<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div dir="ltr"></div><div dir="ltr">Jules,</div><div dir="ltr"><br></div><div dir="ltr">Thank you for the part number! I’ll order a few. </div><div dir="ltr"><br></div><div dir="ltr">George,</div><div dir="ltr"><br></div><div dir="ltr">Thank you for those documents!</div><div dir="ltr"><br></div><div dir="ltr">All,</div><div dir="ltr"><br></div><div dir="ltr">Thank you for all of your great advice, help, and assistance! This was a really good discussion!</div><div dir="ltr"><br></div><div dir="ltr">Thanks again.</div><div dir="ltr"><br></div><div dir="ltr">Jonathan</div><div dir="ltr">KC3EEY</div><div dir="ltr"><br>On Jul 29, 2021, at 5:04 PM, Julius Madey <<a href="mailto:hillfox@fairpoint.net">hillfox@fairpoint.net</a>> wrote:<br><br></div><blockquote type="cite"><div dir="ltr">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<font face="Arial">Jonathan, I think that mix 75 would probably be
better for the VLF range and is available in a snapit core with
0.7inch ID part no. 0475176451. Also available in other sizes
with solid core. Read up on the references that Ward sent for
more detailed information on application.<br>
73,<br>
Jules-K2KGJ<br>
<br>
<br>
<br>
</font>
<div class="moz-cite-prefix">On 7/29/2021 1:23 PM, Jonathan wrote:<br>
</div>
<blockquote type="cite" cite="mid:29865318-FCCB-4A1E-B3DB-EFF738A19F04@gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">
<p class="p1"><span class="s1" style="background-color:
rgba(255, 255, 255, 0);">Phil,</span></p>
<p class="p1"><span class="s1" style="background-color:
rgba(255, 255, 255, 0);">Thanks for letting me know. I’ll
reach out to Earle for more information.</span></p>
<p class="p1"><span class="s1" style="background-color:
rgba(255, 255, 255, 0);">Ward,</span></p>
<p class="p1"><span class="s1" style="background-color:
rgba(255, 255, 255, 0);">Thank you for that reminder and the
great design tip. The feedline I will be using is shielded
CAT6. One pair carries DC power and the other carries VLF
audio. I plan on grounding the shield too. </span></p>
<p class="p1"><span class="s1" style="background-color:
rgba(255, 255, 255, 0);">Jules, </span></p>
<p class="p1"><span class="s1" style="background-color:
rgba(255, 255, 255, 0);">Would mix 31 be appropriate for
VLF? It looks like it’s recommended for a frequency range of
1-300MHz, so it that case, it should eliminate any of those
high frequency transients from EFT? They can’t be installed
in the conduit, but can be installed on the feedline coming
into the Raspberry Pi box.</span></p>
<p class="p1"><span class="s1" style="background-color:
rgba(255, 255, 255, 0);"><br>
</span></p>
<p class="p1"><span class="s1" style="background-color:
rgba(255, 255, 255, 0);">Thanks.</span></p>
<p class="p1">Jonathan</p>
<p class="p1">KC3EEY</p>
</div>
<div dir="ltr"><br>
On Jul 28, 2021, at 4:46 PM, Ward Silver <<a href="mailto:hwardsil@gmail.com" moz-do-not-send="true">hwardsil@gmail.com</a>>
wrote:<br>
<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div dir="ltr">Blocking common-mode RF current using ferrite
chokes is a good technique. So is using shielded cable for
everything and metal enclosures bonded together. Jim has
several tutorials about this available on his web page (<a href="http://k9yc.com/publish.htm" moz-do-not-send="true">k9yc.com/publish.htm</a>)
- see the slide show about reducing received noise. This
was an evolution of a presentation on common-mode chokes (<a href="http://www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf" moz-do-not-send="true">http://www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf</a>)
by Chuck Counselman, W1HIS in the context of reduced
received noise. (The presentation was created before Type 31
ferrite became available which is a much better material for
EMI suppression.)
<div><br>
</div>
<div>73, Ward N0AX</div>
</div>
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<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Wed, Jul 28, 2021 at
3:32 PM Julius Madey <<a href="mailto:hillfox@fairpoint.net" moz-do-not-send="true">hillfox@fairpoint.net</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div> On that note, I wonder if it would be a good idea to
put a common mode choke (multiple turns of the power
feed line through an appropriate ferrite mix) in the
line ? K9YC's audio RFI paper is a good reference.<br>
73,<br>
Jules-K2KGJ<br>
<br>
<div>On 7/28/2021 4:02 PM, Ward Silver wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">A quick note - rectifiers, LEDs, or any
non-linear devices connected to unshielded cables of
any significant length will happily act as mixers or
harmonic generators. Whenever one of these is used,
put a 0.01uF disc ceramic across it to bypass it at
RF.
<div><br>
</div>
<div>73, Ward N0AX</div>
</div>
<div id="gmail-m_-614908389529115639DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br>
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<td style="width:470px;padding-top:12px;color:rgb(65,66,78);font-size:13px;font-family:Arial,Helvetica,sans-serif;line-height:18px">Virus-free.
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<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Wed, Jul 28,
2021 at 11:41 AM Jonathan <<a href="mailto:emuman100@gmail.com" target="_blank" moz-do-not-send="true">emuman100@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px
0px 0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="auto">
<div dir="ltr">Hi Tom,</div>
<div dir="ltr"><br>
</div>
<div dir="ltr">That makes a lot of sense. I’ll
try fit a 0.1uF and a 22-47uF electrolytic on
the feedline loop. </div>
<div dir="ltr"><br>
</div>
<div dir="ltr">Thanks again! </div>
<div dir="ltr"><br>
</div>
<div dir="ltr">Jonathan</div>
<div dir="ltr">KC3EEY</div>
<div dir="ltr"><br>
On Jul 28, 2021, at 10:55 AM, Tom McDermott
<<a href="mailto:tom.n5eg@gmail.com" target="_blank" moz-do-not-send="true">tom.n5eg@gmail.com</a>>
wrote:<br>
<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div dir="ltr">
<div>Hi Jonathan - a concern is that the
DC-DC converter input stage would become
unstable and oscillate</div>
<div>with the cable inductance. If that
happens then there could be high
frequency AC voltages present at the</div>
<div>input of the converter. Would those
over-voltage the input? Possibly.
Would it radiate RFI from the cable?
Likely.</div>
<div><br>
</div>
<div>Good design dictates sufficiently low
source impedance to the DC-DC
converter. Almost all linear regulators</div>
<div>require it. An electrolytic and
ceramic bypass pair right at the DC-DC
input would be considered good design by
many.</div>
<div><br>
</div>
<div>-- Tom, N5EG</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Wed,
Jul 28, 2021 at 7:30 AM Jonathan <<a href="mailto:emuman100@gmail.com" target="_blank" moz-do-not-send="true">emuman100@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div>
<p style="font-family:UICTFontTextStyleBody;font-size:17px"><span style="background-color:rgba(255,255,255,0)">John, </span></p>
<p style="font-family:UICTFontTextStyleBody;font-size:17px"><span style="background-color:rgba(255,255,255,0)">Thanks for the suggestion!
I think I’ll start with the
overvoltage age spike of 50V for
100ms or less based on the
datasheet spec of the DC-DC
converter. I was thinking of some
sort of fusable circuit protection
now that I’ll be using a TVS diode
to mitigate stress from the follow
current. </span></p>
<p style="font-family:UICTFontTextStyleBody;font-size:17px"><span style="background-color:rgba(255,255,255,0)"><span></span><br>
</span></p>
<p style="font-family:UICTFontTextStyleBody;font-size:17px"><span style="background-color:rgba(255,255,255,0)">Tom,</span></p>
<p style="font-family:UICTFontTextStyleBody;font-size:17px"><span style="background-color:rgba(255,255,255,0)">The datasheet wasn’t clear
on the need for input filtering.
On the output of both the IP2415S,
I have 0.1uF ceramic capacitors.
In the datasheet, it only mentions
a spec of “Input Reflected Rated
Current” with a series inductor
and shunt capacitor. I don’t
really understand exactly what
this is, but it lists “20mAp-p
through a 12uH inductor and 47uF
capacitor”. Nothing else is
mentioned about input protection
or filtering.</span></p>
<p style="font-family:UICTFontTextStyleBody;font-size:17px"><span style="background-color:rgba(255,255,255,0)">In both situations that the
DC-DC failed, the cable length was
only 4’ of cat 5. This circuit
that was proved and tested by
Paul, including the receiver and
schematic I attached, did not have
such an issue, but the only
difference is that the voltage was
lower than 30V. That’s why I was
thinking it was a turn-on/off
spike. I think that in a lot of
typical applications, the input
voltage isn’t that high, so spikes
don’t normally present a problem.
The DC-DC that feeds the receiver
DC-DC has never failed and it was
always fed with 18V or less. </span></p>
<p style="font-family:UICTFontTextStyleBody;font-size:17px"><span style="background-color:rgba(255,255,255,0)"><span></span><br>
</span></p>
<p style="font-family:UICTFontTextStyleBody;font-size:17px"><span style="background-color:rgba(255,255,255,0)">Jules,</span></p>
<p style="font-family:UICTFontTextStyleBody;font-size:17px"><span style="background-color:rgba(255,255,255,0)">You recommend the Schottky
diode in parallel with the TVS,
then a series PTC, so during a
spike, the TVS will conduct and
the PTC would fuse, and during a
reverse polarity condition, the
Schottky diode will conduct with
limited current due to the PTC
fusing? I can see the benefit that
the series PTC in normal a normal
circuit condition would drop much
less voltage that the Schottky
diode. </span></p>
<p style="font-family:UICTFontTextStyleBody;font-size:17px"><span style="background-color:rgba(255,255,255,0)"><span></span><br>
</span></p>
<p style="font-family:UICTFontTextStyleBody;font-size:17px"><span style="background-color:rgba(255,255,255,0)">All in all, I agree with
adding some capacitance to filter
voltage spikes and reduce or
eliminate them. I’ll need to be
sure not to exceed the DC-DC max
load capacitance, which is 47uF in
this case. </span></p>
<p style="font-family:UICTFontTextStyleBody;font-size:17px"><span style="background-color:rgba(255,255,255,0)">But, to me, the most
plausible cause for the failures
are turn on/off voltage spikes,
even with a short length of cable.
Adding electrolytics is a bit
difficult due to the tight space
constraint as seen in my previous
email, so I’ll try out the TVS and
a PTC. Other than voltage spikes,
does anything else come to mind? </span></p>
<p style="font-family:UICTFontTextStyleBody;font-size:17px"><span style="background-color:rgba(255,255,255,0)"><span></span><br>
</span></p>
<p style="font-family:UICTFontTextStyleBody;font-size:17px"><span style="background-color:rgba(255,255,255,0)">Thanks guys. </span></p>
<p style="font-family:UICTFontTextStyleBody;font-size:17px"><span style="background-color:rgba(255,255,255,0)">Jonathan</span></p>
<p style="font-family:UICTFontTextStyleBody;font-size:17px"><span style="background-color:rgba(255,255,255,0)">KC3EEY</span></p>
</div>
<div><br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On
Tue, Jul 27, 2021 at 9:34 AM
Jonathan <<a href="mailto:emuman100@gmail.com" target="_blank" moz-do-not-send="true">emuman100@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="auto">
<div dir="ltr">
<div dir="ltr"><span style="background-color:rgba(255,255,255,0)">Hi
Everyone,</span></div>
<div dir="ltr"><span style="background-color:rgba(255,255,255,0)"><br>
</span></div>
<div dir="ltr"><span style="background-color:rgba(255,255,255,0)">Before
the meeting ended last
night, I wanted to discuss
the issues I’ve
experienced with my VLF
active antenna. As I
mentioned, the DC-DC
converter (XP Power
IP2415S) failed after I
applied power. I turned
the volume up because I
wasn’t hearing sferics,
and shortly after, I heard
the squeal of the DC-DC
converter. When I pulled
out the smaller foam core
partially, I heard a
squeal coming from the
DC-DC converter itself. </span></div>
<div dir="ltr"><image3.jpeg><span style="background-color:rgba(255,255,255,0)"><br>
</span></div>
<div dir="ltr"><span style="background-color:rgba(255,255,255,0)"><br>
</span></div>
<div dir="ltr"><span style="background-color:rgba(255,255,255,0)">I
had a failure of the DC-DC
converter when I first
built the VLF preamp. It
was being powered by the
Raspberry Pi box (same
power circuit as my text
box). I had a power
failure and when the power
was restored, the DC-DC
converter failed. In both
situations, it was being
supplied with 30VDC, with
the limit is 36V. The
reason for using 30V is to
overcome the voltage drop
from long cable lengths.</span></div>
<div dir="ltr"><span style="background-color:rgba(255,255,255,0)"><br>
</span></div>
<div dir="ltr"><span style="background-color:rgba(255,255,255,0)">After
both failures, there was a
low impedance across the
input of the DC-DC
converter causing the
supply to be pulled down.
Because the input and
output are isolated, I
figured the fault had to
have been caused by a
voltage spike on the input
due to power being turned
on and off. The datasheet
mentions that it can
withstand 50V spikes at
100ms, but I can’t think
of anything else that
could cause the DC-DC to
fail, especially that 30V
is used to power it and
any voltage spike would
ride on top of that 30V. I
contacted XP Power about
the issue. </span></div>
<div dir="ltr"><span style="background-color:rgba(255,255,255,0)"><br>
</span></div>
<div dir="ltr"><span style="background-color:rgba(255,255,255,0)">Here
is the schematic of the
power path. The blocks are
the IP2415S DC-DC
converter.</span></div>
<div dir="ltr"><image1.jpeg><span style="background-color:rgba(255,255,255,0)"><br>
</span></div>
<div dir="ltr"><span style="background-color:rgba(255,255,255,0)">I’m
powering the DC-DC
converter with 30V from
another DC-DC converter in
the test box and Raspberry
Pi box (Raspberry Pi box
not shown, but same
circuit). </span>Keep in
mind, the length is still
relatively short in my
testing, so cable inductance
isn’t the primary reason for
the spike. Plus, at long
lengths, the voltage would
be much lower due to voltage
drop across the length, and
I think this was why Paul
might not have seen this
issue when he originally
tried and built this
design. </div>
<div dir="ltr"><br>
</div>
<div dir="ltr">To mitigate
this problem with the supply
voltage at 30V, I decided to
use a TVS diode across the
input of the DC-DC
converter. Here is the
schematic: (my apologies for
the TVS diode being
backwards)</div>
<div dir="ltr"><image2.jpeg><br>
</div>
<div dir="ltr">I chose a
unidirectional TVS so there
is also protection if the
voltage spikes have any
negative components. I
picked a TVS with a working
voltage of 33V, a Littel
Fuse P4KE39A. According to
the datasheet, it looks like
this would be adequate. TVS
diodes have a PN junction
that is more rugged, with a
larger surface area for
greater current density. One
thing I overlooked with this
type of circuit protection
is that once the TVS
conducts, current from the
power supply will be shunted
too, known as the follow
current, and in some
situations, this may cause
issues requiring a fuse. In
this case, since the spikes
are probably short duration,
and since the DC-DC
converter in the text/Pi box
has short circuit
protection, this should not
be an issue. </div>
<div dir="ltr"><br>
</div>
<div dir="ltr">So the
questions I have are: do you
also think it could be
voltage spikes that caused
the failures, and if so, was
my choice of TVS diode
adequate. Also, one
important question, if I
connect the anode of the TVS
diode to the receiver side
ground, will I lose
isolation? I know that
during spike current
conduction, I will. I’m sure
I can still get adequate
protection with the TVS
diode anode connected to the
negative of the isolated
power loop too, but I just
wanted to be sure. </div>
<div dir="ltr"><br>
</div>
<div dir="ltr">Lastly, since
the magnetometer board will
undergo another revision, I
feel it may be worth it to
add some sort or adjustable
regulator or use of an
external power source (not
connected to the 5V pin of
the Pi header) because even
with paralleling wires or
pairs, some installations
will require very long
lengths (especially since
interference-free locations
are often far away from the
shack) and the voltage may
drop to where the LDO cant
regulate. Using a higher
voltage at the Pi end (like
I do with the VLF preamp)
may be required for some
installations. I think this
should be considered if it
already wasn’t addressed. </div>
</div>
</div>
<div dir="auto">
<div dir="ltr">
<div dir="ltr"><br>
</div>
<div dir="ltr">Jonathan</div>
<div dir="ltr">KC3EEY</div>
<div dir="ltr"><span style="background-color:rgba(255,255,255,0)"><br>
</span></div>
<div dir="ltr"><span style="background-color:rgba(255,255,255,0)"><br>
</span></div>
</div>
<div dir="ltr"><br>
On Jul 27, 2021, at 7:21 AM,
Dr. Nathaniel A. Frissell
Ph.D. <<a href="mailto:nathaniel.frissell@scranton.edu" target="_blank" moz-do-not-send="true">nathaniel.frissell@scranton.edu</a>>
wrote:<br>
<br>
</div>
<blockquote type="cite">
<div dir="ltr"><br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<div><br>
<br>
<p class="MsoNormal">Thank
you, Tom.</p>
<br>
<br>
<p class="MsoNormal"> </p>
<br>
<br>
<p class="MsoNormal">The
recording will be
available later today at
<a href="https://youtu.be/AammohuygMw" target="_blank" moz-do-not-send="true"><br>
<br>
https://youtu.be/AammohuygMw</a> and <a href="http://hamsci.org/telecons" target="_blank" moz-do-not-send="true">hamsci.org/telecons</a>.</p>
<br>
<br>
<p class="MsoNormal"> </p>
<br>
<br>
<p class="MsoNormal">73 de
Nathaniel W2NAF</p>
<br>
<br>
<p class="MsoNormal"> </p>
<br>
<br>
<div style="border-color:rgb(225,225,225)
currentcolor
currentcolor;border-style:solid
none
none;border-width:1pt
medium
medium;padding:3pt 0in
0in"><br>
<br>
<p class="MsoNormal"><b>From:</b>
TangerineSDR <<a href="mailto:tangerinesdr-bounces@lists.tapr.org" target="_blank" moz-do-not-send="true">tangerinesdr-bounces@lists.tapr.org</a>><br>
<br>
<b>On Behalf Of </b>Tom
McDermott via
TangerineSDR<br>
<br>
<br>
<b>Sent:</b> Monday,
July 26, 2021 10:02 PM<br>
<br>
<br>
<b>To:</b> TAPR
TangerineSDR Modular
Software Defined Radio
<<a href="mailto:tangerinesdr@lists.tapr.org" target="_blank" moz-do-not-send="true">tangerinesdr@lists.tapr.org</a>><br>
<br>
<br>
<b>Cc:</b> Tom
McDermott <<a href="mailto:tom.n5eg@gmail.com" target="_blank" moz-do-not-send="true">tom.n5eg@gmail.com</a>><br>
<br>
<br>
<b>Subject:</b>
[TangerineSDR] Notes
from PSWS /
TangerineSDR call of
07-26-2021</p>
<br>
<br>
</div>
<br>
<br>
<p class="MsoNormal"> </p>
<br>
<br>
<div><br>
<br>
<div><br>
<br>
<div><br>
<br>
<p class="MsoNormal"> </p>
<br>
<br>
</div>
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<p class="MsoNormal">Notes
from PSWS /
TangerineSDR call
of 07-26-2021</p>
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<p class="MsoNormal">1.
Bill is using
chart.js for
magnetometer
charting. He is
setting up a
database using
Django web and
database framework
for Python.</p>
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<p class="MsoNormal">2.
Scotty is looking
at the Intel
(Altera) Arria 10
GX FPGA 10GX270
for the version 2
Data Engine
(supporting 10GE).
These FPGAs appear
to be more
available than the
MAX10 FPGAs. The
intention is to
develop DE Ver 1
and DE Ver 2 in
parallel<br>
<br>
while awaiting
FPGA component
availability. The
10 GX development
boards are pretty
expensive. </p>
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<p class="MsoNormal">--
Tom, N5EG</p>
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