"Generic" Spectrum Analyzer tutorial, demo old Tek 1401A - Video

[w2aew]

I recently picked up an old Tektronix 1401A Spectrum Analyzer Module from the mid 1970s, and it inspired me to to put together this short video to review the basic architecture of a conventional swept Spectrum Analyzer.  I hope you all find it helpful.


73,
Alan W2AEW
@AlanAtTek

[codeboy2k]

Wow. Awesome tutorial, well presented. Thanks so much for taking the time to put this together. 

-- Cheers!

[SgtRock]

Dear Alan:

--Great post. I enjoyed it very much. We used to use a version of these, called panoramic receivers. Same output you showed except we would have little markers at the bottom showing where our receivers were tuned. Because the radio frequencies looked like blades of grass on our green scopes, tuning to a signal was called mowing the grass. You would just move your little marker to the spike, and viola you could hear the signal. Radio stations and other constant sources would be there all the time. What interested us were the "Push To Talk" spikes. And what was most interesting of course was "Complex Working" where signal A would come up for a few seconds then signal B would come up for a few seconds followed by signal A...and Bobs you uncle. I would venture to say that, even with encipherment and frequency hopping, these things are still proving useful in many cases, to the FCC and probably to some other folks, whom I will not mention here.

"Marconi invented the radio but he had to wait years and years till anything decent was on." Johnny Carson

Best Regards
Clear Ether

[w2aew]

--Great post. I enjoyed it very much. We used to use a version of these, called panoramic receivers. Same output you showed except we would have little markers at the bottom showing where our receivers were tuned. Because the radio frequencies looked like blades of grass on our green scopes, tuning to a signal was called mowing the grass. You would just move your little marker to the spike, and viola you could hear the signal. Radio stations and other constant sources would be there all the time. What interested us were the "Push To Talk" spikes. And what was most interesting of course was "Complex Working" where signal A would come up for a few seconds then signal B would come up for a few seconds followed by signal A...and Bobs you uncle. I would venture to say that, even with encipherment and frequency hopping, these things are still proving useful in many cases, to the FCC and probably to some other folks, whom I will not mention here.

Thanks for the nice comments.  You'll probably like the "search marker" functionality of this 1401A as shown in this short video:


The panoramic receiver is interesting.  This type of swept analyzer would be useful to sweep the band for the "grass".  Then, if you move the marker to the blade of interest, you can adjust the SPAN to zero and AM demodulate.  I don't know if there was a FM demodulate option for this analyzer - I'd have to look that up!

Some of today's modern real-time spectrum analyzers can also give you the functionality of the panoramic receiver.  With these units, you can continually "stare" at up to 110MHz of real-time "live" spectrum, and place markers on signals of interest, and listen to any one that you choose.  Hmm, I might have to make a short video about that too...

Alan

[Mechatrommer]

thanx alan for that educational video.