Signal Paths and Reception

13 Apr, 2021, 6:38 AM

Written: August 12, 2016

An Understanding of Signal Paths and Reception is an important part of getting the picture. Written in plain language.

TV Signal is energy and the energy changes (a separate frequency) ever so slightly every time a new TV channel is selected. It is the changed signal that the TV has to recognise and processes.

In Australia we have TV channels from 6 through to 51. Another way of expressing this is to say the antenna collects electromagnetic waves that are long approximately 400mm to 6m long. When I first became aware of this natural thing called a RF wave I was fascinated. You cannot see it but it exists and man has learnt to use this natural occurring phenomena. The above range of channels is the Australian use of the spectrum for Television. In Britain it is different as is in the USA.

Why is this important – it tells us what the antenna has to deal with if it is to deliver quality signals that allow a perfect picture to be viewed.

A couple of examples from my history of testing antennas. Suppliers would come out with new products and quote a fancy specifications to you, which by the way was always exaggerated.

They must have tested the product under perfect conditions. No true specifications can be provided under theoretically conditions.

An antenna’s performance is effected by the ground the signal travels across. A signal that travels across granite rock will stay stronger and be far more reliable than a signal that travels across a sand belt. The rock having some qualities that will enhance the signal while the sands will absorb the signal. That tells us that if you are setting up antenna across a sand belt a clear signal path will be important. While if in granite you can be behind a belt of gum trees and still receive a good signal and consequently a good picture.

Digital is very robust. However it does demand good TV connections and cables – antennas can almost fall apart and yet if they have good cable and connectors they may still be working.

Many antennas sold today are very poor quality. They will either last a few years only or do not work properly all the time or do not work properly from the beginning. Rust on the – particularly on the terminals –  antenna if bad enough will stop it working.

Your received channel changes (this is why you have to retune your TV), if you are on the move like in a Caravan, so the TV antenna has to cover a broad range of energies (signals). Very few antennas will work across the whole range. The truth is that when energy levels are high, even a coat hanger will work or a good indoor antenna. So the mobile user has to do some homework and get some knowledge otherwise he can be sold something that is not suitable. The homeowner has a limited number of signals (energies) he needs to pick up so his job is easier. The exception is the person living a long way away from the transmitter, a weak transmitter or reception issues to do with large buildings, hills or mountains in the way.

In all my years I have failed once to solve a signal problem for a customer. The solutions have varied from been 50 foot  masts, Antennas mounted on top of the highest point on the property and the signals bought back to the house even up to 1.5 Kilometers like at Newport power station when it was built and blanked all the residence behind it. An antenna put in the valley and a cable run to the house. Signals bounced off big glass panels like the Victoria Hotel or multiple antennas installed in a hollow so the resident could view great television on his new large screen TV. Whatever the signal path there is a solution and digital has made that solution easier to achieve. The benefit of digital is that as long as the TV can read the zero or 1 it can convert it into a good picture. When it cannot you get pixilation or no signal.

Signal is always there. You need to understand its nature, how it behaves in various types of topographies and what impact lower and higher energies have in the terrain where the antenna is being used.

A great example was Yallourn the coal fired power station would send particles into the air and as result of these particles signals would be available at Swifts Creek. Particles disappear and so does the signal. I got caught on this one. Temperature and wind also play a part.

The quality of the materials and the correct choice of design of the antenna for the location will effect the reception.

 

Sally Garden
RF Consultant Founder
Wilkgard Technology Group P/L