Versions and possible applications
Antenna switches are suitable for different applications, depending on their design. The category of antenna switches can be roughly divided into the following three groups according to their design and application:
Manual
Manual switches allow manual switching between the connected antennas with a larger, easy-to-grip rotary knob. They are also called coaxial switches and have one input socket and up to five or six output-side antenna sockets in PL or N standard. The relatively simple switching mechanism is built into sturdy metal housings made of injection-moulded aluminium. Because all cables connected to the coaxial switch are grounded with their shielding, only the core of the coaxial cable coming from the transceiver must be switched to the respective output. Due to their construction, they are designed for use in the lower frequency ranges from 1.8 MHz to 30 MHz. Particularly high-quality models are also suitable for the 144 and 430 MHz ranges.
Remote
Remote switches are controlled by a remote control unit and allow the switching operation to be performed electromechanically from a remote location. Another advantage of remote operation is that by having the remote switch near the antennas on the mast, only one cable is required for multiple antennas.
Automatic
Automatic switches select automatically between the antennas. They are controlled by an additional control unit with the band switching logic of the transceiver. Many of these antenna switches are dependent on the manufacturer's control unit, others are more universal. These somewhat more expensive systems, like the remote switches, are particularly suitable for use in larger radio stations where there are several radios and antennas.
Selection criteria
The choice of the right switch depends primarily on the requirements one has for the switch. The basic question is whether the switch should be manual or electrical, local or remote. Some important criteria to consider when choosing a switch are the number and standard of antenna connections (PL (aka SO-239), N, BNC, etc.), the frequency range(s) in which it is to be used, and the maximum transmission power. In this context, it is also of interest to have the lowest possible value of the passband or pass-through attenuation and a high crosstalk attenuation (for more on this, see text box). One feature that all coaxial antenna switches offered by WiMo have in common is the impedance: they are all 50-ohm technology!
Depending on the arrangement of the switch and the space situation at the station, the position of the connections may be relevant for the cable feed. They can all be on one side, on the left or on the right. You should also take a look at the mounting options. The most common mounting option is through holes in the housing flange, with which the antenna switch can be fixed to a suitable place on the wall or on the station table. As a rule, all manually operated antenna switches are not weatherproof and are only suitable for indoor mounting. Most (not all) remote switches are sensibly designed in weatherproof housings for permanent outdoor installation.
Important properties and technical data
For the short-wave range from 1.8 to 30 MHz, all antenna switches available on the market are more or less well suitable. Of course, they are also suitable for even lower frequencies like the medium and long wave range. Higher-quality versions also cover the 2 m and 70 cm bands.
The impedance at all connections is nominally 50 ohms.
The maximum permissible power is depending on the model, apart from some switches designed for QRP operation, between the common transceiver power of 100 W and 1-2 kW for QRO operation.
Due to the small but unavoidable capacitive coupling between the activated switching position and the inactive outputs, which are (usually) automatically connected to ground, a residual HF component always reaches the other outputs that are switched away. If only other, passive antennas are connected there, this is not a problem. With an active antenna or additional receivers or transceivers, the situation is different. A configuration of "two or more transceivers via an antenna switch on one antenna" could be problematic. At high transmit power, the level on the inactive outputs can reach a value sufficient to damage the inputs of the connected transceivers, receivers or active antennas. The property of a coaxial switch to minimise this process, among other things by the design of the switching mechanism, is called crosstalk attenuation. This should be as high as possible; a crosstalk attenuation of 60 dB or more is a good value.
On the other hand, the loss on the activated path between input and output, the pass-through attenuation, should be as low as possible with a value of 0.1 - 0.2 dB.
Practical tips
The switching mechanism of a coaxial antenna change-over switch is subject to wear due to the mechanical load caused by abrasion of the contact surfaces. When silver-plated contact surfaces corrode, an ohmic contact resistance or a diode-like path with a rectifying effect is formed. Interfering signals outside the transmission frequency can occur at the characteristic curve of this unwanted diode path. Therefore, it is advisable to open older coaxial switches once and, if necessary, clean corroded contact surfaces or contact surfaces soiled by abrasion. Under no circumstances should a nail file or fine sanding paper be used for this purpose! A strip of blotting paper and possibly a little spirit afterwards can provide "first aid". Ballistol is often recommended for such contact problems. It is quite effective. But on the other hand, the contact of Ballistol with copper and its alloys has an oxidising effect, even if only slight. Since switch contacts are often made of the copper alloy brass, a fine machine oil is at best suitable for short-term cleaning, but not for long-term preservation.
"Switching under load during transmission must be avoided at all costs! Especially at high transmitting power, this will at least cause the contact surfaces to burn off. In extreme cases, the contacts may even weld together and become inseparable. Therefore - first make sure that no transmitting signal is present - then switch."
"With PL and N connectors, the screw sleeve on the thread of the SO-239 or N socket can loosen over time, so that a secure contact is no longer guaranteed. Occasionally you should check this and, if necessary, ensure that the plugs are firmly seated. But please do not immediately use heavy pipe pliers! Tighten as firmly as possible by hand. If necessary, a thin but firm strip of cardboard can be placed between the plugs and tightened with a suitable pair of pliers. If the centre pin and the surfaces of the internal and external threads of older plugs or sockets are corroded or dirty, a strong toothbrush will provide the "first aid". Loose contacts on simple coaxial plugs always occur if care is not taken during plug assembly to ensure that the outer diameter of the coaxial cable and the inner diameter of the plug shaft match exactly, so that good contact is not made between the plug shaft and the shielding."
Known brands
Diamond
...offers four manually operated antenna switches. In the 2-way or 3-way switch versions, they are available with either PL or N connections. Starting with short wave, all versions can be used up to 3 GHz in some cases and ensure precise switching thanks to the original feel of the switch button.
AlphaDelta
...produces high-quality 2-way or 4-way antenna change-over switches with integrated lightning protection cartridge. The enclosures are made of solid injection-moulded aluminium, and all models are available with either PL or N standard connections. In the centre position "OFF" of these switches, all inputs are grounded, the output remains open and protected against overvoltages by a replaceable lightning protection cartridge. While the connection to the respectively selected antenna is switched, all other unused connections are earthed. The crosstalk attenuation of these antenna switches is specified with a value of > 60 dB.
MFJ
...is represented with a total of two manual and three transceiver-controlled antenna switches, whereby the latter are actually not classic antenna switches, but so-called TR switches (transmit/receive switches) that switch between transmit and receive antennas. Furthermore, a distinction must be made here between switching between the transmitting antenna and a separate receiving antenna to its own receiver input or switching a single transmitting and receiving antenna between the transceiver output and an external (SDR) receiver. All these antenna switchers require a 12 V operating voltage. Of the two manual examples, one is designed as a 6-way antenna switch with a rotary knob. The other is a 2x2 cross switch operated with a slide switch. All these MFJ antenna change-over switches are mainly equipped with PL standard sockets and are suitable for use up to 30 MHz.
Ameritron
...a subsidiary of MFJ, is represented in this category with four powerful and popular remote antenna switches. They are all built into weatherproof housings and are suitable for mast mounting. They are mainly supplied with operating voltage via a separate control line or, in one version, via the coaxial cable. They are operated via separate control units. The power rating of these remote antenna switches, which can be used up to 250 MHz, is between a maximum of 2.5 and 5.0 kW.
Other brands and manufacturers...
... from simple manually operated antenna change-over switches to remote switches and software-controlled switch systems, you will find an extensive range on our pages in the product category "Antenna change-over switches". This also includes those products that are partly only antenna switches in a broader sense. Several remote mast-mounted antenna switches are designed for polarisation switching of VHF antennas. Safety antenna relays with integrated overvoltage protection ensure automatic disconnection of all antenna connections when the station is switched off. A combined antenna and equipment switch for two radios, one PA and two antennas avoids cable clutter in the shack. A switch with the function of an antenna matrix can distribute three antennas in any of six possible combinations to three radios. High-quality, remote-controlled antenna switchers and associated controllers leave nothing to be desired. The associated software enables a multitude of features and functions. Furthermore, TR switches and switches between transmitting and separate receiving antenna also belong to this category.
For the sake of completeness, the suppliers and manufacturers listed in our product category include: Acom, Antenna Amplifiers, Bird, Daiwa, Elad, Emtron, Metropwr, microHAM, Paradan, QRO.cz, SPID, SSB-Electronic and 4O3A.
In our online shop you will find antenna switches from a wide range of the manufacturers mentioned, for use in amateur radio to semi-professional use. Our experienced staff will be happy to help you choose the right switch and answer all your questions.
