Poor Digital TV Reception Bundaberg Region?

SOLVED !

 

tvantenna1

 

 

Background:

We moved to regional Queensland and Analogue TV was fine, then along came Digital TV with all those promises of Picture Quality.

Alas, what might have looked fabulous in the laboratory demonstrations was NEVER going to be a reality for Australians, not unless they lived within a couple of kilometres of a transmitter tower.

The truth of the matter is Digital signals might travel as well/strongly as the old Analogue signal BUT the TV decoding the signal at the other end can't just go "a little fuzzy" and show some "snow" like Analogue used to. Digital just drops out and puts a NO SIGNAL icon on the screen. Now that's a bummer in the middle of a football game!

So that was the problem and we set out to solve it once and for all.

First Step: Change the Coax cable throughout the entire house! The house was about 20 years old and had been cabled with the cheap coax that builders used to throw around. So it was all replaced with quad shielded quality Coax with screw-on "F" connectors at all possible ends, getting rid of those push-on TV fittings.

So now we knew that our cabling was sound and we weren't getting signal degradation or interference at Connections Points.

As an amateur radio operator I understand propagation and could see the possibilities of a better Antenna design so....

The next step was research

The Telecommunications Authority prints some maps with colours and shading but the fact is they can't allow for every dip and hollow that we may be living in.

The maps should be taken as a guide only about the possible signal strength at your house.

With a friend we researched the Phased Array VHF Antenna for Channels 6 - 12 and we settled on the Big Ray 16 Element model - and it's quite a big - 2.4 metres [8ft] wide.

This Antenna is not a "beam" so it is not "pointed" at the Mountain - This antenna sits Broadside to the signal from Mt Goonaneman.

Mt Goonaneman transmits a "Vertical" signal so you'll see in the photo the we put our Antenna with the Aluminium Elements [bars] pointing up and down. [If your local VHF transmitter is a "Horizontal" signal then you would put it with the Bars Horizontal - it can go either way.

OK, that seems to take care of VHF now to get those pesky UHF Channels.

[We no longer require this part of the antenna but we leave this info here, in case you are in a location which still receives UHF signals.]

The 36 Element "X Type" Phased array was suited to our terrain and distance from the TV Transmitter tower. It's much smaller than the Big Ray and as you can see in the photo - it goes at the top of our assembly.

Notice the "GAP" between the two Antennas... we needed to leave at least 450mm [18in] between them [see the Myths section. Myth 3 will explain this]

Construction

We needed height! We have a stand of big old gum trees in our line of sight, so we wanted to be as high as possible to give the signal the best chance of getting in.

We fitted a 6.5M galvanized steel pipe mast to the roof with 3 stainless steel guy wires to brace it. In our sub-tropical location we do experience a wet season so cyclones and high winds can occur.

Next we fitted another 6.5metre length of galvanized pipe. We fixed the mid-point of this pipe to the top of the fixed mast and this means we can swing the pipe down... fit the Antennas .... then by pulling on a rope the pipe swings up into the air and when it's fully upright it slips into a bracket on the fixed mast and is secured.

Where not planning on pulling this up and down very often but it sure does help to have a way of getting to the antennas - there is an additional 2metre pipe at the top holding the UHF Antenna and the whole things is about 13metres [42ft] above the ground.

There are a further 3 stainless guy wires on this upper moveable pipe, giving a total of 6 to stabilize this new assembly.

Cost

No it should NOT cost you an arm and a leg to get good Digital TV.

The VHF Phased array retails for about $160

And the smaller UHF one for about $110

That's top "list" price so you should be able to do better than that if your installer is supplying antennas and getting a labour fee.

What should an installer charge you?.... How long is a piece of string? ..... This will depend on what steel you're putting on your roof, how much of the work you do yourself and a whole lot of other issues that only you and a reputable installer can chat about.

Do ask for a breakdown so you can see that he's charging fair prices for the two antennas and his labour. You worked hard for the money... let's not be giving it away too easily.

As mentioned elsewhere... get some references... go and see the people he's worked for... ask to see their TV picture... switch channels - I know it's a liberty but most people like to spread the word about good installers and we should be weeding out those who are not so reputable.s.

 

Let's talk about some Myths

Myth 1. Antenna salesman know their stuff.

That may sound harsh but... but when Bunnings puts up a display board and shows people what antenna to buy depending on their location - and it's WRONG!

... and when local Antenna Installers go to old pensioners and charge them $600 to get Digital Antenna installed... and it's the wrong antenna, in the wrong position.

You tell me then... just because his shirt says TV Installer if he hasn't studied the propagation of signals and the fundamentals of antenna design why should we believe him?

.... We need to learn about signals, ask for references, talk to people who have GREAT Digital TV and all the other poor sods who don't...

Myth 2. That Digital TV signals are "different" and travel differently and can apparently go around objects.

Whether it's the signal from the old analogue system, or digital TV or your Wireless Internet or Mobile Phone... they are ALL radio waves just travelling at different wavelengths! And radioelectronic signals or waves are governed by science. We don't want this to be too heavy so we won't bore you but just imagine all those similar waves in the air together. Some "carry" digital TV signals mixed in with them... Some "carry" voice signals... that's a simple analogy but you get the point.... Don't mess with science. smile

Myth 3. You can just stick antennas anywhere, near each other... doesn't matter!

WRONG!!! WRONG!!! WRONG!!! And its quite another scientific fact why you can't do that.

If you cheat and stick everything in the wrong place one antenna WILL interfere with the other or BLOCK the signals that it is trying desperately to pull out of the air.

Antennas need "clear air" around them so that together with your TV Receiver have the best chance of locating and holding a signal. If you install your YAGI TV Antenna [that's the regular BEAM antenna you see around town] directly onto a a thick metal mast... you have put a thick piece of metal in the middle of your antenna - How can it do it's job effectively?

The science states that all Antennas have to have a distance from metal and other antennas - technically this is a quarter wavelength but let's keep this simple and say... keep about 450mm [18inches] from your metal mast/post and any other antenna.

This means if you're using one of the Yagi Combo antennas you should fit a 450mm piece called a "stand-off" to get your Antenna away from your Mast.

Myth 4. The "long distance" Yagi Beam antenna which Bunnings sell is good for any distance!

WRONG - from Anecdotal evidence in this part of Queensland their long distance Yagi antenna is good for about 65km [as the crow flies!] from Mount Goonaneman [Childers]. Over this distance it is NOT a reliable antenna.

If you do live a substantial distance from your TV Transmitter you should be investing in a better antenna and that means a phased array... not a Yagi beam.

**There are probably more Myths, we'd be pleased to hear some and we can add them here.... What "fibs" have TV installers told YOU!**

tv1

Partway through the construction.

We have a fixed mast attached to the roof and another length of steel onto which we fit the Antennas and then when we pull on a rope it swings up into the sky

tv2

It's up!

 

The signal strength into the house is 100% on ALL channels

Before this install our signal varied from 42%, 57% and never had over a 70% reception on any Channel

SUCCESS!

 

ADDITIONAL RESOURCES

In the Documents area we have some reference material which may help readers come to grips with the scientific theory and answer some installation questions

1. A sample technical specifications sheet on Phased Arrays: The link is UHF/VHF Phased array .PDF Document

2. A guide published by the TV Networks: Tips on interference & guide to Wide Bay & Hervey Bay Channels

3. ACMA Signal Reports around Bundaberg Beaches: Compiled February 2012 BundyBeachesDVB.pdf

4. Radio Communications Handbook - Chapter 16: VHF UHF Antennas [File size 2.4mb]

5. A good Reference book: Understanding Digital TV [File size 3.6mb]

 

Understanding Digital TV is 73page reference, for those who like Technical info.
It covers Design and Characteristics of Digital Transmission with Graphs and explains also how the Digital Signal is measured

 

 

Some technical notes

Link to some further resources

 

*** Please follow the above link to a Technical Note on Digital TV**