Rohde & Schwarz CMU200

[oh2ftu]

I did some tests last evening, mostly read through the Motorola professional series global tuner and tried out most of the alignment procedures.
In short, it's a PITA.
I recall seeing the power meter in AMPS showing power in watts, I'll have to figure this out (or just use a conversion).
Inserting rf input frequencies under amps really sucks. They must be input as Hz OR decimal MHz + offset in Hz.
If there's any chance in modifying the offset to 25kHz instead of 30kHz it would be superb.
On rx testing (AMPS RF gen) there's no option to enter discrete frequency - it has to be done with decimal MHz + offset in Hz.
I am opting to use both devices to get around the AMPS frequency input restrictions.
There are a dozen frequencies that need to be inputted in both RX and TX tests - for ~20 devices. So I will have to streamline it "a bit".

A note about the powermeter/frequency counter in normal power meter mode: The analyzer frequency and RBW must coincide with the signal for it to work.

I'm going to crossreference my devices when I get the GSPDO running; one has B11 and the other B12 so I hope they would be near each other.

[msraya]

Thank You!

I suppose that K29 not worth it. Only important for me is to adjust deviation on FM transmiter..
K29 have this measurement?

Another option is use a demodulator with a MC3361 and calibrate it in mV RMS with another modulation meter...

Manuel

[oh2ftu]

I suppose that K29 not worth it. Only important for me is to adjust deviation on FM transmiter..
K29 have this measurement?

K29 does show deviation; It is able to inject af signal at given freq to the DUT and analyze the received RF signal (power, deviation, freq error etc)

[msraya]

Interesting...

Now, only I have to find how to activate this option 

Manuel

[danielg]

Danielg:

The generator and power meter both work at the same time in the MSDOS native app.
It is a basic functionality of the equipment, so you not need any special option for it to work.

The program FreRes will use both generator and power meter as same CMU200 unit at the same gpib address..

Manuel

Hi
Little update, I have been searching for way to tune duplex filters by using CMU200. CMU200 is not offering or not licensed to sweep frequency’s so I have been searching for how to get the RF curve of filter. Last week I got Agilent 82357B that is USB to GPIB converter to connect my CMU200 to FreRes software. The short story is that worked very well and I want to say thank you for your help. I will attach pictures to give you and others an idea how gui looks.

Pic1 shows Rf cable looped from Generator to Analyzer
Pic2 shows duplexer. Red line is Duplexer Low input to antenna and black is Duplexer High input to antenna. Duplexer are for 158,1 and 162,7 Mhz.
Pic3 shows blue line as reference of -10 dBm output power from CMU200 in all tests. Black and Red lines are the same as in pic2
This test is done in three parts. FreRes allows you to seep multiple (this case three times) and draw pictures in different colors to compare.

I was wondering if anyone knows or have tested how to measure Reverse power and Forward power by using CMU200.
I’m trying to measure SWR of power going to duplex filter and back to CMU as part of figuring out if duplex tuning is ok.
At the moment I only know how to see power from generator and read it in analyser and I don't know if Reverse power measurement is possible - I the answere out there?   

Thanks
Daniel

[richnormand]

"At the moment I only know how to see power from generator and read it in analyser and I don't know if Reverse power measurement is possible - I the answere out there?"



Not sure exactly what your setup is but here goes.

I use a directional coupler with a -20dB tap to get the forward and, in a second sweep with the tap in the other direction, get the reflection measurement.
Generator (Tx) goes on one end and the load on the other (with proper matching if the load has an output of its own). The SA goes on the -20dB tap.
Then reverse the load and generator so the tap measures the reflected power and redo the sweep.

Works great with my HP SA cant see why it would not work with your CMU200 since you have access to the Tx Rx loop.

[danielg]

"At the moment I only know how to see power from generator and read it in analyser and I don't know if Reverse power measurement is possible - I the answere out there?"



Not sure exactly what your setup is but here goes.

I use a directional coupler with a -20dB tap to get the forward and, in a second sweep with the tap in the other direction, get the reflection measurement.
Generator (Tx) goes on one end and the load on the other (with proper matching if the load has an output of its own). The SA goes on the -20dB tap.
Then reverse the load and generator so the tap measures the reflected power and redo the sweep.

Works great with my HP SA cant see why it would not work with your CMU200 since you have access to the Tx Rx loop.

Hi, thanks for your input.
Do you recommend any type of directional coupler for 153-163 Mhz from ebay or aliexpress, could you point out some types please ??
Is circulator and directional coupler the same thing ?

Using generator that can give max -10 dBm out do you think -20 dBm output might be to much attenuate for such a low power to get realistic measure?

[richnormand]

@danielg,

I have three directional couplers. All three are Narda units, but they were bought from ebay for about $20 to 40 each at various times over the last 10-15 years.  You can find some for several hundred dollars but if you do an ebay search with "directional coupler"  many will show up at much lower prices, in particular if the paint is peeling or they have a few dents. Considering there are no moving parts and stout they are pretty rugged.

You can also find couplers with both forward and reflected taps on the same units. They seem to be more difficult to find though.

I have 0.5 to 2.0 GHz with -6dB tap, two 820 to 960 MHz with -30dB and -20dB taps and 225 to 460 MHz with-10dB tap.

If you are doing ratio measurements they will work quite a ways out of band too if you are careful. With the typical noise floor and dynamic range of the CMU200  (assuming it is working OK) I would not worry too much about a -20dB tap and -10dBm input.

[msraya]

Hi!

I have a MiniCircuits ZFDC-20-5-N N-Type 0.1 to 2000 Mhz ...
It is good to make swr measurements on antennas.

Manuel

[iz4beh]

Hello to all
a brief question about CMU200...
Spectrum analyzer , RF generator and power meter are optional or factory present in this instrument?
Many thanks

[_Wim_]

Hello to all
a brief question about CMU200...
Spectrum analyzer , RF generator and power meter are optional or factory present in this instrument?
Many thanks

As far as I know, these are always present. There can be some diffrences in the type op RF generator, but there is always one present. The following option (hardware) options are available:

B11:   HW-option for CMU200: Reference oscillator OXCO, aging 2 X 10E-7/year
B12:   HW-option for CMU200/300: Reference oscillator OXCO, aging 3.5x10E-8/year
B17:   HW-option for CMU200: IQ/IF interface, analog, one channel
B21:   HW option for CMU200: Universal signalling unit CMU-B21V14 incl. CMUB54
B21/2:   Universal Signalling Unit
B41:   HW-option for CMU200: Audio generator and analyzer
B52:   HW-option for CMU200: Speech codec for CMU-B21/var. 14
B52/2:   Speech Coder f. CMU-B21/2
B53:   HW-option for CMU200: Bluetooth extension for CMU-B21/var. 14
B53/2:   Signalling Module f.Bluetooth
B54:   HW-option for CMU200 signalling module for AMPS, TDMA, GSM for CMUB21/var. 14
B55:   Signalling Module f. €GPRS Applic. Test
B56:   HW-option for CMU200: WCDMA and data E2E for CMU-B21/var. 14
B66:   Versatile base band board
B83:   HW option for CMU200: CDMA2000 Signalling Unit (requires CMU-U65)
B85:   HW-option for CMU200: 8K/8K ENH/13K speech codec for CDMA2000 signalling unit CMU-B83/V12
B89:   HW option for CMU200: 1xEV-DO Signalling Module (requires CMU-B83/V22 and CMU-U65)
B68:   HW-option for CMU200 layer 1-board (3GPP/FDD, DL+UL)
B95:   HW-option for CMU200: Additional RF generator (max. input power 2 W)
B96:   HW-option for CMU200: Additional RF generator, 2 channels for GSM, CDMA, WCDMA

[ZL1CVD]

Where do I get / how to install VISA library. Installed FreRes but no visa library. Contenting to CRTU/CMU via RS232. 

New to SCPI. Got a Lazarus app to talk to my CRTU, reset it, display version. Yet to read data and do something with it. Was hoping I could learn from FreRes - see its commands...

[msraya]

Hi!

I installed VISA library from Keysight IO software because I have some Agilent gear and the library has an application to test the GPIB connection, drivers for the USB <-> GPIB adaptor, etc... The Keysight software can handle also the RS-232 port.

If you communicate via serial port with your CMU200, it does not support multiple addressing and therefore the FreeRes application doesn't work. I think you need a real GPIB connection to use multiple addressing vía gpib32.dll.

The Keysight IO library is heavy, some 120MBytes or more... you can download it from Keysight website.
For the FreeRes app you only need the USB-GPIB drivers and the gpib32.dll in your system.. But Keysight IO assistant is helpful for troubleshooting the connection. And a heavy installation.. 

FreeRes is not very powerful... It is more interesting to program a visual application in phyton that manages the unit via GPIB and can use several instruments at once, this cannot be done from the front panel of the unit, but throuth GPIB you can use the power meter, generator, audio test all units at once..  I have no time to do it... but perhaps someone have time to do it... 

Manuel

[ZL1CVD]

Thanks msraya. I'll skip that for now. Cant really afford more adapters at moment so will use serial for now.

Just managed to read data from CRTU and write to a memo - wahoo! Now to see if I can get the app to send user data from an edit, spin edit, list, etc. Then I'll see if I can populate a tree with the result of system:options?

this is fun ...

[msraya]

Your welcome!

The CMU200 is a great piece of kit. GPIB expand the instrument.

It has a user calibration table that you can edit and send through GPIB. So you can calibrate the equipment with a good meter and keep user calibration in the unit. You can also use several user calibrations to test for example Noise Generator for tracking, Test Antennas, GHz converters, etc.. With some imagination you can use it for several uses..

I am right now working in another endeavour, HI HI.. but I would write software for the instrument if I need it...
Regards

Manuel

[ZL1CVD]

Does anyone know the secondary GPIB address for the 2nd RF channel (RX/TX Board 2) in CRTU-RU?

I want to be able to control the RX/TX Board 2 via SCPI

I know secondary GPIB address's can be changed on the CRTU in Setup>>Remote>>Secondary Address [GPIB] screen. However it only shows 1 RF device.

SYST:REM:ADDR:SEC? only reports 1x RF_NSig.

The CRTU-RU documentation doesn't seem to cover SCPI commands which is not surprising as I suspect its mainly addressed directly via Win2K. when you boot in DOS mode, it basically reverts back to a CMU200. I have a CMU200 & CRTU & can't see any difference between CMU200 & CRTU DOS file systems for SCPI remote control.

[ZL1CVD]

** RF loop path 1 test failed - FIXED **
Was a faulty power supply. This same power supply would also not start up from standby *sometimes*.
At some point, the CMU had been dropped on the, you guessed it, power supply - it was pushed into the case - housing dented. I have seen the same thing with an older K6 CMU (with PS/2 keyboard port). These older units are much more forgiving for case / transit damage as their motherboard does not go completely to the rear of the case like the newer Celeron CMU or Pentium CRTU units. The rear connections are made via ribbon cable to separate rear PCB strip. I was very lucky that there was no PCB damage on this newer Celeron unit.
Now to figure what pins have what voltage and see if I can find the cracked joint...

[richnormand]

** RF loop path 1 test failed - FIXED **

Now to figure what pins have what voltage and see if I can find the cracked joint...

If you are talking about the PSU used in the CMU200 and such look up my thread on CMU200 PSU repair from last year. It has full pinout of the connectors and several diagrams. Hope it helps you.
https://www.eevblog.com/forum/repair/rohde-schwartz-universal-radio-communication-tester-cmu200-psu-issues/

[CJay]

Bear with me, GPIB newby here...

I've managed to get hold of a PCI GPIB card, cabling and have got my CMU200 to talk to FRERES on Win 10, could someone please show me some screenshots of how you configured it to sweep a filter, complete with devices setting and sweep setting as well as the main FRERES screen?

I'm positive it's something simple I just haven't got a grip on yet but I can't work it out.

CMU is set up for SCPI via GPIB only
Primary address 28
Secondary has RF Non Signalling on address 1

Running a sweep seems to work but the data FRERES displays is noise at -86dBm, regardless of how I loop the RF ports on the CMU.

As I said, it's something simple but I just can't see what I'm doing wrong.

[usagi]

what DANL are people seeing with their cmu200?

[ZL1CVD]

..up to -100 - depends on setting, input port, etc...

Same for both CMU-RTU and CMU-200

[ZL1CVD]

Better than -130 with span less than 1MHz & RBW 500Hz or less..

[NavyBOFH]

I have seen the posts about the eBay link for the tracking generator add-on someone created - but has anyone given some real use and performance on it? I would like to know if it comes close to the other service monitors and spectrum analyzers I have used.


Sent from my iPhone using Tapatalk

[Brainbox]

I own one and for me it does what I expect from it.
But how by heaven can I tell You if its meets the specs of Your other service monitors?

[richnormand]

I have seen those, and opted for a different option that does not require opening up the modules and the CMU200.

I got one of the $25 eBay noise source from 1MHz to 3.5GHz. They are not all that flat but are handy for quick measurements. For example here are pics of my HP8561E with it's tracking generator HP84640A looking at the response of a lithium niobate SAW device. The other picture is the CMU200 using the noise source with the same device (but... do note the different dB/div and span between the two photos).

Quick and dirty but it works. All depends of what you want.