Q. What effects may be observed related to cable length and impedance?
A. The CAA-500 is designed to measure the impedance presented to its input connector. If the CAA-500 is
connected directly to the antenna feedpoint, it will read the feedpoint impedance accurately. However, if a length
of 50-Ohm coaxial cable is connected between the antenna feedpoint and the CAA-500, and the feedpoint
impedance is not 50 Ohms, the 50-Ohm cable will act as a "series transformer" and the CAA-500 will only be
able to display the impedance at the end of the cable by the CAA-500. Also, if the coaxial cable's impedance is
other than 50 Ohms (e.g. 75 Ohms), similar "series transformer" effects will be observed.
The length of the cable of reference data
This situation may be mitigated by using a coaxial cable that is precisely ½ wavelength long at the frequency being
used (including the velocity factor of the coaxial cable). The impedance at one end of a half-wavelength cable is
repeated at the other end of the cable, making it convenient for measuring purposes. For example, ½ wavelength at
145 MHz is 1034.5 mm (40.73"). For RG-213 or 3D-2V cable with a velocity factor of 67%, the resulting
half-wavelength cable (including connector) is 1034.5 x .67 = 693 mm (40.73" x .67 = 27.29"). Any integer multiple of
½ wavelength may be used (i.e. ½ wavelength, 1 wavelength, 1½ wavelength, 2 wavelengths, etc.).
Q. Which Antenna connector may I use? Are both active?
A. The frequency range in use determines which output jack is available for measurement purposes; the other output
connector is automatically disabled. For the "A" through "F" ranges, the "M" ("UHF" or "SO-239") connector is used,
and the "N" connector is disabled. For the "High Range" selection, the "N" connector is automatically selected, and the
other connector is disabled.
Precautions During Operation
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Do not drop the CAA-500 or subject it to a strong shock.
●
Keep the CAA-500 away from heat and moisture.
●
Never attempt to perform modification by yourself. Failure to follow this would
cause unexpected accidents.
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After-Sales Service
】
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Should you have any technical questions, please ask our Engineering Department
( [email protected] ).
■
Please ask the dealer from whom you purchased this product if you need repair service.
Appearance and/or specifications are subject to change without notice or obligation.
1st Version
Copyright (C) 2011 COMET CO.,LTD. All Rights Reserved.
COMET CO.,Ltd.
4-18-2, Tsuji, Minami-ku, Saitama City, Saitama-Pref 336-0026 JAPAN
TEL: +81-48-839-3131 FAX: +81-48-839-3136
URL http : //www.comet-ant.co.jp/english/index.html
