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This article in Nov, '06 QST describes an earlier version of the AIM which covered the HF band up to 32 MHz. The principles of operation are the same as the AIM4170. It is presented here with permission of the ARRL. |
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| The AIM4160/4170 compared with several other antenna analyzers.
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The latest versions of the manual and the program are here:
PROGRAM UPDATE
Download the DEMO PROGRAM and sample files for evaluation without the hardware. The manual is included in the zip file. |
| Here is a very nice program for graphically processing AIM scan data for off-line analysis and presentations: Zplots by AC6LA |
 AIM4170
(The earlier AIM430 HF model has been replaced by the AIM4170 VHF model. The basic operating principles are the same. - Sept, 2006). This new antenna analyzer measures the complex impedance (magnitude and phase) at each frequency of interest in the range of 0.1 to 170 MHz. A PC is used to calculate several parameters, including SWR, and plot the results. The test frequency is generated digitally and bandpass filters are used to reject stray signals (like broadcast stations) that are more than a few KHz from the operating frequency. A 12 bit analog to digital converter digitizes the raw data. This avoids non-linearities associated with diode detectors, and results in very good dynamic range and linearity for accurate magnitude and phase measurements. Impedance measurements can range up to 10K ohms. The true phase angle is measured, so inductive or capacitive reactance can be determined without ambiguity. The RF generator can also be used as a signal source for testing receivers. The frequency is very stable and it can be calibrated to WWV. The digitized data is sent to the PC via the RS232 port. Power for the analyzer can be obtained from a small DC power supply or a battery. With a laptop computer, the unit is quite portable and it can even be mounted up on a tower at the antenna feed point if desired, with power being supplied through the RS232 cable. The impedance at the antenna itself can be read with the AIM4170 located in the shack at the receiving/transmitting end of the coax. The cable can be any length. The cable's impedance and loss characteristics are determined by a simple calibration procedure and the antenna's impedance is plotted directly during the scan. There are no internal adjustments for calibration. The frequency range is continuous from 0.1 MHz to 170 MHz. Some of the parameters that are calculated by the PC include:
The scan data can be saved to disk or printed to compare before and after results. It can also be imported in spreadsheet programs for further analysis. The program has been tested with Windows 95, 98, 2000, ME, and XP. It does not require an installation procedure. (It will run directly from a CD or a floppy disk.)
15 meter dipole antenna. Scan = 20.5 to 22.5 MHz.
Open coaxial cable approximately 28 feet long. Scan = 4 to 14 MHz
Same cable as above. Scan = 10.5 MHz to 12.5 MHz 
Scan of unterminated coax and Smith chart. Scan = 5 to 25 MHz 
Updated: Mar 17, 2007
antenna analyzer
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