Antenna vswr indicator

Abstract

The invention described a pocket size antenna VSWR indicator having a self-contained low level wideband RF signal source which is applied to an antenna under test through a four arm RF resistive bridge circuit. The bridge circuit has been designed to be very accurate and reliable and provides a novelly positioned reference against which the reflection co-efficient of the transmission system is compared to reliably indicate the VSWR of the system. The bridge circuit provides a flat response over the desired wideband frequency range and over the range of antenna impedances which may be encountered. The RF null or bridge balance is detected in a radio receiver or transceiver tuned to the desired operating frequency, from which an indication of antenna VSWR may be provided. The antenna VSWR may be indicated in a variety of way, such as by means of a numbered or colored dial, a plurality of LEDs or an audio tone shift against an internal reference. Alternatively, the indicator may be calibrated to read VSWR directly by number or by means of a color-dial indicating good, poor or non-usable VSWRs. The VSWR indicator provides the user with an immediate indication of whether the radio transmitter and antenna of the RF transmission system will be properly matched or coupled at the frequency in use, to assure maximum power transfer and efficiency. Additionally, the VSWR indication will immediately provide an indication of the overall system performance and will avoid the possibility of damaging or destroying the RF transmitter. The antenna impedance bridge of the invention allows the antenna to be tuned while keeping the radio carrier wave off the air so as to avoid interference therefrom or the unwanted detection of transmissions. The VSWR indicator of the invention provides a portable, self-contained VSWR indicating device which is extremely simple to operate and which provides an immediate and direct read out or VSWR accurately.