Re: USB and cold weather


Roland Christen
 

At the frequencies used in USB3, they begin to act more like light going thru various surfaces. At each connection there is a reflection of the signal just like the air-glass surfaces of a lens. So 2 more connections adds 2 reflections which lowers the signal amplitude and adds ringing of a steep rise-time pulse. If you have low signal to begin with, this may knock it down enough to cause the problem. There are hundreds of papers written on this if you care to search, but they are very technical if you're not knowledgeable of gigahertz stuff.

Running your own cable thru the mount would require taking the mount apart, which is highly not recommended and you could damage the internal wiring.

Rolando

-----Original Message-----
From: Micheal Fields Jr via groups.io <mpfjr@...>
To: main@ap-gto.groups.io
Sent: Sat, Jan 9, 2021 6:58 pm
Subject: Re: [ap-gto] USB and cold weather

Hi Roland.  I just did a ton of experimenting.  Xentex was right.  If I simply plug into a usb 2 port the problems go away.  Also if I bypass the mount entirely even with a 6 foot long cable, the problems go away.  It is only if I go through the mount with USB 3.0 do I have issues.    The Pegasus USB box is nice.  Probably worth having anyways but it is also an expensive "test".   I just bought a 3.3 foot female to female cable USB 3.0 to simulate going through the mount so I can see if it is simply having those extra connections or something else.

$10.00 with free shipping from Amazon will let me know.  Lets say it turns out that it works great with that "pretend" through the mount female to female cable.  What is my next step? By process of elimination it seems so far that the internal cable is not up to 3.0 standards.  I am waiting to hear back from my second favorite vendor to see if they have the usb control hub in stock then I'll probably go ahead and order it anyways.  Nice being able to turn off and on usb ports.

--
Roland Christen
Astro-Physics

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