reception of hd dependant on aerial?

[JohnB47]

A friend has been given a modern tv (can't remember the make) that's marked as full hd capable. Today it was connected up in a new flat and a full Freeview scan was done but no hd channels are available in the guide.

Is a special aerial needed to receive hd? Or is it possible that a tv can be marked as hd capable but not actually have an hd tuner? The signal strength was quoted as 75%

Thanks.

PS I may not be able to reply promptly - about to set off on me hols and internet access is uncertain. Perhaps I need to check the make and model and look up the specs.

 

[plugwash]

Firstly the "HD ready" and "FULL HD" branding (which both long predate freeview HD) only relate to the TVs capabilities for displaying signals from external sources, not to the capabilities of the internal tuner. If it doesn't specifically advertise "Freeview HD" on it's specs it probablly doesn't support it.

Secondly in some areas the HD muxes are on very different frequencies from the normal muxes. This can mean you need a different aerial to get good reception of them. Having said that i'd expect in such a situation to see poor reception rather than no reception at all.

 

[Lucid]

Or is it possible that a tv can be marked as hd capable but not actually have an hd tuner?

That's your answer, right there.

Yes, it's possible to buy a TV with a Full HD display (1920x1080 pixels) so it will display HD Blu-rays and any external HD source in all their full HD glory, and yet the TV's own tuner might only be capable of standard definition from Freeview.

Of those TVs with a Freeview HD tuner (DVB-T2), then HD reception does depend somewhat on the aerial. It's not so much a special aerial, as just one capable of picking up the frequencies where the HD channels exist with equal efficiency as for the non-HD channels.

There's been a bit of a con going on for years with aerials. The ", wideband, high gain" aerial is a bit of a myth; a triumph of marketing B.S. and blind faith over education and common sense. The idea that one type of aerial could work in all conditions, and with all signals, and give more reception power than any other aerial type is a huge red herring. But Joe Public never really cottoned on and asked "If these were so good then how come other aerials still exist?"

The truth is that while these areas are wideband , they're only high-gain in a very narrow frequency band. That's okay if your local transmitter happens to send out channels where the aerial works well. But it sucks if you live in an aerial where the channels are in the 20's, 30's, 40's and 60+ before that was sold off to 4G.

Probably the best universal choice for an aerial now is the Log Periodic. This is almost equally as good all the way through the reception spectrum. In some parts of the country then that aerial along is enough because the local transmissions are very high powered (Crystal Palace for London and Winter Hill for the North West for example). In other regions then the aerial will need a booster mounting on the mast because the transmitter is lower powered.

An aerial such as a Log Periodic with its flat response will pick up the muxes that contain the HD channels as well as it will the standard definition muxes.

 

[Sam Gangee]

Probably the best universal choice for an aerial now is the Log Periodic. This is almost equally as good all the way through the reception spectrum. In some parts of the country then that aerial {alone} is enough because the local transmissions are very high powered (Crystal Palace for London and Winter Hill for the North West for example). In other regions then the aerial will need a booster mounting on the mast because the transmitter is lower powered.

Clarification:
A log-periodic is not just "good enough". For 85% of the UK population, a log-periodic will give better reception than a standard "Yagi" aerial because the log-p has better characteristics all round. Only in a few cases will a narrow band Yagi be required. A wideband Yagi will rarely work better than a log-periodic.

Note, too, that most log-p aerials are no longer "wideband". The modern ones are limited to reception of channels 21 - 60 (instead of 21 - 69). This means that they have effectively a higher gain than older types. There's also the V11-20A2, which is a "Group A" log-p (narrow band).

A booster rarely helps when the signal is extremely weak and it's easy to check whether a booster will work: if the Freeview TV works when connected directly to the aerial by a short length of good cable, then a booster will work if required. Otherwise a booster will not help because the signal from the aerial isn't strong enough in the first place. (In rare cases a small amount of boosting will help but, in situations such as this, the reception is going to fail in bad weather and it will be generally intermittent.)

So what use is a booster? It is used when the signal is weak (but not too weak) and has to be split to more than one room and/or the cable run is very long and/or the cable is poor quality.

Since a booster uses electricity, it's usually better to avoid it if possible. Install a better aerial and better cable (shorter if possible) instead.

More about log-p: http://www.satcure.co.uk/tech/best_aerial.htm
More about boosters: http://www.satcure.co.uk/tech/amps.htm

 

[ericmark]

I would agree you can't boost a signal that's not there but both ham radio wise and TV wise there is a huge difference in the receivers and using a booster with a weak receiver does help. First noticed it with my old FT290R with a MM linear pre-amp it really helped. Also crunching out the capacitor to make it suit European voices.

The same with TV stuff my Sky box will fail completely saying no signal but my free to air box works without a hitch.

TV's are no different I am sure there is a minimum standard but some clearly exceed that standard.

Aerials I think should be classed in gain v wind resistance v band width. As one increases the gap between the elements on a simple "Yagi" so the band width increases but so does the wind resistance and so also the likely damage to building it's mounted on. Also of course the bigger it is also the more likely for a lighting strike.

Aerials tend to have gain marked and weight marked but not wind resistance and clearly an aerial which is like a sail will cause anything but the most sturdy mast to move which will also mean loss of signal due to not being pointed in the right direction.

So to my mine to compare a Log Periodic with a Yagi one has to compare two aerials with same wind resistance. Weight is really not important it's the wind resistance which makes all the difference. If you do that then the Yagi wins. Although then we have another factor torque and balance. Aerials tend to be mounted at point of balance but with the Yagi this is often not the centre point for wind resistance so wind tries to rotate the aerial. The Log Periodic however is more even and wind does not tend to rotate it as much.

Clearly not everyone lives on the top of a hill like me and I accept that in some places wind is not a problem for example when mounting in the loft.

But once one factors in wind there is no best aerial. There may be a best for that house but there is no universal best it's just a matter of selecting the best compromise.

 

[Sam Gangee]

I would agree you can't boost a signal that's not there but both ham radio wise and TV wise there is a huge difference in the receivers and using a booster with a weak receiver does help.

Maybe you are referring to analogue reception and human perception? Human ears and eyes are quite good at separating signal from noise.

However, it is very rare for an amplifier to help with digital Freeview reception where the signal is too weak. There's a very fine line between boosting sufficiently to get above the tuner threshold and boosting the unwanted noise above the threshold, which the receiver can't handle.
More about boosters: http://www.satcure.co.uk/tech/amps.htm

 

[JohnB47]

Thanks everyone. Back from hols now.

OK, so the TV is HD ready but doesn't have a HD tuner. Understood

As for boosters, we had our aerial replaced about 18 months ago and the young chap insisted on fitting one with a booster. I wasn't happy with this (I don't really want something eating power all year round) and I'd heard that such things just boost noise and interferance as well as the signal and aren't needed in many cases.

Apart from getting up a ladder and re-configuring the connection to work without the booster (could this be done ?), nothing I can do.

Cheers, all

 

[wkdhd]

It's a little box with 2 coax leads, one to the aerial and one to the tv. You can buy inline joiners in B&Q (for instance) Just unplug them and use the joiner to connect them up.
My aerial in the roof worked fine until it rained when the signal was intermittent. An amplifier fixed it. I don't think the yearly running cost are much!

 

[JohnB47]

It's a little box with 2 coax leads, one to the aerial and one to the tv. You can buy inline joiners in B&Q (for instance) Just unplug them and use the joiner to connect them up.
My aerial in the roof worked fine until it rained when the signal was intermittent. An amplifier fixed it. I don't think the yearly running cost are much!

Thanks.

If I'm feeling brave sometime I'll maybe shimmy up a ladder and try that. Are the 'joiners' something specific, or are they really just a bit of coax with a female connector at one end and a male at the other (or maybe like connectors at each end)? Presumably I'd need to provide some sort of weather proofing?

I know it can't cost too much to run a booster but why pay for something that's not actually needed?

 

[wkdhd]

Like this http://www.diy.com/nav/fix/electric...ex-RG6-Coaxial-Lead-1m-9686601?skuId=10057306

Mine is in the attic. Is yours outside? Should be waterproofed I suppose

 

[Sam Gangee]

RG6 is generally not recommended for modern aerial or satellite TV installations.

TV plugs are generally not recommended for joining cable if you can do it properly, as described here:
http://www.satcure.co.uk/tech/extend_cable.htm

 

[wkdhd]

They show the exact same thing for 39p! Satellite fittings are different are they not, screw threaded

 

[Lucid]

Thanks everyone. Back from hols now.

OK, so the TV is HD ready but doesn't have a HD tuner. Understood

As for boosters, we had our aerial replaced about 18 months ago and the young chap insisted on fitting one with a booster. I wasn't happy with this (I don't really want something eating power all year round) and I'd heard that such things just boost noise and interferance as well as the signal and aren't needed in many cases.

Apart from getting up a ladder and re-configuring the connection to work without the booster (could this be done ?), nothing I can do.

Cheers, all

There's a simple answer to this. Include a masthead amp (what you call "booster") in with the price of the job. Then measure the signal level and slope* on site and determine whether it's really needed. It is far easier to tell a customer that the price just got cheaper because they don't need something than the other way around.

*Slope is how much variance there is between the weakest and the strongest signals. TV signal transmissions don't all emanate from the mast at the same power, and aerials all have a range of sensitivities across their reception range. With the exception of banded (frequency range specific) aerials, Log Periodics have the smallest variance and Wideband High Gain type aerials can have some of the biggest.

There are certain parts of the country where aerial choice can make a massive difference to the signal level received at the TV. If the installer knows his onions then some off-site predictions can be made. But the real test is what happens on site.

 

[winston1]

It's a little box with 2 coax leads, one to the aerial and one to the tv. You can buy inline joiners in B&Q (for instance) Just unplug them and use the joiner to connect them up.

Er, no. Different amplifiers use different connections. Some are hard wired, the cable is wired inside using saddle and clamp arrangements. Some use F type connectors, and others use standard coax connectors.

Also some amplifiers are powered up the coax from a power supply near the TV. If you bypass the amplifier up the mast you must also disconnect the power supply.

Note just disconnecting the power supply and leaving the amplifier in place won't work. An unpowered amplifier will stop most of the signal.

 

[ericmark]

I would agree you can't boost a signal that's not there but both ham radio wise and TV wise there is a huge difference in the receivers and using a booster with a weak receiver does help.

Maybe you are referring to analogue reception and human perception? Human ears and eyes are quite good at separating signal from noise.

However, it is very rare for an amplifier to help with digital Freeview reception where the signal is too weak. There's a very fine line between boosting sufficiently to get above the tuner threshold and boosting the unwanted noise above the threshold, which the receiver can't handle.
More about boosters: http://www.satcure.co.uk/tech/amps.htm[/QUOTE]
I can only go from personal experience I have a very poor VHF aerial a simple loop in the window. The booster is enough to make it work where without it doesn't. I am only worried about Yesterday every other freeview program is also on satellite which does not required retuning every 5 minutes.

As I have said with different TV's on same aerial I have found very different results. With satellite even more with Sky boxes completely failing but free to air having no problem with the same dish. OK there is clearly a fault with either cable or aim of dish but fact is one box still works with that dish the other does not.