Electronics Notes Ham Radio Store: Antenna Analyzer

Antenna analysers are used to understand the properties and performance of an antenna better. Antenna analysers are particularly useful when installing, experimenting with or developing antennas.

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Antenna analysers are a very useful items of test equipment for anyone experimenting with antennas. Whilst a proper vector network analyser would be ideal and provide the best information, these instruments are exceedingly expensive, and an antenna analyser is normally a far more cost effective solution which is quite adequate for most amateur radio situations.

Antenna analysers provide information about the performance of the antenna separately in terms of resistance and reactance. The readings provided by an antenna analyser provide much more information than that which can be obtained from SWR readings.

Also the SWR meter requires a signal to be transmitted, so care needs to be taken not to interfere with other users and the station needs to be identified at each point to comply with regulations. An SWR meter will typically require the transmission of a few watts of power to be able to make sensible readings. By comparison an antenna analyser will only require a small amount of power and this will normally fall below the regulatory requirements for a transmitting licence to be used.

However, most antenna analysers incorporate an SWR bridge into unit as part of the overall functionality. This can be used appropriately when required with the transmitter.

When looking at buying an antenna analyser it will be seen that there are several on the market. What are the points to look for when buying one?

• Computer control:   Some antenna analysers an purely manual and provide readings on either analogue meters or digital displays of the antenna readings. Other meters have a link to a computer and this enables plots to be made of the antenna performance over a range of different frequencies. Obviously the antenna analysers with the computer interface are more expensive, but they provide additional capability.
• Frequency range:   It is obvious to say that is is necessary to check the frequency range of the antenna analyser. Some cover 1 to 60MHz, whilst others may extend to around 250MHz, and others may even just be for the VHF / UHF bands. It goes without saying that the wider the frequency range, typically the more expensive the analyser is.
• Robustness:   Antenna analysers will often be used outside. As they are used outside the laboratory or shack environment, it is best of they are reasonably robust. However much care is taken, they will undoubtedly suffer some knocks and bangs. A more robust analyser is likely to last for longer.

There is a balance between buying a top of the range antenna analyser and one that is much cheaper. If the analyser is only likely to be used occasionally then a cheaper one would be the obvious choice in many instances. If it is likely to be used more often, a greater level of expense can be justified. It may help to borrow one first to assess what is actually needed. Often this can only come with experience and having used one.