Seems to me the devil is in the details. Obviously, if you pump enough
RF power into the input of any SDR (e.g., 100W), eventually it is
going to collapse. If the ADC can handle a few volts, that should make
it pretty immune to any but the most extreme environments. I've not
noticed any overload with my Flex-6300, but I've never used it in
multi-multi-contest situations. I definitely prefer it to my K3 or
FTDX-5K on top band, because signals just seem cleaner with a quieter
background. Haven't tried any quantitative measurements, but I don't
think that's my imagination. (The sales guy at Flex told me the 6000
series radios are significantly better than the earlier 5000 series in
this regard.)
73,
Jim W8ZR
Sent from my iPhone
> On Oct 6, 2015, at 4:29 PM, Tom W8JI <w8ji@w8ji.com> wrote:
>
>
> 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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