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Comet CAA-500MarkII Antenna Analyzer
Reviewed by Phil Salas, AD5X
ad5x@arrl.net
Comet recently introduced their nextgeneration antenna analyzer — the
CAA-500MarkII. Like the original
CAA-500, reviewed in the March
2012 issue of QST, the
MarkII has a large analog cross-needle
meter for displaying SWR and impedance magnitude.1 The MarkII, however, adds a 1.4 ×1.15 inch full-color
TFT LCD (see Figure 1) that displays
the operating frequency, fixed frequency SWR and impedance data, and
swept frequency SWR data.
Overview
The CAA-500MarkII is a fairly large
instrument — almost as big as a classic Bird 43 wattmeter. Connectors are
an SO-239 for 1.8 – 300 MHz, and a
Type N for 300 – 500 MHz. Power requirements are six AA-size alkaline or
NiMH cells (not included) or external
8 – 16 V dc, 250 mA power source (dc
cable included). The CAA-500MarkII
also includes an internal trickle charger
for NiMH batteries, an upgrade from
the original CAA-500. Typical charging time is 15 hours, and typical battery
operating time is up to 9 hours (there is
a battery indicator on the LCD). An autopower-off timer helps conserve battery
life. It’s adjustable from 1 to 9 minutes (default is 5 minutes) and can be turned off.
The CAA-500MarkII provides a single frequency measurement mode and two sweptfrequency modes. The single frequency
mode displays SWR and impedance (Z)
on the cross-needle meter, and digital and
bar graph SWR readings across the full
frequency range. Digital readings of resistance (R) and reactance (X, unsigned) are
displayed below 190 MHz, while only a
bar graph display of Z is available above
190 MHz.
The two swept frequency modes display
SWR in graphical form.
graphs SWR using preset amateur band
frequency ranges.
selection of the center frequency and sweep
bandwidth.
Table 2 summarizes the specifications and
performance of the CAA-500MarkII.
MANUAL SWEEP
CAA
-500
AUTO SWEEP
permits
Test Results
The CAA-500MarkII output level is quite
constant over the full frequency range as
shown in Table 3. The frequency can be
set to within 1 kHz, but this is a tricky adjustment especially at the higher frequencies. Additionally, the signal is noisy and
“warbly.” Further, initial frequency drift
takes about 15 minutes to stabilize when
the CAA-500MarkII is powered from an
While limited in measuring capability and performance compared
to other antenna analyzers in its
price range, the CAA-500MarkII
covers all amateur bands from
1.8 to 500 MHz, making it a single
“all-band” instrument.
Bottom Line
external dc supply but continues after
that period when used with the inter-
nal batteries. Also, just touching the
case or dc power cable caused some
frequency change. For these reasons,
the CAA-500MarkII would probably
not be the best tool for precise receiver
measurements.
Next I checked SWR accuracy, starting with a precision 50 Ω load. Then
I tested the CAA-500MarkII with
shorted microwave attenuators of
5 dB (1.92:1 SWR), 3 dB (3.01:1
SWR) and 2 dB (4.42:1 SWR). I
also used loads made from Caddock
thick-film resistors — a 7.5 Ω load
(theoretically 6.67:1 SWR), a 200 Ω
load (theoretically 4:1 SWR), and a
400 Ω load (theoretically 8:1 SWR).
As Caddock resistors are specified for
high frequency applications, I used
these tests to not only compare the
CAA-500MarkII against a high quality Array Solutions AIMuhf vector
impedance analyzer, but also to see
how good the Caddock resistors really
are.2 As you can see in Table 4, the
CAA-500MarkII SWR readings
compare favorably to the AIMuhf
readings, especially for the lower im-
pedance measurements.
Because the Caddock resistive loads are
not perfect, I used 150, 200, and 400 Ω
Caddock loads to check impedance measurement accuracy at 50, 146, 222, and
440 MHz. As Table 5 shows, the impedance measurement capability of the
CAA-500MarkII is better at lower frequencies and lower impedances.
For my final tests, I built lower impedance complex loads with an SWR of approximately 2:1 for 50 MHz, 146 MHz,
and 222 MHz. Table 6 displays the
CAA-500MarkII resistance (R) and
reactance (X) measurements on 6 and
2 meters, and an impedance measurement at 222 MHz compared to the Array
Solutions AIMuhf. As you can see, the
CAA-500MarkII provides reasonable
impedance measurements at 50 MHz,
but the accuracy degrades as you go
higher in frequency. Again, the sign of
the reactance is not displayed on the
CAA-500MarkII.
QST® – Devoted entirely to Amateur Radio www.arrl.org Reprinted with permission from September 2016 QST
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Table 2
Comet CAA-500MarkII, serial number AA15E0763-1
Manufacturer’s Specification Measured Performance
Frequency range: 1.8 – 500 MHz As specified.
(35 range segments).
Frequency settability: 1 kHz. As specified.
Frequency accuracy: Not specified. Actual frequency is within the 1 kHz
display range.
RF output level: 0 dBm HF/VHF, –1 dBm UHF. See Table 3.
SWR range: Analog meter 6:1; LCD, 9.9:1 As specified.
SWR graphical display: 6:1 As specified.
SWR accuracy: Not specified. See Table 4.
Impedance range: 12.5 – 300 Ω, 190 – 500 MHz. See Tables 5 and 6.
Resistance range: 10 – 500 Ω, 1.8 – 190 MHz. See Tables 5 and 6.
Reactance range: 0 – 500 Ω, 1.8 – 190 MHz. See Tables 5 and 6.
Size (height, width, depth): 3.5 × 7.75 × 2.65 inches. Weight: 2.1 lbs with batteries.
Price: $400.
Table 3
Output Power (dBm) vs Frequency
Power measured with a NIST-traceable MiniCircuits PWR-6GHS+ power sensor.
Specified power output is 0 dBm at HF and VHF, and –1 dBm at UHF.
--------------------- Measured Power (dBm) at Frequency (MHz) ------------------------------
1.8 3.5 7 14 28 50 144 222 440
0 0 0 0 –0.1 –0.3 –0.2 –0.5 0
Figure 1 — The color LCD is a new feature on
the CAA-500MarkII. It displays battery life, frequency, SWR, and impedance data.
Table 4
SWR Accuracy Measurements
Loads measured with the CAA-500MarkII compared to the AIMuhf. See text.
Freq 1:1 SWR 1.9:1 SWR 3:1 SWR 4.4:1 SWR 7.5 Ω Load 200 Ω Load 400 Ω Load
(MHz) CAA CAA/AIM CAA/AIM CAA/AIM CAA/AIM CAA/AIM CAA/AIM
1.8 1.0 2.1/2.01 3.2/3.17 4.6/4.62 6.7/6.76 3.9/3.97 7.9/7.93
3.5 1.0 2.1/2.01 3.2/3.16 4.8/4.61 7.0/6.72 3.9/3.96 7.8/7.93
7 1.0 2.1/2.01 3.2/3.17 4.8/4.61 7.1/6.73 3.9/3.96 7.8/7.93
14 1.0 2.1/2.00 3.2/3.15 4.7/4.59 6.9/6.70 3.9/3.97 7.8/7.95
28 1.0 2.2/2.00 3.3/3.15 5.2/4.59 7.6/6.71 3.9/3.97 7.7/7.93
50 1.0 2.2/2.00 3.2/3.17 5.1/4.60 7.7/6.73 3.8/3.95 7.4/7.92
146 1.0 1.9/1.97 3.2/3.19 5.0/4.75 9.4/7.05 4.0/3.84 7.7/7.59
222 1.1 1.8/1.92 3.2/3.15 5.2/4.76 7.8/7.25 3.8/3.74 7.3/7.18
440 1.0 2.2/2.03 3.1/3.07 6.8/4.81 8.0/8.73 4.2/3.40 >9.9/6.13
Figure 2 — Fixed frequency measurement of
a 160 meter antenna.
Table 5
Resistive Load Measurements
SWR and impedance measurements of 150, 200, and 400 Ω Caddock resistive loads with the CAA-500MarkII compared to the AIMuhf.
The CAA-500MarkII reactive readings are unsigned. See text.
Freq ------------- 150 Ω Load ---------- ----------- 200 Ω Load ----------- ------------ 400 Ω Load -----------(MHz) CAA AIM CAA AIM CAA AIM
SWR/R/X/Z SWR/R/X/Z SWR/R/X/Z SWR/R/X/Z SWR/R/X/Z SWR/R/X/Z
50 2.9/123/50/– 2.9/134/–39/140 3.8/176/49/– 4.0/186/–45/192 7.4/266/165/– 7.9/317/–156/353
146 3.1/50/61/– 2.9/81/–63/103 4.0/74/85/ – 3.8/127/–86/154 7.7/61/132/– 7.6/129/–175/218
222 3.4/–/–/50 2.8/54/–56/78 3.8/–/–/70 3.7/90/–86/124 6.9/–/–/80 7.2/72/–138/156
440 3.0/–/–/18 3.1/21/–25/33 4.2/–/–/25 3.4/38/–57/68 >9.9/–/–/25 6.1/23/–70/74
– = not measured.
Reprinted with permission from September 2016 QST ARRL, the national association for Amateur Radio
®
www.arrl.org
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Table 6
Complex Load Measurements
Loads measured with the CAA-500MarkII compared to the AIMuhf. See text.
Frequency ------ CAA-500MarkII ------ ----------AIMuhf---------(MHz) SWR Impedance |Z| SWR Impedance |Z|
50 2.0 R = 40, X = 30 1.95 47.5 –j33 58
146 2.0 R = 31, X = 21 1.80 45 –j28 53
222 1.9 R,X not measured 25 1.76 42 –j25 49
Using the CAA-500MarkII
The CAA-500MarkII is very easy to use
in the default single-frequency measurement mode. The
frequency range of interest, and the
BAND
switch selects the
FREQ
control sets the measurement frequency
within this range. SWR and the magnitude of the impedance are indicated on the
cross-needle meter, and the LCD provides
additional digital and bar graph SWR and
impedance information.
Both the
AUTO
and
MANUAL
sweep modes
display SWR only (6:1 maximum). For
the
AUTO
sweep mode, the
and
FREQ
control select the amateur band
of interest. Then pressing
BAND
switch
SWEEP CENTER
sweeps the selected full amateur band.
For the
GRAPH ON/OFF
ter frequency. Then press the
CENTER
and press
MANUAL
sweep mode, press
and set the desired cen-
SWEEP/
button, set the band sweep limits,
A.P. OFF
to confirm the settings.
Now manually sweep the SWR of the selected band with the
MANUAL SWEEP
FREQ
control. In the
mode, you can change the
sweep colors and overlay up to five manual
sweep results in the different colors. This
permits you to see the impact of changes as
you adjust your antenna system.
at the lowest SWR point. Figure 3 shows
the full-band SWR sweep of the matched
43-foot vertical on 80 meters. The displayed frequency of 4.061 MHz is the
upper frequency limit of the sweep.
Conclusion
The CAA-500MarkII is a reasonably
priced HF/VHF/UHF antenna analyzer.
The large cross-needle meter is nice when
making antenna system adjustments.
And although it is small, the color LCD
provides additional SWR and impedance
infor mation, as well as band-sweeping
capa bility. A padded nylon soft case with
shoulder strap and belt loop is available
to protect the instrument during field use.
You can investigate the CAA-500MarkII
further by viewing the manual on the
Comet website.
Figure 3 — Swept response measurement of
an 80 meter vertical.
Manufacturer: NCG Companies, 15036
Sierra Bonita Ln, Chino, CA 91710; tel
800-962-2611, fax 909-393-6136; www.
cometantenna.com.
Notes
1
J. Hallas, W1ZR, “A Look at Four Antenna
Analyzers,” Product Review, QST, March 2012,
pp 46 – 47.
2
W. Silver, NØAX, “Array Solutions AIMuhf Vector
Impedance Analyzer,” Product Review, QST,
Nov 2012, pp 57 – 60.
3
P. Salas AD5X, “160 and 80 Meter Matching
Network for Your 43 Foot Vertical — Part 2,”
QST
, Jan 2010, pp 34 – 35.
See the Digital
Edition of QST for
a video overview
of the
Comet
CAA-500MarkII
antenna analyzer.
My primary antenna is a 43-foot vertical
with a 160/80 meter base matching network.3 Figure 2 shows the 160 meter fixed
frequency cross-needle and digital display
QST® – Devoted entirely to Amateur Radio www.arrl.org Reprinted with permission from September 2016 QST
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