| Write/Read | About Swept IMD | 
| Description | Sets and returns the frequency of the F1 tone. Use with IMD sweep types: 
 | 
| VB Syntax | object.F1Frequency = value | 
| Variable | (Type) - Description | 
| object | A SweptIMD or IMSpectrum Object | 
| value | (Double) F1 tone frequency in Hz. The F1 and F2 tones MUST be within the frequency range of the PNA. | 
| Return Type | Double | 
| Default | .9995 GHz | 
| Examples | imd.F1Frequency = 100e6 'Write | 
| value = imd.F1Frequency 'Read | |
| C++ Syntax | HRESULT get_F1Frequency(double *pVal) | 
| Interface | ISweptIMD IIMSpectrum |