4170 to 4170 B

[ei3hg]

Apart from the SO239 connector, is it possible to upgrade an older 4170 to 4170 B spec?

[Bob]

Hello,

I'm working on a document that will show the internal changes. This will reduce the measurement noise somewhat by adding a filter to the 3V supply line and also adding the external sync connector for use with accessories.

73/Bob

[w0qe]

I specifically wait to respond until after Bob did. I have modified my AIM4170 a couple of months ago to include the additional filtering that is in the "B" model. I did not add the external sync and did not change the BNC connector.

The changes involve some trace cutting and about 6 SMD parts. If you don't do SMD parts competently the changes might not be worth it and you could end up ruining the 4170.

The results were that there was an improvement in the noise floor when doing a band scan (spectrum analyzer mode) but I could not see any appreciable change when using the 4170 as a network analyzer. I did new calibrations with the modified hardware (which you should do) before making any measurements which may have masked any changes that I might have otherwise seen. The 4170 measurement accuracy as a network analyzer was and still is super.

I'm not sure how needed the sync output is. I personally didn't have a need for it but I would appreciate how others might use it in case I have missed something.

73, Larry, W0QE

[Bob]

Thanks for the feedback, Larry.

The change in performance is not really dramatic. Those who don't want to modify their 4170 should not worry about missing out on much. Those who want somewhat better performance will find the mods are not too hard to make if they have experience working with surface mount parts.

A firmware change is needed in order to use the sync output. By adding a low cost homebrew log amp, you'll have a system for testing filters. Although not nearly as good as a VNA, it will be inexpensive and should be an interesting project for homebrewers. Such a system can display the magnitude of the filter response but not the phase. The new firmware increases the scan rate for the signal output to several sweeps per second, so you get a good scope trace. It also has frequency markers that can be viewed on the scope. This faster output is for the signal source only, the AIM does not read any data at this rate. You can use a scope to view the output of the filter under test. So far, I've been running it straight into my scope for a linear display, which gives a range of about 30 db. By including a log amp, the dynamic range could be probably in the 40 to 60 db range.

73/Bob