What is an SCU and how do they work?

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I am interested to know how the SCU works. Does it use a crystal oscillator ?
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Bill -VA3WTB

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Posted 4 years ago

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Bill -VA3WTB

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I hope this is not too hard a question....
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SteveM

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Bill, all of the Elmers must be nursing a hangover from the weekend. Here is a brochure with a high level overview of the 6x series front-end.

http://www.jayceecoms.com/files/FLEX-6000_v2.pdf

The essential point is the following excerpt:

"The FLEX-6700 and FLEX-6700R incorporate two independent, synchronous Analog Devices AD9467 16-bit 245.76 Msps (Mega samples per second) analog to digital converters"

Thus, the SCUs directly sample the RF signal (pehaps, after prescale/preamplification), and then feed this massive amount of digital data into an FPGA where begins its SDR journey.

(Edited)
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Tim - W4TME, Customer Experience Manager

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Bill, SteveM is on the right track.  The SCU is the stage in the signal path where RF is preamplified, the preselector and other filtering is applied before the signal is digitized by the wide band ADC.  If feeds the FPGA and other processors the binary data where all the DSP magic happens.  There is a master clock in the radio for the processors.
(Edited)
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Bill -VA3WTB

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Thanks Tim, is the master clock the same as found in legacy radio's?
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Ken - NM9P, Elmer

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Bill, here is my layman's understanding of something much more complex:
Picture an SCU (Spectral Capture Unite) as a high powered analog-to-digital converter that captures a wide amount of spectrum (0 - 74 Mhz) right from the antenna port all at the same time and converts it to digital.

The other processors in the 6000 series are able to manipulate this digital information and provide multiple 14 MHz wide (on the 6500 & 6700) or 7 MHz wide (on the 6300)  panadapter displays anywhere in this captured spectrum.  The rig can also select 8, 4 or 2 (depending upon the rig) different "Slices" of that spectrum and process each one as a separate receiver channel (Up to 10 KHz wide) for am, ssb, cw, Digital modes, and soon, FM.    These slices can be mixed or matched in any combination on the Panadapter displays.

The 6300 & 6500 have one SCU and can listen simultaneously to 2 or 4 different signals anywhere in the captured spectrum as long as they come from the same antenna feed.

The 6700 has TWO SCU's and beefier processors and can do the same thing on 8 pans/slices and the signals can come from TWO different antenna feeds.  The advantage being you can have a 6 meter antenna on SCU#1 and a 160 Meter antenna on SCU#2...or you can have a vertical and a horizontal antenna on each input and have polarization diversity reception.  Later software releases will be able to do other amazing things by mixing two different antenna sources via the 2 SCU's.

I hope this helps.

Ken - NM9P
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IW7DMH, Enzo

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I have a similar question about the audio stage: can be stated that the "whole"  demodulation stage happens into the FlexRig? Or another part of the audio signal is further processed by SSDR?
I have already experienced that my 6300 can receive without a computer, but I would like to understand if doing so I can lost some of the FlexRig capabilities.

73' Enzo
iw7dmh
(Edited)
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Larry da Ponte

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SmartSDR is a control surface for the flex 6000 only. This is why the radio will continue to receive even after SSDR has gone away. Aside from DAX converting the IQ and audio streams into virtual sound cards I don't think SSDR does any audio or I/Q processing.
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IW7DMH, Enzo

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Thank you Larry,

I think it is so too.
I also would like to have an official response (or a link to study from) from Flex people, as my association friends (www.arilecce.it) asked me to talk about (and show them) new Flex Signature rig. I am trying to find differences from other technologies and this is one aspect I like to point out.

73' Enzo
iw7dmh  
 

Edit:  but now that I think about it, can you consider me an "ambassador"? Just kidding of course :)
(Edited)
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Bill Roberts

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Hi, Bill!
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Bill -VA3WTB

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Hi Bill, nice talk today, staying up a little tonight but not much going on HF.