[hpsdr] Distorted audio

[Steve Bunch]

Chris,

On Aug 11, 2011, at 4:55 AM, Chris Smith wrote:

> ***** High Performance Software Defined Radio Discussion List *****
> 
> I'm surprised that the T'bolt continued to work at all let alone at 10MHz although severely modulated. I can't begin to work out what voltages actually appeared at the input to the unit without the 0V connected. I guess that would depend on what current was drawn from each rail. Hmmm...

This is not as unusual as it sounds.  Many CMOS chips have worked for years with the power supply or ground pin disconnected, with power to the core logic and outputs being provided through the protection diodes on the unpowered chip's inputs -- the neighboring chips' outputs provide the power path for the chip!   Until, someday, the wrong pattern on the inputs comes along and doesn't provide enough power to run the core or switch the outputs ;-), at which point you can get a seemingly-random failure.  Or if you're really lucky, it just works...

So in a way you're lucky the symptoms were relatively obvious, you could have had more subtle symptoms!  It's like Bob Pease wrote when he autographed copies of his book on debugging circuits, "may your problems always be middle-sized, so you can find 'em!".

Steve, K9SRB

> Also I'm glad it does not appear to have done any damage to the T'bolt. 
> 
> 73 Chris G4NUX
> 
> On 11 Aug 2011, at 10:44, Jeremy McDermond wrote:
> 
>> On Aug 11, 2011, at 12:31 AM, Chris Smith wrote:
>> 
>>> Hi Phil & Jeremy
>>> 
>>> I eventually found the problem. My rather makeshift connection for power to the Trimble Thunderbold had failed in that the Gnd/0V lead had become disconnected. Having remade the connection all is well and the LEDs on Excalibur are once again cycling red/green slowly. 
>>> 
>>> Thanks once again for your help. I feel rather embarrassed that the problem was of my own making in taking a short-cut.
>> 
>> No problem Chris.  It happens to all of us now and then.  I'm just glad that we could get you back up and running.
>> 
>>> Cheers & 73
>>> 
>>> Chris G4NUX
>> 
>> --
>> Jeremy McDermond (NH6Z)
>> Xenotropic Systems
>> mcdermj at xenotropic.com
>> 
>> 
>> 
>> 
> 
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