The Spectrum Analyzer is by far the most important piece of gear for any RF design work, unfortunately spectrum analyzers are also one of the most costly pieces of gear you can buy (A VNA is right up there too, but that's a different post). I have had access to spectrum analyzers at a few previous jobs which is great whenever you need to test your latest RF design. The problem is when you are at home working at your own bench at 2am, it's annoying to not be able to have access to this gear all of the time. Buying an analyzer is ideal, but costly. Anything new is pretty much out of the question, so the usual source of eBay is the place to go. Both Tektronix and HP/Agilent have some amazing pieces of gear for an 'affordable' amount (the Tek 49N series and HP 85NN series come to mind), the problem is any of these models can easily cost over $1000 in good working condition. The other issue with this equipment (like all older gear) is their age. Since most were used in a production or lab environment, they have been powered on for 8 hours a day for years. This can result in some crt burn in, the devices being way out of calibration, instabilities and other problems as most of the equipment in this class is 15+ years old (note that makes it affordable). I have had a good run with all my HP / Tek gear as this equipment is really built extremely well. As an example, my HP8614A signal generator was built in the 1960s and still works perfect today. So what happens if you want a spectrum analyzer but don't want to spend $1000+? As I found, there are a few options:
1. Buy a really old analyzer. Some of the older HP models will go for under $500. Keep in mind that these models usually have a max frequency range of no more than a few hundred Mhz.
2. Buy a lesser known brand. There are a handful of analyzers by Chinese companies that go for cheap. They may be perfectly fine, I just prefer to go with a good established brand if I'm going to invest in one.
3. Watch local auctions. There are a ton of company liquidation auction houses such as Dovebid that sell off large companies test equipment assets. These are great places to pick up gear. The issue with this is that there is no guarantee that the gear works (no one tests it) and if it is a valuable piece it will most likely get bid up pretty high. Packing and shipping can cost hundreds of dollars as well if you are not able to pick up the gear locally.
4. My favorite option. Buy gear whose primary purpose is not a spectrum analyzer, but has an analyzer hiding inside it. A lot of communication analyzers and cell phone test sets have an available spectrum analyzer option. I will look up unusual gear on eBay that seems to be selling for cheap and read the product literature on them. You will be surprised on what you will find. I have purchased both of my spectrum analyzers this way.
My first spectrum analyzer that I bought a few years ago is an HP8922H GSM test set. It is designed to replicate a GSM cell station to test GSM cell phones. It also has a bunch of options included one of which is option 006, a 10Mhz to 1Ghz spectrum Analyzer. You can find these for around $500 or less. Now 1Ghz is great, but you eventually reach the limits of what you can do with it. One of my current projects is building a hydrogen line radio telescope which at 1420Mhz is outside of my analyzers reach. I needed something to at least 2Ghz at this point to test my down converter so I began my search again.
While recently looking at more gear that was available I came across an Anritsu MT8801C radio communication analyzer. Not being familiar with Anritsu as most of my gear is HP/ Agilent and Tektronix, I did a bit of research into this particular model and discovered that not only was it an amazing piece of gear, but much like my HP8922H, it has an option for a 300Khz to 3Ghz spectrum analyzer (Option 07):
Being a communications analyzer it has a bunch of other nice features such as a 300Khz to 3Ghz RF frequency generator, and an RF power meter:
Here is a full span of 300Khz to 3Ghz to my outside wideband antenna:
A couple nice things about this analyzer is that it has a large LCD screen, is capable of displaying a full frequency span, it has a resolution of 1Hz, and a very fast interface. I checked its calibrated accuracy with my HP 8656B RF generator and it was spot on which made me very happy as well:
The additional 3dBm loss above is from the mini-circuits splitter I was using between the generator and analyzer.
Included with this unit was a nice shielded RF test chamber for no extra cost. I can only guess what this had cost new:
It will be a great tool for testing devices within a completely shielded environment from external interference.