USB lines run from the Hub box to the PC. This early design features USB sound cards plugged into USB hubs inside the Hub box. These sounds cards can work loose over time and electrical issues may also occur.

Rangecast has developed its own "RCX box" (see image). These are individual units which plug onto the back of each scanner by connecting to the audio (either line out for the Bearcat BCT15/X and BCD996XT/P2) or speaker out for the BCD536HP and SDS200 as well as serial data out and converts the audio and data to USB with a single USB data cable per scanner connecting to the PC. The new design is a more reliable long term solution, as there are no internal components that can work loose. 

If you are experiencing NO AUDIO PORT errors and you have the original Black Box Hub we strongly urge you to replace this retired unit with RCX boxes. Contact Rich Barnett at the address below to arrange an order either by credit card or by PO. Rich will arrange a discounted price.


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 14 February 2019     Images shown - [block]