EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: cncjerry on December 09, 2018, 09:41:21 pm
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I picked up this beautiful HP 8350 sweep generator with an 83525A plug-in for $150 as mentioned in the "score" thread. The 83525a plug-in is a combo of an 83522a (.01 to 2.4Ghz) and the 83540a (2.0 to 8.4Ghz) . I am posting the block diagram. A couple of people have made tracking generators for the low band of 0 to 2.5Ghz using the 83522a. This worked out because the IF output of the 8566b worked by replacing the YIG tuned oscillator and then a second oscillator was mixed a little differently and produced the needed TG signal.
I don't need the low band as I have an 8568B with TG as well as my Advantest r3131a with one as well. What I would like to do is somehow use the 2.0 - 8.0Ghz side of the plug-in to cover the 8566b 2nd band from 2.0 to 5.8Ghz. I can't remember the 8566 IF for that band but I think it is in the 321Mhz range.
Anyway, is this possible? Otherwise I can just use the sweep with the SA in max hold mode.
Thanks
Jerry
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Some possible resources:
http://www.kerrywong.com/2016/01/10/building-a-tracking-generator/ (http://www.kerrywong.com/2016/01/10/building-a-tracking-generator/)
https://www.youtube.com/watch?v=e0JF3t8BJe8 (https://www.youtube.com/watch?v=e0JF3t8BJe8)
https://www.youtube.com/watch?v=tQDoe9e0s1o (https://www.youtube.com/watch?v=tQDoe9e0s1o)
https://www.eevblog.com/forum/testgear/diy-tg-for-hp8568b/ (https://www.eevblog.com/forum/testgear/diy-tg-for-hp8568b/)
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Rastro, thanks, but yep, been thru all those.
The problem with Kerry's version is the dynamic range. Curiousmarc's version is built on John's version using a different plug-in. That's what I mentioned above with regards to the low band 0-2.5Ghz. I can do that but doesn't buy me anything because I have the original TG for my 8568B which covers that range.
Jerry
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What I would like to do is somehow use the 2.0 - 8.0Ghz side of the plug-in to cover the 8566b 2nd band from 2.0 to 5.8Ghz. I can't remember the 8566 IF for that band but I think it is in the 321Mhz range.
Basically the info at http://www.ke5fx.com/tg8566.html (http://www.ke5fx.com/tg8566.html) and http://www.ke5fx.com/tr503.html (http://www.ke5fx.com/tr503.html) will apply equally to the higher bands, once you've made allowance for the different conversion scheme. In the case of the higher bands on the 8566, the IF is 321.4 MHz.
Unfortunately, because the IF is so low, the only way you can get rid of the unwanted sideband is to either use a tracking filter or a separate YTO in an offset synthesizer scheme. That's why the 85645A was so pricy (see the block diagram on page 177 of https://nscainc.com/wp-content/uploads/pdf/A_85644A.pdf (https://nscainc.com/wp-content/uploads/pdf/A_85644A.pdf) ). Since there's already a YTF in the 8566B, it would be reasonable in most cases to just mix the LO1 output with 321.4 MHz and let the analyzer itself reject the upper mixing product.
As with the lower-band TG, isolation is of paramount importance to avoid baseline lift. Also, if dynamic range is important, you will want to be able to tune the 321.4 MHz offset source at least a few kHz to either side to accommodate variations in the actual IF center frequency at the narrow resolution BW settings.