Re: USB cable quality and QRM in a spyserver setup with an Airspy Hf+ and Raspberry PI3. 6 microUSB cable test. #airspyhfplus #bestpractice #raspberrypi


Some of the better manufacturers put some details on their web site but
at that is usually still somewhat sparse.

for USB micro and apple cables I prefer Anker which are quite well
reviewed and their web page does provide some technical details.

Also, Sabrent and Volutz.

Tyco / TE Connectivity makes some decent USB cables. In their USB A to B
cables they have versions which have 25 AWG for the data pair and 20
AWG for power.

I have destructably disassembled (i.e. cut apart) a number of cables
from cheap to moderately priced. There are differences and you do get
what you pay for.

You can even buy the end parts to make your own cables with the cable of
your choosing if you are particular.

something else to consider is the cable shields. The metal parts at both
end of the cables should not be connected to the ground pin of the
connectors but should be connected to the shield (if there is any) of
the cable. In fact, sometimes it is better to just have the shield
connected to the shell on the end that plugs into the computer and not
connected on the other end. This creates what is called a Farady shield
(or cage if you prefer) over the cable. Connecting both ends can
sometimes create ground loops in the shield. I have run out of fingers
and toes to count the number of times that I have seen where a cable
having the shield connected at one end only solves EMI/RFI issues where
another cable with the shield connected at both ends only made the
problem worse or was in fact the source of the problem to begin with.

Solving EMI/RFI issues is a mixed bag of science and sometimes a bit of
black magic.

This is a could introductory and practical text on the subject:

cheers, Graham ve3gtc

On 3/14/2018, "David Ranch" <airspy-groupsio@...> wrote:

For a 2-pack of 10' cables [Volutz], $17 on eBay was a deal.
Wow.. 10'? I'd assume there is some pretty serious voltage drop over
that! Regardless, I'll have to give them a look. Thanks.


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