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MFJ-784B center frequency

Solution
The bandpass filter in the MFJ-784B has adjustable center frequency of 300 to 3400 Hz and adjustable bandwidth of 30 to 2100 Hz.  This filter has attenuation of 47 dB at 60 Hz outside the passband.

You can also adjust the lower and upper cutoff frequencies of a bandpass filter.  The lower cutoff is from 200 to 2200 Hz and the upper cutoff is from 1400 to 3400 Hz.  This filter has attenuation of 57 dB at 75 Hz outside the passband.

The maximum current demand will be less than 500 mA at maximum volume but will always be more than 175 mA.

The automatic notch does not work well in eliminating CW since the CW tone is on and off.  However, the MFJ-784B has two manually adjusted notch filters that work great in eliminating CW.  In CW mode the notch is narrower, 45 Hz at -40 dB, and has adjustable notch frequency from 300 to 1000 Hz.  In all other modes the notch is wider, 85 Hz at -40 dB, and has a frequency range of 150 to 3400 Hz.

Regards,

Harry Wong
Project Engineer
MFJ Enterprises, Inc.
Article details
Article ID: 91
Company: MFJ
Date added: 2017-01-12 14:53:48
Views: 15

 
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