[hpsdr] ALEX - Call for Comments - II - Clarification

[Henry Vredegoor]

Hi all, Phil,

What about usage of Alex with a QSD/LO and Janus type receiver setup in this
respect?
I think the situation would then be different?

73's

Henry.

> -----Original Message-----
> From: hpsdr-bounces at hpsdr.org 
> [mailto:hpsdr-bounces at hpsdr.org] On Behalf Of pvharman at arach.net.au
> Sent: woensdag 7 maart 2007 3:07
> To: grahamh at verizon.net
> Cc: 'High Performance Software Defined Radio Discussion List'
> Subject: Re: [hpsdr] ALEX - Call for Comments - II - Clarification
> 
> 
> ***** High Performance Software Defined Radio Discussion List *****
> 
> Hi Graham,
> 
> Thanks for taking the Project Leader role on for Alex.  Re 
> your request 
> below, based on my tests with the prototype Mercury setup the native 
> performance should be very acceptable without any additional 
> input filters. The 
> Mercury board contains a switchable  1.5MHz HPF and 55MHz LPF 
> to remove high 
> level MW broadcast signals and prevent VHF signals from 
> aliasing into the 
> passband. 
> 
> I live in an area close to multiple MW broadcast stations and 
> with the HPF in 
> circuit have no problems on any HF band. If I want to listen 
> on MW then I will 
> bybass the HPF and if necessary turn off the preamps and use 
> the 0-30dB 
> attenuator. 
> 
> I used the Mercury prototype on 40m during the recent ARRL CW 
> contest. As I 
> test I mixed an S9+60 db signal in with the antenna and at 
> 1kHz spacing could 
> still copy a signal at the noise floor. The limit of the test 
> was the sideband 
> noise of my HB8640B not the receiver strong signal performance. 
> 
> Since we have little practical experience in using direct 
> digital conversions 
> receivers (and having a frontend fully open from 1.5 to 55MHz 
> does not feel 
> right to an analogue receiver designer!) Alex is there in 
> case folks live in a 
> high signal environment, require additional front end 
> selectivity for contest 
> or DXperdtion operations etc.  I suspect that in many cases 
> with the natural 
> selectivity offered by antennas, ATUs, HF beams etc then Alex 
> may not be 
> required. 
> 
> 73's Phil...VK6APH
> 
> 
> 
> 
> 
> 
> 
> 
> > 
> > I assume the majority of the users want good ham band performance
> > and casual SWL, WWV, and experimental capability.  The
> > native performance of the underlying SDR should be good
> > enough for the "casual" and incidental uses with the preselectors
> > bypassed. [ Phil H, please comment. ]  Any serious or focused
> > other uses can put a dedicated filter section in the user
> > defined spaces, or rework the whole filter pack.  The PCB
> > layout will accommodate third order (three inductor)
> > bandpass or low-pass filters in each section.
> > 
> 
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