[hpsdr] QSD gain and noise.

[Ramakrishnan Muthukrishnan]

On 9/23/07, Phil Harman <phil at pharman.org> wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
>
> In reply to Ahti and Frank,
>
> Ahti, from memory the NF measurements you suggest are a little high but in
> the right ball park. The problem of connecting the Janus balanced inputs

Hi Phil and the group,

[Appologies if you recieve multiple copies of the email. The first two
versions did not go thru the hpsdr list, but I accedentally copied
Phil and Ahiti when I resent the message.]

Sometime back I created a spreadsheet, mainly for me to learn about
the cascaded analysis for designing the Phoenix gain. The spreadsheet
can be found at:

  http://www.zerobeat.in/hpsdr/nf.xls.gz

Note that the xls file is gzipped. I have used (without permission)
the atmospheric noise data from Gerald's QEX SDR-1000 Part-4 article.

I found an NF of 19.44 for the Janus ADC. Also the spreadsheet shows
that for 6m, we need a min gain of around 7 dB. But this analysis
ignores the effects of QSD switch switch on/off timing issues etc
associated with operating them on higher frequencies.

Please have a look. I still haven't completely understood a way to
create a noise figure calculations for an Opamp differential
amplifier. Marco has a spreadsheet to do that.

73
Ramakrishnan, vu3rdd

 1190565440.0