Skip to first unread message
NZ0I
Mar 8, 2018, 8:05:06 PM3/8/18
to Receiver Development Platform
The new scheme for generating AM modulation in the 2m transmit section of the dual-band transmitter seems to be working. In the O-scope screenshot below, the audio modulation signal (300 Hz) is shown in green, and the envelope of the 145 MHz signal being modulated is shown in purple. The modulation is happening in a very straightforward manner: the attenuation of a voltage-controlled attenuator is being set by a 300 Hz sine wave, while a 145 MHz signal from the Si5351 oscillator is passing through it. This AM signal is only about 0.9V p-p. Currently is is being overmodulated a bit, but that shouldn't be very difficult to correct.
The next step is to see if the weak AM signal can be amplified to > 1W output without introducing too much distortion.
Reply all
Reply to author
Forward
0 new messages