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Antenna in the attic: How good reception? Grounding needed?


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7 replies to this topic

#1 OFFLINE   grunes

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Posted 17 December 2013 - 01:37 PM

We use a local Comcast cable affiliate. Over the past few years rates have gone from $40/month with no box needed for most channels to about $160/month (+$50/month for Internet - and we don't need super-speed - we have an old slow modem and router that can stream video without much extra leftover), with boxes needed for all 3 TVs. They don't charge what they say they will over the phone, and they charge us for equipment we don't have. They keep promising to fix that, but they just hide it - it's not on the paper bill, you have to look for our equipment lists on the Internet connection. (Comcast delivers very good service and lots of channels. Most people are willing to pay for good service. Why annoy customers with broken promises and mischarges if you can deliver a quality product? Oh well.)

I am curious to see how good local OTA TV reception we could get from an antenna in the attic. I'm also curious to know whether it is likely that we get away with putting an ordinary Dish or DirectTV antenna in the attic.

My OTA antenna is an old Shakespeare Seawatch 2030 (round, omnidirectional, about 14" diameter) antenna. It could go outdoors, since it was designed for marine use, but that would mean someone would have to go up on the roof, and we would need to run grounding wires in places that would force us to dig up the paved driveway. My landlord is a retired electrician, but says he is too old to go on the roof.

1. The antenna is Pre-HD. Can it handle the all HD channels? I've already tried it in a second story room with a TV, and it gets about 10 or 15 channels - but reception by channel various with location; I think it needs to be higher up. (It gets about 30 or 40 QAM channels when connected directly to the cable without a box - I wonder whether we would still get all the QAM channels if we just got "basic cable" service - but anyway, the frequencies and subchannels keep changing, and Comcast doesn't publish QAM info, so that may not be a good option.)

2. We have a slanted tar panel roof, tacked on with nails, and the homes around us are the same height as ours. Would OTA and satellite antennae do about as well in the attic as on the rooftop?

3. We tried to look up whether it needs to be grounded. If it needs grounding it can't go in the attic, because code requires that grounded antennae be on the edge of the roof and that the wire from the antenna to the ground follow a straight line path (or something like that - I'm not the electrician).

As near as we can figure out, from the codebook and from Internet sources, we only need grounding to meet code if the antenna is on a mast. My intention is to put it on the attic floor, so no mast is needed. Hence no grounding is needed. We think.

Does that sound right?

(The National Electric Code is a complex document, with lots of exceptions, so my electrician may have missed something.)

4. Regardless of code, is it especially unsafe to put an ungrounded antenna in the attic? We don't have such a large number of lightning storms (we live near DC) that most houses get hit by lightning. But we do have lightning storms a large fraction of summer days, so it isn't, and we know of at least one home whose aluminum siding was hit by lightning a few miles away. Would an antenna in the attic be particularly likely to attract lightning?



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#2 OFFLINE   CCarncross

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Posted 17 December 2013 - 02:51 PM

Well you want the OTA antenna mounted as high in the attic as possible....laying it on the floor is probably not a great idea....I have about a 10' YAGI in my attic, it pulls in the stations quite well from about 35-40 miles away and they are all within about a 10 degree radius of each other.  You cant put a satellite dish in your attic....it has to be outside with unobstructed view of the southwestern sky.  You'll need to go check out tvfool or antennaweb.org to see what stations you can pick up with what size antenna and what direction.  I do not have my attic mounted antenna grounded...but of course my satellite dish mounted outside is.



#3 OFFLINE   gov

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Posted 17 December 2013 - 03:13 PM

Doesn't sound like you are going to, but as a reminder to all, don't shoot through a valley in the roof, many (most? all?) have a wide metal flashing under the shingles, and it messes up reception.

 

Also, a large pile of 'stuff' in the attic in front of the antenna can be a problem, metal appliances, metal venetian blinds, metal anything, can reflect/block signal from reaching your antenna.

 

I generally ground antennas in attics too.  Got lit up on one attached to a defective TV that was putting full 120VAC on the wire to the antenna. Not a fun experience.



#4 OFFLINE   RBA

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Posted 17 December 2013 - 06:45 PM

Shakespeare Seawatch 2030-G is supposed to be a 21" amplified antenna powered by 12volt or 120 volt.

 

College Park MD. on TV fool shows to be about 8 miles away from the broadcasters but it has a 1edge and 2edge reception at that short distance.  I would guess that you are in a low spot so you should mount the antenna outside and as high as possible.  It doesn't have to be on the roof you can run a mast up the side of the house and get it above the roof.

 

You will need to have the amplifier powered to receive TV reception.



#5 OFFLINE   grunes

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Posted 18 December 2013 - 12:27 PM

What is the web page for "TV Foot"?

 

>Shakespeare Seawatch 2030-G is supposed to be a 21" amplified antenna powered by 12volt or 120 volt.

 

OOPS. I took the size off a random web page. It's actually 21.5". Mine isn't labeled 2030-G. Maybe 2030-G is newer model. Mine is 20-30 years old.

 

I'm sure the high mast is a great idea, but would cost money. I just want to see how well I can do without spending more money. 

 

>You will need to have the amplifier powered to receive TV reception.

 

The original amplifier died. Inside the room, I tried it in the room with and without a 20 dB amplifier (an Elabs 6001A) that I originally bought to split the cable TV signal. No discernible difference in quality or # of channels received, so line-of-sight may be more important than signal strength. But that was with a 3' cable. 

 

We are on a hill a few feet high, in North College Park. Everything around here is roughly level, used to be swamp. There are some low hills if you go 10 or so miles west. A few high buildings block part of the skyline, but are too high to bypass. Antenna Web indicates that the number of available channels won't be any higher if the antenna is mounted over 30'.

I wonder if grounding inside a home near the roof is a safety problem. My electrician says that there was once a debate over whether homes should be grounded. Grounding reduces the damage to homes from lightning strikes, but they get hit more often. A ground wire from inside the attic doesn't follow a straight line path to ground, so the lightning might pass through the house wall instead.

 

I do get that grounding establishes a "ground plane" which improves reception. 



#6 OFFLINE   RBA

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Posted 18 December 2013 - 04:07 PM

www.tvfool.com

 

If the built in amplifier died you probably aren't actually receiving any signal from the antenna just from the connected cable.

 

I'm afraid you will have to spend a little money to seriously try and replace cable probably around a $100.  You will need a basic outdoor antenna like an antennacraft HBU22,  masting and 50-100' of RG-6 cable.  Mount the antenna where the cable co. enters the house and use their grounding.



#7 OFFLINE   grunes

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Posted 22 December 2013 - 02:13 PM

Thanks, guys!

 

>If the built in amplifier died you probably aren't actually receiving any signal from the antenna just from the connected cable.

 

Not in this case. Probably because I removed the dead pre-amp, and because I was using a 3' cable. You need pre-amps for longer cable runs.

 

When left next to the TV, I get 6 channels from the cable alone, 29 from cable + antenna. (The same 29 from cable+antenna+amp, with no improvement. Apparently that is pretty normal - the receiver AGC compensates completely for the Amp). 

 

I also may have made a bad assumption that a RF signal distribution amplifier is exactly the same thing as a pre-amp.

When I raised the antenna 1', I got 33 channels, which certainly argues for greater height. Especially since the outside walls of my home has aluminum siding. One source says that attic antenna lose about 50% of signal strength, presumably due to signal losses in the roof. But it has to be better than just putting the antenna next to the TV.

 

I've been doing some Internet "research", reading technical descriptions on the web, such as:

  http://www.solidsignal.com/p/?p=2789

  http://hf-antenna.com/003/

  http://users.wfu.edu...isc/dipole.html

  http://www.avsforum....n-attic-antenna

  http://www.hdtvprime...NAS/basics.html

 

Since my antenna is a marine antenna, and has its own signal ground plane built in, it is not clear I need a ground plane for good signals. Perhaps connecting it to a better ground would help a little - I'm not sure.

 

Apparently my old antenna should be able to receive all the frequencies of HD. The newer antennas have Gold plated connectors, which reduce corrosion and should therefore produce a stronger signal - but my antenna was never used outdoors, and has no visible corrosion.

 

As best I can figure it is a fairly decent omni-directional antenna. Possibly good enough for stations 45 miles away, provided the antenna is high enough to avoid obstruction. I like the idea of an omni, because it is much easier to record programs. No doubt a more sophisticated setup would combine the results of many tuned elements aimed at the specific broadcast towers. (You can make cheap tuned antennae from twin lead wire and a 300/75 ohm transformer, and use reflectors to improve directionality, but I don't feel like working that hard.) 

 

Apparently, for an indoor (e.g., attic) antenna, the probability of being struck by lightning is not significantly affected by grounding. There are already many grounded electric lines running through the attic.

 

The real issue is that any lightning discharge within a few miles can induce enough of a current surge in almost any antenna to damage the TV and other things connected to the antenna. The suggestions that I found on the web for dealing with this are:

 

1. Ground the outer conductor of the cable. Some sources say that on outdoor installations, you actually ground the mast, if there is one.

2. Use a coax lightning arrestor to reduce the surge on the center conductor.

3. Disconnect the antenna during storms - apparently a good idea even if you follow the first two instructions.

 

What this convinces me is that there is a certain amount of risk to my electronic equipment from almost any antenna. I can run experiments on reception in good weather, but I would have to get serious about protection to leave the antenna connected all the time.

 

My electrician tells me that for outdoor installations, connecting to the ground of the current cable outlet would be a bad idea that probably also violates the national electric code. And apparently, both code and good practice require that the antenna be far from overhead electric lines.

 

But I am still pretty convinced that we could get pretty good TV service from a combination of an antenna to pick up local stations, + Internet service from Hulu and Netflix. $16/month for Hulu+Netflix is way cheaper than $160/month from Comcast, and would pay for any reasonable antenna installation, plus appropriate DVRs quite quickly. Not exactly the same list of stations and programs, but comparable.

 

What I really don't get is why Comcast is pushing everyone to do so by making their prices so high. And why Comcast's parent company has made this a better option by running Hulu.



#8 OFFLINE   Davenlr

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Posted 22 December 2013 - 08:36 PM


Since my antenna is a marine antenna, and has its own signal ground plane built in, it is not clear I need a ground plane for good signals. Perhaps connecting it to a better ground would help a little - I'm not sure.

 

Apparently my old antenna should be able to receive all the frequencies of HD. The newer antennas have Gold plated connectors, which reduce corrosion and should therefore produce a stronger signal - but my antenna was never used outdoors, and has no visible corrosion.

 

As best I can figure it is a fairly decent omni-directional antenna.

 

A "ground plane" is only useful for vertically polarized signals. It uses the ground for half of the antennas wavelength.  Most TV transmitters use horizontal polarization and require both "halves" of the antenna to be physically present.

 

Omni-direction antennas are to be used as a last resort for TV reception, because they will pick up reflections (multipath) of strong stations bouncing off all sorts of objects, and cause ghosts (in analog) or drop outs (digital).  Newer digital tuners are able to handle this better than older ones, however, unless your stations are indeed separated by more than 30 degrees, a directional bow tie antenna splitting the 30 degree span would be a much better choice, provide much more gain than an omnidirectional, and will easily fit in most attics.


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