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| JDSU J745A spectrum analyser / VNA repair & mini review |
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| nctnico:
For the money Owon is asking I'd look somewhere else. Owon does not have a good reputation where it comes to firmware. Also, a spectrum analyser + tracking generator is of limited use for measuring RF devices. If you go on Ebay you'll notice that only a few spectrum analysers for sale have a tracking generator. That is because a network analyser is the tool of choice for measuring RF devices because it can also measure phase (which then allows to plot things like a Smit chart). The J745A has limited VNA functionality. It can do a Smith chart but it does not have a way to measure inductance / capacitance and the VNA (vector) and scalar measurements start at 5MHz. It does have a suite with mobile testing features so if you are into that, it can do a lot of analysis (including time synchronisation of cell towers). On top of that the J745A also has a good spectrum analyser module inside. All in all it is a nice instrument even though the software can be a bit quirky at times. If you want to have more/better VNA style features, you should take a look at the LibreVNA device which is priced in the 800 euro ball-park. I'd skip the NanoVNA. I have one myself but it is too cumbersome to use and there are so many different (bad) versions out there that it is very difficult to find the right one and the dynamic range is also very limited. |
| ferorted:
Thank you very much for your reply. For my usual measurements Spectrum Analyzer + Tracking Generator (SA+TG) is enough. That's why I was asking about J745A as SA+TG. I don't really need all the features of a VNA, although it would be nice to have them, but only if it doesn't complicate my main measurements (SA+TG). How do you think about the J745A as a spectrum analyzer + tracking generator? it' has a simple way of use? or better, I look for a standard SA+TG. I am also going to look at the LibreVNA . |
| nctnico:
I have been trying to get the remote control going a bit. Unfortunately I have not been able to find a remote programming reference for the J745A but I have been using these documents from a newer device as inspiration: https://celladvisor.updatemyunit.net/archives/CAA06M_CAA_Programming_Guide_R1.0.pdf https://celladvisor.updatemyunit.net/archives/CellAdvisor5G_Programming_Guide_R8.1.pdf With some trial & error I have found the commands below to work when connected using telnet to port 66 or by using PyVisa: JDSU SCPI commands Telnet port 66 #RBW setting SPEC:RBW 100 kHz #Spectrum analyser frequency settings SPEC:FREQ:STAR 150 kHz SPEC:FREQ:STOP 200 MHz #set attenuator SPEC:AMPL:ATTE? SPEC:AMPL:ATTE 0 dB #select trace SPEC:TRAC:SEL? SPEC:TRAC:SEL T2 SPEC:TRAC:SEL T1 #get sweep time (in milli-seconds) SPEC:SWEEP:TIME? #trace mode (capture, write, max hold, min hold, view on/off SPEC:TRAC:CAP SPEC:TRAC:CLE SPEC:TRAC:MAX SPEC:TRAC:MIN SPEC:TRAC:VIEW? SPEC:TRAC:VIEW OFF SPEC:TRAC:VIEW ON #Set averages SPEC:AVG? SPEC:AVG 5 #set trace detector SPEC:TRAC:DET RMS #read trace data (appears to be always in dBm regardless of screen unit) SPEC:TRAC:DATA? #Reference level SPEC:AMPL:REF? SPEC:AMPL:REF -30 #Set units SPEC:AMPL:UNIT? SPEC:AMPL:UNIT dBuV SPEC:AMPL:UNIT dBm #set scale (units per div) SPEC:AMPL:DIV 20 SPEC:AMPL:DIV 5 ####Cable analyser #frequency start / stop CAA:FREQ:STAR 10 MHz CAA:FREQ:STAR 5 MHz #CAA trace (counts from 0 to 5) CAA:TRAC:SEL 0 CAA:TRAC:CAP CAA:TRAC:CLE 0 CAA:TRAC:VIEW 1 CAA:TRAC:VIEW 0 #Get data CAA:TRAC:DATA? For now I know enough to use it remotely for spectrum analysis tasks. I still would like to be able to switch the J745A between various modes (or at least set it to spectrum analyser mode). At this point the best way forward would be to install the remote control software and see which commands are exchanged between the devices. I have attached a text file with what seems to be all the SCPI tokens that de J745A can use. These tokens appear to be different at some places compared to the documents I linked to above. |
| ag4zp:
Did you need to change any settings to enable SCPI commands on port 66? My GC747A allows me to connect to port 66 but does not respond to any commands (e.g., even basic ones like *IDN?). Also, tangentially related, have you heard of any efforts to reverse engineer the trace file format? I would love to be able to retrieve S-parameters with these units. |
| Tiberius1:
Hi Did you fix the intermittent spec analyzer input issue using the reflow method? I have the same issue when touching that area the input will fail or high attenuation. Looking at reflow as a possible fis Thanks in advance |
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