Is a Spectrum Analyzer with an integrated TG a Scalar Network Analyzer? - Page 1
Forum section: electronics / testgear

author: Cicada
author_rank: Regular Contributor
timestamp: October 21, 2015, 09:23:29 am
content: Hi.I am buying new RF equipment before I actually have started doing RF work. Know it is a bit backwards but I need some help.Question1Look at this Hameg HMS-X Spectrum Analyzer with internal tracking generator.http://assets.tequipment.net/assets/1/26/HAMEG_BR_HMS-X_EN.pdfCould this Spectrum Analyzer with an integrated Tracking Generator be used as a Scalar Network Analyzer?Question 2Could this Spectrum Analyzer with internal tracking generator together with the addition of the VSWR Bridge be used as a Vector Network Analyzer? Maybe limited version of a proper Vector Network Aalyzer.http://www.tequipment.net/Hameg/HZ547/http://assets.tequipment.net/assets/1/26/HAMEG_MAN_DE_EN_HZ547.pdfAny comments and help will be appreciated.PS I wonder if the comparable Rigol equipment would be a better bet?

author: Cicada
author_rank: Regular Contributor
timestamp: October 21, 2015, 09:49:59 am
content: I guess page 39 answers question 1 and sort off question 2.http://cp.literature.agilent.com/litweb/pdf/5965-7917E.pdfBut the question remains what will the use of a VSWR unit add to a SA with a TG. Will it add the ability to measure phase or S parameters?

author: VK5RC
author_rank: Unknown
timestamp: October 21, 2015, 10:28:32 am
content: Qn 1 Yes,Qn 2, I think not, the vswr bridge just gives you the return loss or reflected signal, your analyser (the spec analyser) still can't tell you the vector of the return signal, I wouldn't worry. VNAs often don't have the sensitivity of SAs. They also cost an arm and a leg, you need a calibration kit also serious dough! But I still sort of want a VNA!

author: G0HZU
author_rank: Super Contributor
timestamp: October 21, 2015, 01:13:59 pm
content: Just to muddy things a bit, my old Advantest TR4172 spectrum analyser has a built in tracking generator and it can also mimic a VNA if it has the impedance measuring option fitted. This requires an external bridge option (made by Wiltron) and also an internal option to be fitted.However, this impedance option isn't as nice to use as a regular VNA and I wouldn't recommend anyone to buy a TR4172 for its impedance measuring capability. It is a very nice (but very big and heavy) old school spectrum analyser though.

author: Zad
author_rank: Super Contributor
timestamp: October 21, 2015, 02:08:00 pm
content: You would need a second (synchronous) signal generator to discriminate the signal phase. Measuring the reflected signal at each port would give you the scalar response., being able to analyse the phase would produce a vector analysis.

author: G0HZU
author_rank: Super Contributor
timestamp: October 21, 2015, 02:53:22 pm
content: Quote from: Zad on October 21, 2015, 02:08:00 pmYup, that's the party trick the TR4172 spectrum analyser can do. With an external bridge it can use the measured level and phase data to calculate impedance.

author: hendorog
author_rank: Super Contributor
timestamp: October 21, 2015, 06:28:22 pm
content: The Signalhound spectrum analysers (SA44/SA124 + TG) can measure phase, but at a single frequency only - i.e. you calibrate it at one frequency and then it can display a smith chart showing magnitude and phase of the reflection at that frequency.The phase of the internal PLL's is not maintained by the Signalhound devices when they switch frequencies - which means the calibration is invalidated every time the frequency is changed. Thats why it only works at one frequency.

author: G0HZU
author_rank: Super Contributor
timestamp: October 21, 2015, 06:46:19 pm
content: The TR4172 isn't as limited in this respect as the Signalhound because it can measure and plot impedance (or phase or group delay) across a normal frequency sweep once calibrated.However, I have to repeat that I don't recommend buying a TR4172 for making measurements like this. It really is a chore to set up the calibration and it isn't going to give measurement accuracy in the same class as a decent VNA.

author: hendorog
author_rank: Super Contributor
timestamp: October 21, 2015, 08:26:39 pm
content: Quote from: G0HZU on October 21, 2015, 06:46:19 pmWhich also applies to the SH. It's just a little side benefit which results from the SDR architecture.@Cicada: Signalhound make great little devices and very reasonably priced for the bandwidth and performance. The support is excellent and they have been releasing significant software updates for all of their devices. (even the older models).As a novice I think you will get better bang for buck from SH compared to Rigol or Hameg in this space - if you don't mind the USB form factor.

author: Performa01
author_rank: Super Contributor
timestamp: October 22, 2015, 08:11:35 am
content: Quote from: hendorog on October 21, 2015, 08:26:39 pmBut I understand the SH don't have a TG option at all - or am I wrong with that?

author: hendorog
author_rank: Super Contributor
timestamp: October 22, 2015, 08:20:48 am
content: Yep they do - the Tracking Generator is a separate device which looks the same as the Spectrum Analyser.Check their website and it will make sense, they have combo deals for the parts you need for an SNA.https://signalhound.com/product-combos/scalar-network-analyzer-products/

author: Performa01
author_rank: Super Contributor
timestamp: October 22, 2015, 10:41:25 am
content: Quote from: hendorog on October 22, 2015, 08:20:48 amLooks tempting indeed, and at a first glance much more attractive than e.g. the Rigol offerings like the rather pricey DSA832-TG.Frequency coverage and DANL at low frequencies appear to be clearly superior, but on the other hand the data sheet isn't very comprehensive and a lot of specs are just missing. So it's hard to decide how good the SH actually is in practical use...

author: hendorog
author_rank: Super Contributor
timestamp: October 22, 2015, 07:58:44 pm
content: Quote from: Performa01 on October 22, 2015, 10:41:25 amYes that was what I found too. However there is some good info on their forums and facebook page should help on the practical use side.Shahriar has done some vids covering the BB60C - e.g.They have always been very responsive and helpful when contacted so perhaps just ask your questions direct to them.One plus with SH compared to Rigol et-al is that you can talk to the guys who actually designed the thing.I have the SA124B and the TG124 combo, let me know if you want any specific info.