Full Freeview on the Dover (Kent, England) transmitter

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10:16 AM

Dr. John Pritchard: I will go out and come in again. I now see that you are in Northwood and therefore that the industrial buildings are not between you and the .

However, I do note that on images, there are a number of 'stub' of roads off New Haine Road which makes me think that the industrial estate will spread into the fields behind you, which are obviously likely to be in the way as far as from is concerned. Or more to the point, perhaps it already has done and the photos are out-of-date.

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10:23 AM

Dr. John Pritchard: Of course, what I said about the path being low to the ground for about a mile still applies. It is just that I hadn't corresponded the terrain to the right location.

So have there been other developments in the area that may be the cause?

Below the terrain plot there is a link to see a line between the two points. Whilst it isn't exact, it should give you a rough idea.

For example, Streetview photos taken in April 2009 show the early development of buildings on Manston Road, with new roads being shown on maps.

Monday, 18 February 2013

Dr. John Pritchard
8:34 PM
Ramsgate

Thank you, Dave Lindsay! The stub roads are still stubs, and you are right in noting that the Cross development is growing. However, the copse and park to the South of us are scheduled to remain as local amenities for the foreseeable future. My guess is that the stub roads will lead into a new Sainsbury (for deliveries) and out to Newington Road along an existing hedgeline, probably replacing an existing footpath between two schools. All a bit bizarre, but there we are.

From line of sight when sitting on the next to the ariels (real sight, not through a telescope) there does not appear to be any obstruction in the way. My cabling is all WF125 with F-plugs so on a presumption, now, that my strength is too strong, not too weak, I'm going to try an adjustable attenuator and taking my preamp/splitter out of the circuit with the best aeriel see if that may in bringing the 's 80 kw MUCS within tolerances that my HDMI television can accept. I'll also see if the attenuator will do the decent thing in downgrading a less powerful aeriel to our kitchen tv to make to restore domestic harmony there, too. And your suggestion regarding the b&w/colour shifts on our bedroom computer makes sense: I've checked the RF lead to the (it, too, is WF125) and the plugs at each end are fine, but the digibox connects to the tv via a ribbon lead that runs up the back of the tv case to the digibox on top of the set. So the SCART lead now seems to me the most likely culprit as that's the only link in the chain. If that fails, I guess the next suspects are (1) the digibox itself notwithstanding the fact that it is the only one in the house that is now delivering all from Dover, or (2) the 20-year-old set which must be getting near its end of life anyway. Anyway, your advice that the b&w/colour shifts must be an analogue problem is hugely helpful. I'll report on the outcome of these changes in case that helps others!

Dr.'s: D's Freeview map D's terrain plot D's frequency data D's Freeview Detailed Coverage

Dr. John Pritchard
8:48 PM
Ramsgate

Oh, one more thing: Manston Airport does lie less than a mile away and the incoming flights do cross my line of sight to . Strangely enough, this has never affected my at all, even during Air Shows (and be it remembered that in the distant past, Manston was capable of launching whole squadrons of Hurricanes & Spitfires all abreast, and later the place was used by lumbering great B-52s. Nowadays, while the debate over Boris Island continues, Manston seems fated to remain underused until the powers that be build a parkland there and our tracks to suit our existing local Javelin 140mph train on the line to St. Pancras International via Ashford. At present, however we don't have as much as one single scheduled flight a day into or out of Manston's 8000 foot nunways and the odd freighters that use the airport really cause no perceptible nuisances at all to a few homes that sit right under the flight paths (most of which end up out over the or the North Sea except for periods that can be measured in seconds.

Dr.'s: D's Freeview map D's terrain plot D's frequency data D's Freeview Detailed Coverage

Dr. John Pritchard
11:51 PM
Ramsgate

The Hi- for my HDMI tv is a Televes DAT 45; the aerial for the kitchen tv is a high gain 52-element aerial from a leading supermarket (ahem). The oldest aerial is a straight-forward group C/D 18-element log without any balun but with a "solid" flat-sheet reflector (with slots): I think it might be an old Antiference: not sure. The Televes and log aerials share the same cranked pole, and I'll see if I can increase the distance between them to avoid possible resonances or other interactions between them. Dave, any advice on how far apart they should be?

Dr.'s: D's Freeview map D's terrain plot D's frequency data D's Freeview Detailed Coverage

Tuesday, 19 February 2013

jb38

_{sentiment_very_satisfied}Platinum

7:51 AM

Dr. John Pritchard: Purely on the subject of your older television alternating between B & W and colour, I don't really feel that anything done will rectify this problem as its most likely being caused by either a bad PCB joint on the crystal used in the colour decoder (commonly known as the colourburst crystal) or its the actual crystal itself that has developed a fault, this usually where the wire from the lead in pin is fused onto the crystal, something not exactly unheard of hence their relatively low cost.

jb38's 7,179 posts GB flag

_{sentiment_very_satisfied}Platinum

11:30 AM

Anything, particularly within the first Fresnel zone (look it up), can affect , by refraction. I imagine that it's likely, particularly with the path being close to the ground, that there's quite a lot of clutter in the first Fresnel zone. Reflections can also affect reception because the reflected signal (the echo) is combined, or summed, with the main signal at the receiving . The worst case extreme is that they are 180 degrees out of phase and therefore cancel each other out and you get nothing (I give the extreme merely to illustrate the point). Even the professionals say that RF is a black art.

reception requires a good signal, where the digits are intact. A requires the signal strength to be over a lower threshold, but not greater than an upper threshold, over which it becomes unstable. Basically, you need the strength to be within that window. As a matter of good practice, the objective is to have the signal strength sufficiently above the lower threshold such that natural variances in strength (owing to the weather etc.) aren't likely to mean it dipping under. By the same logic, there should be room for the signal strength to increase a bit without putting it OTT. The point is, therefore, that the is exactly the same irrespective of strength, and so the objective is *not* to get the strength as high as possible; it is to get the quality high and strength within the window.

The WF125 flylead isn't going to make much difference unless it happens to be sited within lots of . WF100 is more than sufficient for frequencies, although WF125 does have a PE sheath, rather than PVC, which is better on the odd day that the sun does shine bright enough for the UV levels to be high.

You could try swapping the end-to-end. This scart system encompasses several different types signal and not all TVs support all types. RGB is best as all three colours go along separate wires, as opposed to being combined when sent and uncombined when received (which means quality isn't as good). If the set supports RGB, and I'm not sure how likely it might be to do so, then use RGB - it will need activating in the box's setup menu. You can, of course, take the digibox and scart to another TV and see how it works with that, and you may be able to try the old TV with a box in another room; this should give you an idea whether it's the box, the lead or the TV.

I'm not a professional, so can't say how much gap should be allowed between multiple aerials on a . However, I think that you should be looking to run all three TVs from a single aerial. It may be that you can do this using an unpowered splitter, or you may need some amplification, but you have some at your disposal anyway!

See A.T.V (Aerials And Television) TV Aerial, DAB Aerial, FM Aerial. for lots of information. For a start off, the old C/D aerial you have sounds like a crappy contract aerial; see A.T.V (Aerials And Television) TV Aerial, DAB Aerial, FM Aerial. aerials.html

The question you've got to ask is: is this a strength issue or a quality issue? I shall assume that you've looked at strength.

What could be the cause of poor quality, I ask myself. Remember I'm not a professional.

For a start off, the industrial buildings that are around you could be causing reflections. How were the signals before they were switched off? Were there any clues such as ghosting which gradually got worse as more and more units were errected? Obviously before the digital was weaker, so any reflections would also have been weaker and therefore have been less of an issue.

I can see your aerials on Streetview (June 2009) and they don't look very high, whilst your neighbours' are. Height isn't necessarily everything though. Could the single tree at the back be in close enough proximity to have an effect, I wonder?

There is a triangle-shaped clump of trees behind Cherry Tree Gardens and Highfield Road; might they be the cause of poor reception and could increasing the height of the aerial reduce their impact?

The thing with aerials is that the , in one direction, is at the expense of greater "loss" in other directions. So, generally, a higher gain focuses on a narrower "beam". This is an important point to bear in mind because you are interested in getting a good quality signal. Imagine you are the aerial looking out over a narrow angle and within that space there is a lot of clutter which is resulting in refracted (poor) light. Having a wider angle might allow you to see, on average, better quality light.

Now consider something like trees which are moving and so it follows that any effect of those trees must be changing. In some cases, these changes mean that the signal, at the receiving point, isn't usuable and so the picture breaks up.

If you have an , you can boost the strength if it isn't great enough, but you can't rebuild a poor quality signal; quality starts at the aerial. Even with a lower gain aerial, you may find that there is ample signal strength to feed one or more TVs.

See A.T.V (Aerials And Television) TV Aerial, DAB Aerial, FM Aerial. polardiagrams.html Log periodic aerials have a much neater polar response whereas yagis tend to have lobes. If the issue is poor quality caused by reflections, perhaps from the nearby industrial buildings, then these would appear to behind you and to the sides. A log may fare better at "rejecting" those reflections.

Read the bits on log aerials on the ATV site; the saying is "If you can use a log, use a log."

There are plenty of suppliers out there. I came across this one which sells a range of logs, each for less than £20 including delivery:

Aerials [Aerial Type: Uhf Log-periodic] > AerialSat.com

Thursday, 21 February 2013

Dr. John Pritchard
9:40 PM
Ramsgate

Thanks, Dave. This is exceedingly helpful.

Changing the lead didn't on the colour shifts: you're right. It did appear to make the colours more intense, which was unexpected. I'll check the other things out, by swopping the ancient tv for another that I can put in that bedroom. Adding the attenuator to the kitchen tv immediately brought back two of the three missing MUCs, including the BBC and ITV stations. I'll fine-tune the adjustable attenuation and see if the fifth MUC can be recovered, too. The bricks and AC cabling appears to be affecting hum levels on the tv audio in the kitchen: more careful positioning dropped that back to a fraction of what it was. The fly lead to the decoder is very poorly shielded (I'd ignored that before): the rest of the cabling is WF125 but that last two metres is a joke, especially as it is in close proximity to poorly shielded rfi sources. I'll just make up a new MF 125 and see what happens. I expect that to sort out the hum problem, at least!

What you say about the height of the aerial is highly relevant. I kept it low deliberately in part because there's a large aerial array not far from us (behind a local fire on the Road) and I felt keeping the aerials low helps to shield us from any rear lobe on our aerials. But the copse about 100m between us and the route to the has grown like crazy in the past few years. All you've said on that score and on reflections from other near-ground topographical features between us and our horizon makes sense. In the case of the copse in particular, that extra 15 - 20 feet of height added in the past six years since we moved here won't be doing us any favours. Likewise two tall trees on our property line with our neighbour nearest to my best aerial have grown rapidly, too, and their span as well as their height could be adding all kinds of reflections, not least because there's a catenary cable between the bottom of the aerial pole and outbuildings to the rear: that catenary line carries two CAT 6e cables but when the trees and cabling are wet and swinging, well, probably not good. In the spring I to be able to put that cabling into underground conduits. One of the trees is also likely to go. Raising the pole will also happen as soon as I get another -bracket to take part of the weight and dampen oscillations in windy conditions. But tomorrow I'll also be testing the effect of the adjustable attenuator on our HDMI decoder and main tv: with a little luck that will restore domestic bliss within our household until the other work can be done with the weather improves!

In case all of this helps others, and just to offer further , I'll record here any further developments as I continue to try to sort this out in the days or weeks ahead. Meanwhile, thanks, Dave!

Dr.'s: D's Freeview map D's terrain plot D's frequency data D's Freeview Detailed Coverage

Dr. John Pritchard
9:52 PM
Ramsgate

PS, Dave: I've taken onboard your observations about Log periodics, Yagis and high- one-size-to-fit-all models like my Televes DAT 45 (which to the unitiated is like the model shown on the chimney in the photo to the left of this forum). Having looked at the stats and your remarks, it all does make sense to me. The Televis was probably over-kill, but in the pre- years when freeview was just building up, the Televes was highly recommended by one of our best local electrical supply houses. Very glad I was sensible enough not to go for the DAT 75 model. Those are beautifully crafted products, however, and I did have in mind the possibility of multipath problems that the Televes are said to cope with well.

Dr.'s: D's Freeview map D's terrain plot D's frequency data D's Freeview Detailed Coverage

_{sentiment_very_satisfied}Platinum

11:05 PM

Dr. John Pritchard: I was looking at the tower you mention on Road. Whilst we obviously can't say for certain, it may be a pretty safe bet though that it will carry 4G, particularly as it's so high up and therefore well-place to serve a large area.

This got me wondering whether it is home to a Tetra base , but according to Sitefinder, there are Airwave's base stations elsewhere within a few miles of you.