tv ariel installation

[ericmark]

Since DAB is a different frequency to VHF you can't use the original set-up so really a non starter in a Car.
At home why it is already there on Freeview so why broadcast same digital signal on two frequencies?
Whole DAB system is waist of money.

As to standby power I will agree that "Sky" boxes use nearly as much on standby as in use. But other makes are very different and my free to air box uses so little I can't measure it with plug in power usage meter.

As to original question one has to balance the amount of metal in the air to the use of amplifiers and the more metal in the air the higher the wind resistance and the more likely it is to get a lighting strike. So a banded aerial of around 20db gain is about the maximum anyone would want to fit on a roof. OK I have seen radio hams with 9 yargi beams aimed at the moon for EME contacts but the band width is very narrow and they are not on the roof.

So to split a TV signal unless one lives under the transmitter will normally involve an active amplifier and since rubbish in gives rubbish out the closer it is to aerial the better and the mast head amp with multi outputs must be best.

However working on ones roof is not easy and often one also wants to distribute Sky and Videos from main room with same cable so fitting the amplifier in the main room with the main TV has some advantages.

There is no one size fits all and each house has to have what is best for that house and with my house I can receive TV from 4 locations and aerials are selected with as much thought to rejection as to anything else. I want English TV.

99% of the time my TV's work on analogue since I use satellite in the main and distribute signal through house and once converted from digital to analogue the aerial or LNB has no effect on signal strength.

 

[Mickymoody]

Eric - It's not a question of using DAB in cars, that IS what the government are doing - not suggesting!
Sky boxes use as much power on as in off..no argument. apart from the red LED..

Metal in the air, and wind resistance - now I'm confused! A keen HAM radio operator, and CB user, never heard that term before..

 

[Monkeh]

At home why it is already there on Freeview so why broadcast same digital signal on two frequencies?
Whole DAB system is waist of money.

Reeeaaaallllyyy. I'd love to know what Freeview channel Planet Rock is on.

 

[electronicsuk]

Eric - It's not a question of using DAB in cars, that IS what the government are doing - not suggesting!
Sky boxes use as much power on as in off..no argument. apart from the red LED..

Yes argument. Sorry, but your statement is just not true, and I think you have been misinformed by reading too many newspaper articles written by people that don't have a clue what they're talking about.

For example, TVonics MFR-200 freeview receiver specifications state; Power Consumption (in use): 5 Watt / Power Consumption (standby): 1.5 Watt.

As far as I can see, Sky do not provide official power figures for their boxes, but an independent test on Sky+ boxes found standby consumption to be 13w, viewing 20w, and recording and viewing at the same time 23w.

Although I do refute what you're saying with regard to Sky STBs, I do agree that there are some receivers out there that do use almost as much power in standby as when running. One such culprit is the Virgin Media V+ box.

I also don't think that it's fair to try and blame this whole situation on the government - much of it is down to consumer demand. As you might have noticed, the majority of people now have some form of TiVo/Sky+/V+ or other brand of receiver with built-in recording capability installed in their home. In order for these to be able to record your chosen programs, they need to have their power supplies and CPUs running more or less all of the time to keep track of the recording schedule. They must also run the tuner at least periodically to update the Electronic Program Guide, and at all times during recording. They will also spin up the internal hard disk during recording, even if the box is in standby.

Most of the above are givens right now. If you want the comfort and convenience of being able to record at the touch of a button without discs or tapes, you'll have to do so at the expense of energy consumption. The only way I can see to work around this is more efficient power supply design and the use of CPUs and RAM then can throttle back their clock frequency when the box is in standby, leaving just enough processing power to perform basic timekeeping and scheduling. Whether or not this technology or some alternative thereof is already being employed in the design of new receivers, I am not sure.

 

[ericmark]

I tested my own boxes and I found my Philips hard-drive/DVD recorder player used under 1W and my Free to Air box I could not measure it was so low and this was after programming it to auto turn on at pre-set time so using both together I could set them to record at a set time within the 1W limit.
However the two Sky boxes where very different stories. Main thing is LNB's are still powered in standby and because around 6W is used by LNB a SKY+ box will never drop below around 12W. It was hard to measure as it takes some time after entering standby for the hard-drive to stop and one could re-visit and find anywhere between 12W and 20W being used. The older one was also on high side with around 10W on standby although we do expect that with older machines.
I will admit the Sky+ box is far easier to use and after a power cut it requires no resetting and once power is restored will record all one has set where the other boxes tend to lose what has been set to record. However there is really no excuse for using so much power in standby there is no real need to power the LNB when nothing is being viewed or recorded.
As to the aerial starting as VP8BKM wind was something I thought a lot about and I have lost a few aerials to the wind. Also lost them due to birds fighting on them. And when one makes an aerial one has to build them strong enough to take the wind in the area. However most aerials are mounted on the chimney or eves I know they should not be mounted on a soot lined chimney or on the sharp edge of gable end but they often are and vibrating and waving structures attached to the house this way as well as attracting atmospheric discharge also can cause structural damage to the house and the larger they are the more damage they will likely produce. OK a sturdy bracket on side of house with a large aerial set below the top of house will likely cause no problem but these are rare.
Most amateurs use masts away from house and reduce the aerial height in high winds or electrical storms but people watching TV don't ever touch their aerial until it stops working or falls off the roof and even then seen many houses with aerials pointing to sky or lying on tiles where the wind has caused damage but it would seem they are still working.
A 10db aerial banded will weigh a few ounces where as a 20db wide band will likely weigh the same in pounds i.e. 16 times the weight and I see not point in using huge wide band high gain aerials when not required. A small mast head amp would be far better even if it does require a couple of watts to drive it.
health and safety is also an issue. The way it is all going soon any but the lightest of aerials will need a cherry picker to fit them.
OK now I do very little transmitting mainly with hand helds but I have in the past and as GW7MGW I have never was HF. Done that been there and got the log book and QSL cards when running in VP8 land but I have used VHF and UHF both to fixed stations with Packet and sideband and Packet was very like TV small aerial aimed at local BBS but sideband one used silly amounts of metal and rotators even with azimuth for EME and there is no way normal people will ever want lumps like that stuck to the side of their house.

73 Eric