[Elecraft] OT: Dayton New Equipment Show

[amsctalx at comcast.net]

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 

amsctalx at comcast.net ----- Original Message -----
From: "Joe Subich, W4TV" <lists at subich.com> 
To: elecraft at 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<kl7uw at 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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