[hpsdr] Phoenix synthesizer

[John Kolb]

Hi Brian,

So what do I have to do to make my DSP-100 run under Win98 or later,
besides finding a mothgerboard with ISA Slots  :)

I found your comments about dithering very interesting - without looking
into it, I had assumed that spur reduction was done by moving the DDS freq to
discrete freqs where spurs were minimized and shifting the effective IF
freq in the DSP processing to tune between DS steps.

John
KK6IL
Ramona


At 06:50 AM 3/24/2007, you wrote:
>***** High Performance Software Defined Radio Discussion List *****
>
>
>This is my first post to the HPSDR group so before giving my 
>thoughts it may be useful to give my SDR background. I designed and 
>marketed Radware, an SDR using I&Q mod/demod and a sound card, under 
>Comer Communications Inc. thirteen years ago. Radware was a business 
>failure for many reasons most of which have no relevance today.
>
>The most serious limitation to the performance of this early SDR 
>were second order products, IMD2.  I played with the SDR 1000 to see 
>how much better it did on this issue. At first I was unable to find 
>any IMD2 products. After some thought I realized that the dithering 
>introduced by the spur reduction process was spreading the IMD2. 
>When the spur reduction is turned off, IMD2 can be 
>measured.  Although the mixer selections have improved over the 
>years IMD2 is still an issue, typically worse than IMD3, with low IF 
>receivers.  Dithering produces a very significant improvement in 
>this respect, although it is increasing the noise floor when present.
>
>  Now to my real comment.
>
>Reading the PHOENIX article synthesizer choices, I liked the 
>"Microwave PLL divided down" choice, similar to Radware, but then 
>I  got to thinking. If this is used dithering will be much harder 
>and I still think IMD2 is a bigger problem than the spurs produced 
>by the AD9951.
>
>As a second consideration, dividing by 4 using a single AD9951 puts 
>an upper limit of less than 50 MHz on the receiver. Using 2 AD9951's 
>puts 6 and 2 meters within range.
>
>73 Brian KF6C   G3ZVC
>
>_______________________________________________
>HPSDR Discussion List
>To post msg: hpsdr at hpsdr.org
>Subscription help: http://lists.hpsdr.org/listinfo.cgi/hpsdr-hpsdr.org
>HPSDR web page: http://hpsdr.org
>Archives: http://lists.hpsdr.org/pipermail/hpsdr-hpsdr.org/
>Internal Virus Database is out-of-date.
>Checked by AVG Free Edition.
>Version: 7.5.432 / Virus Database: 268.16.13/632 - Release Date: 
>1/16/2007 4:36 PM

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/attachments/20070324/dc3269e8/attachment-0004.htm>