Try the simpler things first
Before contacting a technician or attempting to modify the scanner, I would recommend trying several things first:
- Step 1A: As mentioned above, check the scanner for a "line out" jack, different than the "headphone" jack. If "line out" exists, then connect it to "line in" on your computer (often a blue-jack not the pink/red-jack on the computer).
- Step 1B: If "line out" is not an option on the scanner, then connect the headphone jack to the "line in" jack on the computer, instead of the "mic" jack on the computer. Only use the computer's "mic" jack as the last resort.
- Step 2: Regardless of which jack you use on the radio, after connecting to the computer, turn down the volume on the scanner to its minimum/no-sound position. Then increase the scanner-volume slightly. Open the squelch on the scanner. While listening to the static-noise caused by the open squelch, use the computer's "Volume settings" (the control in the system-tray, not the knobs on your speakers) to set the volume for "line-in" or "mic", depending on which one you plugged into.
- Step 3: You should be able to hear the static-sound on your computer. After you set the computer-volume at the lowest-volume at which you think you would be able to understand radio-transmissions, then adjust the squelch to silence it, and let the scanner start scanning.
- Step 4: When radio-traffic is frequent enough, you can set the scanner in manual mode (or pause mode) on the busy channel, and make any fine-adjustments you need to make using the computer's volume-settings, so that radio-traffic sounds clear. If the computer's volume-settings are max'ed out, then consider slightly increasing the volume on the scanner itself. But, in general, the scanner's volume should be as low as possible so that the signal is clear, clean, and not over-driving the computer's input-jack circuits.
So, ideally, the scanner's volume would be at about 10-15%, the computer's volume-settings would be at around 65%, and your computer speaker's knobs would only need to be 25-50% depending on your level of ambient noise.
Once you make the adjustments, try to listen to the feed's volume from another computer, or ask someone to check the feed's volume for you.
Your exact settings might differ slightly from the above suggestions, but many scanners can be connected to a computer without major modifications. It just might take some careful adjustment to get the right volume-levels -- in and out.
Hope this helps,