Signal loss with RG59 cable at Higher DTV Channels?

[rboy177]

Hi All,

I just setup HDTV for my parents out it Loma Linda, CA. They are in the Los Angeles Market, about 55 mi. from the towers.
We have DirecTV and just got their H20 box to get the OTA signals.

I installed a new Deep Fringe antenna in their attic, it is pretty large, so didn't want to try to install in the roof myself. There was an older antenna up there, so I just connected the old RG59 coax cable that was already fished through the wall.

We can seem to get most of the local channels with about ~50% signal strength. But seem to have trouble with KTTV and KCOP which operate at RF channel 65 and 66. These are higher mhz ranges (700 mhz +).

I know the RG59 cable has more signal loss than the RG6 at higher freq.. But not sure if this is the issue. Wanted to see if there were other things to try before having to fish the new line though the wall.

Other things to note.
- The antenna is pretty large, so I do have some trouble adjusting the direction, but it is aiming pretty much in the direction of the tower.
- I think the old antenna was just a VHF one, but I left it up in the attic, not sure if being close to the other antenna will make a difference.

Any input you guys may have would be helpful. I will try to answer any additional questions you may have.

Thanks

[dsanbo]

rboy177....
This week I had to re-do a couple of connections on my cable box. When I went to install a compression fitting on one coax line and noticed it was RG/59; the tool I have only works with RG/6. The nitwit that prewired our house (no, it wasn't me.....;) ) fished RG/6 UPstairs to the master bedroom, but used RG/59 to the living room!!!:mad:
Not knowing this until I removed the wall plate a few days ago...I have since fished RG/6 up from the service entrance in the basement , up along a cold-water pipe, along the baseboard (under the edge of wall-to-wall carpet.....) to the cable box.
My point....Yes, IMHO, get rid of the 59 if you can....and go with RG/6. Using compression fittings, it should last many years and provide top-notch quality.
Good luck!

[Bill R]

I agree, get rid of the RG-59 if you can. It has much higher loss (especially on high UHF channels) than RG-6.

Another thing you could try (if it is too difficult to replace the RG-59 cable) is to get an amp. Sometime, even a "small" amp (with 3-6 db gain) can sometimes make quite a bit of difference.

[Fifty Caliber]

I'm actually partial to RG-6QS due to its increased shielding.

[Jim5506]

Quad shielded RG-6 is overkill unless you are near enough to a signal source (of any kind) to get signal into the line directly.

If you are shielding against general interference, the best place for it to come in is your antenna.

[mssturgeon]

You didn't mention how long the cable run was from the TV to the attic. In my experience, RG59 starts to (noticeably) lose quality after about 25-30 ft, and RG6 after about 75-80ft. You can increase those distances quite a bit with an in-line amplifier, which can be purchased at your local Radio Shack, or wherever.

Another thing to check is direct-cabling the antenna into the TV if you have a built-in tuner just to test reception. I have heard of some terrestrial tuning problems with the new H20 boxes.

Hope that helps,

- Shane

[Jim5506]

You didn't mention how long the cable run was from the TV to the attic. In my experience, RG59 starts to (noticeably) lose quality after about 25-30 ft, and RG6 after about 75-80ft. You can increase those distances quite a bit with an in-line amplifier, which can be purchased at your local Radio Shack, or wherever.

Another thing to check is direct-cabling the antenna into the TV if you have a built-in tuner just to test reception. I have heard of some terrestrial tuning problems with the new H20 boxes.

Hope that helps,

- Shane
Beware of Radio Shack amplifiers - they have poor signal to noise ratios - add noise to signal and can make things worse.

[dave1234]

Beware of Radio Shack amplifiers - they have poor signal to noise ratios - add noise to signal and can make things worse.

I have used many RS amplifiers over the years and never seen this. I even use them in front of HP spectrum analyzers to increase the low end dynamic range.


Good RG59 with foam dielectric has a loss around 8db per 100ft. at 700 Mhz. RG59 that's not foam dielectric would be worse.

RG6 would be on the order of 5db per 100ft. loss at 700Mhz.

I have a run of about 60ft of RG6 and use a Radio Shack amplifier at the antennae. This works well for me.

[BornToFish]

If you can, RG-11 is the best you can use, other than RG-6QS. You can even get RG-11QS, but it is very expensive. Keep in mind RG-11 is much bigger in diameter than standard tv coax. You also might try adding a preamp, or distribution amp to the system. Preamp being the better choice do to lower noise factor.:D

[Jeff McClellan]

I have used many RS amplifiers over the years and never seen this. I even use them in front of HP spectrum analyzers to increase the low end dynamic range.


Good RG59 with foam dielectric has a loss around 8db per 100ft. at 700 Mhz. RG59 that's not foam dielectric would be worse.

RG6 would be on the order of 5db per 100ft. loss at 700Mhz.

I have a run of about 60ft of RG6 and use a Radio Shack amplifier at the antennae. This works well for me.

Great post and right on the money. thanks

[bpayne]

If you can, RG-11 is the best you can use, other than RG-6QS. You can even get RG-11QS, but it is very expensive. Keep in mind RG-11 is much bigger in diameter than standard tv coax. You also might try adding a preamp, or distribution amp to the system. Preamp being the better choice do to lower noise factor.:D

Let me offer a different view- the RG-59 is actually more than suitable for the application the OP is using it for then most of us realize. Increasing the gauge of the cabling is only going to help us so much here and is not the primary limiting factor in this situation as far as signal strength/quality is concerned.

Let's look at the actual facts:

- The OP is not getting some channels that are at UHF 65-66 which corresponds with a frequency range of about 774.25-786.95 MHz.

- The deep fringe antenna (no model # given) is mounted in the attic

- We are trying to get OTA signal from a range of about 50-55 miles.

- There is no mention of a preamp so let's assume there is none.

- Let's assume we're receiving some number of lower frequency UHF channels (just the upper ones i.e. UHF 65-66). Depending on model of antenna, the gain penalty is usually higher for the lower frequency channels then the upper ones. However, the higher frequency channels are more prone to signal degradation from obstructions and signal loss through the cabling, but only marginally so. A high gain antenna will usually minimize this affect, or even reverse it altogether...

I think we're all missing a step here.

Instead of worrying about the -3b delta between RG-59 vs. RG-6 (at 100 ft), the real worry should be the 60-80% total signal loss that we're suffering because the antenna is in the attic and not outside. I can understand not wanting to install the antenna outside because my first option is to always attempt an attic install. As someone who has installed a couple hundred OTA installs under my belt, half of which are in attic placements, range and roof composition are the two most important constraints to success. Antennaweb.org suggests a medium-directional w/preamp for the 92350/354/357 zip codes- and that's if the antenna is mounted outside!

Go ahead and install RG-6 or (gasp!) RG-11 if you really feel that this is your limiting factor in signal quality. Ask yourself this: "On the channels that I'm actually receiving, am I getting ~50% on those because of signal loss within the coax or because of signal loss attributed to the range from the broadcaster and the antenna placement being in the attic? Then ask the same question about your missing channels. If your answers happen to be the same, then your course of action should be pretty clear.

Then again, if everyone else is telling you that you should use different cabling, maybe you should use different cabling...

[BornToFish]

I agree. Antenna placement is critical. I'm only 25 ft. up, and I get a better signals, then I did when I had my system at 40 ft. elsewhere. Uhf is especially effected by the loss you are speaking of. Also the elevation angle is a factor, depending on his location.

[rboy177]

Thanks for all the great input guys. I unfortunately I broke my ankle early Feb. so I haven't been checking the forums and wasn't able to do any cable runs.
Will probably be able to try some stuff in a month or so.

Just to add to the post:
- I am using a Channel Master Deep Fringe Antenna, Model 3020.
- The run is probably only about 40 ft. (2 story house)
- There is currently no amplifier.
- The roof is concrete tiles.

I will probably at least switch the wire to RG6.
If I were to get a amplifier, what model might be recommend for this application?
Where do you normally get the power from when in the attic or outdoors? I don't think i have any power outlets in the attic.

I know placing the anntena outdoors would be ideal, but trying to avoid it if possible, I would only be getting a few HD channels that are not supplied by D*.

Thanks for all the great info.

[Richard King]

I broke my ankle early Feb.I hope this wasn't from falling off the roof while installing an antenna.
Where do you normally get the power from when in the attic or outdoors?What you want to use is a pre-amplifier. This is a two piece contraption that is powered from inside the house through the coax.

[oljim]

You need a CM7777 amp