If the communication goes through a repeater, then there is a need to analyze if the frequency used by the repeater is within the range of the antenna used.

If the problem is only on a small quantity of the radios supplied, it could possibly be a radio archive error.

The radio operating in a 25 KHz channel spacing will have better sensitivity, hence longer range.

The radio is able to switch to high and low power setting. The higher the power, the longer the range would be.

Need to check if the correct antenna is being used.

If the problem is portable to base, then it could be due to a transmitter problem, and if it is base to portable then it could relate to a receiver problem.

VHF offers two types of antennas, 9cm and 14cm. The longer antenna will provide a higher gain and longer range.

Emphasis is a type of audio shaping a noise filter. Both the transmit and receive radios must have this feature turned on for proper operations. If either is turned off, then there will be poor audio clarity, which can be construed as a range issue.

At maximum volume, LLE can degrade the intelligibility. This kind of problem usually exists in high noise environments. Again, intelligibility can also be construed as range issues.

Compression is also another type of filter for audio. It is a feature to be used within the HT Professional series radios. The audio level will drop slightly also. When used with other types of radios, the audio quality will also be affected. All of these side effects of the compression feature can be construed as a range issue.

Auto power mode will automatically adjust the power accordingly to the RSSI level received on the last transmission. It is there for optimum battery life. It is usually a problem when there is a base station involved. The strong signal from the base station will switch the radio to low power and cause the radio's low power signal not to reach the base.

This audio filter will clip the audio level that exceeds the threshold level for better audio clarity. This will reduce the actual audio level and sometimes may be construed as a range issue.

This condition prevents the radio from transmitting while it is in busy mode or receiving.

This can be checked by supplying signal from a communication analyzer and if the radio opens squelch at a level of -118dbm or below, it means the squelch setting is at least 10dB Sinad. If it is already 10dB Sinad, it is recommended that the setting be changed to 8dB Sinad for improved range performance. This is especially the issue when comparing to the GP300, which has lower squelch settings.