The Old Motorola Pin Plug vs. the Modern DIN 41585 Automotive Antenna Connector
Anyone who worked with automotive radios, scanners, or mobile communications equipment in the 1960s, 1970s, and 1980s will probably recognize the traditional Motorola-style antenna plug, often simply called the Motorola plug or Motorola pin plug. For decades it was a common antenna connector on American AM/FM car radios and was also widely used on scanners and other receiving equipment.
Today, the smaller automotive antenna connector commonly encountered as its replacement is generally identified as the DIN 41585 automotive antenna connector.
This is where some confusion arises. Many modern catalogs, cross-reference lists, sellers, and online references treat “Motorola plug” and “DIN 41585” as interchangeable names for essentially the same connector. In practice, that is not always the case.
There are older Motorola-style pin plugs and mating jacks whose physical dimensions, particularly around the outer spring contacts or “ears,” differ enough from modern DIN 41585 versions that the two should not automatically be assumed to be mechanically interchangeable.
Traditional Motorola Pin Plug
The traditional Motorola plug is a relatively large coaxial connector with a long projecting center pin surrounded by a cylindrical metal outer contact or shell. The outer portion commonly incorporates projecting spring sections, tabs, or “ears” that provide mechanical retention and the outer RF/ground connection.
On some of the older versions, these outer ears or spring-contact portions are larger and extend farther outward than those found on many modern DIN 41585 plugs.
This difference can be particularly noticeable with older radio scanners. Some scanners designed for the earlier Motorola pin plug have a larger chassis or cabinet clearance hole around the antenna jack. The larger opening provides clearance for the wider outer portion or ears of the original plug.
Consequently, the chassis opening itself can sometimes provide an identification clue. If a vintage scanner has what appears to be an automotive antenna jack surrounded by an unusually generous clearance opening, it may have been designed around one of the older, physically larger Motorola-style pin plugs.
DIN 41585 — Similar Does Not Always Mean Identical
The modern connector commonly sold for this application is identified as DIN 41585. It performs essentially the same function and is sufficiently similar to the traditional Motorola automotive connector that the terms are now frequently used interchangeably.
That interchangeability should not, however, be considered universal.
A modern parts listing may describe a connector as “Motorola / DIN 41585,” “Motorola-type,” “Motorola automotive antenna plug,” or simply “DIN antenna plug.” That description may be entirely satisfactory for a modern automotive installation while still failing to duplicate the dimensions of an older Motorola pin plug exactly.
The difference is particularly important in the outer mating structure. Some older Motorola plugs have wider spring contacts or ears, while modern DIN 41585 versions can have a smaller outside profile. Likewise, an older mating jack or the equipment's chassis opening may have been designed specifically around the dimensions of the earlier connector.
Therefore, a replacement that looks correct in a photograph and is advertised as a Motorola equivalent may not reproduce the exact mechanical fit of the original connector.
Look Beyond the Center Pin
When identifying one of these connectors, do not rely solely upon the projecting center pin.
Compare:
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the diameter and length of the center contact;
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the diameter of the outer mating section;
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the width and outward projection of the spring contacts or ears;
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the depth and shape of the mating jack;
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and, on older equipment, the diameter of the chassis clearance hole surrounding the jack.
These mechanical details can reveal differences that disappear when both connectors are simply grouped under the modern Motorola/DIN 41585 description.
Electrical Considerations
The traditional Motorola automotive connector was designed primarily as an economical antenna connection for broadcast receivers rather than as a precision constant-impedance RF connector.
Unlike RF connector families such as BNC, TNC, Type N, or SMA, the geometry through the traditional Motorola mating interface does not maintain the tightly controlled coaxial dimensions expected of a precision RF connector.
For its intended application, this was generally of little consequence. At AM broadcast frequencies and 88–108 MHz FM, it performed its job quite adequately. Its low cost, rugged construction, and ease of connection made it particularly suitable for automotive installations.
The same basic connector was also widely used on radio scanners, where it provided satisfactory performance for general VHF and UHF reception despite not being a precision RF interface.
Why the Names Became Blurred
Over time, the original Motorola-style automotive antenna connection became sufficiently associated with the later standardized automotive connector that the terminology largely merged in the replacement-parts market.
As older equipment disappeared and replacement connectors were manufactured around modern dimensions, “Motorola,” “Motorola-type,” and “DIN 41585” increasingly became treated as synonyms.
For most current automotive applications that may cause no problem. It becomes more significant when restoring or servicing equipment from the period when the older Motorola pin plug was actually in widespread use.
A technician working on a vintage scanner or car radio can therefore encounter the seemingly contradictory situation where a catalog says DIN 41585 and Motorola are the same connector, yet the replacement connector does not fit the original equipment correctly.
Both observations can have some truth behind them: the connectors belong to essentially the same automotive antenna application and have become commercially cross-referenced, but historical versions were not necessarily dimensionally identical to every connector now sold as DIN 41585.
Practical Identification
The old Motorola pin plug is generally recognizable by its long projecting center pin and comparatively substantial outer spring-contact structure. Some versions have noticeably wider outer ears than today's DIN 41585 replacements.
The modern DIN 41585 connector is generally more compact through this outer mating area.
This also explains an otherwise puzzling feature found on some vintage scanners: the antenna connector may sit inside a chassis opening noticeably larger than seems necessary for a modern DIN 41585 plug. That larger opening may have been necessary to accommodate the wider outer ears of the original Motorola-style connector.
The Important Point
It is common today to see Motorola plug and DIN 41585 listed as the same connector. For many applications they effectively are. For vintage equipment, however, that assumption should not be made without checking the actual mechanical dimensions.
If a modern DIN 41585 plug will not properly fit an older scanner, automotive radio, or other receiver that originally used a Motorola pin plug, the equipment is not necessarily damaged and the connector has not necessarily been misidentified. The original Motorola-style connector may simply have different dimensions—particularly in the outer spring contacts or ears—from the modern DIN 41585 version being used as its replacement.
For vintage equipment, measure the connector rather than relying solely on the name.