When it comes to the representative symbol of amateur radio, it is estimated that a large number of enthusiasts will vote for the antenna (to be precise, the Yagi antenna). The remaining enthusiasts may choose radio equipment, and it is estimated that few people will notice the little thing like a connector. However, if you find a ham and ask why your device uses an M-head, and what is its performance, about nine out of ten will be asked. In order not to be asked, don’t come and learn!

The most common connector-M head (UHF connector)

M head for welding and installing feeder

This type of connector has a long history, and it has been used in the period before World War II. Another name "UHF connector" comes from the definition of UHF at that time (frequency higher than 30MHz is the UHF frequency range). And now the test of this connector shows that its characteristics are mainly suitable for use at frequencies around 100MHz and below. This is the VHF frequency band that is now usually referred to.

The most significant feature of this connector is a thicker center conductor (about 4mm thick) in the middle of the plug. The connection and fixation adopts the way that the internal thread on the joint and the external thread on the socket engage with each other. This kind of plug is not waterproof, so you should be especially careful about the impact on natural conditions such as rain when installing it outdoors.

 Tests from Hamradio prove that the UHF connector standing wave increases with increasing frequency

In terms of electrical characteristics, the characteristic impedance of the M connector is not fixed. For shortwave and VHF bands, the impedance is generally good. As for the UHF frequency band mentioned now, its impedance is relatively high, and considerable reflection waves will be generated when used above 100MHz, and M heads are generally no longer used on professional UHF radio stations. However, it is still widely used in the field of amateur radio (such as equipment from Japanese manufacturers). The M head has better endurance and can withstand more than one kilowatt of power output. Fully enough for amateur radio.

A true all-rounder-N head (N connector)

High hopes were placed on the N head when it was first designed. It was born about 10 years later than the M head. The initial design index of the N head for military applications can carry signals at 1 GHz. However, the current N head can easily carry signals around 11 GHz. Several engineers at HP Labs even used N-head connectors to carry nearly 18GHz radio frequency signals.

The identification method of this connector is that the center core material is thin, and there is a metal protective layer on the outside. Similar to the M head, the connection between the connector and the socket is also through threaded engagement. The difference is that the N head has limited all-weather waterproof capability. This is consistent with its initial military use.

The center is a 50 ohm N block, and the right is a 75 ohm N block

In terms of electrical characteristics, the N head has two fixed impedance types: 50 ohms and 75 ohms. The reason for choosing these two resistance values ​​can be clicked here. It should be noted that the diameters of the center conductors of the two connectors with different resistance values ​​are different, and forced use will cause damage. The power that the N head can carry is much larger than that of the M head. It can carry nearly 5kW at 20MHz, and it has nearly 500W at about 2GHz.

Small and exquisite high-powered weapon-SMA connector

 
SMA connector is one of the most commonly used connectors on hand consoles, and its development history can be traced back to 1960. With its extremely high performance, it has been widely used. Until now, SMA connectors have also been used in civilian WiFi and microwave communication applications. For amateur radio, SMA connectors are often used for mobile stations and software-defined radios.

The SMA connector uses a thin needle as the center conductor, and the polymer is used as the dielectric between the inner and outer conductors. Because it is not suitable for multiple plugging and unplugging, this type of connector is not suitable for use as a test instrument connector. This kind of connector is mainly divided into two types, which we often call the inner screw inner needle and the outer screw inner needle. The former is called an SMA connector, and the latter is called an anti-SMA connector. Generally, the former is used for ordinary signal transmission (such as radio frequency equipment, etc.), while the latter is used for WiFi and other equipment. The two connectors cannot be used interchangeably.

As for its performance, this connector can carry electromagnetic waves with frequencies up to 18GHz, and the highest frequency record is 46GHz created by a 2.92mm type interface. The smaller the caliber, the higher the carrying frequency.

A good helper for self-made equipment-BNC connector

Many of the antenna connectors used in the CW kits we usually buy use this BNC connector. The name "BNC" of this connector comes from its two inventors Neill and Concelman and its mechanical connection method "Bayonet". Its characteristic is its Bayonet connector, which clamps the connector on the socket by rotating. This is also its most distinctive way of identification.

This connector can carry signals with frequencies up to 4GHz, and its maximum carrying voltage can reach 500V. Similarly, it can also be used with 50 ohm and 75 ohm impedance cables. These relatively moderate parameters and very convenient connection methods make it widely used not only in the radio field, but also in the laboratory application field.

The RF connectors we usually use are basically these four types. According to the application environment, frequency range, power and other parameters, the appropriate connector can be selected to achieve a multiplier effect. Next time you buy an antenna, you won’t make a mistake again!