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 General Scanner Troubleshooting

Question: How do I troubleshoot scanner problems?

see Troubleshooting in our Guide to Scanners.

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Question: My scanner hangs up on a particular frequency; however, the problem goes away when I remove the antenna.

If you remove the antenna and it goes away, this indicates that the problem is either a signal in the air OR a strong nearby signal is mixing with something else and forming an IMD (Intermodulation) product at that/those frequencies. To fix this, you will need to either:
  • Use the lockout key to program that/those frequencies as "search skip". When the scanner stops on the undesired frequency during a search, hit the lockout button to store the undesired frequency, and the scanner will automatically skip over it after that.
  • Use an external antenna with either high shielding OR an external antenna with an attenuator (such as the 6 dB Attenuator 150-1257) and the appropriate adapters.

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Question: Why does my RadioShack scanner pick up the same transmission on a different frequency from the frequency I receive on a super-heterodyne or dual-conversion scanner?

The frequencies that you're picking up on your original scanner are images or harmonics of the frequency that you are actually listening to. This is a common result when changing from a scanner that utilizes simple super-heterodyne versus a scanner with triple conversion. The actual frequency that your original scanner is picking up is a second or third harmonic away from the actual frequency being transmitted. The RadioShack scanner should be picking up the correct frequency.

For example, 145.000 MHz has the following harmonics:

F (tx) = 145.000 MHz

F (image) = 144.545 MHz and 145.455 MHz (1st order harmonics).

F (image) = 144.090 MHz and 145.910 MHz (2nd order harmonics).

F (rx super-heterodyne) ~ 144.090, 144.545, 145.455, or 145.910MHz

F (rx triple-conversion) ~ 145.000 MHz

This is an example of triple conversion versus simple super-heterodyne, or dual conversion methods of receiving. The frequency received will be truer to the actual frequency transmitted on a scanner/receiver with triple conversion than on one with dual conversion and much the same when comparing dual conversion to simple super-heterodyne. The methods of using double or triple conversion aid in eliminating unwanted images (ghost frequencies) and other types of noise present in the different band of frequencies.

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Question: I need a service manual, and the local store said there isn't one for my scanner. Why?

Early in 1997, representatives from the scanner industry, including RadioShack, met informally with the FCC to discuss current problems in the scanning hobby. Identified as a major problem was the ability of some scanner hobbyists to develop illegal modifications that allow scanners to receive cellular telephone transmissions. Among the possibilities discussed for eliminating this problem were the total epoxying of all circuit boards, which would render scanners both unmodifiable and unserviceable, or the restriction of technical information regarding scanner circuit design.

As a result of this meeting, RadioShack limited the availability of scanner service manuals to RadioShack Service Centers only.

While RadioShack understands the desire of the do-it-yourself community to have easy access to service information, we feel the interests of the scanning hobby as a whole are best served by making it more difficult to develop illegal modifications by restricting access to some service manuals containing schematics. Therefore, in response to industry concerns, RadioShack is implementing the following policy in regards to the release of service information and the servicing of scanners.

RadioShack will withhold schematics (service manuals) for all scanners that can receive 800 MHz or above which were submitted for FCC certification after April, 1997. As of December 12, 1997, this means that service manuals for the following RadioShack scanners will not be available: 20-417 (PRO-2048), 20-430 (PRO-2050), 20-512 (PRO-67), and 20-520 (PRO-90), along with all future service manuals within the stated criteria.

To the extent that service manuals exist and are in stock, schematics (service manuals) for scanners that can receive 800 MHz or above that were submitted for FCC certification before May, 1997 will continue to be available to customers and others.

To the extent that service manuals exist and are in stock, schematics (service manuals) for scanners that cannot receive 800 MHz or above will continue to be available to customers and others.

Modified scanners (regardless of frequency or date of manufacture) will not be serviced by RadioShack. These scanners will be returned to the customer with a notice indicating that the unit appears to have been modified and if the scanner is returned to its original specifications, RadioShack will use reasonable efforts to repair it.

To the extent that scanner parts are available and in stock, scanner replacement parts will continue to be available regardless of the scanner's frequency range or date of manufacture.

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Question: Why do I get constant noise on a particular channel?

It may be a birdie channel. Birdies are frequencies your scanner uses when it operates. The most common birdies to watch for are listed below.
31.05 MHz 124.20 MHz
41.40 MHz 134.55 MHz
51.75 MHz 144.90 MHz
113.85 MHz 155.25 MHz

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Question: When I plug a speaker into the earphone jack, the audio volume cuts down a lot, and I have to turn the volume up - is this normal?

To connect to an earphone jack requires an amplified extension speaker; if your speaker is not amplified, you get significantly lower volume as you describe.

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Question: My scanner will accept 821.2620 but then rounds it off the 821.250? Why can't I enter the right frequency?

The scanner frequencies must correspond to the preprogrammed step rate; this is normal operation.If you cannot tune directly to a frequency, you would need to tune to the closest frequency to the desired frequency. Usually, either the tunable frequency immediately above or immediately below the desired frequency will be close enough to pick up the desired channel.

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Question: I tried charging NiMH batteries in my scanner &' the batteries appear to be expanding.

NiMH batteries require a different charging circuit from NiCd. You should never charge NiMH batteries in any device or charger unless it clearly specifies that it will charge NiMH batteries.

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Question: I put new batteries in my scanner but it shuts off after a few seconds.

Clean the battery contacts using a rubber eraser. If the problem continues, try different batteries. If the problem still continues, you would need to have the radio serviced.

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Question: My scanner stops on a particular channel or frequency when using the DC adapter and the engine is running; it works fine when the engine is not running.

Something in the engine is generating RF interference. You would need to determine where this is coming from and install a filter. The best place to start is with a noise filter on the DC line, such as:
270-030 Basic Noise Eliminator
270-051 10-amp Noise Filter
270-055 20-amp Heavy-duty Noise Filter

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