Barry reviews the RigExpert AA-650 Zoom

Many thanks to Barry (KU3X) for sharing the following review originally posted on his website:

Product Review: RigExpert AA-650 Zoom

by Barry G. Kery, KU3X

If you are building a ham radio station, whether it be a contest station, a station for working DX or just daily rag chewing, this may be the tool you need to help you maximize your signal.

The AA-650 Zoom is a very user friendly antenna analyzer. It is super easy to navigate through the menu to choose what task you want the analyzer to perform.

Let’s start with frequency range. This unit will cover from 100 kHz up to 650 MHz. To get accurate readings, you must enter three factors. You must enter, “Frequency, span and sampling points. “  Here is one of many areas where the AA-650 Zoom shines and that is, “Sampling Points.”

When you sweep a frequency range, whether it’s just the 20 meter band or maybe sweep from 7000 kHz to 30000 kHz, sampling points have a direct impact on the results.

Antenna analyzers do not take a reading one Hertz at a time. They take a reading at numerous points within your sweep range. You can select how many sampling points you want to use. The 650 Zoom gives you 5 options. They are 20, 50, 100, 250 and 500 sampling points.

Let’s say you want to sweep from 7000 kHz to 30000 kHz, like the usable frequency range of a 40 meter off center fed antenna. If you choose to use 50 sampling points, the 650 Zoom will take a reading at every 460 kHz in that range. Once the sweep is finished, the analyzer takes an average and fills in the display with an SWR curve. So it kind of guesses what’s between each point.

Now take that same frequency range but sweep it with 500 sampling points. The 650 Zoom now takes a reading at every 46 kHz.  Remember one thing: the more sampling points you use, the slower the sweep but the higher the accuracy. For single band use, I like to use 100 sampling points.

Most of the time, that’s all you need. But let’s say the antenna you are testing has some quirk at a given frequency. If your sampling points are set too low, your sampling points may not be close enough to detect the problem. So now the analyzer will not know there’s an issue and fills in the display with an average reading.

There are two ways to setup the analyzer for a frequency and range. To the left shows where you can manually enter the center frequency and the span of the sweep. Press the, “Frequency key” on the keypad to access this feature. Within that display, to the far left you will see meter bands. If you press the, “F key” on the keypad, a band will be highlighted. Use the up / down arrow keys on the keypad to select your band of choice. When you let up on the, “F key” the analyzer will program that band with a predetermined span.

The picture on the right shows yet another super easy way to set up the analyzer. To access this screen, press and hold the, “F key” and then press the zero key on the keypad. The rest is easy. Pick a number that corresponds to the band you want to check.

Top picture shows an SWR curve of my 40 meter beam. This reading was taken from my shack. Take note of the bottom of the display. The analyzer lets you know what the minimum SWR is at a given frequency. On the top of graph, the SWR is shown in relation to the pointer.

The top right picture shows the SWR of my 20 meter beam at a given frequency. You may find this feature useful for adjusting a manually operated transmatch or adjusting the tuned inputs of your home brew amplifier. On the bottom of the display, it shows return loss at 14150 kHz.

When you sweep a frequency, you can save the SWR plot in any one of the 99 non-volatile memory slots so you can retrieve them at a later date.

If you want to check more than one frequency at a time, like on a tri band Yagi or an off center fed antenna, the AA-650 lets you pick up to 5 different frequencies to check at one time.

Shown below are return loss figures for a low power 4 to 1 Guanella Current Balun. The balun was designed to be used from 80 to 10 meters. The sweep is from 2 MHz to 30 MHz.

Let’s talk OSL Calibration…

Using Open, Short, Load calibration is a way to cancel out your transmission line so you can take a reading of your antenna like you are attaching the antenna analyzer to the feed point of the antenna. Let’s take a 100 foot length of RG-8X as our coax used for testing antennas. Hook the coax to the 650 Zoom and run OSL Calibration. Once you do that, it’s like the coax is transparent.

Hook the coax directly to the antenna and take a reading. Now you know what’s happening at the antenna’s feed point.

So why is this useful? Most efficient quarter wave verticals or inverted L’s are not 50 ohms. Most delta loops can easily range from 90 ohms up to 200 ohms, even more and sometimes less. Now you need to match these antennas to 50 ohm coax. If you are like me, some kind of matching network or coax stub is used and placed at the feed point of the antenna. Here’s is where you need to gather as much information as possible. Both Smith Chart and complex impedance readings come into play.

The above readings were taken of my 20 meter beam in the primary station. But let’s assume they were taken at the feed point of my antenna. The feed point of my beam showed 57.4  ohms and the reactance would be -.99 ohms. Probably as close to resonant as possible. If you want a completely perfect match, an L/C network will do fine. I’m really splitting hairs here so let’s assume it showed R=23 and X = -67. Now you have an issue.

Enter, “SimSmith.” This is a free smith chart download that will let you enter different components for building a matching network. Between my old RigExpert AA-600 and SimSmith, it was able to build an L/C network to create a perfect match for my 160 meter half sloper. NJ3I, Jon Matson, told me his inverted L for 160 meters was R=20 X=0. I built him a 22.22 ohm to 50 ohm UnUn and tested same with the RigExpert and he was one happy camper when he attached the UnUn to his inverted L.

How’s your coax?

Is it new and you think it’s good or maybe just very old. Coax has loss and I had one run that water migrated in and the shield from one end to the other was black. One way you can test coax is to attach a watt meter at both ends of the coax, attach a 50 ohm dummy load to the far end and apply power. Here’s an easier way. Attach the AA-650. You still need to get to the far end of the coax. The test is a two part process. Run the test with first the far end open and then shorted.

The above picture shows a coax loss test of a 50 foot length of RG 58 coax that I use when operating portable POTA. At 7079 kHz it shows a loss of 1.11 db. The RG 213 coax that I tested where the water got in had a loss of over 3 db on 40 meters. So half of my power was gone by the time it reached the base of the tower. Not all coax is created equal. I ordered a short run of coax with BNC’s on each end because I was too lazy to put my own ends on. It was for portable so no rare DX would have been lost by using it. I tested it and it was the worst coax I ever purchased. It had a 3 db loss on 20 meters and it was a very short length of coax. Needless to say, I never used it.

TDR:  Time Domain Reflectometer.

This is one of the handiest features of the AA-650 Zoom. TDR runs a trace single through the coax to find faults. My beam crapped out and the SWR went through the roof. Now what? Where do I start? Enter TDR.

I went to the shack, hooked the RigExpert to the coax run that had the issue and ran a trace. At the 89 foot mark on that coax it showed an open. That was at the base of my tower. At that location was a PL-259 and a barrel connection. I took the tape off of the connection and took the connection apart. The connectors were black and had melted. I fixed same and was back in business.

The above two pictures are two bench test traces.

The picture on the top shows an open failure at the 57.86 foot mark on a piece of RG 123. The picture on the bottom shows the same coax with a short on the far end. The trace goes high when opened and the trace goes low when shorted. Without a TDR, how are you going to find a fault if your coax is under ground and the fault is under ground? Let’s say you prepare a 150 foot run of coax and put a PL-259 on each end. You check it with an ohm meter and it shows a short. So which connector do you cut off? You have a 50 /  50 chance. With a TDR, it will show you exactly which connector has the issue.

PL-259’s are not 50 ohms. You have to look very close at the trace and when you do, you can see the impedance bump a PL-259 connection creates. It does not stick out like a sore thumb, but it’s there. Another use for the TDR is finding out how long a length of coax is. Maybe the coax is still on a spool and you don’t want to remove it. Just put a connector on the free end of the coax, enter the velocity factor of the coax in the 650 Zoom’s setup menu and run a trace. Since the other end of the coax is usually open, once the open shows up on the display, you will know how much coax is on the spool.

Have a full size Delta Loop and you need a quarter wave length of 75 ohm coax to couple the antenna to your 50 ohms coax? Or maybe you want to make a quarter wave stub to attenuate harmonics? The 650 Zoom will simplify this task.

Again enter the VF of your coax and hook one end to the antenna analyzer. Go into the stub tuner menu and you will know the exact wavelength of you coax. Above is a 50 foot length of RG 58 coax. At 3088 kHz it’s a quarter wave long and it’s a half wave long at 6329 kHz. Start out doing a little math and make a quarter wave stub. Quarter wave: 246 / F(MHz) * VF. “Make sure it’s longer than needed !” Hook one end to the 650 Zoom, lay the analyzer on the bench and keep trimming the far end of the coax until you zero in on the needed length.

The 650 Zoom can also tell you the value of capacitors, inductors and with the use of a little coupling loop check traps for their resonant frequency. If you do not know the velocity factor of a known length of coax, you can find out what the VF is with this analyzer. You can also find out what the impedance of the transmission line is.

When I received my 650 Zoom, the firmware was version 1.1 and 1.6 was available. I updated the firmware post haste.

The 650 Zoom is advertised to provide up to 3 hours of continuous use on battery power. If you are doing a lot of bench work you can extend this time by plugging the 650 Zoom, via USB cable, into either a computer or a USB battery pack. The USB cable then supplies power to the 650 Zoom.

There are three ways to program the AA-650 Zoom: it can be programmed with the use of the keypad as a stand alone hand held unit, it can be programmed via Bluetooth or it can also be programmed with the use of a computer.

You may want to download, “AntScope2” from the RigExpert web page. By using the computer to operate the 650 Zoom, you can sweep with up to 2,000 sampling points. Once the sweep has been completed, you can put your cursor at any test point on the screen and you will be shown all of the complex impedance readings at that point. You can save your data to a file and you can also take screen shots that are displayed on the 650 Zoom and save them to a file.

The RigExpert AA-650 Zoom is not an inexpensive instrument. HRO price is $700. Other than the frequency range and the battery choice, the AA-230 Zoom has the same features as the 650 Zoom.

The 650 Zoom has Bluetooth and the 230 Zoom has two models: one with Bluetooth and one without Bluetooth. The 230 Zoom with Bluetooth costs $429 from HRO. The 650 Zoom uses three each AA size batteries and the 230 Zoom uses four each AAA batteries. Unless you need to be able to cover up to 650 MHz, the AA-230 Zoom may be a better choice for your needs.

Click here to check out the AA-650 Zoom on RigExpert’s website.

3 thoughts on “Barry reviews the RigExpert AA-650 Zoom”

  1. Yes, great article, very complete and lots of good info. I have a RigExperts AA54, near the bottom of the line analyzers. I am mostly interested in HF only. I do like the feature of being able to put in 5 frequencies and the SWR is displayed for all 5. This is useful for multi-freq antennas like a multi-band vertical. One can see as the antenna is adjusted the effect at each band and can make quick adjustments. IMHO RigExperts have the best antenna analyzers. They are not cheap, but are competitive to others. The newer ones have color displays so makes them easier to read.

  2. Excellent overview – I just joined the RigExpert family and it was a great tool for working on my EFHW this past weekend.

    What was interesting was comparing its readings to the SWR app on the X6100. The Xiegu was finding close to 1:1 at times when the RigExpert was 2:1 or worse. Every setup has its own electromagnetic idiosyncrasies; it just goes to show that the X6100 can do a great job of measuring and matching its own antennas but can’t necessarily be used as a more broad-based analyzer.

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