Outdoor Antenna's. Why so many designs?

Factual Questions
1

Today I was noticing all the houses that still had outdoor antenna’s and almost all of them were different in some way or another, it seemed no 2 were exactly alike. Some appeared like arrows of various designs, some had a plethora of different levels with rods shooting at seemingly random directions, others appeared to have a dish like shape, others squared…etc. All of them appeared to be made of either aluminum or stainless of some sort.

Now back before we had over the air HD, everyone’s reception within the same neighborhood was different ( I assume). My house back in the 80’s sucked, we had the basic arrow design. Amplified indoor antenna’s did worse and of course tin foil on them seemed to help. Now aside from distance from station and height:

  1. Did antenna design itself make much of a difference in reception of radio/UHF/VHF or HD for HD antennas?
  2. Is there one design that is superior?
  3. What about the material it’s made of, would something like copper or another metal capture a better signal or does any metal work?
  4. Why did adding tin foil to an antenna capture a better signal at times and why does your body position/touching the antenna effect how well it picks it up?
  5. Does HD signals work with old style antenna’s?
  6. Why did amplified antenna’s make reception worse the more you boost it? I had best reception with them off. Did they work for you?

As an 80’s kid, we could pick up channels 2/49, 4, 6, 8 and 13. 2/49 always came in like cable tv with no static and 13 had the least static while 4 had the most. Now 59 which was Fox I believe was impossible which sucked because that’s the station that had all the good cartoons like GI Joe, TF…etc. We didn’t get cable TV until very late 80’s I believe but bad reception probably ruined my childhood.

What were your experiences with over the air broadcasts in your area back in the day? How is your over the air HD reception now?

2

Because of the many channels.

You basically have low VHF (2-6), high VHF(7-13) and UHF

Depending on your city you need an antenna designed to pull the correct signal in.

Since digital TV few stations actually broadcast on low VHF anymore, though they retain their old channel numbers.

For instance, WCBS in NYC broadcasts on UHF channel 33, though the virtual channel is still channel 2, the old analog channel.

In some cities like New York and Chicago, you have most of the stations broadcasting from the same antenna site, so you can have an antenna that only needs one direction.

In other cities TV stations broadcast from more than one area, so you need a rotor or you need to have other directional masts on the antenna.

Digital TV is more sensitive than the old analog system to certain things so you need different designs. There is no such thing as a digital TV antenna. It’s the same frequencies used, but just a different method of broadcasting.

3

To answer question #5, yes, old-fashioned style antennas can pick up digital HD signals. In most cases you can use the same antenna you were using for analog signals.

I live in Tucson, and pre-digital, the signals varied from pretty good to full of snow and ghosts. I also only got about 5 or 6 channels. I got rid of my cable a few years ago and switched to over the air. I use a set of rabbit ears on top of my set. Nowadays the stations can multiplex their signals so that they can run 3 or more channels on the same frequency so that I can now pick up 21 channels, including channels like MeTV and Antenna TV. I also pick up 5 major networks. All of the channels come in looking as good or better than cable, with some occasional dropouts once in a while on some of the more distant channels.

4

#2: No. The design of an antenna controls the pattern of its radiation / reception. Sometimes you wish to radiate / receive equally in all directions. Sometimes you’d like to be highly directional, concentrating on one specific direction.

Googling “antenna pattern” and/or “directional antenna” produces lots of relevant links.
[nitpick]“antennas” needs no apostrophe.[/nitpick]

5

Neither do antennae.

6

Yagi attennae, linear arrays ike a triangle (VHF) or ladder (some change in width, perhaps, UHF), are very directional. Also , they might be accidentally in a dead zone in terms of height above ground.
Big boxes are for VHF to pick up signals that are varying in height and direction.
rectangular patches, grid array , do the same for UHF.

7

Ah, modern civilization marches on. When I lived in Tucson as a kid we had a grand total of one tv stations. KGUN, kiddie show host Marshall KGUN. I was in the kiddie seats on air twice; 1962 and 1964. TV choices were ON or OFF.

8

Since I use a paper clip and get fine reception, I’m assuming that the design doesn’t really matter very much, and manufacturers keep creating fresh designs to avoid patent infringement.

9

Does concentrating on one specific direction increase reception strength? Could you also not just use various antennas and attach them altogether for best signal?

10

Yeah, no.

Antenna design doesn’t matter very much in a strong-signal area, but matters a great deal in the fringes. Most TV antennas (the old-fashined ones) consisted of three basic parts:

  1. A Yagi VHF array (a series of isolated and grounded rods of varying sizes (directors and reflectors) that amplify the signal in a very narrow beamwidth to a final detector on one end.
  2. A corner reflector for UHF (looks like two pieces of screen at right-angles, with a rod in the center.
  3. An FM dipole.

This basic design was used for decades, with only minor changes - mostly having to do with the number of elements in the Yagi, which increased it’s gain at the expense of wide directionality.

11

Interesting thanks. I wonder how engineers came about that? Must have been a lot of experimentation or perhaps it was once military designs?

12

To expand a little.

For TV reception you are dealing with a range of issues, some of whihc overlap with more conventional radio communication, and some which are a bit more unusual.

For the older TV transmission a big issues was bandwidth. The antenna needed to perform across a very wide (up to about 5:1) ratio of frequencies. Anything from about 40MHz to 200+MHz.

Antennas of any kind are directional to a greater or less extent. Once the frequency is high enough you can use the ubiquitous Yagi design to create very directional antennas. But a simple Yagi has quite low bandwidth. The advent of UHF TV transmission was both high enough in frequency 400+MHz, and requiring a proportionately lower fraction of the frequency as bandwidth, that a Yagi was viable.

You may still need a mixture of frequencies, some areas may be a mix of VHF and UHF, and you antennas that are essentially two antennas bolted together. Also useful when you still want FM reception.

You can extend the bandwidth of a Yagi in various ways - even making the thickness of the elements greater helps - which is why you will see the elements made of flat slats of aluminium. But beyond that other designs help. The Log-Periodic is a design that looks like a Yagi at first glance, but has a wide range of element lengths, and if you look closer, there are a number of elements that are driven (all connected together in alternating phase along the boom). A og periodic can have a much wider bandwidth than a Yagi, but it sacrifices some directionality for a given size of antenna to do so.

Some areas have MDS - microwave distribution for their TV, especially pay tv. This runs at about 2.3 GHz (or thereabouts) and at this frequency you can start to use small dishlike antennas. Those square grid dishes with a spike pointing out of the front.

Once you get used to the general principles you realise there are not actually all that many designs in use, and you can quickly pick out the outliers. Antennae that are not for TV, but whose design and size (which is directly linked to the frequency of operation) put them outside any use for TV. Amateur (ham) radio is easy to pick, the frequencies are quite specific, so you can easily pick a 2 metre and 6 metre rig out. You see the odd wide range log periodic around. And becoming ever more common, 2.4 and 5GHz antennae (either dish like, Yagi, or helical) for digital communications. Utilities will often have a small Yagi on a remotely monitored or controlled device pointing back to wherever it is controlled from. I see that a lot here on the municipal water supply.

Antenna design is something of a black art. The theory is well understood, but the creativity and very firm understanding of what is a complex (pun intended) problem requires a special sort of mind. I knew a couple of people that designed antennas. One was and EE and ham radio guy. He did it for fun. The other was John Dunlavy, who is credited with inventing the Log Periodic. He also designed ground station antennae for NASA for the Gemini mission (after, as he claimed, their in house guys messed up.) Nowadays computer sim of the designs allows much ore easy playing bout with designs, but the problems are messy enough that there are still test ranges where designs get tested out for real. Some problems remain just plain awful - like designing the antenna set up for a naval vessel.

13

As an aside, the there is tremendous design activity these days in tiny antennas.

The “Internet of Things” is driving the development of small, cheap, efficient printed antennas:
Here’s a comparison of a few designs - there are thousands!

14

In a previous life (pre internet), I lived 180 miles from a FM station (NPR) that I liked. Somehow, I found a formula to build and antenny specific for its wave length. As I said it was pre internet, so, I don’t know how I found it.

It was constructed out of twin lead wire, and its wire length was determined by this formula. I mounted it on a 1x4 wood slat. Worked awesome!

Another style of antenny. But, now all you need is a modem.

15

Just re-read my last post. Lordy, I need to proof read a bit more, and not post in the early hours of the morning so much. Insomnia has a lot to answer for.