[time-nuts] Bodnar "Precision Frequency Reference (GPS Clock)" AND LeoNTP Networked Time NTP Server Questions
k8yumdoober at gmail.com
Fri May 18 08:16:18 EDT 2018
Caution, folks, about USB cable radiation. While the intended signals
flowing through the
cable presumably contribute a bit to the overall picture, common-mode
currents on the cable
are the most likely cause of severe radiation problems. These currents
arise not merely from
intended USB signals, but from *all* the digital activity within the
device, and will be present
whether or not USB communications are going on.
The keys to controlling this problem are:
1) Shielding on the USB cable.
2) Proper design inside the USB device, rarely done beyond the point of
government regulations, which are far too forgiving IMHO.
3) Use of a ferrite choke on the cable to reduce those residual currents
that get by anyway.
Note that only item 3 might be under the control of the user to any useful
So please don't just assume that using a USB cable for charging only solves
Note that the above comments are also generally applicable to *all *cables,
cables, that are plugged into *any* digital device.
On Fri, May 18, 2018 at 5:15 AM, David J Taylor via time-nuts <
time-nuts at febo.com> wrote:
> Anyone who is using one (or both) of these, and/or folks who have a
> logical opinion:
> There's more... but this is a good start. Just want to try and get
> parts on the way. Have to build a separate outboard regulator for the
> timing GPS antenna, too.
> Clay Autery
> I have all three of these units, all powered off USB. I don't see any
> reason why you shouldn't use a USB cable with just the DC part connected,
> so that there's no issue about radiation. A standard USB port would only
> supply 0.5A so that's an upper limit on the power consumption. If it's a
> very long USB cable (you mention mast-head) check the resistance.
> As a crude guide...
> - The (larger box) NTP server feels cold to the touch.
> - The smaller, single output frequency source feels very slightly warm to
> the touch (feeding an Icom IC-R8600)
> - The larger, dual-output frequency source feels slightly warm to the
> There's an e-mail address where you could ask: support at leobodnar.com
> SatSignal Software - Quality software written to your requirements
> Web: http://www.satsignal.eu
> Email: david-taylor at blueyonder.co.uk
> Twitter: @gm8arv
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