[DSP-10] DSP-10 with DSPx problems and solutions

[DC9UPGermany at aol.com]

Hello  DSP-10 friends...I just have finished the third DSP-10. Two of them 
were with  the original EZ-Lit-Kit and worked out very fine. I made a lot of 
changes  (including the known changes by the Assembly Manual) to all three DSP-10 
 projects and noted them down for whom it may concern.  
The  third one now includes the new DSPx processor and it’s also a fine 
instrument on  receive. I can not detect any birdies over the range 144 to 146 MHz 
(this  range is used in Europe!) and maybe this has to do with  the shielding 
technique I used. 
First: 
The  top-cover of the DSPx box has extra lids with 14 screws around to hold 
them  down to the box. The box should be "watertight". 
Second: 
I  used very thin white shielded Aircraft-wires for most of the back-plane  
connections, especially the once which distribute signals. Besides  this, I 
used fine semirigid cable for the LO oscillator signals which can be  soldered 
directly with the outside to backplane. 
Third: 
The  cable routing inside the box and outside the box is done in a very  
different way compared to the original project. 
I  also build the DSP10 PCB not the way the assembly manual and the 
associated  parts layout show. The building process was done by "Group-building" and  
testing each group of circuits after soldering. By this way problems can be  
traced down easy and when ready with all groups the DSP-10 works right  away. 
The  main changes I made are in the LO parts and their amplifiers. Their  
inter-stage gain and levels must be corrected not to overdrive the following  
amplifiers (MSAs) and deliver the right undistorted level to the  mixers. 
All  changes are documented down here. 
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The  only program working after the download from the PC to the DSPx is the 
one from  Bob on his website. (_http://www.proaxis.com/~boblark/uhf3x_25.zip_ 
(http://www.proaxis.com/~boblark/uhf3x_25.zip) ) 
No  other version will work with the DSPx !! 
Download  is done by the EZFast Loader with the command line: 
Ezfast L 1 uhf3x.exe  G 
The  L stands for loading with 9600 b/s; no fast loading with an "M" is  
possible.!! 
The  1 stands for the COM port, 1 in my case. 
So  far so good. The DSPx seems to work as good as the old EZ-Kit. Good work  
done by Lyle. 
Now  I run into the first (maybe small) problem. 
On  transmit the Codec in the DSPx part can easily overdriven by the 
Microphone  input in all modes, FM, USB, LSB etc. 
SSB  sounds very bad and it does FM-ing and after scoping around and looking 
to the  output signal with an SA, I could see that the carrier is wandering 
when  overdriven and has some FM on it. 
Bob  came around this problem in the original EZ-Kit and installed a  
"Clipper". 
But  this clipper does not work properly with the DSPx.!!! 
I  think it must be reworked to match the new CODEC. 
One  more remarkable problem occurred to me. 
Changing  the MIC gain from 61 to 60 completely shuts off the clipper  !!?? 
After  shutting down the program and the DSP-10 and restart again it will 
work  again....curios..??? 
Did  somebody else experience this too?? 
Best  73 and happy work with this outstanding TRX DSP-10...I am lucky with  
it. 
Hermann,  DC9UP     
E-Mail:    _DC9UPgermany at aol.com_ (mailto:DC9UPgermany at aol.com)  
(mailto:DC9UPgermany at aol.com)