An AEA Via Bravo Review

During the year 2003, AEA Wireless began shipping its new Via Bravo vector impedance analyzer. With a list price of approximately $2000 (USD), the unit is several times more expensive than the analyzers compared on another page. It promises greatly improved accuracy, and is still substantially less expensive than laboratory grade impedance analyzers, which can range from several thousand to several tens of thousands of dollars. It is the same size as the AEA CIA-HF, which means that it is highly portable and convenient to use in the field.

At the end of June, 2003, John Kaufmann, W1FV, published a review of his Via Bravo on the Topband Reflector, located at www.contesting.com. This review included measurement comparisons with the CIA-HF, and a General Radio 1606A impedance bridge. His review also included some general use and impression information.

I contacted John, and asked for his permission to reprint his message on this web page. The message should also be available on the reflector, but in case the reflector server ever disappeared, I wanted this information available from a second source, and that's me.

The only change I made was to reformat the review in HTML. I would like to thank John for the information in the review, and permission to reprint it here.

The Review

Recently I posted a request for information on any experience people have had with the new AEA VIA Bravo analyzer (http://www.aea-wireless.com/viabravo.htm). I got no responses, probably because it's still quite new and also quite expensive (about 5x the price of the popular AEA CIA-HF analyzer). Since I do a lot of impedance measurements, I decided to get one for myself.

I didn't realize how new this product is until I discovered I had serial number 17! It also came with a note saying that the PC interface software wasn't ready yet and would be sent to me later. The software package, that allows the instrument to download and plot data on a PC, is one of the strong points of the AEA analyzers.

The popular antenna analyzers from MFJ, AEA, and Autek are all more than adequate for the kinds of SWR measurements most amateurs require. I was more interested, however, in the accuracy of the complex impedance measurement capability of the VIA Bravo. I have an old General Radio 1606-A R-X bridge that has long been a reference standard for antenna measurements. The GR is quite tedious to use, requires an external signal generator and receiver, has no PC interface capability, but, being entirely passive, is immune to RFI overload. Its specified accuracy is very good--generally on the order of 1 percent for resistance and 1 to a few percent for reactance--although the readings come off an analog dial.

To test the complex impedance measurement capability, I connected the VIA Bravo, the GR, and also my CIA-HF analyzer to various loads and compared the readings. Here are the results for some selected loads.

First, I did some measurements on a real antenna:

Antenna @ Frequency	Via Bravo	CIA-HF	GR-1606-A
60 ft vertical @ 1830 kHz	10.5 -j235	51.8 -j222	8.4 -j243.2
60 ft vertical @ 3500 kHz	30.3 -j8.1 3	33.5 +j7.3	31.0 -j9.4
60 ft vertical @ 7000 kHz	45.8 -j194	65.8 -j200.6	46.0 -j201.4

The VIA Bravo showed a small bit of instability on the 160 meter measurement whereas the CIA-HF did not. It's possibly the effect of a local low-power BCB station 3 miles away. The Bravo does have a built-in spectrum analyzer that allows you to determine if there are strong RF signals present that might interfere. The analyzer did show the local BCB station strength at -25 dBm against a background of weaker stations, but that doesn't seem strong enough to present a problem.

Next I connected various discrete component loads to the different instruments and measured them at 1830 kHz:

Component	Via Bravo	CIA-HF	GR-1606-A
50 ohm precision dummy load	49.8 +j0	49.6 +j0	50.5 -j0.5
180 ohm resistor	183 -j4.0	186 +j1.5	188 -j7.7
470 ohm resistor	478 -j45	490.8 +j1.5	490 -j50.8
470 pF 10% cap	3.4 -j170	30.0 -j168.1	0.5 -j180.3
7500 pF 5% cap	0.3 -j7.8	3.34 -j4.85	0.1 -j8.5
100 pF 2% cap	17.0 -j729	588.2 +j519	1.3 -j770.5
large toroid coil	.01 +j280	89.6 +j289.8	0.8 +284.7
air wound coil	0.5 +j27.5	7.04 +j27.7	0.2 +j26.8
small toroid coil	0.4 +j12.3	3.9 +j9.5	0.1 +j10.4
51 ohm in series with air wound coil	53.9 +j28.8	54.8 +j27.1	57.0 +j27.3
270 ohm in series with 470 pF	258 -j186	296 +j130.3	261 -j196.7
18 ohm in series with small toroid	19.1 +j13.6	20.2 +j9.8	19.0 +13.1

The discrete components have up to several inches of wire leads connecting to them, which does influence the measurements a bit.

There's a lot of data here, but you can start to see some trends. The VIA Bravo and the "reference" GR bridge track each other pretty well. The Bravo does tend to overestimate somewhat the resistance component of a load which is primarily reactive, but the CIA-HF is much worse here (for example, in measuring the 100 pF cap). The CIA-HF sometimes gets the sign of the reactance wrong, when the reactance is either very small or very large.

AEA claims the accuracy of the VIA Bravo as follows:

+/-1 ohm at 10 ohm load
+/- 1.5 ohm at 50 ohm load
+/- 4 ohm at 100 ohm load
+/- 35 ohm at 500 ohm load
"for indication only" above 500 ohm load

I'm not sure if these tolerances are for resistance and reactance separately or total impedance, but I suspect it's the latter. There is no accuracy spec given for the CIA-HF, but it's intended primarily to measure load impedances accurately only in the vicinity of 50 ohms, which it appears to do. The VIA Bravo is much more capable at measuring much smaller or large impedances, but it should be for the asking price.

Unlike the CIA-HF, the Bravo has built-in non-volatile memory (24 memory locations to be exact). This allows you to take data in the field, store it, and retrieve it at a later time. That can be very useful.

The LCD display of the VIA Bravo appears to be identical to the CIA-HF, which means it's sometimes hard to read because the characters are small and the contrast is not great, especially in low lighting situations. Also, like the CIA HF, the user keypad interface is not very intuitive, only worse because the Bravo has a lot more features. However, it's not hard to learn. The MFJ259B, on the other hand, could almost be used without reading the manual.

In summary, the Bravo appears to be fine instrument at a premium price. For typical amateur work, however, it's probably hard to justify, considering the cost, and the more inexpensive MFJ, AEA, or Autek units will do just fine. For almost all the measurements I'll be making (except for the most critical ones), I'll be using it in place of my GR bridge.

73, John W1FV

Via Bravo Review, by John Kaufmann, W1FV (June 29, 2003, Topband Reflector)

Introduction

The Review