TV antennas and what is possible indoors Answered
Back in my young years a TV antenna was on the roof, quite big and only required to get 3 or 4 channels at best.
The basic design of these Yagi antennas has not really changed since then.
Same for the antennas required to get UHF and VHF channels at the same time.
They either comes as two seperate antennas with a mixer or as a UHF antenna with some added loops for UHF.
To talk some basics:
For UHF you can get away with quite small dimensions for your antenna bits.
After all a quarter wavelengths here is only around 15cm long.
With VHF though we get already 30 to 40cm here depending on the channels.
So called bradband antennas claim to be able to get a wide range of frequencies.
That however is only true for their dedicated frequency band.
If you take a normal whip style antenna then this becomes obvious - just compare the lenghts required and you realise "going the middle way" will mean neither UHF nor VHF would get any usable reception.
For a long time now there is the option of so called "fractal antennas" to get better TV reception....
Fractal antenna? What the heck is that?
The theories behind them are about as old as fractal antenna designs that were not even considered to be fractals.
Let me explain with the example of a standard FM radio antenna.
For them we use frequencies from about 88 to 108MHz.
And of course, for our cars they are always on the roof or mounted somewhere around the wheel arches.
Some cars however does not seem to have any antenna depsite having a working radio.
In this special case rest ensured they do have one, usually behind the plastic bumper bar ;)
I like to go off road every now and then and lost count how many times I had to replace my antenna after getting to close to some bushes and trees.
As a solution I used some thin wire to create a L-style anteanna on the inside of my windscreen.
And funny enough it picks up more stations than a "proper" antenna outside.
Really old design and if you think about it then an antenna with a kink that looks like L is ""self similar" - the definition of a fractal ;)
More complex shapes like the Sierpinski models do exactly the same just in one more dimension.
Cell phones use them as well as you WiFi router that has no external antenna anymore.
Their designs and looks are so different that it is next to impossible to list the currently used shapes here.
What it comes down to, when you just take a very basic flat or wire shape is that the straight single segment of the active antenna is split into one or many shorter segments that change the angle.
They all have similar relations to the wavelenght still.
Means really long segments might be half of a wavelength while the shortest bits are just 1/64 of a wavelength.
Think of it (far too simple of course) like amny matched antennas combined into a single one.
With that often comes a destinct radiation pattern, usually with a quite narrow beam angle that provides a quite high gain.
Are fractal antennas any better than for example a proper Yagi antenna?
You can ask 100 people and you get 100 different opinions for this one.
This is mostly due to some simple facts like:
Not caring about actual comparisons.
Not being accurate enough when building the fractal antenna.
Using just very basic equippment to compare results.
For example when you have a 30 year old and quite small TV antenna on your roof and struggle with digital TV reception than you might want to just replace it all.
In some case even the old rabbit ears on your TV set will work better.
But take modern Yagi antenna with 12 or more segments and even station that are 100 miles away have a good chance.
Comes down to possible gain, frequency match and of course how well the antenna is aimed at the transmitter.
Then why is it that some fractal antennas still seem to perform so much better?
The big antenna scam....
If you paid attention during the intial DVB-T rollout in your country then noticed two things.
a) You were told you need a TV or set top box capable of receiving DVB-T signals.
b) You need a suitable antenna.
Well, A is obvious but for B a lot of people got scammed badly.
You see, in almost all cases the frequencies allocated for TV signal did not change at all.
And an antenna really does not care if the incoming signal is analog or digital - it only cares about the frequency.
But more and more local stations often meant that the trnsmit power is limited.
After all it makes no sense to have a 500kW transmitter if the area to cover is only about 20 square km big.
So people were told they need new antennas once the noticed digital TV is more like playing Tetris, blocks everywhere....
You analog TV had no problem with a slightly weak signal, you did not really notice it unless the weather was really bad as well.
All the benefits of digital TV however only work with a proper signal strength.
If your areas still has both analog and digital TV channels then have a look on how your local transmitter provides the signals ;)
Part of the big scam was hiding a very simple fact:
All analog TV is transmitted in a horizontal orientation while almost all digital TV is transmitted in a VERTICAL orientation.
Ok, we already gain and ignored it but why would the orientation be important?
Your radio antenna is vertical because the FM signal is transmitted the same way - the "waves" if you like go up and down like a sine wave.
You still get reception if you turn the antenna 90° to make it a horizontal one but you will realise that weak station are no longer available.
The same happened with digital TV.
And if there is only digital TV left in your area then simple turning your antenna 90 on the mast to have the single elements vertical instead of horizontal gives you top reception again ;)
If you struggle to get all station then just try it out before buying a new antenna ;)
Modern fractal TV antennas come paper thin and often with rediculous claims in terms of gain and range.
On Fleabuy you can even find models claiming to get stations from over 2000 miles away LOL
Some even come with the fake claim of being omnidirectional, meaning it does not matter where you place them or how you orient them.
A fractal antenna can't change basic phsyics though...
High gain mean highly directional or at least with a very flat radiation pattern instead of being more like a sphere.
A high bandwidth means you compromise on the gain and/or the phsical dimensions.
For example a thin whip antenna is quite limited in the optimum bandwidth while a piece of tubing provides amuch higher bandwidth but at the expense of gain (and some other problems).
A fractal antenna can compromise between the two worlds much better than anything straight.
And you would even need to make the traces on the plastic extremely wide because you can simply add different lengths for different frequencies.
Means a wideband fractal antenna for FM, VHF and UHF basically is three different antennas combined into a single one.
It also means that there is usually always more than just one single element of the antenna that is receiving a signal.
If you experimented with WiFi antennas for your router or modem than you certainly found the famous Pringles can antenna - highly directional and with an insane amount of gain.
Works exactly like a simple directional microphone.
And you could, at least in theory do the same with a TV antenna - if there wouldn't be the problem of the wavelenght.
A pringles can works for WiFi because the wavelenght only requires an antenna of about 3cm in lenght.
You might not want a row of steel drums with a diameter of around 80cm on your roof just to watch the news though...
Ok, if I need a new antenna anyway then should I get a fractal antenna or not?
I try to make it simple:
Roof option not possible or too costly AND your transmitter is not too far away then try one of the cheap paper thin antennas you find online.
If you already have an antenna on the roof that is suitable for the frequencies you need then check it to know if it is still any good.
With age and weather comes corrosion and some antennas are connected badly in this regard.
Sometimes you are lucky and all it takes is to cut off a few cm of cable to get back to clean copper and to give the terminals on the antenna a good fine sanding or a wire brush treatment.
In other cases you might find an amplifier under the roof that has faulty power supply ;)
And well, certain animals love to chew through your cable...
If all is goo from antenna to TV then as said try to flip the antenna 90° to get it vertical.
No, I did not mean to point it up to the sky..... ;)
I mean rotate it around the x-axis if X is pointing in the direction of the transmitter...