In an effort to understand how some of the experts and non-experts make their recommendations on antennas here, I have a few questions. This of course applies to DTV and HDTV.

1. At what distance do you consider an indoor antenna too far to receive digital television signals? (Conditions are: Home is within Line of Site of broadcast tower)

2. When recommending an antenna, what are the most important items that should be considered when you're helping someone with their reception problems.

3. Does mounting an antenna inside an attic (at a minimum 10') help with reception of digital signals over mounting on top of a TV?

4. When is the best time to use a pre-amp?

Consider this thread to use as a platform for discussion and debate about using and or recommending TV antennas.

This is yet another terrific thread idea, Aaron. Thanks!

1. When line of sight is available, this distance is usually in the range of 20-25 miles for nearly uninterrupted reception. It will be a lot less when there's a ridge, many large buildings or other obstructions standing in the way outdoors, or if the home was built with signal-blocking materials such as brick, stone, aluminum siding, stucco (a tight steel mesh holds it on to the wall), foil-lined vapor barriers or "Insulfoam" foil-backed rigid panels.

2. My own MO has always been to recommend the best antenna(s) (and pre-amps, if needed) that also offer(s) the best value, particularly in cases where the questioner has a budget number in mind. A modest, 7-69 antenna is the best choice for those with one or two TVs, 30 miles out, with a couple of VHF high stations and willing to put the antenna above the roof; the handsomely styled, smallish antenna that costs twice as much and was really only designed for UHF broadcasts isn't, because chances are good our reader would need to add on a separate VHF-high antenna to get all the network stations in his market... and a lot of people balk at separate antennas, anyway.

Once the writer is out in the far suburbs or beyond, though, the budget has to take a back seat to top performance; this is the point at which only the various "deep-fringe prescriptions" will do the job right. Case in point: The guy in the Texas boonies who wrote in to another forum, wondering which indoor antenna might pull in DFW, 86 miles out. Seems the set-top antenna he was using could only pull in one station... sometimes. Consensus was that he was extremely lucky to be getting that much on an indoor antenna that far out, of course. A couple of big rigs high in the sky were out of the question for this apartment dweller. Bet he's a satellite subscriber by now.

3. In most cases, you'll pick up maybe a couple of extra dBs in signal strength for each story higher the same antenna is mounted -- as long as the roof deck is plywood covered in traditional asphalt shingles or wood shakes. All bets are off with a tile roof. Most roofing tiles these days are concrete, which will stop signals dead. True clay tiles are a smidgen less dense than concrete, but remember, clay can be a component of brick, too.

4. THE GOLDEN RULE: Only as a last resort. We've had excellent discussions of the technical details of why this is the case from FoxTV, Piggie and others here. The non-technical summation goes something like this: With analog, one could get away with throwing a bigger amp at a mediocre antenna and get better reception. Brute gain was a successful strategy. Digital TV signals stand this tactic on its head: Try it and you're a sitting duck for amp or tuner overload that will very likely preclude reception of one or more of the stations you're trying to get until the source of the overload is removed. DTV has greatly increased the importance of the antenna and de-emphasized that of the amp.

Looked at another way, an antenna is the "green" choice if it's adequate to serve a household's needs without an amp. The wall warts amps use can consume as much as 150 kWh a year if left plugged in all the time. (For you skeptical skinflints out there like me, that amounts to about 20 bucks a year at average rates... just to run a little pre-amp. Why, that there is what I call "found beer money" )

The average DIYer installing a new antenna is better off by:

• Erecting it, then fine-tuning its aim by hooking it up directly to ONE tuner in a multiple-set household. Once the best signal-meter readings have been obtained on each channel...

• Adding new receivers one at a time and observing what impact each addition has on reception at all locations.

• If reception begins to decline anywhere as sets are added, a pre-amp or distribution amp with the lowest gain to do the job, and no more, is what's needed in most cases. Ten to 15 dB ought to be plenty for up to three sets just about everywhere but true fringe locations. Many of us know of those pre-amps whose gain figures push 30 dB, but most DIYers don't need anywhere near that much gain. A home needing power like this is one whose owners will most likely hire professionals to do this work, anyway. Most of us call homes like these "mansions."

• If reception begins to deteriorate on an existing system, it's time to troubleshoot the tuners, wiring, antenna and other components. What's that? Electrical troubleshooting is a pain? We hear you -- it sure is. This much is also certain: More amplifier gain by itself won't surmount increased resistance or short circuits from rust, water ingress, or other incipient mechanical issues. So, the system needs troubleshooting to determine the real cause -- and find its permanent solution.

Wonderful answers so far everyone!

Originally Posted by Don_M

2. My own MO has always been to recommend the best antenna(s) (and pre-amps, if needed) that also offer(s) the best value, particularly in cases where the questioner has a budget number in mind. A modest, 7-69 antenna is the best choice for those with one or two TVs, 30 miles out, with a couple of VHF high stations and willing to put the antenna above the roof; the handsomely styled, smallish antenna that costs twice as much and was really only designed for UHF broadcasts isn't, because chances are good our reader would need to add on a separate VHF-high antenna to get all the network stations in his market... and a lot of people balk at separate antennas, anyway.

Don, when you say modest, are you talking about size of the antenna or cost, or both?

3. In most cases, you'll pick up maybe a couple of extra dBs in signal strength for each story higher the same antenna is mounted -- as long as the roof deck is plywood covered in traditional asphalt shingles or wood shakes. All bets are off with a tile roof. Most roofing tiles these days are concrete, which will stop signals dead. True clay tiles are a smidgen less dense than concrete, but remember, clay can be a component of brick, too.

Great information. I've often wondered if spending time and money to install an antenna in a attic is even worth the effort vs. the extra few minutes it takes to drill a hole in a roof and mount the antenna outside. Out here in Cali, we see our share in tile roofs mostly made with concrete and clay.

4. THE GOLDEN RULE: Only as a last resort. We've had excellent discussions of the technical details of why this is the case from FoxTV, Piggie and others here. The non-technical summation goes something like this: With analog, one could get away with throwing a bigger amp at a mediocre antenna and get better reception. Brute gain was a successful strategy. Digital TV signals stand this tactic on its head: Try it and you're a sitting duck for amp or tuner overload that will very likely preclude reception of one or more of the stations you're trying to get until the source of the overload is removed. DTV has greatly increased the importance of the antenna and de-emphasized that of the amp.

Very good to know!

Originally Posted by Piggie

If you want a general statement. I would say from experience in Florida. A 300 meter tower gives at 15 miles of coverage to an indoor (conservative) and a 500 meter tower is about 20 to maybe 25 miles.

I never thought about broadcast tower height! Is there any way to find what heights broadcast towers are built at on the net?

A good point here is the signals a TV antenna receives are NOT digital. They are analog. The information or more properly modulation on the TV signal is digital. Strictly speaking the TV signal itself, which is all the antenna cares about (since it can't decode anything itself) can't tell analog from digital broadcasts, again, because the actual carrier wave hasn't changed and is analog.

Good to know but I guess my question is, how can a signal be analog and have a digital modulation? Guess I need to look up what modulation is.

Several reasons to use an amp.

You buy a high quality preamp with a noise figure of 3 db or lower, that will do what is called lowering the system noise figure. This can often give you as much added signal as doubling the size of the antenna.

Piggie, is a quality preamp strictly based on noise figure? I see people recommend low noise preamps a lot on forums, and if it is so important, why are other higher noise preamps made and sold?

Originally Posted by Aaron62

Piggie, is a quality preamp strictly based on noise figure? I see people recommend low noise preamps a lot on forums, and if it is so important, why are other higher noise preamps made and sold?

I'm sure Piggie will provide an answer to this in due course, but I have a few minutes to I'll take a stab at it.

Every pre-amplifier is a design compromise. Some of the factors that need to be considered are: bandwidth, gain, gain uniformity, noise figure, overload resistance (1dB compression point), linearity (Third order intercept point), stability, shielding (susceptibility to unwanted EMI/RFI), survivability (think static protection), power draw and temperature range. Of course we can't forget cost!

Most consumers never get past the idea of gain and the simple notion that more is better. Those reading this forum generally know that you also need to consider noise figure too. The rub is that if you go after maximum gain and minimum noise figure you'll likely find that you have an amp with poor overload and linearity. This can cause major problems in situations where you have a mix of strong and weak signals. Amps with high P1dB and OIP3 however are generally not the cheap, but its currently possible to find affordable amps with decent figures if you reduce gain requirements (say 10 to 20 dB) and can live with modest noise figures (say 2 to 4 dB) instead of the ultra low (0.5 to 1 dB) values.

The biggest problem is that its hard to find specs for P1dB and OIP3 for most consumer grade amps. If you can find P1dB though, you can estimate OIP3 by simply adding 10 to 14 dB to the P1dB figure. This is not hard and fast, just an empirical rule of thumb.

Hope that helps!

Originally Posted by Tower Guy

1. I ignore all requests for indoor antenna recommendations.

Personal preference? Or is there an other reason?

Originally Posted by Aaron62

Don, when you say modest, are you talking about size of the antenna or cost, or both?

Both. There's no reason to put up a big, expensive antenna outdoors for short- to medium-distance reception. The extra cost, additional installation hassles and, possibly, greater vulnerability to wind and ice damage won't improve a thing for most viewers under the specified conditions.

Plenty of modestly priced (say, under $75) antennas are available that perform well and should stand up to the elements outdoors for many years of reliable service. But please remember that this general recommendation included a long list of attached conditions. If any one of them changes ("My antenna has to be mounted in the attic," for example), all bets are off.

Originally Posted by Aaron62

Personal preference? Or is there an other reason?

EV has covered indoor reception as well as can be done. I have nothing more to add.

I don't believe that you can predict indoor reception with enough precision to make additional suggestions.