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PUBLISHED 8/20/2024
WRITTEN BY Christopher McRae
Realistic/RadioShack produced many radio scanners over the past 30 years and many can be bought off used market places for cheap. Though most of models are analog only, many local services in the US still use analog FM technology for 2-way radio communication making these scanners quite useful in 2024 and beyond. Mods such as the "discriminator tap" make it possible to use a computer to decode paging, P25, DMR, MotoTRBO and other digital transmissions without the need of a more expensive scanner that includes these features built in. Though low cost Software Defined Radios (SDRs) have made scanners and mods like these somewhat obsolete, a dedicated scanner may offer better receive performance than something like an RTL-SDR This website has an index on most, if not all, of RadioShack's scanners made since the 1970s.
Manufactured in 1989, the Realistic PRO-2022 is a fairly run of the mill scanner for the time. It offers 200 channels and no trunking, but it does have a decent frequency range (30 - 960 MHz, with gaps of course). It is similar to the more well known PRO-2005, however the PRO-2022 is much more attainable on sites like eBay.
The "Discriminator Tap" mod refers to "tapping" in to the discriminator of an FM demodulator in order to get a raw baseband signal that has no filtering. This signal can then be sent to a computer's sound card for decoding various digital signals such as POCSAG or FLEX . The baseband audio is much clearer than a headset or speaker output which has a lot of filtering that can make it difficult to decode a digital signal.
The mod for the PRO-2022 is very simple. This page describes the process in detail, but I will show what I did too.
Parts List:
The first step is to remove the antenna on the top, it unscrews. Then remove the top casing by unscrewing two screws on the back of the case. Now locate the “TP5” post on the motherboard, it is located near the Samsung chip.
"TP5" highlighted in red, located to the left of the Samsung chip.
You must solder a resistor and capacitor to TP5 and ground.
What my setup looked like after I was done. It would be ideal to use a jack that can be easily mounted to the metal casing of the radio, then you would not need to run a ground wire.
During the time the PRO-2022 was manufactured, the existing cellular phone service relied on a technology called AMPS (Advanced Mobile Phone System). In the US, AMPS operated on the 800 MHz band (824–849 and 869-894 MHz) and relied on ordinary FM for voice channels. The FCC required that all radio scanners have this band blocked to prevent eavesdropping. In 2024, all cellular phone systems are digital and incorporate some level of encryption, making eavesdropping pretty much impossible, especially with a 35 year old scanner. Having access to these frequencies may be useful however, such as for the purpose of experimenting with AMPS cell phones in 2024 and beyond.
In order to “unlock” these frequencies on the PRO-2022, you must simply disconnect the diode, D44. This reference includes very useful information on the topic.
D44 intact
D44 cut
The entire 806 to 960 MHz range is now unlocked.