Any need for 75 ohm terminators on unused cable RG6 RF outlets? - AVS Forum
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post #1 of 26 Old 09-25-2008, 10:03 AM - Thread Starter
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Hello-

I was wondering if anyone knows if placing 75 ohm terminators on unused cable outlets does anything to boost signal strength on the other connections.

something like this: http://www.amazon.com/Type-75-Ohm-Te.../dp/B000AAN76Y

Thanks much for any info. AL
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post #2 of 26 Old 09-25-2008, 10:19 AM
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They don't help signal strength or boost signals. Just helps prevent interference entering from unused/unterminated ports. They are good to use and worth the $5 expense.
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post #3 of 26 Old 09-25-2008, 10:26 AM
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You can also buy them in 2 packs from Radio Shack. You may want to call ahead though. I had to check with 3 stores before I found them.
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post #4 of 26 Old 09-25-2008, 10:26 AM
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Quote:
Originally Posted by Ratman View Post

They don't help signal strength or boost signals. Just helps prevent interference entering from unused/unterminated ports. They are good to use and worth the $5 expense.

They also prevent reflections.

CIAO!

Ed N.
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post #5 of 26 Old 09-25-2008, 01:15 PM
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Quote:
Originally Posted by egnlsn View Post

They also prevent reflections.

... or in layman's terms, "ghosting".
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post #6 of 26 Old 09-25-2008, 01:53 PM
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Quote:
Originally Posted by egnlsn View Post

They also prevent reflections.

I dunno. I screwed one onto my forehead and now I don't dwell on the past so much.

Walking the fine line between jaw-dropping and a plain ol' yawn.
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post #7 of 26 Old 09-25-2008, 05:32 PM - Thread Starter
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Thanks for all the feedback- I do have ghosting on one or two channels on two of my old analog TVs. I'll check out radio shack. Too bad monoprice doesn't seem to carry them- I'm about to place an order from them...

Thanks again! AL
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post #8 of 26 Old 09-25-2008, 07:32 PM
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Does a small static multipath signal make a crap of a difference with digital TV?
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post #9 of 26 Old 09-25-2008, 10:25 PM
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Quote:
Originally Posted by mattdp View Post

Does a small static multipath signal make a crap of a difference with digital TV?

Wow. What a good question. I am serious. The effect of an open tap is dependent on the loss proceeding the open port. For example, an open 7 dB tap will have less effect then an open 3.5 dB tap. I would think the effect would be very small for analog TVs since the time delay of the reflection is very small. Does anyone know the answer for digital TV?

If it isn't 720p or 1080i/p it isn't HD. If it is 720p or 1080i/p it may not be HD content.
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post #10 of 26 Old 09-26-2008, 04:39 AM
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Just get the terminations and install them they are very inexpensive, and may save you some headaches!!

It is really the isolation from port to port but again just terminate the unused ones.
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post #11 of 26 Old 09-26-2008, 07:16 AM
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Quote:
Originally Posted by txrose View Post

Wow. What a good question. I am serious. The effect of an open tap is dependent on the loss proceeding the open port. For example, an open 7 dB tap will have less effect then an open 3.5 dB tap. I would think the effect would be very small for analog TVs since the time delay of the reflection is very small. Does anyone know the answer for digital TV?

Another result of reflections (in addition to multiple images (ghosting)) is standing waves. If the standing waves are severe enough, some packets don't make it to their desired destination. The result can be disruption of service.

CIAO!

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post #12 of 26 Old 09-26-2008, 07:20 AM
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Quote:
Originally Posted by pnkflyd51 View Post

Thanks for all the feedback- I do have ghosting on one or two channels on two of my old analog TVs. I'll check out radio shack.

That ghosting could be ingress.

There are some high return loss terminators here. Definitely better than the ones at Rat Shack.

CIAO!

Ed N.
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post #13 of 26 Old 09-26-2008, 10:04 AM
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Quote:
Originally Posted by egnlsn View Post

That ghosting could be ingress.

Yeah... from an unterminated port.
Get thee to the Radio Shack for (hopefully) a quick fix!
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post #14 of 26 Old 10-05-2008, 06:43 AM - Thread Starter
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I finally bought some terminators last night and terminated my two unused cable outlets in the house. The two channels on two of my old SD TVs that weren't coming in clearly improved in quality- they're now as good as the others! Amazing!

Two additional questions:

1. Some devices, like VCRs have a Coax Out. I think a couple of my TVs have these too. If these are unused (but have a coax cable going in), should I put terminators on them?

2. Also, I noticed a grounding block like this in Radio Shack when I was looking for a terminator:

http://www.amazon.com/RiteAV-1-way-C...3214046&sr=8-6

Should I put one of these in my coax wiring right before the first splitter in my house to protect against lightning? Will this reduce signal quality at all?

Thanks much!
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post #15 of 26 Old 10-05-2008, 06:52 AM
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FWIW, ingress ghosts are usually to the left of the images, because they get there first, whereas multipath ghosts are always to the right of it.

I'm going to be bummed out when the analog transmitters get shut off because when I am troubleshooting an underperforming, tapped "riser" coax in a highrise, multiple dwelling building, seeing double images to the left of the main image immediately tells me there is ingress in the line, and seeing them go away immediately tells me that whatever I just did has eliminated the problem, but I won't have that to rely on anymore after the February 17, 2008 shut-off occurs.
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post #16 of 26 Old 10-05-2008, 07:16 AM
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Quote:
Originally Posted by AntAltMike View Post

FWIW, ingress ghosts are usually to the left of the images, because they get there first, whereas multipath ghosts are always to the right of it.

I thought about saying that awhile ago, but figured I'd probably get shot.

Quote:


I'm going to be bummed out when the analog transmitters get shut off because when I am troubleshooting an underperforming, tapped "riser" coax in a highrise, multiple dwelling building, seeing double images to the left of the main image immediately tells me there is ingress in the line, and seeing them go away immediately tells me that whatever I just did has eliminated the problem, but I won't have that to rely on anymore after the February 17, 2008 shut-off occurs.

I would think that in your area there would be more than enough OTA traffic in the 140-165MHz range to still allow you to do that (although not double images -- herringbone and other such crap. Heck, I used to have people listen to their police calls on WTBS, which was channel 20).

CIAO!

Ed N.
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post #17 of 26 Old 10-05-2008, 07:39 AM
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Quote:
Originally Posted by pnkflyd51 View Post

I finally bought some terminators last night and terminated my two unused cable outlets in the house. The two channels on two of my old SD channels that weren't coming in clearly improved in quality- they're now as good as the others!

Two additional questions:

1. Some devices, like VCRs have a Coax Out. I think a lot of TVs have these too. If these are unused (but have a coax cable going in), should I put terminators on them?

2. Also, I noticed a grounding block like this in Radio Shack when I was looking for a terminator:

http://www.amazon.com/RiteAV-1-way-C...3214046&sr=8-6

Should I put one of these in my coax wiring right before the first splitter in my house to protect against lightning?

Thanks much!

There should be a groundblock outside where the cable comes to the house. If not, there definitely needs to be one, unless the first splitter is outside and it's UL listed. Then, it (the splitter) can be used as a groundblock.

Not a bad idea on terminating the VCR out, I guess. Although, the return loss on a VCR's connectors is probably along the lines of 5dB, which means that you probably wouldn't see much, if any, difference.

Some TVs have a second input. Some TVs used to have 3 connectors on the back. One was the main input. There was an internal 2-way splitter, with one side going to the "A" side of an internal A/B switch and the other side going to the second connector on the back, which was intended for a converter box. The output of the converter box would then connect to the third connector on the back of the TV set. The only TV sets that have in and out connectors are CCTV monitors.

CIAO!

Ed N.
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post #18 of 26 Old 10-05-2008, 09:59 AM - Thread Starter
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Thanks for the feedback Ed. I have extra terminators, so I'll put them on the "out" jacks on the various devices around my house.

You were right about the grounding block- there is one on the outside of my house and it has a wire that's attached to my electric meter box.

Thanks for all the help. AL
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post #19 of 26 Old 10-06-2008, 05:08 AM - Thread Starter
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In addition to the two unused jacks in my house, I added terminators to the "out" ports on my hd cable box, a VCR, a DVR and the one TV that has them. I didn't see any additional improvement in SD video quality over what I saw when I added the terminators to my two unused jacks, but that's okay...

I'm sure I'm smoking something- I swear that my HD cable box is switching HD channels more quickly- half second to switch instead of a full second. Again, I'm probably imagining it...
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post #20 of 26 Old 10-06-2008, 07:27 AM
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Quote:
Originally Posted by egnlsn View Post

That ghosting could be ingress.

There are some high return loss terminators here. Definitely better than the ones at Rat Shack.



A 75 ohm terminator is just a 75 ohm resistor inside a cap.

How can this one be " Definitely better than the ones at Rat Shack"?

It must be the gold plating?

I think you are just Radio Shack bashing.

A 'phile and his money are soon parted...
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post #21 of 26 Old 10-06-2008, 09:50 AM
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Originally Posted by 11001011 View Post



A 75 ohm terminator is just a 75 ohm resistor inside a cap.

How can this one be " Definitely better than the ones at Rat Shack"?

It must be the gold plating?

I think you are just Radio Shack bashing.

From the manufacturer's website: "Our F Series Terminators (same ones that are at Radio Shack and many other places) are used to provide a 75 Ohm termination on F type connections. Our F-59TH uses precise machining and component matching to achieve high return loss."

F59 specs are: Return Loss; 1GHz: 15dB; 2GHz: 10dB, 3GHz: 8dB Made out of Brass.

F59TH specs are: Return Loss; 1GHz: 40dB, 2GHz: 30dB, 3ghz: 22dB Made out of Zinc.

CIAO!

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post #22 of 26 Old 10-06-2008, 07:59 PM
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Quote:
Originally Posted by pnkflyd51 View Post

I'm sure I'm smoking something- I swear that my HD cable box is switching HD channels more quickly- half second to switch instead of a full second. Again, I'm probably imagining it...

Time it, pull them off, and time it again. It's actually not an unreasonable symptom.
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post #23 of 26 Old 10-07-2008, 02:20 AM
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Quote:
Originally Posted by egnlsn View Post

F59 specs are: Return Loss; 1GHz: 15dB; 2GHz: 10dB, 3GHz: 8dB Made out of Brass.

F59TH specs are: Return Loss; 1GHz: 40dB, 2GHz: 30dB, 3ghz: 22dB Made out of Zinc.

For cable TV applications, the loss figures above 1 Ghz aren't useful.
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post #24 of 26 Old 10-07-2008, 08:15 AM
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Originally Posted by vman41 View Post

For cable TV applications, the loss figures above 1 Ghz aren't useful.

True. The question, though, was "How can this one be " Definitely better than the ones at Rat Shack"?"

CIAO!

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post #25 of 26 Old 10-07-2008, 09:45 AM - Thread Starter
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Quote:
Originally Posted by nybbler View Post

Time it, pull them off, and time it again. It's actually not an unreasonable symptom.

I'd like to, but I dinged the finish on my cabinet when I pulled the cable box out and I don't want to get yelled at by the wife again...
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post #26 of 26 Old 10-07-2008, 01:34 PM
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Quote:
Originally Posted by pnkflyd51 View Post

I'm sure I'm smoking something- I swear that my HD cable box is switching HD channels more quickly- half second to switch instead of a full second. Again, I'm probably imagining it...

If reflections are present, it might take the equalizer a little longer to settle in enough to extract the clock and decode the stream. The minimum time for lock up is determined by the GOP length (group of pictures or the number of frames from one I-frame to the next), and a half a second is fairly typical.
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