Re: Spectrum Analyzer Question

David Berlind

Dennis, thank you for helping me to frame my inquiry better. Your guidance is always appreciated. As you probably saw by now, I responded with a summary in which I mentioned that as I further my exploration into electronics, I often don't know what I don't know. So far, with all the answers that I've received, I know so much more and have many avenues to explore that I never even considered before. A year from now, I hope to have experimented with an SDR and/or nanoVNA device, the FFT capability on my TDS 480B, and with any luck, a dedicated spectrum analyzer. Even so, I did not want to leave your questions unanswered as I'm sure I will still see some answers come in that further my education.

Q1) First and most important: Explain what you intend to use a spectrum
analyzer for. Include every single thing it will be used for.
A1: I don't know every single thing that I will use it for. When I acquired my first oscilloscope, I thought I knew the one or two use cases that I'd apply it to. But, as I learn more about electronics, I'm glad to have my oscilloscopes to do experiments that I never thought I'd do (just to further my understanding). It will be the same with spectrum analysis. But at the onset, I am interested in observing a carrier, its sidebands, and harmonics and do some experiments with audio signals. If I'm performing an alignment of an old tube radio, I'd like to make pre and post mixer observations. There are bunch of videos that I've watched on YouTube that I'd like to reproduce in my own lab. Sometimes, these videos work off of a fixed configuration of everything in an effort to fix one DUT. But when I watch these videos, I wonder what would happen if some of the variable inputs were changed. I suspect I know the answer in some cases, but I would enjoy seeing this in my own lab.

Q2) What is the most money you can afford to spend for a spectrum analyzer. Be
specific. Do not say a few hundred dollars.
A2. Right now, I'm going to say $500. I say this based on the responses I have received so far and the understanding that spectrum analyzers are just expensive. However, I do not have $500 right now. My plan is to get my feet wet with some other options and save some proceeds from gear that I have here in the lab that I have to fix and sell. I try to keep my hobbies self-funded. So, it may take me a while to get to $500. But at the same time, it looks like I have some other short term options that will help me to develop a much better understanding. But I will continue to keep my eyes peeled for a viable stand alone unit. If I've learned enything from the gear that I've acquired so far, it's that patience pays. Sooner or later, something will come along.

Q3) What brand of Spectrum Analyzers are you considering? Be specific.
A3. If you recall my first question was really about trying to understand the 7000 plug-in option vs. a stand alone unit given that I have a few 7000-series mainframes here. So, while this started as a Tek specific inquiry, the answers here have taught me to be open to other options. I'm still interested in the plug-in approach but have a better understanding of the risks. I learned about the T1401A which looks like an interesting approach if you already own an oscilloscope but am not clear on its compatibility with all scopes or just one family. I like staying with brands that I can find help for. This forum is one reason I have a lot of Tek stuff. I know that I can get help here and in many cases, if I don't ask a question that I need the answer to, someone else will. Like today, I woke up to a thread about first time startup recommendations for a 545A. I am paying very close attention because I have two 547s here and I'll need to go through the same thing at some point. The availability of the HP/Agilent forum means that that looks like a good brand to keep a watch for too.

Q4) What research have you done to to familiarize yourself with the prices and
availability of spectrum analyzers?
A4: Beyond this thread and some local searches of Craigslist and the Facebook marketplace, none.

Q5) Spectrum Analyzers come in many different physical variants. Which do you
want? Please explain why you chose the ones you did.
A5: If the answers to this thread taught me anything, it's that there are a lot of variants I didn't know about. I know so much more than I did before and am a much more educated consumer as a result. I've yet to establish a preference. This is one of those areas where I don't know what I don't know. For example, when I acquired my first oscilloscope (a Tek 466), I didn't know that oscilloscopes came in 2 and 4 channel versions or why I might need 4 vs 2 channels. Nor did I know there were modular mainframes. Thanks to a member here, I acquired my first mainframe with four channels and was able to simultaneously observe the multiple 90 degree phase shifts of the A/C signal that traverses a guitar amplifier's tremolo circuit. When I first started fixing guitar amps, I didn't even know what phase shift was, much less why a four channel oscilloscope would help me to observe it better than a two channel one.

* A spectrum analyzer plugin. If so what scope does will it plug into?
If I get a plug-in, more than likely a 7603. I also have a 7633 here but it's in my service queue and will be a while before it's ready.

* A portable spectrum analyzer
Maybe. I'd like to keep an open mind.

* A PC based spectrum analyzer, if so, how fast is the PC it will be connected
I own a MacBook Pro. 2.8 Ghz. 16 GB RAM

* A stand alone spectrum analyzer?
Yes, of course I'd be interested in this option.

Again Dennis, thank you for your guidance on this issue. I know some answers were not as specific as they could have been. But I am learning thanks to everyone here and as I learn more, and do more, my desires are sure to clarify themselves.


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