Direct digital conversion radio receivers rarely connect the A/D "directly" to
the antenna input, the term "direct" referring to a lack of analog frequency
conversion (mixing). The Flex 6000 series is no exception to this trend. There
is a gain and filter stage ahead of the A/D, and presumably an AGC.
This is how dynamic range is managed on this, and many similar receivers.
Blocking is a concern, but not even the greatest concern. Analog signal levels
should, regardless of the number of discrete measurement steps ("bits"), should
be kept well above the minimum input level to avoid excessive quantization
error levels.
Mike Alexander - N8MSA
amsct...@comcast.net ----- Original Message -----
From: "Joe Subich, W4TV" <li...@subich.com>
To: elecraft@mailman.qth.net
Sent: Saturday, May 19, 2012 7:29:24 PM
Subject: Re: [Elecraft] OT: Dayton New Equipment Show
The Flex 6000/6700 is an "on frequency" direct digital conversion
radio - that is a 16 bit analog to digital converter operating at
the "front end" of the radio with no intermediate conversion/IF
and filtering stages. In addition, all of the DSP is contained
in the radio (no more PowerSRD). The new software for the Flex
6000/6700 (reportedly "PowerRX") is essentially a "glass control
panel").
A general purpose computer is required for PowerRX but communication
between the computer and transceiver is via TCP/IP which means the
computer can be anywhere. Audio input and output will be available
both on the transceiver and from PowerRX (interesting for remote
operation scenarios).
The issue will be the severely limited dynamic range of the 16 bit
ADC. Without effective AGC ahead of the ADC there *will* be overload
problems on crowded bands (e.g. 160/80/40) where any transceiver must
deal with many extremely strong ("local") signals while maintaining
maximum sensitivity. With AGC, the strong local signals will cause
"blocking" as the gain is reduced to prevent overflow of the ADC.
The new Flex design is certainly "interesting" but may not truly be
ready for critical "real world" use with the widely varying signal
levels in amateur service.
73,
... Joe, W4TV
On 5/19/2012 3:43 PM, Tony Estep wrote:
> On Sat, May 19, 2012 at 11:53 AM, Edward R. Cole<kl...@acsalaska.net>wrote:
>
>> ...website now shows the Flex-6000/6700 newest entry into the SDR
>> market....
>
> ===========
> Said to be digital from antenna connector to output. Their hardware has
> long needed updating, so perhaps this will be it. However, Flex's really
> weak link has always been their software/systems integration, so it remains
> to be seen if this does anything to mitigate that.
>
> Tony KT0NY
>
>
>
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