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. Continue reading Barry reviews the RigExpert AA-650 Zoom
