Zebra TV

Mark Maulden · Jun 10, 2014

What inverter are u using? Some don't get "pure" until loaded up a bit..

JohnShannon · Jun 10, 2014

So if the inverter is unpowered and you are running on shore power you still have this problem??? If so then probably not the inverter.

Benny17441 · Jun 11, 2014

Detecting the source of signal interference can be difficult. I would as a test eliminate the Coax/Converter and run straight RCA cables. Test with both shorepower and the inverter. If the problem continues to be the same I would say the source of interference is coming from a component in the Nav station. In order to eliminate the DVD player itself I would remove it and place it close to the TV and again test it with both sources of power. What is a little bit puzzling is that you indicate that prior to installing the inverter every thing was working fine I presume in the same configuration. The only explanation I can think of is that some component or connection got disturbed during the inverter installation but the suggested tests would either point to or eliminate the possibility.

Brian D · Jun 11, 2014

Could be what is known as a "common-mode" issues. This happens when there is a mismatch between signal devices. Coax is either 50Ω or 75Ω. RCA cable might be 600Ω. If there is a mismatch you might be getting voltage on the return path and that is causing the lines on your screen. It might need a 12:1 matching device.

Benny is correct in trying with RCA cable for testing purposes. If the lines go away then you will need to pull out the coax and replace with RCA cable (or higher impedance cable).

Brian D · Jun 11, 2014

Yes, it could be a ground loop. Find two points that do not share the same ground and grab them (LOL). Or better yet, if you have a DVM use that. Check to see if there is a voltage on the the two ground points.

walt · Jun 12, 2014

There is a rca-coax converter installed ( also powered from the inverter)

What is this converter that needs to be powered? It sounded like you just needed a passive RCA cable to coax cable adapter but if something needs to be powered.. Its more complicated and possibly the source of the noise.

RCA video (composite) is 75 ohm and coax is generally 50 ohm but the RCA video signal is barely over 4 MHz so the cable impedance pretty much does not matter.

Back in the "old days", if you were sending the video from a DVD to the TV using a UHF modulator, you could easily have noise like you mentioned from an inverter. But you pretty much can not even buy a TV now with the old analog tuners or modulators.

Might be some sort of ground loop and if your converter is noisy, might also be the cause. But that powered coax to rca converter - whatever it is - might be worth taking a look at (and something to get rid of)

walt · Jun 12, 2014

Do you have a link to that converter? Your problem is that technically speaking, you can not simply mix a 50 ohm to 75 ohm system without a loss if its passive (which you would notice in the video). So its possible that a powered impedance converter was used because no one sells a passive adapter (and might only sell one unit in the products life time).

However.. terrible overkill for 4.2 Mhz composite video. You would be better off just splicing an RCA connector to the coax cable (assuming that cable is only carrying 4.2Mhz composite video - which I really cant tell without knowing what converter is being used and how its being used??). Just do a good job with the shield connection of the splice but it does not need to be at all perfect.

HDMI - WAY better way to go plus better video quality... but 50 foot... might be pushing things. If you hook up the HDMI cable (still powering with the inverter), does the noise go away?

Also confusing.. if that is a composite video cable run done with coax, you would also need seperate audio cables run. If its only one cable carrying both audio and video.. could be the old UHF analog stuff and very likely to pickup noise from an inverter.

walt · Jun 12, 2014

You cant splice the coax cable to RCA - sorry I didnt understand your original hookup.

The converter box in the link looks like it uses the channel 3/4 VHF analog modulation. Your DVD player must be fairly old and has a channel 3/4 VHF output that is on the long coax cable run (which is likely 75 ohm - but that does not matter).

The converter box takes the channel 3/4 VHF signal and converts it to the baseband RCA video and audio (red, white, yellow). Edit - the box takes RCA baseband A/V and conversts to 3/4 VHF - the TV must have an old analog tuner if that worked..

That setup is definately going to be susceptable to picking up noise from the inverter... plus its really about the poorest quality video possible even when working well.

Assuming I understand the system, I think I would dump the DVD player and converter box, buy a new DVD player that has HDMI and use the HDMI cable (which has both audio and video).

walt · Jun 12, 2014

35 foot RCA cable run.. might work just fine but some risk in picking up noise because of poor cable shielding. Not all RCA cables are created equal for the shields. You might lose a little audio and video bandwidth but you probably will not notice and its still better than using a channel 3/4 VHF.

Also, that HDMI cable seems fairly long and could have issues - dont know. But you might also use an RCA A/V to HDMI converter like this
http://www.monoprice.com/Product?c_id=101&cp_id=10114&cs_id=1011406&p_id=9994&seq=1&format=2

I beleive the output of the DVD player you have is RCA baseband ("composite" yellow, red, white) and this would get converted to HDMI. The long cable run would be HDMI and most likely much less likely to pick up noise. This assumes your TV has a HDMI input.

If you have a different DVD player that has a HDMI output, I would test that 50 foot HDMI cable first. HDMI is digital so will either work or not. If the second DVD player works, chances are some sort of converter box like Google found in the link above might also work.

kito · Jun 12, 2014

I looked online at your manual and it may be state of the art for having 10 lbs of stuff in a 2 lb bag but as a dvd player it's 15 years behind. It only has the low quality yellow cable video connection. Not even s-video or component video output. You have a HD tv, may as well buy a seperate blu ray player and run your 50 ft HDMI cable to it and enjoy HD. It will still play dvds too. Btw, I run a 50ft Hdmi cable at home to my Epson projector and does fine.

Brian S · Jun 12, 2014

Following on Kito's heels, if you decide to get rid of the old DVD player and go for a Blu-Ray with HDMI, if you've got a 50' run, you can still run into problems, because HDMI is a shitty video interconnect to begin with. You can read up on a few of the challenges of long HDMI runs here: http://www.bluejeanscable.com/store/hdmi-cables/hdmi-cable.htm, and I've been led to believe they sell good cables...

kito · Jun 12, 2014

Brian S said:
Following on Kito's heels, if you decide to get rid of the old DVD player and go for a Blu-Ray with HDMI, if you've got a 50' run, you can still run into problems, because HDMI is a shitty video interconnect to begin with. You can read up on a few of the challenges of long HDMI runs here: http://www.bluejeanscable.com/store/hdmi-cables/hdmi-cable.htm, and I've been led to believe they sell good cables...

Agree. I went through a couple hdmi cables until I found one that worked. Kind of a hit a miss deal. The one I have now has been going strong for over 5 years now. Also, Monoprice sells 50ft component cables (the red,green,blue cables). They pass the video hd signal too.....just not the audio that hdmi does. Just make sure the blu ray player has the rgb connections.....most will.

walt · Jun 18, 2014

FYI, because the ground on the inverter was involved, you cant assume its a "ground loop".

You are sending an AM modulated signal over that coax in the 60 to 70Mhz range - very susceptible to noise. More likely is that the ground on the inverter was involved in noise ingress into the AM modulated video signal on the coax.

But.. doesnt matter if your happy with the video now. You nearly have the two ends of the video quality spectrum covered with that setup. Try comparing the off air ATSC HD signal (better than what a lot of cable and satellite providers have because the cable and sat providers compress the signal a lot more) with the channel 3/4 AM modulated signal (what you are sending over the cable)

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