Power output is firmware adjustable via PWM, then filtered and switched to the PA for fast turnaround. This is a low bandwidth path and is not designed for modulation.
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However, you can still do amplitude modulation via the IQ modem, which is the preferred method anyway, provided you reduce the power to a more linear range like 10W.
The UDR56k is not characterized for modulations other than FSK and GMSK.
--- In UniversalDigitalRadio@..., "zl2wrw" <ross@...> wrote:
--- In UniversalDigitalRadio@..., Dean Gibson AE7Q <yahoo@> wrote:
Are these power steps fixed in hardware, or are they soft-adjustable by firmware (eg PWM output from MCU determines DC voltage delivered to TX RF amplifier chain)?
From the PDF file on the web site: TX Output Power @ 13.8VDC: 25, 10, 5 W
If the TX power is adjustable over a wide range by software (ie the above mentioned PWM output), then how much bandwidth does the TX power control circuit have? (how quickly can the TX power output be changed).
If it has sufficient bandwidth, and the radio had the right firmware, would it be feasible to modulate both the phase of the TX RF and it's amplitude in order to achieve polar modulation, which would enable the use of modes like n-PSK, n-QAM, narrowband OFDM, and even SSB...