From Stu, K6TU
As with any technological change, there are many myths, past truths or part
truths that get repeated endlessly and out of context by those frightened or
challenged by the change.
Software defined radios are no exception to this in the world of Ham Radio.
Steve Hicks, N5AC and the VP of Engineering at FlexRadio has posted an
excellent explanation and bust of the ADC overload myth on the FlexRadio
community. You don’t need to be registered on the community to read this
excellent write up:>>>>>>
Regardless of the fact they cannot possibly overload, they overload here.
I don't understand his explanation at all.
We had ONE transmitter on while trying to receive. The ADC could not handle
the level of one transmitter. Because there was no in-band front end
selectivity, the spacing did not matter. We could not get the strong local
signal outside a roofing filter.
With two transmitters on different non-synchronized frequencies, there will
be periods of time when the voltages add. There will be periods when the
voltages subtract. Anything following the summing point has to handle the
random peaks, even an ADC.
The Flex we tried here, using it to listen while ONE transmitter was
running, just went nuts. It was equally bad no matter what the spacing. At
least with a radio with roofing filter, we could move the radio up or down
band and use it.
73 Tom
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