[Elecraft] KSYN3A FAQ

[Wayne Burdick]

Another interesting issue regarding the Flex 6xxx series (and radios with a similar direct-digital-sampling RF architecture) is that "A/D Limit" descriptor in the blocking dynamic range column in Sherwood's chart. An ADC limit is a hard one; it does not gracefully soft-limit in the presence of strong signals, like an amplifier stage. Multiple signals in the passband can cause additive peaks that hit this ADC limit sooner, causing ghost signals (IMD) to appear. 3-tone (or higher) testing may be needed to quantify the effect of the ADC limit in DDC receivers. Perhaps "A/D Limit" can then be converted into a useful number.

Wayne
N6KR



On Feb 13, 2015, at 12:07 PM, "Joe Subich, W4TV" <lists at subich.com> wrote:

> 
> On 2015-02-13 2:37 PM, Jim Brown wrote:
>> And in the real world, this is the limiting factor. In my real
>> world, it's an IC7600 with a legal limit amp ten miles away.
> 
> Consider yourself lucky.  In my real world, it's an IC-746 and legal
> limit amp 0.65 miles away!
> 
>> Yes. While I've seen statements (I hate the word "claim" in this kind
>> of sentence, since it implies that the person making the statement is
>> a liar) that the latest Flex series radios are as clean or cleaner,
>> I've not seen ARRL measurements to confirm that.
> 
> No, but one can infer that from the Receiver data published by Sherwood
> on the Flex 6700 (receive LO Noise = 145 dBc/Hz).  Given the design of
> those "radios" the phase noise is generally clock jitter and would be
> reciprocal in transmit.
> 
> 73,
> 
>  ... Joe, W4TV
> 
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