[hpsdr] Atlas slot positions

[Murray Lang]

Thanks Kirk,

Is a plug full of of resistors likely to help with the current version 
of Atlas?

Murray

Kirk Weedman wrote:
> Yes, its a termination & design problem. I am working towards a 
> solution with a new version of FPGA code for Mercury, Penny, Ozy and 
> Janus.  It may be awhile as I've hit some snags along the way.  I am 
> fairly new to this group but recognized the design problem soon after 
> joining and hope to have a good solution one day.  Unfortunately, due 
> to the current design there's not really a proper way to terminate the 
> signals.
>
> 73, Kirk Weedman  KD7IRS
>
> Murray Lang wrote:
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> Hi all,
>>
>> I'm stepping outside of my comfort zone here, but it's bugging me 
>> enough to risk looking silly or covering old ground.
>>
>> I gather that the slot position dependencies are the result of data 
>> pulses bouncing backwards and forwards along the atlas bus. Is this 
>> right? In other words the bus lines are transmission lines and the 
>> reflections are the same as we'd see in an unterminated RF 
>> transmission line (standing waves and all). Yes?
>>
>> Can we apply the same solution to Atlas as we'd apply to our 
>> transmission lines and apply a correct load or termination? This 
>> could be tested by putting a waveform generator on just one of the 
>> lines and trying a termination at the end or ends. An oscilloscope 
>> would reveal the difference. If it's effective then a card could be 
>> built with nothing but terminating resistors for placement in the end 
>> slot (or maybe both end slots?). Is the impedance of the bus is 
>> already known? At at any rate the best termination value could be 
>> found by trial and error pretty quickly, if indeed this is effective 
>> at all.
>>
>> Just a thought.
>>
>> Murray - VK6HL
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>


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