Re: Could the iPhone become an Ultralight ?

Graeme Zimmer <gzimmer@...>

ferrite61 wrote:

OK, thanks Graeme. Seems to be nothing more than an audio processor/amp. Or does it actually have IF filtering?
The next step in the evolution of radio technology involves "Direct Conversion" (or "Phasing") type receivers and transmitters.

Single Signal Direct Conversion rigs have been around forever, but until recently have not been entirely practical due to the difficulty of constructing accurate Quadrature Oscillators and 90 deg audio phase shifters.

DDS oscillators and Digital Audio processors has completely changed all that and so we are seeing a revolution in radio design under the name "Software Radio".

The first step was to use a PC to do the audio processing, but increasingly we are seeing small stand-alone processors which can do the work. Using an iPhone is a brilliant step in that direction.

Most of the modern cellular phones use this "Direct Conversion" technology, as does the little Si4734 "SDR-on-a-chip" IC which makes your UltraLight class possible. The Superhet is now dead and buried.

So the question "does it actually have IF filtering?" is pretty much meaningless, as the technology avoids the use of IF filtering entirely.

It does all the bandpass processing at Audio frequencies.

......... Zim

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