Topband: Preliminary report on new AEA VIA Bravo analyzer

[John Kaufmann]

Tom Rauch wrote:

> I wonder if the AEA VIA uses selective detectors (receivers), instead of
> broadband detectors.

<snip>

> If they didn't use selective detectors, how did they reduce BCI?? 


The user manual for the VIA Bravo doesn't shed any light on whether the detectors are frequency selective or broadband.  The fact that the manual does mention the possiblity for RFI in discussing uses for the built-in spectrum analzyer seems to indicate the detectors are not selective.

I just thought of a test I can perform as a check on interference immunity.  I'll connect the analyzer directly to the output of my RF signal generator.  The analzyer should try to measure the output impedance (50 ohm nominal) of the generator.  Then I'll crank up the generator output level until I see some signs of disturbance in the analzyer reading.  I believe my generator can put out up to 0 dBm or so.  I'll do this for various frequency offsets between the analzyer measurement frequency and the RF generator frequency.  I'll report the results next week after the long weekend.

> What is the reactance and impedance range?

The user manual only says it can be used for impedances up to 2000 ohms, but doesn't distinguish between resistance and reactance measurement capability.  I quoted AEA's claimed measurement accuracy specs in my previous post and you'll note that it merely says "for indication only" for impedances greater than 500 ohms.

I'll try to get some more measurements for higher impedance loads.  My General Radio bridge can only measure resistance up to 1000 ohms, but reactances up to several thousand ohms at 1.8 MHz, so it will be of somewhat limited use as a benchmark for comparison.

On the subject of analyzer measurement accuracy, I received an e-mail from W8WWV who has some very interesting analyzer comparison information on his Web site (http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/EvalAnalyzers.htm).  I'm sure he won't mind my publicizing his site.

73, John W1FV