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This is not your father's antenna analyzer ... or, for that matter, yoursfive years ago. If you're used to taking single-frequency measurements,check out the swept-frequency readout of the Array Solutions AIM 4 170.

CQ Reviews:

The Array Solutions AIM 4170Antenna/Lab RF Analyzer

BY PHIL SALAS,' AD5X

Photo A- The AIM 4170 is packaged with everything necessary for operation.(Photo courtesy Array Solutions; all other photos by the author)

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Along with SWR meters andVOMs, I'll bet that one of themost-commonly owned and

used accessories in the ham shack isthe antenna analyzer. Antenna analyz­ers have revolutionized our way of mea­suring and adjusting antennas andrelated components . Since purchasingan MFJ-207 in the ear1y '90s. I haven'tbeen without one of these pieces ofequipment. Over the last several years,antenna analyzers have started evolv­ing from analog, manually tunablefixed-frequency measuring devices toDOS (direct digital synthesis) software­controlled swept-frequency devices.One of the newest antenna analyzerson the market is the Array Solutions AIM4170, designed by Bob Clunn. W5BIG.Since Bob lives just one mile from me,I ran over to his house to pick up a unitfor this review.

Basic DescriptionThe AIM 41 70 antenna analyzer covers100kHz to 170 MHz using DOS tech­nology. A 12-bit analog-to-digi tar con­verter digitizes the raw data for pre­cessing, thereby avoiding diode­detector non-lineanties. This results inexcellent dynamic range and linearityfor accurate magnitude and phasemeasurements. Impedance measure­ments can range from 1 ohm to 1OKohms, and true phase angle is mea­sured so there is no ambiguity whenmeasuring inductive or capacitive reac-

·Contributing Editor, cc. 1517 Creek­side Dri lle, Richardson, TX 75081e-mail: <adSxOcq-amateur-radio.COffl>

44 • c o • June 2007

tance. Intemal bandpass filters rejectout-of-band high-power interlering sig­nals, which makes the unit very robustin the presence of broadcast transmit­ters or other high-power signals nearthe measuring frequency. Also, sincethe internal RF generator is very stableand can be calibrated to WWV, the AIM4170 can easily be used as a signalsource for testing rece ivers.

The AIM 4 t 70 is very compact at just5- x 4" x 1.5" and weighs only 9.6ounces (see photo A). This compactsize comes with a bit of a penalty.though. as you do need a PC in orderrun the unit and display the results .

However. the AIM 4170 is quite portableeven with a laptop computer. It can bemounted remotely at your antenna feedpoint if desired , with power suppliedthrough a user-provided internal bat­tery. As an alternative, you can read theantenna impedance with the AIM 4170located in the shack using the "Refer toAntenna- function. Here the softwareguides you through a cable calibrationprocedure. alter which AIM 41 70 es­sentially subtracts-out the feedline,the reby providing the actual antennaimpedance data as if the AIM 41 70 werelocated directly at the antenna.

RF parameters that are measured,

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Using the AIM 4170The AIM 41 70 comes with pretty mucheverything you need (see photo A).There are three standard calibrationloads (open, short, and a standard resis­tor). a 'wall-wart" power supply, and anRS-232 computer-interlace cable. Sincethe AIM 4170 uses a BNC connector. aBNC~to~UHF adapter is also included.

a .csv file that can be imported into aspreadsheet program for additionalanalysis off line. Finally. too, the soft­ware has been tested with WindowS®95.98,2000. and XP and does not evenrequire an installation procedure; it willrun directly from the included CD ifdesired!

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calculated. and displayed include thefollowing :

• SWR referenced to any impedance(' :11020:')

• Impedance at the cable input or atthe antenna terminals

• Return loss• Reflection coefficient• Cable length. impedance. and joss• Distance to fault (open or short)• Smith Chart display• Resistance and reactance of discrete

components at the operating frequency• Ouartz-crystal parameters

All measured and calculated infor­mation can be saved to disk or printedin order to compare before and afte rresults. The data saved to disk includes

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Photo C- The 1.7- 29 MHz SWR swept response of the Butternut vertical.

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Photo B- Massive amounts of data can be plotted. The user can decide what isimportant and tum off the undesired plots.

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electrically short antenna and a decentground system. I use a remote relay toshort turns on the 6O-meler coil 10 give6O-meter operation, and shorting theseturns also shifts the 160-meter reso­nance. The AIM 4170 software lets youdo a re-trace. holding the original tracein place so you can see the effects 01tuning your antenna.

Photo E is the 40-10 meter sweep ofthe MFJ·1775 rotatable dipole. This isa short dipole (about 14 feet overalllength), so the bandwidth is narrow on40 and 20 meters. Photo F shows a 40­meter sweep of this antenna.

As mentioned earlier, the AIM 41 70inc ludes internal bandpass filters to pro­tect against undesired strong out-ot­band signals that can overload the unitand corrupt readings. However. verystrong signals may still overload theunit. If Ihe readings on the AIM 4170appear "tlaky," you can use the "BandSCan" feature of the un it, whereby itoperates as a spectrum analyzer to helpyou locate any strong problem signals.My main potentia l problems occur dueto the nearby KALD 50·KW AM broad­cast station on 1080 kHz. Photo G is thespectrum scan I took 01 the AM broad­cast band, which clearly shows KALD.The top red line of the scan represents150 mV peak. Signals above this levelmay overload the AIM 41 70 and makethe readings inaccurate. As you cansee, the 150-mV peak maximum level01 the AIM 4170 is not being exceededby KALD. although il is close! This"Band Scan" feature can also be valu­ab le in helping to figure out who is over­loading your receiver on Field Day!

Next I wanted to look at some crystaldata. While I've built homebrew crystalfilters for Q RP rigs for many years. I'vealways used defau lt designs by others,as I didn't want 10 bui ld the lest setupnecessary 10 actually directly measurethe crystal parameters. However. theAIM 4170 makes measuring crystalcharacteristics trivial. My current ORPproject is a 30- and 2O-meler CW radiousing a 2-MHz VFO and a crystal filtermade up of inexpensive 12·MHz micro­processor crystals. In order to measurethe 12-MHz crystals. I used a Banana­to-BNC adapter (Mouser 565·1296). Irecal ibrated the AIM 4170 with thisadapter in place. Then 1 attached thecrystals and clicked on the "MeasureCrystal" funct ion . Within seconds thescreen shown in photo H appeared. AsI said belore-a trivial effort!

Another interest of mine is using theAIM 4170 as a signal generator for mak­ing receiver measurements. The nomi­nal ou tput level is 30 mV RMS into 50

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a manual antenna analyzer. The AIM4170 will plot simultaneous curves 01SWR (red) , impedance magnitude(green) , reactance (yellow). and thephase angle of the load impedance(magenta). as can be seen in photo B.However, this is too much informationfor these preliminary tests. so with a fewmouse clicks I turned off everythingexcept the SWA graph. I also enabledthe SWR ruler and set it to 2:1 so as togive a feel for the usable bandwidth.andthe "Highlight Band" feature so the hamband limits are obvious on the scans.

The full SWR sweep of photoC clear­ly shows the individual band reso­nances of the Buttemut vertical. I tooka closer look at 160 meters (see photoD). since the 2:1SWR bandwidth is verynarrow-as it should be if you have an

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Photo D- The BuNemut 160-meter swept response.

Photo E- Swept response of the MFJ·1775 rotatable dipole.

There is the CD with software and a pnnt­ed quick-start guide as well. Calibrationis a snap, requiring no tools or adjust·ments, and in just a few minutes you'llhave everything up and running. II yourcomputer only has a USB interface, youwill need to purchase an inexpensiveUSB·to-serial adapter. which is easilyinstalled using simple instructions in theAIM 41 70 manual.

Now it is time to get down to business!First I wanted to look at the broad-bandresponses of my Butternut HF-9V ver­tical with the teo-metar coi l, and myMFJ·1775 rotatable dipole. I had set theband resonance points on both anten­nas with an MFJ·259B antenna anelyz­er. However, I had never looked at thebroad-band responses, since this is toodifficult and time consuming to do with

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Photo H- The 12·MHz crystal parame­ter measured data.

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charge, you won't have to worry aboutproduct obsolescence.

I've only touched on the basic capa­bilities of this unit, so please investigateit further on the website referencedabove. Once you get used to displayingswept responses of your antenna sys­tems, you will find it difficult to go backto single-frequency measurements.

The AIM 4170 is ava ilable from ArraySolutions: <hnp:lfwww.arraysolutions.com>. Price is $400. •

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component analyzer, I feel that the needfor a PC lor operation is somewhat of ahindrance, especially for outs ide tuningof an antenna. It would be nice if ArraySolutions had a compact LCD displaywith a few buttons that could maybejust enable the SWR function at specif­ic frequencies for outdoor use, andmaybe one of these days, expand thecapability to include the 450-MHz hamband as well.

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ConclusionThe AIM 41 70 is a reasonably priced,lab-grade antenna and component ana­lyzer that quickly will become an indis­pensable item once you begin using it.Plus, with softwa re and firmware up­dates available for down load at no

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Photo F- The MFJ-1775 40-meter swept response.

ohms, which means you need about 56dB of attenuation to give you a 5O-~JV

59 signal . I use the AIM 4170 with a 52­dB fixed attenuator and an MFJ·762step attenuator (see "The Weekender;CO. September and October 2006) toprovide me with a stable and accurateRF source for tests and measurements .

There are many other features andcapabili ties of the AIM 4170thatl haven'teven begun to describe. For everythingthis device can do, download the com­plete user manual from <http://www.w5big.com>, as well as a demo programthat runs without the hardware.

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WishesWhile the AIM 4170 does almost every­thing I'd like to see in an antenna and

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Photo G- Band scan of the AM broadcast band.

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