Long range attic antenna?

[sleddriver]

Originally Posted By: Digital2k2
Interesting... I appreciate the suggestion, but I've already put as much back breaking work as I'm willing to do into running the line I have.
It's a shame I don't have an easier wall to fish the line down the other end of the attic. 50ft would have been enough to go directly to the junction box for the tv I need it at.

Some of the channels that were coming in weak but good enough before I hooked the 50ft to the other 50+ft run are actually in the other direction!

Something I find odd is that CBS (RF channel 40, 950.0 kW) and ION (RF channel 46, 1000.0 kW) are both the exact distance and heading, but CBS has more than twice the signal strength.


A few notes occured to me:

• Plenum or riser-rated RG-6 isn't necessary for residential applications. Only commercial. You mentioned getting a good deal, so OK here.
  _
• Don't allow the cable to hang off the end of your UHF section as shown in the photo. Instead, gently pull it back so it runs parallel to the antenna's beam and then another gentle 90° bend to run down the mast. Don't kink it! It's not just wire: It's transmission line. Hold it in place losely with zip ties. Don't duct-tape it to the antenna beam either.
  _
• To get the full benefits of RG-6, it needs to be 100% RG-6 from the antenna to your TV. Do you know the type of cable that you didn't replace? If you have 100% RG-6, then I misunderstood and ignore this *.
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• Fishing cable. That's the only way we do it down here: No basements! So we're in the attic. You can use fiberglass rods. However, I like to use ball chain attached to a large key-ring. It's inexpensive, very slinky, and every hardware store has it. Add two feet to the height of the wall and buy that amount. Drill a hole in the top plate in the attic big enough for the coax, but don't over size. If there's no insulation in the wall (indoor wall), nor a fireblock, it'll fall all the way to the bottom. If there is a fire-block, you'll have to drill it or remove some sheetrock. I use a neodymium magnet on a flexable wire wand to retrieve the ball chain from the room below. Drill a hole, bend the flex. magnet about 90°, insert and wave it back and forth. It'll catch the ball chain and follow it right out of the hole. Lacking this, you can duct tape a couple of small neo-dym magnets to a stiff piece of 12 or 14 gauge copper wire.
  _
  .....If you drill your hole close to a corner of the stud cavity facing the interior wall, it'll help. You can then run the magnet along this stud, down stairs, in the room, and it'll grab the ball chain and guide it.
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• Don't attempt to pull RG-6 with ballchain! It'll probably break. Instead tie on some pull cord.
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• Good luck with it!

 

[Digital2k2]

Thanks for the tips. You got me thinking about the other half of the cable. I noticed the copper seemed thinner when making connections, but didn't think to check closely to make sure it was RG-6. It's RG-59U... I found some info on signal loss between the two:

RG 59 Signal Loss (in dB) per 100 ft:

Loss at 50 MHz: 2.4 dB
Loss at 100 MHz: 3.4 dB
Loss at 400 MHz: 7.0 dB
Loss at 900 MHz: 11.1 dB
Loss at 1000 MHz: 12.0 dB

RG 6 Signal Loss (in dB) per 100 ft:

Loss at 50 MHz: 1.5 dB
Loss at 100 MHz: 2.0 dB
Loss at 400 MHz: 4.3 dB
Loss at 900 MHz: 6.8 dB
Loss at 1000 MHz: 7.0 dB

 

[Papa Bear]

A cheap amp will make up for all that loss.

 

[dishdude]

The jacket on the RG-59 should say if it is 20 or 22 gauge wire. 20 I wouldn't worry about, but 22 you might want to think about replacing.

 

[Papa Bear]

I'm a retired electronics tech (since 2001) and have forgotten a lot of info.

If I remember correctly the signal loss in different cables is due to construction design and material, not centre conductor gauge.

It is loss due to capacitance, not resistance.

Most of your TV channels will be in the 500-800 MHz range

Invest in an amp and carry on.

 

[Digital2k2]

Originally Posted By: dishdude
The jacket on the RG-59 should say if it is 20 or 22 gauge wire. 20 I wouldn't worry about, but 22 you might want to think about replacing.

I'll check for that tomorrow. Think I remember seeing it, just can't remember which it was.

I hooked up an RCA TVPRAMP1R tonight and got no signal at all. The power supply felt very warm at first, then didn't seem to produce near as much heat later.
I checked the connections and switch configurations numerous times to be sure it wasn't an error on my end. Guess I managed to get a bad one.

 

[Lubener]

Long range and attic antenna don't go together, you'll need to get it on the roof if you are that far from the towers. The link I posted in the thread Warstud pointed to is still a great source of information.

I had to get my antenna onto the roof. With aluminum siding, my attic installation did not work well. Big difference with signal strength after rooftop installation.

 

[Lubener]

Originally Posted By: dishdude
The jacket on the RG-59 should say if it is 20 or 22 gauge wire. 20 I wouldn't worry about, but 22 you might want to think about replacing.


Quad shield RG6 is the only way to go, not RG59. RG 59 is video cable, not meant for RF.

 

[Lubener]

Originally Posted By: dishdude
Not for use in walls means it is not plenum rated, so if it burns it will generate noxious fumes.


Plenum rated cable is only required for commercial, not residential applications where the cable is run between muliple floors(riser), healthcare facillities and in plenum ceilings where the whole area above the ceiling is acting as a large cold air return. You wouldn't want noxious fumes being distributed by the HVAC system. I always used teflon in commercial installations because the price difference was little and not worth violating any codes and the stoarage space needed for all types of cabling.

Romex is run in residential walls and I never seen teflon in those installations.

 

[Digital2k2]

Well all I see on there is C5770 RG-59/U. The way the line is run, replacing it really isn't an option for me. I would probably have better luck fishing the 50ft of RG-6 down the other wall (not going to tackle that now either).

Without an amp I really wasn't expecting to get the channels I'm getting now even before this long run of cable.

Reading the reviews of the RCA TVPRAMP1R, it looks like about a 50/50 chance of getting one defective out of the box. The only other one in the store already had a broken seal, so I imagine the chances of it being defective are fairly high too.

 

[dishdude]

Well if you're getting all the channels you want without the amp, then you don't need it and you're set!

 

[sleddriver]

Originally Posted By: Digital2k2
Thanks for the tips. You got me thinking about the other half of the cable. I noticed the copper seemed thinner when making connections, but didn't think to check closely to make sure it was RG-6. It's RG-59U... I found some info on signal loss between the two:

RG 59 Signal Loss (in dB) per 100 ft:

Loss at 50 MHz: 2.4 dB
Loss at 100 MHz: 3.4 dB
Loss at 400 MHz: 7.0 dB
Loss at 900 MHz: 11.1 dB
Loss at 1000 MHz: 12.0 dB

RG 6 Signal Loss (in dB) per 100 ft:

Loss at 50 MHz: 1.5 dB
Loss at 100 MHz: 2.0 dB
Loss at 400 MHz: 4.3 dB
Loss at 900 MHz: 6.8 dB
Loss at 1000 MHz: 7.0 dB

Yep. RG-6QS is all I've ever used in these situations. It has even lower loss, I believe. And it's not just the diameter of the center conductor, it's the entire construction of the cable itself. It's characteristic impedance, propagation delay, dielectric used, etc. Remember: It's not just wire: It's a transmission line. 99% of the signal itself travels on the skin of the copper center conductor, not inside of it. A whole different animal than just "wire".

You'll pick up some additional dB of signal when you get around to fishing.

Glad to hear your seeing improved results. That's good news!

 

[Digital2k2]

Originally Posted By: dishdude
Well if you're getting all the channels you want without the amp, then you don't need it and you're set!


Knowing that with just 50ft of RG-6 I can pick up a weak signal of ION, IND, CW and a FOX broadcast from the other direction, that's what makes me want that preamplifier on there.

Also CBS is coming in a little weak for my comfort... Don't want to take a chance of missing The Price is Right haha.

 

[Papa Bear]

Why does it have to be an attic mount antenna? Why not on the roof?

 

[DBMaster]

Originally Posted By: Papa Bear
Why does it have to be an attic mount antenna? Why not on the roof?


Generally, roof mounted antennas aren't the most attractive things in the world. That said, I did read that using the attic instead of the roof results in approximately a 50% loss of signal strength. In my case, the antenna I have in the attic is huge. It's an old one. If I had to mount one outside I would get a newer, more compact one. It is important to know the frequency range of your local channels. Most of the digital channels here (DFW) are in the UHF range. So, a roof mounted antenna would at least be small. That means that I pick up most of my local channels with just the "front" portion of my old antenna.

 

[Ramblejam]

Originally Posted By: DBMaster
So, a roof mounted antenna would at least be small.


My stations are 40+ miles away, and I've been extraordinarily pleased with the ClearStream 2V.

 

[JHZR2]

Originally Posted By: Digital2k2
Originally Posted By: dishdude
Well if you're getting all the channels you want without the amp, then you don't need it and you're set!


Knowing that with just 50ft of RG-6 I can pick up a weak signal of ION, IND, CW and a FOX broadcast from the other direction, that's what makes me want that preamplifier on there.

Also CBS is coming in a little weak for my comfort... Don't want to take a chance of missing The Price is Right haha.


Do you have to terminate it to get that performance or just let it be open ended?

My home is wired for cable, but I don't subscribe. I tried using the network of cables in the house, which go up to the attic, as an antenna themselves. No luck. Has to be a lot more than 50' too...

And I'm less than 15 mile from all the major stations' towers.

 

[Lubener]

Not sure I understand your question but all cable ends should be terminated at their final ends.Noise can be introduced into the system. If you have un used lines, disconnect them from the system. I have always used a terminating resistor at all open connection points.

 

[supton]

Originally Posted By: sleddriver
99% of the signal itself travels on the skin of the copper center conductor, not inside of it.


Gotta quibble here: All of the current is on the "skin" of the center conductor--and on the skin of the outer foil also. It's still electricity, current flowing on the center conductor has an equal but opposite current on the foil. And, the current on the outer foil flows on the inside of the foil, not the outside--those currents are trying to be as close as possible.

Here's where the loss is: the inner conductor is a smaller diameter than the outer conductor. Thus, the loss on the aluminum outer foil is less than the loss on the center conductor. Center conductor diameter matters--larger is better. The copper on the inside of the wire doesn't matter, so you could think of it strictly as a surface area problem. [Big 3" diam coax uses hollow center conductor!]

At UHF though the dielectric can start to introduce loss of its own, but I think most of the loss at these frequencies is still from the copper.

When buying RG6, check to see if it is "copper clad steel". Nothing wrong with the stuff but your standard snips won't like cutting steel. [Remember the comment about all the current flowing on the outer surface of the copper? the steel center is just a cost cutting measure--and has no impact on signal loss. Cheap way to get even large diameter inner conductor less loss--copper is more expensive than steel.]

 

[supton]

Originally Posted By: JHZR2


Do you have to terminate it to get that performance or just let it be open ended?


Do you have a bunch of splitters? I would think they need to be terminated for best performance (to prevent ghosting). But for best performance, ditch any unneeded splitters, as each one is cutting the signal by more than half. The TV antenna receives "power" (just really low power!) and each splitter cuts the signal in half, so half the power goes down one coax, the other down the other. But nothing is perfect, so it might add a little bit of loss of its own too.

[Disregard if you have some sort of active splitter with a preamp in it. On those you should be able to leave unused ends unterminated, as they should not impact the other lines.]