Adelaide digital TV stations tuning

If your TV tuning suddenly messed up in Februrary/March 2025, it seems like channel 7 has changed all their main channels to be high-def, and using MPEG-4 video encoding, leaving just a couple in standard definition.  Older sets may not be able to decode MPEG-4 or only the sound, some sets have a MPEG-4 option that you'll need to switch on in the tuning menus, and very old sets can't do HD.  Leaving you with fewer channels to watch (on those TVs).  There's the obvious solution of buying a new set, or using a set-top tuner box, or recorder, if you'd like to keep using the TV.

My TV popped up one of those messages letting me know there was a channel change, and I decided to let it search for new channels.  It erased all the channels, found all the channel 7 stations, then aborted with no other stations.  And, yes, I am in a strong signal area, with an outside antenna that's wired-up well, with direct line-of-sight of the 50 kW TV transmitter towers that are only about 20 km away.  I could barely have a more ideal situation to receive their transmissions.

It seems mine is one of those that searches for the first channel (which is the 7 Network on RF channel 6 VHF in the main metropolitan areas of Adelaide), then expects metadata from that station to inform it about other local channels, and 7 wasn't providing it.  (Are they deliberately sabotaging the other stations?)  It was a couple of days of fighting with the set trying to get the other channels, trying factory resets, letting auto-tune try to find the other stations (and never doing so), eventually manually tuning in all the stations (I had to find a list, first) one by one.  Previously, the set had been perfectly fine at auto-tuning.

If you have a set where the auto-tuning takes a while scanning to find a station, then suddenly tunes in the rest very quickly, chances are that it's using the method where it uses data from one station to find the others.  If your set slowly tunes through the entire band, it's actually scanning for stations (not that my set found anything when it did that).

To manually tune a modern TV, without stepping through about 80 channels, it helps to have a chart, and know that the stations aren't actually on the channels you expect them to be.  In the olden days, the station on the TV's channel 9 was called Channel 9.  Now their station ident is whatever they want, and the actual broadcast channel number can be anything.

Where I live, if I go to manual tuning and get my TV to tune in RF channel 8, it'll find all the stations that Adelaide's NWS Channel 9 broadcasts in one hit (their main channel, 9, and all their other associated stations, like GEM & GO, etc, are all broadcast from one transmission carrier, as multiplexed digital data, on channel 8).

Each TV station is the same, they broadcast a bunch of multiplexed data streams as different channels from a single transmission carrier frequency.

The old station numbers mean very little other than a brand name, now, except for grouping all their ancilliary channels on a bunch of similar channel numbers (91, 92, 95, etc).  These are called logical channel numbers (LCNs), and don't have to be the same as the radio channel frequencies they actually broadcast on.  If you find your set has the channels in a muddled mess of channel numbers that don't match what you expect, look for a LCN option in their tuning settings.

Frequencies

For the main metropolitan area, all the big stations are on VHF with only the community station UHF.  So either you need a VHF band III aerial, or a combination VHF band III & UHF band IV aerial pointed at the towers on Mount Lofty with the bars on your antenna poking out horizontally.  For manual tuning you can consult this chart:

RF means radio frequency.  It simply means a broadcast signal, it doesn't only mean radio.  A channel is a range around the main carrier frequency that the transmitter uses.

A band III VHF antenna covers VHF channels 6 to 12, a band IV UHF antenna covers for UHF channels 28 to 35, and a band V UHF antenna covers UHF channels 36 to 69.  An antenna will pick up some signals from outside of its frequency range, but reception gets worse the further out of specification the channel is.  You can use separate antennas through a combiner unit, or get a combined antenna that covers all those bands itself.

There is no such thing as a digital antenna.  If you still have a working antenna from the analogue TV days that covers the channels you need to receive, you do not need to change it.

If you're in the Adelaide foothills areas where the Mt Lofty transmissions go past overhead with poor reception, you'll use a UHF band IV & V aerial mounted horizontally and pointed at the Grenfell building in the middle of Adelaide, and tune to these transmissions:

It is possible that a band IV UHF antenna will also pick up channels 37 and 39, even though they're in the band V range.  The signal may or may not be strong enough.

Further north of Adelaide, there's a low-power transmitter broadcasting from Uley Road Elizabeth on these UHF frequencies with a vertically polarised UHF band IV & V antenna (mount the boom so the fins on your antenna are vertical, the boom still points towards the transmitter):

The community TV channel (44) only transmits from Mount Lofty, and is a much weaker signal than the other stations.

If you move location taking a TV with you, you may have to retune the set.  For example, Channel 9 in Adelaide will probably be broadcast on a different frequency outside of the metropolitan area.

Aiming an antenna

Most TV antennas are a Yagi (or a similar arrangement).  Traditionally there's a boom pole that you aim at the transmitter, there's a series of spokes sticking out of the boom, with shorter ones at the front and longer ones at the back.  In essence, it's somewhat arrow-shaped pointing at the broadcast site.  The front spokes are called directors, they direct signals towards the receiving parts of the antenna behind them; the rear spokes are called reflectors, they reflect signals towards the receiving parts; and there's a folded dipole that the antenna cable connects to somewhere near the back.

In low signal areas TV aerials may be a phased array, this is a stack of receiving antennas mounted on top of each other, and wired together.  They look somewhat like a box kite.  Again, aim the booms at the transmitter, the spokes sticking out sideways.

Most TV transmissions are horizontally polarised.  Very simply put, the spokes of the antenna on the transmitter and the receiver stick out sideways.  Some transmitters are vertically polarised, their spokes stick upwards and downwards.  For good reception both the transmitter and receiving antenna need to be oriented the same way.  In either case, the boom points towards the transmitter.  Telescopic “rabbit ear” antennas should be similarly oriented as the spokes on an antenna, as if there were mounted on a boom, although they're commonly arranged in a V shape (amongst other things, this gives them a bit of extra height, and the higher an antenna is mounted it usually helps with reception).

There is such a thing as circular polarisation, where the transmission is not horizontal or vertical, and the receiving antenna can be oriented in either direction.  This is commonly used with FM radio transmissions.  And is useful for things like receiving radio in the home from an outside TV aerial, or a portable radio with a single telescopic pole sticking upwards (this includes radios in vehicles).

Antennas have gain.  That is, they receive a signal stronger than a simple bit of bent wire, by a certain amount measured in decibels (or dB, for short).  The more decibels the better.  3dB is barely better than a homemade antenna from a bent wire coathanger, 6dB is twice as good, 18dB is really good.  High-gain antennas have lots of spokes, low-gain antennas just a few.  It is possible to receive too much signal and overwhelm the tuner in a TV, but generally you lose some signal strength through the length of cable between the antenna and TV, and any splitters, that it's not usually a problem.  And most stores selling antennas tend to sell ones reasonably suited for the local area.

A prime signal antenna is one meant for people living in a very strong signal area, it has little gain, it's main feature is directionality.  A fringe antenna is one meant for people living on the fringes of reception and need a higher gain antenna to receive something.

Antennas are directional.  They receive mostly from the front (where they're pointed at), they receive little from the back, and even less from the sides.  This is how they have “gain,” you can think of them like a funnel.  Any why they need to be aimed.  The reason for directionality is two-fold, increasing their gain for where they're aimed at, decreasing the reception of echoes and reflections from beside and behind the antenna which will cause cause signal disruption.

Most modern digital TV receivers have some kind of signal meter, that gives you a rating of signal strength and signal quality.  Signal strength is fairly obvious—how much signal is being received.  Signal quality will be a mix of how well the antenna is receiving a direct signal without interference from other things or reflections of the same signal, and with the antenna cabling between aerial and receiver.

Cabling is important too.  Signal will be lost along the length, good cabling is better than bad cabling.  Interference can get into the cable, and the better the shielding around the core the less that happens.  The cable need to be correctly wired to the antenna, and any plugs and sockets.  Bad termination of wiring can cause significant signal problems.

Adelaide stations

Once you've tuned things in, you can expect to see the following TV and radio (through your TV) stations around the Adelaide area.  These radio stations are also broadcast on the same carrier as the TV stations, and are a separate transmission than DAB+ digital radio broadcasts.  DAB+ is also a multiplexed system, all the ABC and SBS radio stations are broadcast from one transmitter, and all the other Adelaide stations on another (commercial and community) from another transmitter.

For no other reason than I'm old, I'll list this in their original order from back when we didn't have digital TV.  We had ABC channel 2, SAS channel 7, NWS channel 9, ADS channel 10, SBS channel 28, and Community TV channel 31.  Glossing over that SAS7 and ADS10 used to be SAS10 and ADS7 until they swapped transmitters for marketing reasons (the owners of the 10 network interstate owned the 7 station in Adelaide, and vice versa, and they wanted to use the same channel numbers everywhere for their programming and branding).

2, 20, & 21 are showing the same program as each other.  They could be separate simultaneous data streams (the standard definition channel is definitely a separate stream from the high definition one), but the two standard def channels could simply be the same stream with two different names.

7, 70, & 71 are showing the same program as each other.  I don't know if this is three simultaneous streams, or the one stream appearing with three different channel names.

9, 90, & 91 are showing the same program as each other.  I don't know if this is three simultaneous streams, or if the two standard-def channels (9 & 91) are one stream appearing with two different channel names.

The community TV station has always been living on borrowed time, only having their transmission license renewed for short periods, as the government is hedging their bets if they can sell off the spectrum that they're using for other uses (mobile phones and internet, most likely).  And the station protests that their audience needs to be broadcast reception rather than on-line streaming through the internet.

I expect the other stations will start to drop their standard definition channels over time, too.  They can only broadcast so-much data, so it's divided between a larger number of standard definition channels, or a lower number of high definition channels.  It'll depend on how many channels they want to transmit, and the impression they want to create.

Since all of a station's channels come from a single transmision, the ability to receive a clean standard-definition or high-definition signal ought to be the same.  It'll depend on error handling if your set is better at coping with a poor signal on standard-def than it is on high-def.  Your tuner gets them all from just one broadcast signal.