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Rohde & Schwarz CMU200

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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:

--- Quote from: richnormand on November 02, 2016, 09:09:02 pm ---"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.

--- End quote ---


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

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