Digital antenna v analogue antenna - does it affect quality?

[Rudyard]

My father in law has the same antenna on his roof for the last 15-20 years and has someone in his ear telling him that all new antennas are digital these days and buying a digital one will give him better picture quality from his digital broadcasts.

Now I said I didnt think that was true but wanted to check first. Could someone tell me if this is how it goes:

Digital TV (over the air we are obviously talking) is sent as a bunch of 1's and 0's like digital stuff is. Your antenna either receives this info or it doesnt, meaning your actual picture quality you are watching is not determined by the quality of the antenna (like analogue) but whether or not you simply receive the 1's and 0's.

The only thing I thought it could affect is whether or not the picture drops out or breaks up from not recieving the 1's and 0's (is that what it is when every now and again the picture freezes or half freezes?).

So you could probably get a more stable reception but the picture itself when received will look exactly the same no matter which antenna received it?

This other bloke has put it in his head that the picture quality will be improved if he buys a new antenna and I just didnt want him to shell out for it and its installation if it wont make any difference.

[Marvingj]

Most TV sets are now receiving an "Analog" signal. The same type of transmission that has been used since TV started to become popular in the 1940s. Analog TV signals are very similar to AM and FM radio signals and can be subject to interference, snow and ghosting. Digital TV signals are transmitted as data bits of information in a way similar to computer data or the way music is written on a CD. A Digital signal either works or it doesn't. No fading or interference. It is either on or off. Plus a Digital signal can carry much more information than existing Analog signals. While full implementation to Digital was originally believed to happen in 2006 it is now thought that Analog signals will end in 2009 but set top converter boxes are available now and will be available at a reasonable price in the future. These boxes will convert Digital back to Analog to enable older TV sets to still be used.When the you receive a digital broadcast vs. an analog broadcast, you are able to more information to your television. What this means is that you will get a better picture and sound than you would with analog. You will also be able to get more channels in the future, as the broadcast station (WJFW) will be able to have as many as 6 channels broadcast simultaneously

[guns1inger]

When I put my first digital box in, I just used my existing, standard analogue antenna. It worked without any problems at all. When it finally died (damned birds - I need a scarecrow on the roof), I replaced it with a model that said it was designed for digital reception, and it cost probably $20 more than the 'non-digital' one. And the difference ? For all intents and purposes, none. Yes, according to the signal meter in the set top receiver the signal is stronger. However as there are only two states for digital reception - you have it or you don't - getting a stronger signal than one that works perfectly don't result in a better picture.

Bottom line - if you get good analogue reception, and digital is being broadcast from the same towers, you will get good digital (even moderate analogue can produce solid digital). If you get poor analogue now, you will get poor digital unless you change the antenna. But you should do that first for your analogue reception anyway.

[edDV]

Digital broadcasting is still sent as a modulated analog radio wave in either the VHF or UHF bands so basic rules of channel number (frequency) and RF propagation still apply. An old antenna can work if it is optimized to the broadcast band being used (usually UHF)* but VHF can also be used.

First step is to find the frequencies or channel numbers being used at your location and their direction and distance.
http://www.dba.org.au/index.asp?sectionID=22

You may need a UHF only antenna or a combo UHF/VHF. If the stations are scattered, you may need multiple antennas.

Most likely the old antenna will be useful.


* It looks like what is called UHF in America is called VHF band III and IV in Australia but the same issues apply.
http://www.dba.org.au/index.asp?sectionID=133

[guns1inger]

Us oldies still remember UHF, but the newer TVs call it VHF III/IV

[lacywest]

Us oldies still remember UHF, but the newer TVs call it VHF III/IV

I live between Fresno and Bakersfield ... California ... and the TV channels in our area are broadcast on UHF.

Zip Code for my Town of Hanford California ... is 93230

I've mounted a nice Bow Tie type of UHF antenna on a 15 foot mast connected to my chimney and I pick up all
the major stations in my area ... ........ including Smallville on channel 59

[edDV]

This may be helpfull.
http://www.dba.org.au/index.asp?sectionID=121

"Antenna Bands and Digital Television Channel Planning

The Australian Communications & Media Authority (ACMA) has endeavoured to plan digital TV channels in the same frequency bands as the current analog TV channels available in a particular area. This means that the same antenna can be used for both analog and digital TV reception. However due to shortages of available frequencies in some parts of Australia, this has not always been possible."

[Rudyard]

Thanks for the info.....so I assume I was correct in that the channels he now gets will look identical with a new antenna and it wont improve the actual picture quality?

He isnt having trouble receiving the signal, he was just told a digital antenna would give him better picture quality.

I understand in the future if they broadcast other channels or features on different frquencies that he may need a new one but for now it wont affect what he already has.

[edDV]

Thanks for the info.....so I assume I was correct in that the channels he now gets will look identical with a new antenna and it wont improve the actual picture quality?

He isnt having trouble receiving the signal, he was just told a digital antenna would give him better picture quality.

I understand in the future if they broadcast other channels or features on different frquencies that he may need a new one but for now it wont affect what he already has.

Is he currently getting the digital broadcast?

While digital broadcasting uses the same RF bands and channels, the way the signal is modulated is very different and it is true in weak reception areas the signal either demodulates near perfectly or it fails to demodulate. It may drop out, then come back but there is no snow or ghosting. In those cases you need to focus the antenna better or use a larger antenna to improve reception. At great distances you may need both a large directional antenna plus a booster amp. like these.

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Once the signal is stable, there is no advantage to amplifying further. If the signal is too strong you may lose reception.

[Rudyard]

Yes EdDV he is getting the digital signal and watching the digital channels. He occasionaly gets a breakup in 1 room only but its rare.

He had no issues with his reception he just now thinks he can get better quality (as in a sharper, cleaner picture like going from vhs to DVD)

[edDV]

The RF part of digital is a "it works" or not situaltion. A cleaner picture may require a better tuner, a different way of connecting the tuner to the TV or a better TV.

Big city reception has other problems mostly dropped reception or difficulty finding the station with an indoor antenna. There is no "weak" reception. If it is weak you don't see it. That is why you need to know where to point the antenna.

[guns1inger]

If he is using a composite connection then his picture will only be slightly better than a good analogue tuner. He will be free of any noise and interference, but the image may still be soft and have colour bleed. The same as you get if you connect a DVD player using composite.

Most digital boxes sold over here originate from Europe, so it is common to find scart connectors on the back. If you only have scart and composite, get an s-video back-shell for the scart connector and use this to get a better picture (if the TV supports it). Finally, most also support component, but often it is RGB component, which isn't compatible with Asian made TVs.

[Richard_G]

I understand the bandplan for Australia is much the same as in the UK. For analogue broadcast the channels used were Grouped. The transmission band runs from UHF Channel 21 (471.25 MHz) to Channel 68 (860.25 MHz) but transmitters from each site used a group within that. Antenna design is a tradeoff, narrow operating bandwidth with high gain or wide operating bandwidth with lower gain. In my area, all the analogue transmissions are in Group A which is Channel 21 to Channel 35 therefore a grouped antenna that was optimum for that part of the band was normally used. The digital transmitters are operating within other parts of the band so an existing Group A antenna would receive little or no digital multiplexes. To receive digital, a wideband antenna is required (ie, one that is resonant over the whole band). The so called digital antennas are merely high gain, wideband ones as opposed to grouped. The antenna itself is no different but it is capable of giving digital reception because it can receive over the whole band and not just a portion of it.

To prevent picture break-up due to impulsive interference it is recommended that fully screened coax feeder is used (CT100 or what is often referred to as satellite cable) and only use amplifiers as an absolute last resort. An amplifier will amplify everything and not just the wanted signal, so adding an amplifier to a system that is suffering from break up due to an interference source will often make it worse. If signal level is marginal, increase the antenna gain to get more, don't try and amplify what little is there.

Finally, the standard test to see if signal level is adequate is to put a 6dB attenuator in the antenna input to the DTV receiver. If the picture doesn't break up you have adequate, if it does, you haven't. Received signal levels will vary slightly due to changes in propagation caused by atmospheric conditions, weather, time of day, time of year, etc. If it is marginal at the time it is tested chances are it will get worse.

[edDV]

That is interesting. All American "UHF" antennas cover the full 470-890MHz band. After analog shutdown the band will be narrowed to 470-698MHz (37 6MHz channels). The upper channels will be auctioned to wireless licenses.

[Bjs]

Masthead / Amplifiers should be reserved as a last chance attempt .

Older antenna's are fine , but check http://www.dba.org.au/index.asp?sectionID=25#New_Antenna

Difference between grounded and non-grounded mounts also have affects on signal .

If you are between two broadcast towers , you may need to find a method to shield the antenna from the other tower , or reception is degraded / distorted .

Signal source should remain around 75 - 90% strength , a rise above will cause disruption to signal , and reported to damage devices .

House Installation DON'Ts , the two to watch out for :

DON'T leave an installation with digital signal levels just above threshold
DON'T let any signal level applied to the DTT receiver exceed 77dBµV

Yes ... I already have a cooked unit .