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post #1 of 14 Old 02-09-2016, 08:25 PM - Thread Starter
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Reducing Coax Cable Length for Better Reception?

I just installed a Clearstream 4 rooftop antenna pointed towards the TV transmitters. (Live about 15 miles southwest of DC) The pre amp I went with is the Winegard Boost XT and I have used Monster RG6 coax cables. I have a single 6 ft cable running from the antenna to the pre amp, a 100 foot cable running from pre amp to a small rg6 cable running through the wall into the house (connected together with a coupler), and another 50 ft rg 6 running inside to the TV. I was wondering if I reduced the 100ft RG6 coax to a 50 ft one, would this reduce the db loss through cable distance and improve my signal strength?
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post #2 of 14 Old 02-09-2016, 08:51 PM
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You need to go to TVFool, put in your address and see what is available to you for your location. Post the results, minus your complete address, in the Local HDTV forum that is specific to you and see what others in your area are doing.
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post #3 of 14 Old 02-09-2016, 08:57 PM
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Originally Posted by mak7912 View Post
I just installed a Clearstream 4 rooftop antenna pointed towards the TV transmitters. (Live about 15 miles southwest of DC) The pre amp I went with is the Winegard Boost XT and I have used Monster RG6 coax cables. I have a single 6 ft cable running from the antenna to the pre amp, a 100 foot cable running from pre amp to a small rg6 cable running through the wall into the house (connected together with a coupler), and another 50 ft rg 6 running inside to the TV. I was wondering if I reduced the 100ft RG6 coax to a 50 ft one, would this reduce the db loss through cable distance and improve my signal strength?
yes it most definitely would.
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post #4 of 14 Old 02-10-2016, 03:41 AM
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Where is the power inserter located?

If you can not measure it, you can not improve it.
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post #5 of 14 Old 02-10-2016, 04:20 AM
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would this reduce the db loss through cable distance and improve my signal strength?
Yes, it would do each of those things but IT WON'T MATTER for your actual reception. The signal amplification provided by the preamplifier will overcome the insertion loss of the cabling, that's its primary purpose for existing. There's enough gain there to accommodate 200+' of RG6 (less any splitters) easily. There is no need to shorten your cable based on the information provided. There's also no need to pi$$ away money on overpriced Monster-brand coax.

If you're having an ACTUAL RECEPTION PROBLEM, describe it to get help. Otherwise, go watch your TV and carry on with your life.

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You need to go to TVFool, put in your address and see what is available to you for your location.
TVFool remains down as of this time, at least for me. It last worked Sunday evening.

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Where is the power inserter located?
If it wasn't installed in a proper location, he'd likely be complaining of no or very poor reception since the un-powered amp will attenuate signals by a minimum of 20 to 30 dB. However, he should have included its location in his system description.

Last edited by ProjectSHO89; 02-10-2016 at 04:25 AM.
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post #6 of 14 Old 02-10-2016, 04:50 AM
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My concern was about voltage drop for the preamp. The general guideline is 100 ft max of RG6 with copper coated steel center conductor, and 200 ft max for solid copper center conductor.

I made the assumption that he had followed the instructions to connect the power inserter and power supply.

If you can not measure it, you can not improve it.
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Last edited by rabbit73; 02-10-2016 at 04:54 AM.
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post #7 of 14 Old 02-10-2016, 05:57 AM
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TVfool is down for me, too. Remember when we used to rely on something called RAI or RIA for our signal strength tables? The last name, "Sexton" was on that site page but I don't know who he was or why he was hosting it.

I think someone has posted here that preamps now commonly use 10.5 volt regulators on-board. If their circuit design requires a 2 volt input surplus, then once the voltage measured less than that at the preamp, amplification would be adversely affected. When I was a boy - heck, when I was a middle-aged man - the preamps didn't even have on-board regulators, and the gain varied with the voltage that the preamp saw. As recently as a decade and a half ago, Radio Shack sold a 10dB bullet inline amp where, when I toggled my supply voltage back and forth between 13v and 18v on my scope, I could see the signal strength jump up and down by several dB. I bought them anyway because their frequency range was 5-1,000 MHz, so I could use them to boost weak, sub-band return signals, but anyway...

Is there presently much variation in the source voltage of pre-amp power supplies? Are there still some linear pre-amp power supplies, or are they all switching now? I know this would be beyond the pay grade of anyone coming here looking for help, but I've used higher voltage voltage supplies to compensate for voltage loss over long lengths. None of which helps the original poster, as, if he is experiencing reception problems, they are almost always caused by his antenna situation which we cannot further analyze with the information we have been given.
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post #8 of 14 Old 02-10-2016, 11:13 AM
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Mike & rabbit73,

A lot of the preamps and distribution amps I've opened recently have an lm7808-type volt regulator inboard which is supplied by a 12-15 volt unregulated wall wart. These include our Juice (regulated 12 volts, actually), our distribution amps, and the pre-amps and distribution amps from CM/PCT.

The LNA200, however is different. It is normally supplied by either a USB port on the TV or from a wall-wart with a USB power connector. That means it cannot pull more than 500 mA at 5 volts.

When I hooked a four month-old LNA200 up to my HP bench supply, I show it as drawing 145 mA at 5.01 volts with no RF input signal so it doesn't have much margin for voltage drop in the coax. Someone would have to do the math for the DC resistance of the particular coax in use to determine the max length of the various possibilities for the feed coax.

Tech support for Antennas Direct

Last edited by ADTech; 02-10-2016 at 11:24 AM.
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post #9 of 14 Old 02-10-2016, 04:50 PM - Thread Starter
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Originally Posted by ProjectSHO89 View Post
Yes, it would do each of those things but IT WON'T MATTER for your actual reception. The signal amplification provided by the preamplifier will overcome the insertion loss of the cabling, that's its primary purpose for existing. There's enough gain there to accommodate 200+' of RG6 (less any splitters) easily. There is no need to shorten your cable based on the information provided. There's also no need to pi$$ away money on overpriced Monster-brand coax.

If you're having an ACTUAL RECEPTION PROBLEM, describe it to get help. Otherwise, go watch your TV and carry on with your life.

TVFool remains down as of this time, at least for me. It last worked Sunday evening.

If it wasn't installed in a proper location, he'd likely be complaining of no or very poor reception since the un-powered amp will attenuate signals by a minimum of 20 to 30 dB. However, he should have included its location in his system description.
I wanted to know whether I would see increases in the signal strength as I am still getting occasional pixelation and the strength bar on my TV is not anywhere near full. What would need to be done to get it consistently close to 100%? Sorry I'm very new to this stuff.
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post #10 of 14 Old 02-10-2016, 05:15 PM
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Quote:
Originally Posted by mak7912 View Post
I wanted to know whether I would see increases in the signal strength as I am still getting occasional pixelation and the strength bar on my TV is not anywhere near full. What would need to be done to get it consistently close to 100%? Sorry I'm very new to this stuff.
What I am sorry to have to report to you is that we have at least temporarily lost our best "seeing eye dog". This forum has become reliant upon a reception analyzer website that I think was operated by a retired engineer, but it has been down for several days now. It is highly unlikely that your situation can be improved by shortening your cable or by increasing your amplification.
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post #11 of 14 Old 02-10-2016, 06:23 PM
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Quote:
Originally Posted by mak7912 View Post
I wanted to know whether I would see increases in the signal strength as I am still getting occasional pixelation and the strength bar on my TV is not anywhere near full. What would need to be done to get it consistently close to 100%? Sorry I'm very new to this stuff.
If you are willing to tell us your location as close as you dare, either in a post or a PM, we will try to give you a useful answer using the FCC DTV reception website. It gives the signal power and direction of your channels. It isn't as accurate as the tvfool website, but it is more realistic than AntennaWeb.
http://transition.fcc.gov/mb/engineering/dtvmaps/

If you can not measure it, you can not improve it.
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post #12 of 14 Old 02-11-2016, 07:57 AM
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I wanted to know whether I would see increases in the signal strength as I am still getting occasional pixelation and the strength bar on my TV is not anywhere near full. What would need to be done to get it consistently close to 100%? Sorry I'm very new to this stuff.
You do not need a "full" signal bar, you only need one that is "full enough" to provide error-free reception. More quantity (amplification) does not automatically equate to more quality unless you have a specific situation where the signal power isn't adequate to overcome all the accumulated insertion losses in the distribution system.

This looks like it's going to morph into a reception issue. You're going to need to provide specifics about what is actually wrong and, with TVFool, being sporadic this morning, attempt to get a TVFool plot (with an attached image, just in case) posted.

Most commonly, these issues boil down to two or three common diagnoses:

1) Attempting to receive VHF with a UHF antenna. It's unpredictable. If you have the C4 (sans dipole) and the problem is channel 7 &/or 9, add the VHF dipole kit. It's far more effective than the C4 is without it and it's completely predicable about how it is expected to operate.

2) Antenna location problem. It is an oversimplification to assume that all signals emanating from a single tower cluster, tower, or even the same antenna will arrive in a random point in space where you happened to plant an antenna because the location was convenient and then to expect everything to work perfectly. Sometimes it does, usually there's more work to it. There is a very specific reason that all our antenna installation sheets include, in LARGE RED LETTERS at the beginning of the instructions, the advice that the new owner should follow. It states "Before attaching the antenna to antenna to any surface, TEST RECEPTION in that area." I can't begin to estimate how many times a week we have to tell customers to do that critical step when they're missing one or two channels. They tend to get upset because they expected it to work without doing any testing first. My advice, when requested, always includes the advice to " Do not drill any holes until you've proven that reception is adequate in that spot".

3) There's always the possibility that you ave some localized electrical or electronic interference. ATM, there is insufficient information to pursue that avenue.

Tech support for Antennas Direct

Last edited by ADTech; 02-11-2016 at 08:03 AM.
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post #13 of 14 Old 02-11-2016, 03:24 PM
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Quote:
Originally Posted by mak7912 View Post
I just installed a Clearstream 4 rooftop antenna pointed towards the TV transmitters. (Live about 15 miles southwest of DC) The pre amp I went with is the Winegard Boost XT and I have used Monster RG6 coax cables.
I see the tvfool website is up now. About 15 miles SW of DC would put you in Alexandria, VA 22304 near Landmark Mall, and your report might look something like this (Attachment 1):
http://www.tvfool.com/?option=com_wr...51346528e61733

Attachment 2 shows the FCC site using zip 22304. If you click on the callsign after entering zip, you will see signal power and azimuth:
http://transition.fcc.gov/mb/engineering/dtvmaps/

Attachments 3 and 4, after entering zip 22304, show the results using AntennaPoint:
http://www.antennapoint.com/


Please go here to do your report and tell me how close my guess was:
http://www.tvfool.com/index.php?opti...pper&Itemid=29

Quote:
I wanted to know whether I would see increases in the signal strength as I am still getting occasional pixelation and the strength bar on my TV is not anywhere near full.
How low can the reading go and still have good reception?

What channels are you having trouble with?

Is your antenna the CS4 or the CS4V with a dipole for VHF-High?
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If you can not measure it, you can not improve it.
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www.megalithia.com/elect/aerialsite/dttpoorman.html

Last edited by rabbit73; 02-11-2016 at 06:42 PM.
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post #14 of 14 Old 02-14-2016, 02:13 PM
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Quote:
Originally Posted by mak7912 View Post
I wanted to know whether I would see increases in the signal strength as I am still getting occasional pixelation and the strength bar on my TV is not anywhere near full. What would need to be done to get it consistently close to 100%? Sorry I'm very new to this stuff.
From the ESTIMATED tvfool location, I note all signals are 1-edge (going over hills or big things). That suggests your problem is multipath considering the strong signals.

As others have said, pull the amplifier and try to get the antenna as high as possible. If you input your real location into tvfool, you can play with antenna height to see how high you'll need to be for line-of-sight reception.

It's not unusual to find better reception pointed other than at the transmitter with reflections inherent with multipath (made worse with 1-edge signals)
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