All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Roy Barton: As you say, the tri-boom aerial is based on the yagi principle: there is a dipole, which is the active part (the bit that the cable connects onto), and elements whose purpose is to focus the signal onto the dipole. The elements are connected electrically to the cable.
With a yagi there are a number of factors which result in it being a compromise to make it more sensitive across the whole band at the expense of a level gain curve.
With a log periodic there is a double-boom. The cable connects across the two booms at the transmitter-facing end and the boom are connected together at the mast end. Each element acts to receive at a particular frequency.
I wouldn't bother with the tri-boom wideband. Don't buy a crappy contract aerial either. If you get a log then wideband is fine because their gain curves are much flatter than yagis.
There are plenty of aerial suppliers online selling the aerials that the professionals fit. No longer do you have to rely on what the DIY shops sell.
If you were using an aerial horizontally, have you tried turning it vertical?
Just going back to your original posting, have you checked the cable for signs of damage and water ingress? This could perhaps be chafing on guttering on guttering or a roof tile.
I'm not a professional, but at 28 miles, and just out of line-of-sight approximately 1 mile away, I think that the signal strength will be quite good.
If you're in a good signal area then a log will be fine. If (and I say this as your "Plan B" incase Plan A doesn't work) it doesn't have enough gain then you can use the amplifier.
I came across this shop which sells a range of logs for less than £20 including delivery:
Aerials [Aerial Type: Uhf Log-periodic] > AerialSat.com
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David: There is the issue of cost of producing separate feeds which is why both BBC and ITV regional channels do what they do.
In order for them to provide different feeds, they would need whatever equipment is required for each. However, most of the time they are all broadcasting the same, so that additional equipment will only be of benefit for short periods. Looking at it from a cost-benefit angle it doesn't make sense.
There is also the question of whether the regional programmes are shot using HD cameras, and if they are not then these will need to be upgraded.
At the moment, I can't see that there is a real benefit other than perhaps rectifying the terrible injustice that viewers face of having to switch channels. Or maybe they would prefer that the Licence Fee went up in order to fund different BBC One HD regions. Maybe they would be happy for ITV to be allowed to show more adverts in order to generate revenue to create more ITVHD regions...
So the cost to provide different HD regions will not just be that of the equipment to produce the feeds, but cameras and other studio equipment. Or to put it another way, if they don't upgrade the cameras, the HD feeds will just be filled with standard definition content.
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Peter Henderson: If you're lucky enough to be able to receive from Divis then you might get some more BBC HD channels:
Ten more HD channels on two new Freeview HD multiplexes on air from 2014-18 | Freeview news | ukfree.tv - 10 years of independent, free digital TV advice
As with anything these days, only believe it when it happens....
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Lynn Steenson: COM4 is on C23 which is co-channel with Mount Leinster, which is a powerful transmitter.
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David: I see what you're saying now.
Reading your latest posting has reminded me of Royal Mail's policy for latest sending times from Post Offices. This was brought in a few years ago and is intended to offer consistent cut-off times across all branches.
My Post Office says that the cut-off for mail being sent that day is 16:10, and I shall assume that this is the case at others.
I'm a practical person, and when I send a letter, I want it to get there as quickly as possible. Rather than it going that day "if" the last collection has been, I am victim to this policy.
This sort of thing is a product of the consumer society we are now in.
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David: It should say:
Rather than it going that day "if" the last collection has *not* been, I am victim to this policy.
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Roy Barton: Yagis and logs work on different principles.
See:
Aerials, TV Aerial and Digital Aerial
The yagi focuses the signal onto the "active" element (the dipole).
With a log, each element acts to receive at a different frequency.
Google log periodic antenna. There are two booms and they are parallel and perhaps a centimeter apart.
Log-periodic antenna - Wikipedia, the free encyclopedia
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Craig Hanson: According to Radio & Television Service, BBC channels returned at 17:03.
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Mike: Firstly, looking at the aerials on Claygate Road via Streetview, there are a number of transmitters being used. The first thing to do is ensure that the TV is tuned to the transmitter to which the aerial faces.
The Dorking relay transmitter is close by:
mb21 - The Transmission Gallery
It is within the trees and is visible from Streetview. It could be that your TV has tuned to it for PSB channels and it is this that you need to correct.
If you're on another transmitter, then I guess that it's likely to be Crystal Palace or Reigate. The tower blocks may be acting to block these transmitters for some of the houses on Claygate Road.
Crystal Palace and Reigate broadcast all Freeview channels, and Dorking only carries PSB channels. For a list of Freeview services (including which are PSB and which are COM) see:
DTG :: DTT Services by Multiplex
Dorking broadcasts on 44, 41 and 47(HD)
Crystal Palace's are 23, 26, 30(HD), 25, 22, 28
Reigate's are 60, 57, 53(HD), 21, 24, 27
These numbers are the UHF channel numbers of each multiplex (mux): PSB1, PSB2, PSB3(HD), COM4, COM5, COM6, respectively. Most receives give UHF/RF channel numbers, but some anti-quated ones only give frequencies in MHz, so you will have to convert. The frequencies are given by this website on each transmitter's page.
Whilst viewing one service from each mux, bring up the signal strength. So check BBC One, ITV, BBC One HD, ITV3, Pick TV and Film4 (these are the first services from each mux).
If you find that the PSBs from Dorking have been tuned in when they should be from Reigate or Crystal Palace, then unplugging the aerial during the middle part of the scan should hopefully do. I say "hopefully" because it might be that the signal from Dorking is that strong that it picks them up with no aerial, for that reason it's probably best to unplug the aerial lead where it goes into your TV/box rather than at the wall socket.
Crystal Palace's channels are in the bottom third of the band, so unplugging at 30% and leaving it out until the end of the scan will do. For Reigate, unplug at 30% and then plug in again at 58% so as to miss out Dorking, in the middle.
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Tuesday 19 February 2013 12:27PM
Vaughan: Commercial broadcasters are under no obligation to provide an explanation for their actions.
The answer would appear be to do with the fact that the North East regional multiplex is to close and that Smooth, Real and Crapital need to be on DAB as a requirement of their FM licences.