I don't know if this has any application for you or not but here it is. I
have had ground loop problems between the power safety ground and the TV
Cable shield. I used two 300 to 75 ohm transformers and coupled their 300
ohm sides with 27 pf capacitors. I put them in an aluminum box with
On 7/19/2014 6:38 PM, Richard (Rick) Karlquist wrote:
Or
another way of putting it is you do a bunch of
measurements and then construct a theory to
explain what you already know experimentally.
I like that. Or perhaps, stated another way, in the real world engineers
are just as important as
Good morning!
On Sat, 19 Jul 2014 18:38:17 -0700
Richard (Rick) Karlquist rich...@karlquist.com wrote:
I did some tests of residual phase noise using an
Agilent E5505A and found that air coil inductors
did not add noise (at least down to my noise threshold)
but that ferrite core inductors
On Sat, 19 Jul 2014 22:16:33 -0700
John Miles j...@miles.io wrote:
That may be due to tempco, as Tom mentioned. The ferrite cores don't seem
to be noisy in and of themselves,
My current research tells me, that transformers have an inherent
noise (Barkhausen noise), but so far i could not
All that said, the real hazard with transformers is that people tend to
use
them to drive unbalanced coax cables with balanced signals. This turns
the
coax shield into an antenna, at which point you may end up with with
more
noise and spurs than you had before.
Could you explain this a
On 7/19/2014 3:45 PM, paul swed wrote:
Attilla I did look at some of the documents. But none showed practical HF
class injection locking. Say as an example a 6 MHz xtal to a 1 or 2 MHz
reference.
It maybe as easy as a single transistor in the oscillators ground lead.
Paul, everything I seen
Hi Alex,
Thanks for this level of detail. Fascinating. Is the fundamental physics behind
the quartz angle-of-cut well understood, or does this fall into advanced
alchemy and industrial magic?
I understand about the time constant now. Yes, on the order of a few seconds
makes sense. Would it be
Kit wrote:
From my (past) CATV experience, ferrite-based devices don't introduce
noise as such but they can certainly pick up noise (or transmit) unless
they are toroidal or otherwise well screened.
Ferrites do create noise. The permeability of ferrites is a complex
quantity, so it has a
Moin,
On Sun, 20 Jul 2014 07:55:23 -0700
Tom Van Baak t...@leapsecond.com wrote:
Thanks for this level of detail. Fascinating. Is the fundamental physics
behind the quartz angle-of-cut well understood, or does this fall into
advanced alchemy and industrial magic?
From what i gathered from my
Moin,
On Sun, 20 Jul 2014 03:41:44 -0700
John Miles j...@miles.io wrote:
I often find that when I use coaxial baluns to cut down on ground loop
noise, I end up with more noise and interference than I started with. Not
always, but often enough that I'm leery of them.
[...]
Thanks for the
I've seen a few pieces of equipment that use a transformer-coupled
output and an isolated BNC jack to break any ground loops. Then they
connect the shield to the chassis with a parallel RC network. The C
might be in the 1-10 nf range while the R is a few hundred ohms. I know
of one piece of
Hi
The simple way to take care of the coax shield issue is to use a common mode
choke.
Bob
On Jul 20, 2014, at 12:16 PM, Attila Kinali att...@kinali.ch wrote:
Moin,
On Sun, 20 Jul 2014 03:41:44 -0700
John Miles j...@miles.io wrote:
I often find that when I use coaxial baluns to cut
Hi
With the Cap to ground, you “short out” the transformer at RF. The resistor
takes care of static, and if it’s low enough shorts out the transformer at
lower frequency.
More or less - you break the 60Hz ground loop (sort of). You do very little for
RF isolation.
Bob
On Jul 20, 2014, at
Common mode choke works fine for RF, hard to reject 60Hz ground loop
currents using ferrites. (Although there is a website I found once where
the guy shows an entire bucket of miscellaneous ferrites cobbled together
for a common mode choke!) For a DC-to-daylight instrument that is suffering
60Hz
Attila you do not need triax cable, a good coax will do the job, but
open shield is always a source of trouble, just imagine there is a vey
good coupled line -- which at certain frequency is n times the 1/4
wave length.
cat 5 or cat 6 you get what you pay for .. it was never made for
1) Axtal makes a direct temperature sensing crystal, see Bern Neubig's
former note, but since I grew up by learning how do you make one iron
wheel from wood, I tried and used the transistor PN junction method many
times, it works and it is not a which craft to calculate the tree
resistors for
A long time ago in one of my excursions into medical electronics,
I was involved in developing a microwave hyperthermia cancer treatment
system that used a quartz thermometry unit to sense the tumor temperatures.
The quartz thermometry unit had optical fibers with quartz crystals (about
the size
Hi
The “coax is an antenna” problem comes in well before you get to DC. Even with
no transformer involved, the skin depth of the coax shield gives up well above
60 Hz (and likely well above 100 KHz). If you want to do full isolation over a
very wide range you need some combination of shielding
On Sun, 20 Jul 2014 15:57:24 -0400
Chuck Harris cfhar...@erols.com wrote:
I initially thought that it might be a transmission sort of effect, where
the light intensity changed with temperature, but its total lack of
sensitivity
to being in a liquid, kind of makes that unlikely.
Nope, it's a
What I am missing in all these discussions is what do we want to archive
or is this an other paper only discussion. I am used to starting out with a
goal, and tackle the challenge from there.
We have a saying in German Papier ist geduldig. Translate You can write
any thing on paper.
Bert
I'm not sure what you are saying.
skin depth = (2.6/sqrt(fhz))inches for copper.
So, at 60Hz, skin depth = 0.336 inches.
and at 100KHz, skin depth = 0.008 inches.
and at 1MHz, skin depth = 0.0026 inches.
Are you saying that at 60Hz, because the
skin depth is deeper than the coax shield is
Thanks
On Sun, Jul 20, 2014 at 8:11 AM, Oz-in-DFW li...@ozindfw.net wrote:
On 7/19/2014 3:45 PM, paul swed wrote:
Attilla I did look at some of the documents. But none showed practical HF
class injection locking. Say as an example a 6 MHz xtal to a 1 or 2 MHz
reference.
It maybe as
That sounds sort of like what they must have been doing.
But, they were quite clear that it was a Quartz thermometry
unit, and that the crystals were quartz.
And, this was before solid state IR laser diodes, around 1982.
Each temperature measuring module was plug in, and about 3/4 inch
by 5
No, the current passing the outside f the shield will not induce any
voltage inside of the coax, but the voltage drop caused by the current
on the ohmic resistance [!!!] of the shield will show upbetween the two
ends of the cable -- and that will show up as it was added to to the
voltage
Back in the 1970's I was tasked with coming up with a thermometer that could
be read in the studio of an AM radio station. I bought a Heathkit
indoor-outdoor unit. It worked great at night but was all over the place in
the daytime when the AM transmitter was on the air. Turned out the sensor
Hi
Yup
It is impractical to make coax that has a shield thickness of 1/3”. Even if you
do, it’s not going to be very flexible. For a real world system that needs good
isolation, coax is not the way to go below 100 KHz. There are a few other
issues that come up, but skin depth is a big part of
TNX Chuck!!
73
Don
W4WJ
In a message dated 7/11/2014 6:52:30 A.M. Central Daylight Time,
cfhar...@erols.com writes:
Are you sure?
According to my 1982-1986 catalogs, the combination
of a HP3586A/B, HP85 and an optional HP3336A/B is
called a HP3046A/B.
In 1980 there was a HP3040A
On Sun, Jul 20, 2014 at 7:07 PM, Al Wolfe alw.k...@gmail.com wrote:
Seems like there are IC's that contain two diodes, one as a sensor and one
as a heater. Part numbers escape me now.
You might mean the TMP36 family of sensors. They use diodes and must be
the most common sensor out there.
alw.k...@gmail.com said:
Apparently, the forward biased silicon diode was temperature sensitive
enough that a small D.C. amplifier could drive a meter to read-out with
reasonable accuracy. Well, maybe not accurate by Time-nut standards but
close enough for its intended purpose.
I think that
Lots of meanings to the word induce. The one I was using was: to
bring on, or about; effect; cause... I was not intending to imply
transformer action. As an engineer I should know better than to
try to use English to describe electrical phenomenon.
My intention was to find out what: ...the
Hi Bob,
I agree, but most of the time, you can use good design
practices to keep the currents flowing through the outside
of the shield to a minimum... avoiding ground loops, stuff
like that.
Simple coax is used for shielding very high gain circuits
from 60Hz noise all the time in PA systems.
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