I hv following problem with my 8970B.
In the frequency range 97~102 Mhz the equipment is showing more noise.
First i set the frequency from 78Mhz to 118Mhz in the step size of 2 mhz.
Than i connect the test cable from noise source 346B to input of 8970B.
Then i press the calibrate button twice. Then i press the noise figure & gain button. I tested the DUT under this conditions. It was not showing proper gain & noise figure, Hence sent the equipment to HP service station at Banglore.
I got the info from service station that the RF connector is defective so there is some clip around 800 Mhz. After changing connector, calibration will be required.
I agreed for this in hope of getting the equipment fully perfectly done. I was billed almost US$ 750 for this. This amount is quite high according to Indian standards.
Then i received the equipment. I tested it after few months as there was no development job on my hand. I found that it is showing 10db more gain than shown by vector network analyzer also made by HP.
During the test of just testing cable the noise figure from 78~118 Mhz, for 97mhz to 102 Mhz band noise figure was showing quite high. Even after changing the test cable also we got the same results.
Hence i sent back the equipment to HP. I got the call from agilent about the service problem. I explained it to the agilent engineer.
Yesterday i got the equipment back.
But this time i am getting some new problem.
The gain in the band of 88~108 Mhz is showing ok except 97~102 Mhz. In the 97~102Mhz gain is less & noise figure is quite high during DUT test.
During only test cable test ( without DUT) from 78~118Mhz also the 97~102Mhz noise is quite high. This is just testing passive cable. So unable to understand why it is happening.
Previously the gain was showing 10 db more but this time it showing ok except 97~102 Mhz. This is difference between two service.
kindly let me know, what can be the problem or solution to this problem.
In the frequency range 97~102 Mhz the equipment is showing more noise.
First i set the frequency from 78Mhz to 118Mhz in the step size of 2 mhz.
Than i connect the test cable from noise source 346B to input of 8970B.
Then i press the calibrate button twice. Then i press the noise figure & gain button. I tested the DUT under this conditions. It was not showing proper gain & noise figure, Hence sent the equipment to HP service station at Banglore.
I got the info from service station that the RF connector is defective so there is some clip around 800 Mhz. After changing connector, calibration will be required.
I agreed for this in hope of getting the equipment fully perfectly done. I was billed almost US$ 750 for this. This amount is quite high according to Indian standards.
Then i received the equipment. I tested it after few months as there was no development job on my hand. I found that it is showing 10db more gain than shown by vector network analyzer also made by HP.
During the test of just testing cable the noise figure from 78~118 Mhz, for 97mhz to 102 Mhz band noise figure was showing quite high. Even after changing the test cable also we got the same results.
Hence i sent back the equipment to HP. I got the call from agilent about the service problem. I explained it to the agilent engineer.
Yesterday i got the equipment back.
But this time i am getting some new problem.
The gain in the band of 88~108 Mhz is showing ok except 97~102 Mhz. In the 97~102Mhz gain is less & noise figure is quite high during DUT test.
During only test cable test ( without DUT) from 78~118Mhz also the 97~102Mhz noise is quite high. This is just testing passive cable. So unable to understand why it is happening.
Previously the gain was showing 10 db more but this time it showing ok except 97~102 Mhz. This is difference between two service.
kindly let me know, what can be the problem or solution to this problem.
Can you check the "uncorrected noise figure" at these frequencies?
Just connect the 346 noise source output directly to the 8970B input.
Press the UNCORRECTED noise figure key.
Check the noise figure, and compare the good frequencies to the bad frequencies.
This test will check the noise figure of the 8970B input. Its a good functional test. A typical 8970B will have a noise figure of 4 to 5dB around 100MHz. If the noise figure suddenly increases at some frequencies, this indicates a problem. This could cause your symptom.
The problem may be caused by:
A bad adapter (dirty connectors, poor frequency response, etc)
An incorrect ENR table loaded into the 8970B.
A bad noise source (again, poor frequency response).
A bad 8970B...
If this test looks good, then I would suspect bad cables or adapters in your measurement setup. Noise figure measurements use extremely low power levels - this means inaccurate results can easily be caused by interfering signals (mobile phones, nearby test equipment, etc).
It is also possible that the 8970B has some special function enabled that is causing confusion. It is possible to rest all special functions in the 8970B by pressing "0.9 SPECIAL". This will clear ALL settings back to "normal" - the green "PRESET" key does not reset all functions, only 0.9SP can do this.
good-luck!