Want to buy my first spectrum analyzer, question about tracking generator. - Page 1
Forum section: electronics / general

author: ErnieEngineer
author_rank: Contributor
timestamp: May 25, 2012, 04:04:13 am
content: I posted a while ago about how i was going to buy an Agilent scope, but I never followed through. It was kinda expensive ;-)Anyway I am thinking about buying a spectrum analizer. A model such as the HP 8594E seems to be the top of my price range. I would like to spend $3500 tops. Of course less would be better. I really want a model with a tracking generator so I can test cables and do basic network analysis. My big questions is... can I just use an external synthesized signal source if i don't have a tracking generator? I would probably get an HP 8657B. Can I accomplish the same thing as with a tracking generator? Also could I use the tracking generator as a general purpose signal source?Any suggestions woud be appreciated. I would like recommendations as to which models would suit me, and the prices they go for.I do some basic amateur radio radio stuff, and also mess around plenty with analog and digital electronics. I would really like a model that goes to 2 GHz. Thanks!

author: w2aew
author_rank: Super Contributor
timestamp: May 25, 2012, 04:42:56 am
content: A tracking generator is a really nice thing to have - I wish I had one myself!In general, a synthesized signal source can not be used as a tracking generator. The idea with the tracking generator is that it provides an output whose frequency follows the sweep settings on the spectrum analyzer - such that it's output is centered in the RBW as it is swept across the selected span. It is generally not practical to try to synchronize the sweep of an ordinary synthesizer with the sweep of a spectrum analyzer. The combo of a SA and a TG are great for sweeping filters, etc.A good synthesized signal generator is also a very nice thing to have. Given the choice of a good sig-gen, or a TG, I'd opt for the signal generator (but just barely!). I would think that if you have a TG, and you put the SA into zero-span, then you basically have a CW signal generator. However, this will not give you AM/FM modulation on the RF output, which is typically available on a decent signal generator. I've found the flexibility of a good signal generator more valuable than having a TG. Of course, I'll definitely pick up a SA+TG if I can find a decent one at a good price.

author: free_electron
author_rank: Super Contributor
timestamp: May 25, 2012, 05:14:41 am
content: No tracking generator is no network analysis. And you cant use an external generator. The network analyser needs control of the generator to do the sweep.If you want a good rf generator keep your eyes peeled for a 8656a or b. or even a 8657a b c or d.Those go cheap and have wide bandwidth and do am fm and others.A d can even do i/q modulation. Some go for around 200$.. I got mine for 50 ( had problems , blown transformer due to short in wiring harness... Some moron tried fixing it and ran a screw through the wirirng harness... Found a transformer for 25$ on ebay.. Works like a charm!

author: ErnieEngineer
author_rank: Contributor
timestamp: May 25, 2012, 05:51:58 pm
content: awesome! Great advice. I really want to do basic network analysis so I will make sure to get the tracking generator. Which models do you guys recommend? I am still interested in the HP 8594E. Is it worth the price premium over a new Rigol DSA815-TG (only $1500). Recommend any other models?

author: vk6zgo
author_rank: Super Contributor
timestamp: May 27, 2012, 04:41:25 am
content: One downside of the tracking generator on some Spectrum Analysers is that you can't separate the TG function from the SA.In other words,theonlyway to have an unswept TG output is to set the SA to "zero span".This means you can't use the TG as a normal CW Sig gen & have your Spec Analyser available as well.You can use an RF sweeper,a detector,& an Oscilloscope to examine the passband of networks in a similar way to the SA/TG method.In fact,that was the way just about everybody did it,back in the day!.This procedure is relatively insensitive to any other signals within the band of interest,(sometimes this is an advantage,as when looking at antenna impedance!),whereas the SA retains its normal capability to see other ,maybe important,signal components.

author: dfnr2
author_rank: Regular Contributor
timestamp: July 27, 2012, 10:34:56 pm
content: Quote from: ErnieEngineer on May 25, 2012, 05:51:58 pmI don't have experience with the Rigol, but it looks really nice on paper, and in the reviews I've seen. Try to get one for evaluation. I have an 8594E with the high-performance options and TG, so I can comment on it--it's a great piece of gear, but it will take up space. I keep it on a tek model 200 cart, and wheel in out of the way when not in use. The 859xE analyzers at baseline don't match the specs of the 856x analyzers, but are much more affordable, and if fully optioned out, are still quite nice.My suggestion: If the Rigol specs are good enough for you (they should be), and the bandwidth covers your needs, go for the Rigol, if the bandwidth covers your range. No dealing with Ebay, bad packaging, finding manuals, setting up HPIB, etc. It will be new, have a warranty, and LCD screen, USB and ethernet/LXI interfaces, and will take up little space on the bench.

author: olsenn
author_rank: Frequent Contributor
timestamp: July 27, 2012, 11:35:13 pm
content: I have the DSA815-TG and I am very happy with it. The tracking generator is a VERY useful feature if you want to measure the frequency responce of filters, etc, so don't cheap out and get the one without it! Keep in mind that the TG starts at 1MHz, not 9KHz which is the lowest frequency (specified) that this unit covers.Some key features about the Rigol DSA are:* 9KHz - 1.5GHz Bandwidth* Built-in preamplifier (often overlooked, but very useful)* 1Hz resolution frequency counter* AM/FM demodulation (not the greatest, but apparently this has been made better with a new firmware update?)* Small, light-weight, and well builtOne thing I don't like about this particular unit is its low input threshold of 20dbm. I highly recommend you purchase a good 30db attenuator and leave it perminantly attached, because if you don't, you can easily damage this sucker. Most SA's are rated to 30dbm which is much more forgiving, but still easy to overpower. On the plus side, it IS AC coupled, so you can have up to 50V DC without it causing too much trouble.Another thing that pisses me off, is that all the advanced measurements are disabled by default and cost an extra $600 if you want them; I probably would never use them, but still. There's also an optional VSWR software add-on that will cost you about the same if you want it.

author: vk6zgo
author_rank: Super Contributor
timestamp: July 28, 2012, 01:04:25 am
content: Quote from: olsenn on July 27, 2012, 11:35:13 pmBuy or make, a cheapo directional coupler,combine this with an old scientific calculator,pencil & paper,& you can do all the SWR stuff you need!