[hpsdr] Atlas slot positions

[Murray Lang]

Thanks Graham and sorry for the bum steer.

I guess the transmission line view of Atlas might be more relevant if 
the frequencies were much higher (?)  Its length is only a small 
fraction of the wavelengths involved.
I really should stick to software.

Murray

Graham / KE9H wrote:
> Hi Murray:
>
> Good thoughts and ideas.  I have run some experiments with adding bus 
> terminations on extra
> cards at the end of the bus.  It helps a little bit, but does not 
> solve the root problem, which is
> not reflections on the bus.
> Phil and Kirk and others are working hard to fix this position 
> sensitivity issue.
>
> --- Graham / KE9H
>
> ==
>
> Murray Lang wrote:
>> 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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