Peter, why are you making your own cable instead of buying a cable from a
reliable and quality manufacturer? (I don't expect an answer to this question)
I personally don't think braids are great. I prefer to use cables with foil
and braid shields. Or at least multiple braided shields. What percentage of
coverage does your braid have?
I haven't looked at the HDMI spec in a long time, but it likely has twisted
pair requirements. Does your cable meet those requirements? How good is
your termination of the twisted pairs?
Jim Bacher, WB8VSU
[email protected]
JBRC Consulting LLC
Product EMC & Regulatory Consultant
https://www.trc.guru/ email:[email protected]
IEEE Life Senior Member
On May 15, 2025 1:15:21 PM "[email protected]"
<[email protected]> wrote:
Thank you all. It happens with every source and sink. However the frequency
changes depending on what source I use which tells me it could not be the
cable. I use laptop or PC and monitor.
On Thursday, May 15, 2025 at 09:19:28 AM PDT, John Woodgate
<[email protected]> wrote:
I agree: a cable only radiates what it is fed. If it is properly
terminated, circuit-wise and shielding-wise, it's being fed too lavishly.
In this case, the good shielding indicates high common-mode current in the
shield. It could be interesting to measure the emissions with a cable
shield connected at the sending end only. This obviously stops the CM
current, but the CM then appears as voltage on the shield. Interpreting the
results requires thought; one deduction might be the internal impedance of
the source of the CM, leading to identifying the source.
On 2025-05-15 16:55, Ted Eckert wrote:
Hi Peter,
The last time I had a similar problem with HDMI, the issue wasn't the
cable. The host device had an improper PCB layout for the HDMI signals.
Paired signal traces weren't properly matched leading to extra noise. Is
your issue with just one host product or with multiple products?
Ted Eckert
The opinions expressed are my own and do not necessarily reflect those of
my employer.
From: [email protected] <[email protected]>
Sent: Thursday, May 15, 2025 8:43 AM
To: [email protected] <[email protected]>
Subject: [EXTERNAL] [PSES] HDMI cable emissions
You don't often get email from
[email protected]. Learn why this is important
Hello group,
I am working on a HDMI cable where it does not pass radiated emissions with
good margin. I have great braid coverage and have soldered the braid to the
connector shell and have fully sealed and covered it with copper tape. Is
there anything else that I need to do? My issue is mainly at below GHz when
I use 1080P resolution.
Thank you
Peter
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