HDMI interfering with Coax cable

[slider09]

Hi,

I have routed a HDMI cable and coax cable up a stud wall to feed my TV.
The Freeview on the tv only works if the bluray player is turned off (HDMI source).

Turning the Bluray on, causes Freeview to stop working with a weak or no signal message on the tv. Turn the Bluray off and within a few seconds Freeview comes back.

I have used satellite cable from Wilko's as the coax, guessing this is my issue. Would replacing this with WF100 solve this issue do you think?

Regards,

 

[Gees]

What happens if you disconnect the HDMI cable at the TV end ?
Also why would it matter as if you have the disc player turned on then i assume you would be using it?

 

[winston1]

This seems to be a common problem though I have never had it. Whether WF100 will help I don't know. If the Wilko's cable is tape and braid it should be OK. Try to separate the cables in the stud wall as much as possible and do make sure the coax plug is fitted properly including soldering the centre pin.

Http://www.megalithia.com/elect/bellinglee/index.html

Methods which bunch the screen under the claws result in an unsatisfactory screen connection letting in interference.

 

[slider09]

What happens if you disconnect the HDMI cable at the TV end ?
Also why would it matter as if you have the disc player turned on then i assume you would be using it?

I haven't disconnected the HDMI at the tv end, will try it shortly.

The bluray was only used as a test to see if the HDMI cable was ok. Eventually the HDMI will be connected to a Sky HD box in the other room (other side of the stud wall). The tv is a second tv, watching freeview whilst sky is being watched in the other room (or watch sky)

 

[slider09]

Disconnecting the HDMI from the tv with the bluray on, results in freeview returning after a couple of seconds.

Plugging it back in and after a couple of seconds freeview goes off.

 

[Lucid]

The problem you have is two-fold. You've correctly identified the Wilko cable as part of the cause. If it is the same as this then it's just a longer version of the naff freebie/cheap coax flyleads supplied with some gear. It has very poor shielding and is extremely lossy. Just a short length of 1~1.5m is enough to reduce the signal level getting to the TV by a couple of dB. If the signal was already marginal then poor coax cable like this will tip the balance in a bad direction.

The shielding problems surface when there's a source of interference. PC power supplies are a good example. They radiate a lot of high frequency electrical noise. The poor coax doesn't deal well with this and the result is that the Freeview signal gets swamped. HDMI cables also carry very high frequency signals so they're often a source of electronic interference too. It's more than a little surprising to read that there's no requirement for shielding within HDMI cables according to Steve Venuti, Director of Marketing, for the HDMI Licensing LLC. But that statement only dealt with the issue of individual conductors interfering with each other. It doesn't take account of signal interference leaking and affecting other cables running parallel which is the situation you have. Unfortunately there's a lot of HDMI cable sold in the budget market (and some that are not so cheap) where the manufacturers try to get away with the bare minimum. That, combined with cables running parallel for some distance and weak shielding in the RF coax all combine to create the sort of problems you're seeing.

As a first step then change over to Webro WF100. If things are still a bit hit and miss on occasions then have a think about changing the HDMI cable for something that is quad-screened. It doesn't have to be an expensive cable, I think some of the Amazon basics range is quad-shielded.

 

[Sam Gangee]

Methods which bunch the screen under the claws result in an unsatisfactory screen connection letting in interference.

The foremost UK professional aerial installer says you are mistaken.
http://www.aerialsandtv.com/wiringup.html#KinkyCentreCore

 

[bernardgreen]

There is also the possibility of ground loops creating current flows along the cable screens and Ov conductors. These currents create potential differences between the ends of the cable's screen. These voltages are aded to the signal and thus the TV ( and other equipment ) then get corrupted signals. Most common of these currents is a 50 Hz current from the chassis ( ground ) of equipment that does not have a mains earth. The chassis floats around 120 volts AC due to capacitive coupling between mains and the chassis. The capacity of the coupling is very small the curent is too small to create a hazard of electric shock but it can sometimes be felt as a mild tingle. But if it is flowing along a signal cable screen to a ground in other equipment then it can be large enough affect the quality of the signal passing laong the cable. When the equipment has a switched mode power supply then the 50 Hz is accompanied by high frequency currents

Disconnecting the HDMI from the tv with the bluray on, results in freeview returning after a couple of seconds

The cables are still close together so capacitive coupling from HDMI to the TV coax will still be there, the disconnection on the HDMI plug will have only removed the ground loop

 

[winston1]

Methods which bunch the screen under the claws result in an unsatisfactory screen connection letting in interference.

The foremost UK professional aerial installer says you are mistaken.
http://www.aerialsandtv.com/wiringup.html#KinkyCentreCore

Don't know why you think he is the foremost UK professional aerial installer. He is just one of many.

He also said, "Some people recommend splaying the screening strands back over the “claw” (see picture on the right), as opposed to folding them back over the insulation and under the claw, as above. Theoretically this puts the cable`s screening directly in contact with the body of the plug. On the other hand it`s messier, and personally I can`t remember ever having a problem with the “conventional way”. - See more at: http://www.aerialsandtv.com/wiringup.html#KinkyCentreCore"

I can assure you I have had problems with screening bunched up under the claws in the form of ingress and egress of interference.

What he refers to as the "conventional way" is the wrong way that many people do. The CAI recommended way is screening over the claws. I believe the CAI is more professional than one installer who happens to have an extensive website.

 

[Sam Gangee]

I don't think that Justin will be too chuffed about being called less professional than an organisation set up to promote aerial sales. His web site is extensive because he's done all the tests and come up with the best solutions.

It's quite common for the theorists to suggest one solution, only to find that the people actually doing the job have a simpler, quicker way that does the job as well if not better.

Here's another supplier that actually makes and sells cables this way - apparently thousands without complaint:
http://www.satcure.co.uk/tech/tvplugs.htm
www.youtube.com/watch?v=KdBINEM3uS4

And this guy: www.youtube.com/watch?v=Z44TBGhf6j8
And this guy: www.youtube.com/watch?v=ax_3x_nbsoc
And this guy: www.youtube.com/watch?v=5waKUYyZ96o
And this guy: www.youtube.com/watch?v=MJgELXrfVJc
And this guy: www.youtube.com/watch?v=fxHXPltuZ74
And this guy: www.youtube.com/watch?v=CfJrneEKdZM

I really looked but I can't find anyone doing it your way.

 

[Lucid]

I can assure you I have had problems with screening bunched up under the claws in the form of ingress and egress of interference.

It would help tremendously if you could point to some peer reviewed rigorously tested evidence to support your case.

Also, I wouldn't be so quick to rely on the CAI as the arbiter of quality. Firstly, CAI stands for Confederation of Aerial Industries and from that you can see that it's there to promote the interests of the companies making money from making equipment. Secondly, a confederation is simply a group of like-minded individuals... So are the Moonies.

Anyone can form a confederation. I could meet up with the other installers I know and form the Confederation of Bacon Butty Eaters. Just because there's a group of folk ganged together and made up some rules doesn't mean they're always correct. Remember, it was the CAI that told us that screw on F connectors are bad and we should all be using crimp plugs. That is until compression plugs came along and suddenly crimps are bad (They are actually as they rely on crushing the cable to make a connection, but it's curious how they glossed over that when telling us we should all buy crimp plugs and crimp tools. Now I wonder who makes those? )

The situation isn't black and white. I'm in favour of some of the aims of the CAI, but that doesn't mean I tow the whole party line. As Sam Gangee rightly said, organisations can come up with theories of how things should be done, but it's only after field testing that those theories are are validated or dismissed. That's actually the basis of modern science.

 

[winston1]

I don't think that Justin will be too chuffed about being called less professional than an organisation set up to promote aerial sales. His web site is extensive because he's done all the tests and come up with the best solutions.

It's quite common for the theorists to suggest one solution, only to find that the people actually doing the job have a simpler, quicker way that does the job as well if not better.

Here's another supplier that actually makes and sells cables this way - apparently thousands without complaint:
http://www.satcure.co.uk/tech/trvplugs.htm
www.youtube.com/watch?v=KdBINEM3uS4

And this guy: www.youtube.com/watch?v=Z44TBGhf6j8
And this guy: www.youtube.com/watch?v=ax_3x_nbsoc
And this guy: www.youtube.com/watch?v=5waKUYyZ96o
And this guy: www.youtube.com/watch?v=MJgELXrfVJc
And this guy: www.youtube.com/watch?v=fxHXPltuZ74
And this guy: www.youtube.com/watch?v=CfJrneEKdZM

I really looked but I can't find anyone doing it your way.

 

[winston1]

It is not my way. It is the CAI recommended method. The Megalitha site I first linked to does it this way. Justin also admits it is a way of doing it, though he says he has had no problems doing it the other way. Sat cure also admit it is a way of doing it.

I have done it this way for over 50 years and have come across many instances of problems doing it the other way. If you ever worked in the cable or RF distribution industry you would come across these problems yourself. It is most noticible at VHF frequencies (still used in the cable industry) where the poor screen connection causes moire patterning. It is less noticible at UHF as the capacitance of the break is much lower impedance at UHF.

Believe me we are looking at causes of HDMI interference and making up a coax plug this way will contribute to it.

 

[bernardgreen]

from my days workng in radio comms I recall that screen UNDER the claw was the companies prefered method. It was if I recall correctly the method use by Home Office engineers as well. In some plugs there was no option as the hole in the claw was a tight ft over the insulation with no space for the screen.

That said most of the plugs on comms equipment ( both TX and RX ) were N type where the screen was soldered to the connector.

 

[winston1]

I really looked but I can't find anyone doing it your way.

Look here then.

http://www.megalithia.com/elect/bellinglee/index.html