OT Cat 7 Ethernet Cable

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OT Cat 7 Ethernet Cable

David Ahrendts
A quickie as I work through my RFI house cleaning. Anyone have experience in using Cat 7 cable vs. Cat 6 in a home network? It’s my understanding Cat 7 is extensively shielded while Cat 6 is not which ought to help that ethernet “hash” issue.

David A., KK6DA, LA



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Re: OT Cat 7 Ethernet Cable

Clay Autery
What exactly are you trying to fix...  Class 7 has higher twist rate,
overall shielding and shielding per pair.  It is certified for use up to
600 MHz at up to 100 meter runs.  Terminated with 8P8C connectors.  CAT
7a is augmented 7 good up to 1GHz...  And there is a draft in the works
for CAT 8 (good to 1.6-2.0 GHz)  still with 8P8C connectors.

I'm not sure what the RFI issue would be that would require CAT 7...
Tell me what you're trying to fix and I can offer more info...

______________________
Clay Autery, KG5LKV
MONTAC Enterprises
(318) 518-1389

On 3/7/2016 12:32 PM, David Ahrendts wrote:

> A quickie as I work through my RFI house cleaning. Anyone have experience in using Cat 7 cable vs. Cat 6 in a home network? It’s my understanding Cat 7 is extensively shielded while Cat 6 is not which ought to help that ethernet “hash” issue.
>
> David A., KK6DA, LA
>
>
>
> David Ahrendts   [hidden email]  
>
>
>
>
> ______________________________________________________________
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Re: OT Cat 7 Ethernet Cable

Jim Brown-10
On Mon,3/7/2016 11:07 AM, Clay Autery wrote:
> I'm not sure what the RFI issue would be that would require CAT 7...
> Tell me what you're trying to fix and I can offer more info...

There are well known issues with equipment using one of the wired
Ethernet standard rates (have forgotten which one) generating carriers
at several frequencies in the HF bands and on 6M. I'm primarily a CW
guy, so the ones I run into are around 14030, 21052, the low end of 10M,
the low end of 6M, and a couple of frequencies on 30M. These signals are
radiated as a common mode signal, and I've been told that properly
terminated shielded CAT5/6/7 eliminates it. Properly terminated means
both in the cable-mounted plug and the equipment-mounted jack. I've also
experienced broadband hash on 2M with a talkie within a foot or two of
unshielded CAT5/6, including Belden's excellent Mediatwist cable.

In addition to its use for wired Ethernet, unshielded CAT5/6/7 is quite
useful in noise sensitive circuits because of its high twist ratio. As
with Ethernet, twisted pairs reject noise and crosstalk ONLY when wired
with one pair per circuit -- that is, or and or/blk as a circuit, bn and
bn/blk as a circuit, and so on.

73, Jim K9YC
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Re: OT Cat 7 Ethernet Cable

Clay Autery

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Re: OT Cat 7 Ethernet Cable

Clay Autery
In reply to this post by Jim Brown-10
something is acting up on my end... my last response came through "blank".

Here's another try:
*************************************************************************
There is no unshielded CAT 7/7a...  at lower classes the
cable/connectors may be chosen as UTP or STP...  Cat 7 and above is
DOUBLE shielded.  Overall shield (braid) and shield per pair (aluminum
tape).

Any device putting out RFI as common mode are NOT in spec....  Whether
they can be "fixed" or not has a lot to do with what "mistake" in design
caused the problem in the first place.  That has to be determined by
device.  Depending on the cause of the RF generation, there are a number
of ways to mitigate/eliminate the problem...  Shielded cable is only ONE
possible component in the overall solution.

A non-inclusive list of causes:

Badly designed and/or shielded switch mode power supply (wall wart OR
internal).  A wall wart can radiate via the DC cord to the device and/or
send the signal into the device via the DC cable and then radiate via
the chassis or signal cables..  USUALLY internal PSs are adequately
shielded... but poor input filters or none at all can let the bad stuff
through.

Wireless radios that are improperly designed or shielded can also be the
culprit.

Not having a separate logical and chassis ground can be a problem...

Crappy fans...  (best devices have properly designed passive cooling).

Lots of ways for a bad design to create noise.

Shielded cables work best in my experience when you can create an
isolated chassis (or supplemental Faraday cage type superior to the
chassis (or internal to a plastic case) where the outer shield of the
cable and connector housing can be connected in one continuous shield
around the device(s) and the cable, etc, etc...

The benefit to CAT 7/7a would be the double shielding and the superior
connector termination and housings... make for easier continuous shield
external connections to drain/ground, et al.

Typically, it would be cheaper/more reliable to buy a properly designed
device in the first place...

Note: there is a CAT 8 draft spec out now...

CAT 7(+) would make an excellent 4 circuit control wire for remotes and
the like since it has shield per pair...
CAT 7(a) cable, connectors, and tooling is insanely expensive by
comparison to 5/5e and even 6(+)

______________________
Clay Autery, KG5LKV
MONTAC Enterprises
(318) 518-1389

On 3/7/2016 4:48 PM, Jim Brown wrote:

> On Mon,3/7/2016 11:07 AM, Clay Autery wrote:
>> I'm not sure what the RFI issue would be that would require CAT 7...
>> Tell me what you're trying to fix and I can offer more info...
>
> There are well known issues with equipment using one of the wired
> Ethernet standard rates (have forgotten which one) generating carriers
> at several frequencies in the HF bands and on 6M. I'm primarily a CW
> guy, so the ones I run into are around 14030, 21052, the low end of
> 10M, the low end of 6M, and a couple of frequencies on 30M. These
> signals are radiated as a common mode signal, and I've been told that
> properly terminated shielded CAT5/6/7 eliminates it. Properly
> terminated means both in the cable-mounted plug and the
> equipment-mounted jack. I've also experienced broadband hash on 2M
> with a talkie within a foot or two of unshielded CAT5/6, including
> Belden's excellent Mediatwist cable.
>
> In addition to its use for wired Ethernet, unshielded CAT5/6/7 is
> quite useful in noise sensitive circuits because of its high twist
> ratio. As with Ethernet, twisted pairs reject noise and crosstalk ONLY
> when wired with one pair per circuit -- that is, or and or/blk as a
> circuit, bn and bn/blk as a circuit, and so on.
>
> 73, Jim K9YC

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Re: OT Cat 7 Ethernet Cable

Jim Brown-10
On Mon,3/7/2016 6:47 PM, Clay Autery wrote:
> Any device putting out RFI as common mode are NOT in spec

Perhaps, but such devices are VERY common in the consumer world. I have
no contact with the pro world of IT.

> ....  Whether
> they can be "fixed" or not has a lot to do with what "mistake" in design
> caused the problem in the first place.  That has to be determined by
> device.  Depending on the cause of the RF generation, there are a number
> of ways to mitigate/eliminate the problem...  Shielded cable is only ONE
> possible component in the overall solution.

Yep. Suitable common mode chokes can make a big dent in the RF trash
radiated by the cable.

> A non-inclusive list of causes:
>
> Badly designed and/or shielded switch mode power supply (wall wart OR
> internal).

The Ethernet birdies/carriers I listed are from the data stream, NOT
from the PSU. Of course the PSU often generates trash, but it's
DIFFERENT trash. :)

>   A wall wart can radiate via the DC cord to the device and/or
> send the signal into the device via the DC cable and then radiate via
> the chassis or signal cables..  USUALLY internal PSs are adequately
> shielded... but poor input filters or none at all can let the bad stuff
> through.

Trash that radiates to our antennas is COMMON mode, not differential
mode, and common mode is caused by improper return paths, and it cannot
be "filtered." Filtering affects differential mode trash.

> Wireless radios that are improperly designed or shielded can also be the
> culprit.

I can't see any way that a 900 MHz or 1.8 GHz radio can cause RFI at HF.
It is the baseband digital signals that have HF components.

> Not having a separate logical and chassis ground can be a problem...

WRONG -- that is a CAUSE of problems, not a solution. See Henry Ott's
classic text on EMC.

> Shielded cables work best in my experience when you can create an
> isolated chassis (or supplemental Faraday cage type superior to the
> chassis (or internal to a plastic case) where the outer shield of the
> cable and connector housing can be connected in one continuous shield
> around the device(s) and the cable, etc, etc...

EXACTLY WRONG. For shielding to be effective, it must be continuous,
including a termination to the shielding enclosure at both ends. Again,
see Ott.
> The benefit to CAT 7/7a would be the double shielding and the superior
> connector termination and housings... make for easier continuous shield
> external connections to drain/ground, et al.
>
> Typically, it would be cheaper/more reliable to buy a properly designed
> device in the first place...

Of course. :) IF you can identify one. But that requires a published,
competent, technical review of products on the market that include RFI.  
Call me collect when you find such a thing. :)
> CAT 7(+) would make an excellent 4 circuit control wire for remotes and
> the like since it has shield per pair...

Those working in the world of pro audio deal every day with microphone
signals in the range of -140 dBu, with required dynamic range of at
least 110 dB, and typically have 24-32 mics active in a given recording
or production. Any coherent noise that is present in multiple inputs
will degrade s/n by 3 dB per doubling of the number of inputs, and
modulation of an RF signal present on multiple inputs will be coherent
after detection. My point is that pro audio faces a s/n problem FAR
worse that we do in the radio or computer networking world. In that
world, we have learned that TWISTING is at least as important as
shielding, and often MORE important.

That said, serious contesters with extensive IT background have reported
that STP does kill Ethernet birdies, and I believe them. I've never
heard a suggestion that CAT7 was needed, nor have I ever read a spec for
any of these cables.

73, Jim K9YC
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Re: OT Cat 7 Ethernet Cable

Clay Autery
On 3/7/2016 9:50 PM, Jim Brown wrote:
> On Mon,3/7/2016 6:47 PM, Clay Autery wrote:
>> Any device putting out RFI as common mode are NOT in spec
>
> Perhaps, but such devices are VERY common in the consumer world. I
> have no contact with the pro world of IT.

Yep... just like a LOT of consumer grade electronics, the manufacturers
intentionally ignore or falsify the FCC certifications.  Generally, you
get what you pay for.

>> A non-inclusive list of causes:
>>
>> Badly designed and/or shielded switch mode power supply (wall wart OR
>> internal).
>
> The Ethernet birdies/carriers I listed are from the data stream, NOT
> from the PSU. Of course the PSU often generates trash, but it's
> DIFFERENT trash. :)

That's a very definitive statement...  while an unlikely cause of
multiple HF region emissions, switch-mode PS frequently switch at
frequencies in/around HF frequencies.

>>   A wall wart can radiate via the DC cord to the device and/or
>> send the signal into the device via the DC cable and then radiate via
>> the chassis or signal cables..  USUALLY internal PSs are adequately
>> shielded... but poor input filters or none at all can let the bad stuff
>> through.
>
> Trash that radiates to our antennas is COMMON mode, not differential
> mode, and common mode is caused by improper return paths, and it
> cannot be "filtered." Filtering affects differential mode trash.

As I said, it is a NON-inclusive list and there are multiple ways to
generate "trash".
>
>> Wireless radios that are improperly designed or shielded can also be the
>> culprit.
>
> I can't see any way that a 900 MHz or 1.8 GHz radio can cause RFI at
> HF. It is the baseband digital signals that have HF components.

A wireless "router" radio is a radio just like any other...  they take
an input signal, massage it and send out a signal...  they are subject
to the SAME design issues as any other radio.  IF frequency(ies),
mixers, oscillators, et al.  Subject to the same mixing products and
improperly shielded can radiate any product, harmonic, etc.
>
>> Not having a separate logical and chassis ground can be a problem...
>
> WRONG -- that is a CAUSE of problems, not a solution. See Henry Ott's
> classic text on EMC.
Perhaps I should have been more precise...  logical ground and a chassis
shield.  Although, there ARE in fact many electronic devices where the
device itself has an isolated logical "ground" and the entire device is
located WITHIN a totally separate shield from end to end essentially
floating the devices on each end and the signals inside their own "space".

>> Shielded cables work best in my experience when you can create an
>> isolated chassis (or supplemental Faraday cage type superior to the
>> chassis (or internal to a plastic case) where the outer shield of the
>> cable and connector housing can be connected in *one continuous shield*
>> around the device(s) and the cable, etc, etc...
>
> EXACTLY WRONG. For shielding to be effective, it must be continuous,
> including a termination to the shielding enclosure at both ends.
> Again, see Ott.

Read what I wrote again.  Chassis/shield to cable connector shield to
cable shield to connector shield on the other end to the
chassis/shield.  One continuous shield...
What may have confused you is that I was considering both well-designed
devices with chassis designs that act as or contribute to the shielding
vs. the majority of consumer grade devices which do NOT have a shielding
chassis...  e.g. plastic case with venting, etc.  MOST of this consumer
grade stuff has 8P8C modular jacks that are designed to accept UTP RJ-45
connectors made of plastic thus they do not provide any means for a
metal shielded connector (a la STP CAT 5/5e/6+ or all CAT 7 and above.
IF you didn't do anything else, the STP cable and connectors would do
little to assist because they are NOT connected to the
chassis/supplemental shield and have no path to ground.

On a device with a plastic case providing no overall shielding and/or if
the radio shield or PS shield, or any other potential "trash" maker
(common OR differential) circuit is not properly designed and/or
shielded, and/or filtered, or other mitigating method, you're peeing
into the wind by simply adding shielded cables.  You can connect a drain
to ground from the cable/connector housing and that will help...  BUT
what you really have to do to clean up a non-FCC compliant device
putting out harmful/unwanted IF is to either/both/hybrid:

1) Construct an internal shield that will block the radiation from
leaving the enclosure AND connects to the signal cable shields and
thence to ground...  OR, if you can't do it internally,...
2) create and EXTERNAL shield with the same electrical characteristics.
3) Some hybridization of the 1 and 2.

Bottom line...  we said the exact same thing...

>> CAT 7(+) would make an excellent 4 circuit control wire for remotes and
>> the like since it has shield per pair...
>
> Those working in the world of pro audio deal every day with microphone
> signals in the range of -140 dBu, with required dynamic range of at
> least 110 dB, and typically have 24-32 mics active in a given
> recording or production. Any coherent noise that is present in
> multiple inputs will degrade s/n by 3 dB per doubling of the number of
> inputs, and modulation of an RF signal present on multiple inputs will
> be coherent after detection. My point is that pro audio faces a s/n
> problem FAR worse that we do in the radio or computer networking
> world. In that world, we have learned that TWISTING is at least as
> important as shielding, and often MORE important.

On that we agree...  Back in the days of IDE hard disk drives, the
standard was 12-24 inches MAX cable length because of the flat ribbon
cable (and other considerations).  I successfully designed shielded
twisted-pair cables terminated to the 40-conductor internal connectors.
We got multiple increases in the spec length with no performance
degradation out to many feet and external HDD enclosures (used for
thermal design and other in chassis considerations).  Ultimately, after
tweaking wire size, twist rate, and adding overall shielding (properly
terminated), we were able to remotely locate ALL of the HDD for a 12
board/ 1 master encryption cluster more than 100 feet away with perfect
performance and no RF, cross-talk, or timing issues.  Same thing with
Ethernet cables and others.  You can frequently multiply the spec length
or signal frequency/data capacity using many of the same methods.

Signals are signals... whether they are in audio interconnects, mic
cables, computers, et al.  You do what is required to keep signal
integrity and not cause external interference.

> That said, serious contesters with extensive IT background have
> reported that STP does kill Ethernet birdies, and I believe them. I've
> never heard a suggestion that CAT7 was needed, nor have I ever read a
> spec for any of these cables.

IF they have an "extensive IT background" they'd know a floating STP
cable won't work nearly as good as one where the shield is properly
terminated/utilized.


Have a good evening...

______________________
Clay Autery, KG5LKV
MONTAC Enterprises
(318) 518-1389


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Re: OT Cat 7 Ethernet Cable

Jim Brown-10
On Mon,3/7/2016 8:56 PM, Clay Autery wrote:
> On 3/7/2016 9:50 PM, Jim Brown wrote:
>>
>> The Ethernet birdies/carriers I listed are from the data stream, NOT
>> from the PSU. Of course the PSU often generates trash, but it's
>> DIFFERENT trash. :)
> That's a very definitive statement...  while an unlikely cause of
> multiple HF region emissions, switch-mode PS frequently switch at
> frequencies in/around HF frequencies.

Actually, switch-mode power supplies run in the range of 10-50 kHz, NOT
at HF.  It is the unfiltered high order harmonics that we hear at HF.

>
>>> Wireless radios that are improperly designed or shielded can also be the
>>> culprit.
>> I can't see any way that a 900 MHz or 1.8 GHz radio can cause RFI at
>> HF. It is the baseband digital signals that have HF components.
> A wireless "router" radio is a radio just like any other...  they take
> an input signal, massage it and send out a signal...  they are subject
> to the SAME design issues as any other radio.  IF frequency(ies),
> mixers, oscillators, et al.  Subject to the same mixing products and
> improperly shielded can radiate any product, harmonic, etc.

But the IF and mixing products are NOT at HF. Trash from WiFi systems is
produced by the baseband digital electronics and the switch mode power
supplies, NOT from any part of the RF system.

>>> Not having a separate logical and chassis ground can be a problem...
>> WRONG -- that is a CAUSE of problems, not a solution. See Henry Ott's
>> classic text on EMC.
> Perhaps I should have been more precise...  logical ground and a chassis
> shield.  Although, there ARE in fact many electronic devices where the
> device itself has an isolated logical "ground" and the entire device is
> located WITHIN a totally separate shield from end to end essentially
> floating the devices on each end and the signals inside their own "space".

As Ott has observed, there are holes in that design logic.

>
> What may have confused you is that I was considering both well-designed
> devices with chassis designs that act as or contribute to the shielding
> vs. the majority of consumer grade devices which do NOT have a shielding
> chassis...  e.g. plastic case with venting, etc.

Yes, I did miss that.

> MOST of this consumer
> grade stuff has 8P8C modular jacks that are designed to accept UTP RJ-45
> connectors made of plastic thus they do not provide any means for a
> metal shielded connector (a la STP CAT 5/5e/6+ or all CAT 7 and above.
> IF you didn't do anything else, the STP cable and connectors would do
> little to assist because they are NOT connected to the chassis/supplemental shield and have no path to ground.

Exactly right.

> On a device with a plastic case providing no overall shielding and/or if
> the radio shield or PS shield, or any other potential "trash" maker
> (common OR differential) circuit is not properly designed and/or
> shielded, and/or filtered, or other mitigating method, you're peeing
> into the wind by simply adding shielded cables.  You can connect a drain
> to ground from the cable/connector housing and that will help

I don't get "drain to ground."

It IS possible to make unshielded equipment RF-quiet with proper circuit
layout and construction. The return for current in a circuit trace over
a continuous "ground" layer flows in the very small area of the "ground"
trace directly under the circuit trace, forming a transmission line. In
effect, the "ground" layer shields the conductor. Thia single "ground"
layer technique is called "microstrip; a second "ground" layer on the
other side of the trace provides much more shielding, and that
construction is called stripline.

With this sort of construction and no chassis, shield return would need
to be to an island of copper at the perimeter of the board, and all
cable shields and external "ground" paths (like power supply) would need
to be terminated to that perimeter shield. As with a chassis, shield
current stays "outside the box." But if that "ground" layer is broken
under the signal trace, return current follows whatever path left to it
by the whim of the PC board layout "artist," which often forms a large
loop that includes the chassis or some long return path on the board.
Now, it's no longer a transmission line, it's an antenna (and a magnetic
loop), so signal escapes both by antenna action and magnetic coupling.

> ...  BUT
> what you really have to do to clean up a non-FCC compliant device
> putting out harmful/unwanted IF is to either/both/hybrid:
>
> 1) Construct an internal shield that will block the radiation from
> leaving the enclosure AND connects to the signal cable shields and
> thence to ground...  OR, if you can't do it internally,...
> 2) create and EXTERNAL shield with the same electrical characteristics.
> 3) Some hybridization of the 1 and 2.
>
> Bottom line...  we said the exact same thing...

Not quite. What I've observed is that MOST of the noise we hear on HF is
common mode current on cables connected to the device, NOT due to the
device being poorly shielded. Yes, SOME noise is radiated directly from
poorly shielded and/or equipment with the PCB layout issues I noted, but
that part of the noise is rarely dominant because the antennas inside
the box are too small to be efficient at HF, whereas the antennas
carrying the common mode current (the interconnecting cables are usually
much longer (including path to other equipment, power supply, facilities
ground, etc.)

I would NEVER waste my time shielding a poorly shielded box that was bad
enough for me to hear. I would dump it and buy something without that
problem.

73, Jim K9YC
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Re: OT Cat 7 Ethernet Cable

Clay Autery
On 3/7/2016 11:56 PM, Jim Brown wrote:
> Actually, switch-mode power supplies run in the range of 10-50 kHz,
> NOT at HF.  It is the unfiltered high order harmonics that we hear at HF.
Yep... I was wrong, you are right.  Not fundamental, but harmonics.  I
should stop writing in the middle of all-nighters.


> But the IF and mixing products are NOT at HF. Trash from WiFi systems
> is produced by the baseband digital electronics and the switch mode
> power supplies, NOT from any part of the RF system.
>

I agree that the much more likely candidate is the Ethernet switching.
But the standard Ethernet signaling is differential...  PoE could
definitely be a culprit, since one of the methods involves tapping the
Ethernet pulse transformer for a voltage source.  But, whatever the
SOURCE of the trash, it is generated inside the device and inadvertently
being radiated over the UTP.

Bottom Line: There is no shortage of potential places inside a typical
Wireless Switch/Router where RF issues can be created...  especially
when their designs are targeted to meet a price point rather than comply
with PART 15.  I'm a bigger fan of eliminating the source than I am of
mitigating the effects... at least these days I am.  There was a time
when I enjoyed "making stuff work".

I confess, I don't design wireless data radios, so I have no idea what
the IF/oscillator freqs are.  I was simply stating that wireless data
radio is a radio.

>> Perhaps I should have been more precise...  logical ground and a chassis
>> shield.  Although, there ARE in fact many electronic devices where the
>> device itself has an isolated logical "ground" and the entire device is
>> located WITHIN a totally separate shield from end to end essentially
>> floating the devices on each end and the signals inside their own
>> "space".
>
> As Ott has observed, there are holes in that design logic.

Don't shoot the messenger.  Tell the DoD, NASA, NSA, and a host of
private companies to include Cisco, etc.  I'm just telling you what's
out there.

Ott wrote a lot...  are there specific references you'd care to share?
I'd be interested to read some of his theories with respect to this
subject.  Online refs if possible; I've exceeded my book budget for the
month... heck for the year.  ;-)

> I don't get "drain to ground."

I apologize... perhaps I stated it wrong.  Many shielded cable types
(not typically STP cable)  come with a "drain" wire to make it easier to
terminate the shield...  not used a lot in data cable...  but I
sometimes use the term to refer to a conductor that connects to a cable
connector housing or to the cable shield whose purpose is to assist in
grounding the cable shield or creating continuity between the cable
shield and the shielded termination.  In the case of the "plastic crap"
I described above without additional shielding added and internal
connection to the cable connector somehow, the alternative solution of
trying to make the STP cable a less efficient radiator involves using
"drain" conductors to try and shunt the RF to ground before it can radiate.

> It IS possible to make unshielded equipment RF-quiet with proper
> circuit layout and construction.
Yes, of course.  But MOST manufacturers have "discovered" that they can
design to a price-point and ignore Part 15, et al. because of the
unlikelihood that the FCC will pursue them for their massive violations
(think of the number of non-compliant consumer data devices in the filed
and sold each year).  Sad really, because it doesn't take all that much
more time to design and manufacture a proper board.  One would think
that a couple hundred thousand HAMs making complaints against a massive
number of obviously non-compliant crap consumer electronics might
generate a response... Needs to be coordinated.

<PCB design criteria was here>  We agree on that entirely.

> Not quite. What I've observed is that MOST of the noise we hear on HF
> is common mode current on cables connected to the device, NOT due to
> the device being poorly shielded. Yes, SOME noise is radiated directly
> from poorly shielded and/or equipment with the PCB layout issues I
> noted, but that part of the noise is rarely dominant because the
> antennas inside the box are too small to be efficient at HF, whereas
> the antennas carrying the common mode current (the interconnecting
> cables are usually much longer (including path to other equipment,
> power supply, facilities ground, etc.)
Gotcha...  Having never needed to chase RFI to HF in my own home/office,
I'll defer to your obviously superior level of direct experience.  I
think it might be interesting to actually have the harmful RFI tracked
to specific causes in a large range of device models to see if the
sources cluster around a particular design "flaw"/choice(s).

> I would NEVER waste my time shielding a poorly shielded box that was
> bad enough for me to hear. I would dump it and buy something without
> that problem.
Absolutely...  Today, I would agree with you, but there was a time when
I would not have had the economic luxury of "dumping" a piece of
equipment.  It's nice to know that you CAN do something because you've
done it before.

Have a good day, Jim!

Clay,  KG5LKV
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Re: OT Cat 7 Ethernet Cable

Jim Brown-10
Without repeating a long response to my long post, we do agree on all
key points. Including the fact that the vast majority of manufacturers
get shield bonding wrong.

Here's a link to Henry Ott's website. Scroll down to find a reference to
the latest edition of his book. It is often used as a text for EE
courses in EMC.  I attended his 3-day EMC course about ten years ago. It
was time and money well spent. I'm past chair of the Tech Committee on
EMC for the AES, and subsequently invited for him to present expert
lectures to two AES Conventions.

http://www.hottconsultants.com/

73, Jim K9YC

On Tue,3/8/2016 7:24 AM, Clay Autery wrote:
> Gotcha...  Having never needed to chase RFI to HF in my own home/office,
> I'll defer to your obviously superior level of direct experience.  I
> think it might be interesting to actually have the harmful RFI tracked
> to specific causes in a large range of device models to see if the
> sources cluster around a particular design "flaw"/choice(s).

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Re: OT Cat 7 Ethernet Cable

Jim Brown-10
In reply to this post by Jim Brown-10
Thanks, Brendon.  Hopefully the miniaturization offered by SMT reduces
the size of the antennas that radiate any trash. :)  But that may be
wishful thinking -- W6GJB encountered massive noise on HF that he
tracked down to computer extension speakers with built-in power amps
that were powered from a USB port. I suspect that this sort of circuit
was used.

73, Jim K9YC

On Tue,3/8/2016 8:33 AM, Brendon Whateley wrote:
> Guys, surface mount switch mode power supplies run at up to 4MHz (and
> much more) nowadays in pursuit of efficiency and small size. A lot of
> digital circuits have them embedded on the board to convert voltages
> for low voltage/high current chip cores.
>
> Here is the first design doc I could find:
> http://www.digikey.com/en/articles/techzone/2015/feb/design-trade-offs-when-selecting-a-high-frequency-switching-regulator 
>
>

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Re: OT Cat 7 Ethernet Cable

Eric Swartz - WA6HHQ
Administrator
Folks - Let's rest this thread for now as we have seen a number of posting on
this OT today.
Thread closed.

73,

Eric
Lost moderator
/elecraft.com/
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