[AMPS] Total-IMD measurement using the step-attn method

[Rich Measures]

TOTAL-IMD MEASUREMENT:

Equipment List: 
-  Double-filter radio such as a TS-830S, FT-1000, TS-930S, TS-940S, et 
cetera (used as the test receiver).  
-  1db increment, 50-ohm, step-attenuator that covers 0 - 70db.  (H-P 
355A/B, et cetera)
-  Male coax connector with a roughly 15cm wire probe soldered to center 
conductor.  

Test Procedure:
- Connect the radio/amplifier under evaluation to the antenna.  
- Connect the probe to the input of the step-attenuator. 
- Connect the output of the step-attenuator to the test receiver.  
- Tune the test receiver to the transmit frequency of the radio/amplifier 
under evaluation. 
- Say 'ahhhhh', or whatever, into the microphone of the radio/amplifier 
under evaluation.
- Adjust the step attenuator for a reading of S9 on the test receiver.  
Record reading.  
- Tune the test receiver 3.6KHz above the transmit frequency for 
measuring LSB IMD, or tune 3.6KHz below the transmit frequency for 
measuring USB IMD.  
- Sah 'ahhh' and adjust the step-attenuator for a reading of S9.  Record 
reading.  

Total-IMD is the difference between the two readings.  
Rich---



R. L. Measures, 805-386-3734, AG6K   


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