400-MHz Ham Transceiver HTX-404

The RadioShack HTX-404 is a 70cm (440 MHz) UHF handheld amateur radio transceiver originally released in the 1990s. Known for its solid build quality and clear audio, it was manufactured for RadioShack by Standard Radio. 

Technical Specifications:
The RadioShack HTX-404 is a mono-band FM transceiver designed for the amateur UHF band. 
Frequency Range: Transmit and receive from 440 to 450 MHz.
Power Output: Offers a high/low power slider. At low power, it outputs 0.5 watts. High power varies by voltage: approximately 1.5W at 7.5V and up to 5W with 13.8V external power.
Memory: Includes 30 memory channels for storing frequently used frequencies.
Features: Built-in 47-tone CTCSS encode/decode and DTMF capabilities.
Connector: Uses a standard BNC antenna connector.
Power Supply: Operates on 7.2–9 VDC (typically via six AA batteries) or 7.2–13.8 VDC from an external source.

Common Maintenance & Issues:
Reviewers on eHam.net and RadioReference.com highlight specific areas for maintenance. 
Memory Battery: A common issue is the internal memory coin cell battery, which is soldered to the board and difficult to replace.
Audio Quality: Praised for excellent transmit and receive audio, often described as better than competing models from the same era.
Interface: The menu system is noted as non-intuitive and cumbersome to program compared to modern radios.
Reset Procedure: If the display shows "ER1," a full factory reset is required by turning off the radio and holding F + CLR while turning it back on.

Accessories and Replacement Parts:
Batteries: Replacement Ni-MH battery packs, such as the HQRP 1600mAh Ni-MH Battery, are still available for this model.
Power Adapters: Compatible wall chargers like the AC-DC Power Adapter for RadioShack Realistic HTX can still be found through online retailers.
Manuals: Full documentation, including the HTX-404 Owner's Manual and Service Manual, is archived on sites like Repeater Builder. 

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