Your ability of receive all the Freeview transmissions depends on the suitability of aerial
the design style,
the "group", and
its physical location.
Standard type - Yagi aerial
The standard type of TV aerial is known as the Yagi aerial. It is mounted on a pole, and consists of a rod with a reflector (shown green) at the back and many spiky elements (in grey) at the front. The connecting cable connects to the element nearest the reflector, known as the driver (shown in blue).
These Yagi aerials are directional and so pick up signals best from a transmitter that the rod points towards. The more elements the aerial has, the better it picks up a signal and becomes more directional.
A standard-type aerial is all that is required for analogue TV reception in most places. These antennae have between 10 and 18 elements and a single reflector. These are not recommended for new installations for good digital television reception, but will more often than not function perfectly in good reception areas.
Typically these aerials are designed to receive only some transmission frequencies - see "groups" below.
Digital High Gain
These aerials are designed for poor digital reception areas, and have two reflectors. For maximum signal strength, some digital high gain aerials have up to 100 elements. A more expensive aerial is only required where the signal strength is low, but can often provide Freeview reception where it might otherwise be impossible.
The CAI (that represents aerial installers) has four standards for digital TV aerials. The highest standard "1" is for homes on the fringes of coverage areas, intermediate standard "2" is suitable for use within the coverage area; minimum standard "3" is for good coverage conditions.
These aerials can be either wideband, or receive only selected frequencies - see "groups" below.
Grid aerials have been used to improve analogue reception in poor reception areas. They are generally unsuitable for Freeview reception, however some installations may work. Otherwise replace with a digital high gain Yagi aerial.
Indoor aerials are generally not suitable for Freeview reception. In areas of good signal strength it is often possible to receive some transmissions.
Loft mounted arrivals are not generally recommended for Freeview reception, as the roof tiles and plumbing will degrade the signal. Some compensation for this loss of signal can be made by using satellite-grade cable to connect the set top box to the aerial.
The best position for a TV aerial is mounted outdoors, as high from the ground as possible, pointing directly at the transmitter. The signal can be blocked by hills and tall buildings. It should be positioned away from any other aerials.
Horizontal or vertical?
The transmitter will either use vertical mode which requires the elements of your aerial to be up-down, or horizontal mode which requires them to be level with the ground.
Both analogue and digital television is transmitted the same group of transmission frequencies (known as channel 21 through to 68). A coloured marking on the aerial shows the group.
To create the best possible analogue picture, TV transmissions from adjacent transmitters have been designated to several different groups of frequencies. By using an aerial that receives only the channels in the correct group, the analogue picture can be kept free from interference.
To receive Freeview transmissions from the same transmitter it has been sometimes necessary to use frequencies that are not part of the transmitter's normal group. When this has occurred, the aerial will need to be replaced with a "wideband" aerial (also known as group W) - one that covers every group.
Mike O'Pray: Although I have my suspicions that something "might" be amiss with the masts radiation in the W/NW direction towards the Northampton area as too many people from all around that area are making complaints about bad reception on Ch51 since May 9th for it to be just a coincidence, but if your Goodman's TV allows manual tuning I would like you to go into the tuning menu and enter Ch51 but do NOT press scan, as if any signal is there its strength should immediately appear on the strength bar, if it does then give an update on whatever it might be.
The reason for requesting this action is that I suspect that the Ch51 signal is actually there but at a level that's just underneath the reception threshold as far as resolving a picture is concerned, although this would not stop the level still being seen on a signal check.
I havent as yet had time to check on your Goodman's or Panasonic as far as any known problems are concerned but will try to find time tomorrow, although I dont really think that there is anything to worry about in that respect as it could just be a low signal level that's causing the difficulties, as Ch51 is belting in at not far off 100% strength in the Stamford area where I am located.
The 8 way splitter is powered. The reason the aerial is in the loft is because we are not that far from the sea and the aerial would'nt take long to corrode.
We got excellent pictures with analogue and we had a digi box prior to switch over which I believe gave better results than what I am getting now.
If you are suggesting boosting the aerial signal before going into the 8 way splitter can you recommend a particular amplifier?
Mike O'Pray: With regards to "scan", its just that every manufacturer has their own idea about wording, and on the manual tune menu screen there is usually a box for the channel number to be entered into plus underneath a button bar marked scan / tune / search or whatever, that being obviously the next stage in the procedure "if" a person wanted to carry out a manual search, which of course you cut short as you were only using that facility as a fixed channel signal level checker, and with the strength indicated on the channel concerned proving as being inadequate for the TV to lock and why you cannot receive it.
As you may already have gathered, there are quite a number of complaints from people all around the Northampton area who are experiencing reception difficulties with the commercial channels, and it was noticed that most of the problems reported are from people who are all on very similar bearings from the station, Sandy being at 101 degrees @ 41 mls from your own location and another person with similar problems to yourself with a heading of 104 degrees but at only 32 mls from the station, and a third on a bearing of 97 degrees @ 24 mls, so it appears to be the radiation beamed in that particular segment that's deficient.
With regards to your own SDN (ITV3 etc) problem, its a pity that you couldn't manage to get hold of an aerial amplifier of about 15db gain or so for a test as you might well find that the amp would most likely lift the signal level of Ch51 up to above the reception threshold for your set and enable you to view the channel, as apart from that action I cant really see anything else improving your situation except by experimenting with the aerial in different positions, and I am not necessarily meaning being mounted much higher up, as in difficult areas its frequently found to the amazement of some, that a signal can rise coming downwards towards a gutter level, as in non line-of-site situations the signals paths get bent by reflections and this has to be taken advantage of by positioning the aerial in a hot spot thats found to be stable, the type of job only really suitable for DIY as its time consuming.
That said though, trees are a killer if less than a mile away from the receiving aerial.
Nigel: These 8 way splitters have minimum gain irrespective of what might be claimed for them, and this is why you dont really notice much difference whether its in circuit or not, as they are really devices thats best classed as a no-loss splitter.
By the way, I am in no way being derogatory about them as they serve a purpose.
Stephen P / Nigel: The aspect of the signal that I would be concerned about is the fact of it fluctuating by about 20% or so as well as it dropping to zero on occasions, as this type of problem is usually always associated with trees as well as in many cases the actual signal received being partly achieved through reflection, and in these type of circumstances using a Unix 52W is liable to be detrimental to reception rather than assist it, this being mainly caused by its relatively narrow pick up acceptance angle of only +/- 15% or so and creating the situation whereby the 52W's output level will drop with even the slightest deviation in the angle that a signal is received from, whereas on an aerial with a wider beam width this would hardly be noticed, or at least very much less!
To help this situation it would be much better to use an aerial such as a DM log or similar through an amplifier, but though (and dastardly as it may seem) if about half the directors on the 52W were removed then that would widen the aerials beam width, then the aerial could be fed into an amplifier of about 10 - 15db or so and with its output being fed into the 8 way distribution amp.
Getting back to the 8 way splitter, the only way that you could properly judge the difference between it being in and out of circuit is to note the level seen on the TV's signal check screen with it in circuit, then pop up to the loft and by-pass the splitter by connecting its aerial input plug straight into the coax that's used to feed the TV being used for checking purposes.
This said taking it that the splitter is self powered.
This is a link for the type of aerial being referred to.
Mike O'Pray Wednesday 16 May 2012 11:33PM Daventry
jb38 Thanks for your reply. It seems that there are complaints in this area and some from people closer to Sandy Heath than I am which is bad news for me. What you haven't said is what if anything the "authorities" are doing about it? Any idea?
As far as I am aware I do have an amplifier in the loft. It was fitted several years ago way back in the analogue era. At that time an aerial fitter came and installed two aerials One pointing to Anglia and the other to the E Mids. The reason for this was that in front of the house there is a line of tall trees that block the reception from the W Mids which is Sutton Coldfield but no obstruction in either the E Mids or Anglia areas.
The reception chart seems to show that the E Mids transmitter ( Waltham?) should be much poorer than Sandy Heath but I do get both the E Mids and Anglia news at about equal strength which is strange.
I have the standard Yagi aerials for both directions.
I am confused as to what is being done to address the current reception issue and what I might try to get ITV3 which is the only channel I might want to receive occasionally.
SDN from Waltham is on C29 which is a Group A channel and therefore won't reach your receiver if there is a diplexer. Also, Sandy Heath's SDN is now on C51 which could be filtered out in favour of the Waltham aerial.
The question is, which aerial are you using to pick up ArqA and ArqB. To find out, go to Pick TV and Yesterday and find out what channels they are on. They may both be coming from Waltham which are 56 and 57 respectively. Or for Sandy they are 52 and 48.
If you are picking up ArqA and ArqB from Waltham, then you will either have to replace the whole lot with a single wideband aerial, or just turn the Waltham aerial round to face Sandy. The suggestion latter assumes that the channel at which the diplexer splits is below C48.
Nigel: Just in addition to my main posting, even although I very much doubt that this would apply, but so that I can completely exclude a niggling thing I have in my mind regarding the possibility of circumstances applying that might (albeit remotely) be the cause of your reception difficulties, I would like that if you have access to a set top aerial could you plug that into the TV and see if anything is picked up, or if you do have access to this type of aerial just try a short piece of wire of about 12" or so connected into the TV's inner part of the aerial socket, giving an update on results.
The only reason I am asking this is, that with you being located at only 27 miles away from the 200Kw transmitter you should (in theory anyway) be getting reasonably good reception without any form of amplification unless some other factor is applying, like as referred to in my main posting.
Stephen P: If you are referring to Nigel these are the two indications I get, and the reason for my extra comment is because that a large section of the signal path between the transmitter and Nigel's location is over water, and a signal passing over water can in many cases appear stronger because of the skipping effect than if over the same distance on land, this having the effect as though the person receiving the signal is closer than they are in reality.
That said though, and as mentioned in my additional posting, I very much doubt if the signal is too strong, as although this can totally upset the accuracy of indications given on a TV or boxes check screen it cant on the Labgear checker that Nigel used.
Mike O'Pray: Well, certain areas of Northampton are (and have always been) known for iffy reception and the fact of others having made similar complaints to yourself has to be taken into consideration, although when a person has previously received a signal which magically disappears when its transmitter changes frequency and moves to high power then some other factor applies.
Now you have mentioned the fact of the other aerial facing a different direction and being diplexed onto your Eastern facing aerial used for Sandy then this could be the other factor that's causing the problem, that is "if" the other aerial is picking up a really strong reflection of Ch51 from a distance away, as diplexers don't kill a signal they just reduce it as well as having the effect of slightly reducing the signal that's actually required to under what it would be if the diplexer wasn't in circuit, and so to cut a long story short I suggest that the diplexer is by-passed so that your signal is purely from the aerial facing Sandy without another being tagged on to it.
Is the diplexer installed on the aerials supporting pole?
Mike O'Pray: Also meant to add, that although the diplexing of two aerials facing different stations was maybe OK back in the analogue days its not necessarily the case now, and in your own situation is totally useless and is even detrimental to your reception.
The reason being, that Waltham's analogue transmissions covered a channel span of from Ch54 - 64 but with Ch35 (Ch5) being added later, and in the case of Sandy it spanned Ch21 - 31 with Ch39 having been added for Ch5, so excluding the blip that Ch5 caused you can see that diplexing both stations was perfectly OK.
However the reason that the diplexer on your aerial is of no use nowadays is because that Freeview from Waltham spans Ch29 - 61 and from Sandy its Ch21 - 52, and you cannot diplex these two without reducing the strength of channels that you require as the majority of the channels are intertwined.
jb38 / Mike O'Pray: Surely if the aerial on Sandy is a wideband one, then it will work on its own (i.e. remove the diplexer and connect only the Sandy aerial).
However, if it is Group A (see the link I provided at 12:04AM), then it won't be suitable for receiving the COMs from Sandy on 48, 51 and 52. In which case, perhaps the solution is to swing the Waltham aerial around to Sandy (so that they are both facing the same way).
Dave Lindsay / Mike O'Pray: By-passing the diplexer and using only the aerial that faces towards Sandy is exactly what I said in the latter part of my posting made this morning @ 08.19am, the removal of the diplexer being particularly important as you don't want anything of a signal filtering nature incorporated into the aerial system.
And with regards to the aerial used for Sandy, if it is an original group A aerial installed that pre-dated the start of Ch5 let alone Freeview, and with it never having been updated at any time, and if this is the case then obviously as you drift upwards from the end of the frequency range covered by a band A group aerial (Ch34) then signal levels received will not be quite as high as they would be with a wideband aerial, however irrespective of the aerial group fitted Mike has only complained about the reception on ITV3 on Ch51 and not anything else, so if by any chance the aerial is still a group A and programmes on mux Ch52 such as EPG11 - Pick TV or EPG19 - Dave cant be received either then the aerial will require to be changed to a wideband type.
Mike O'Pray: Regarding the programmes I mentioned, can you receive those two channels? and have you had the aerial changed since analogue days when Freeview had first started?
Thanks all for the replies. Much of what you said went over my head. I had never even heard of a diplexer until your replies. What does it look like and how do I tell if it is on the aerials' supporting pole? If it is how do I by-pass it? If it isn't on the supporting pole where might it be? In the loft?
However when I switch to receiving the signal via the Panasonic HDD by switching to SCART I get a much bigger range of channels including 10 ITV3 but no signal, 11 Pick TV, 12 Yesterday, 13,14 15 but not 16 and 17, 18,19, 20-22, So most of the channels from 15-28 which the DTV doesn't even register
ITV3 shows no signal but at least shows as ITV3. Pick TV shows as 11 and Yesterday as 12 and Film 4 as channel 15.
All these channels via the HDD get good signals. Why the big difference between DTV in the Goodmans's set and the much enhance range of channels via the HDD except for ITV 3 which is know to the HDD set up but records as "No Signal"
Sorry I do not know how to relate what I have said about the numbers for Pick TV and Yesterday to the channels in the 50s range that have been mentioned
No the aerial has not been changed since I was analogue. The currently two YAGIs( I only know about YAGI because of the opening section on this site shows a YAGI aerial) were installed sometime in the late 1990s if my memory serves me correctly.
Frankly I need replies to take me through what I need to do in easy steps.
I am capable of being educated but you need to assume little or no knowledge on my part.
Mike O'Pray: If you see ITV3 mentioned on the EPG list whilst on the Panasonic recorder then go into its signal strength check screen and have a look at the level being indicated, as a signal must have been picked up or EPG10 would be missing from the list, so a signal is likely there but just under the level that can resolve a picture.
The diplexer (or combiner) is usually in a red (but can be grey or black) plastic box strapped to the mast pole, and you should see the coax lead from each of your two aerials going into it and one coming out downwards towards the roof or wherever.
The two programmes I mentioned are (or should) be seen on the EPG number channel listing, 11 being Pick TV and 19 being Dave, but if these numbers are not seen then you might not be picking up mux Ch52 either, that is as well as Ch51.
As its not known if your aerial is wideband or not, "if" though you can see the end of the long square horizontal bar that supports the elements check if you can see a red square plastic blanking plug on the end that faces Sandy, and if you can then that's an original aerial and will require changing to a wideband type such as a log 40 or similar, if though the end piece is a black plug then its a wideband aerial.
What you require to do as far as improving your situation is concerned is removing the diplexer and having the cable from the Sandy facing aerial coming straight down into your house, and the Sandy aerial being changed to a wideband version if its not already that.
By the way the manual tuning instructions are on page 71 of the Panasonics user manual.
I think you are saying that despite getting good reception for ITV 3 Film 4 etc before the final retuning on 9th May, those days are gone and I have lost these channels permanently unless I take action. I cannot expect that the problems experienced by others in the Npton area will result in any change to circumstances ie. no-one is going from the digital authorities is going to help me. In other words nothing will change to improve things short of action on my part.
That action needs to consist of:
Checking whether I have an appropriate aerial on the roof and if not obtaining a Log 40 aerial. On the other hand if I have the correct aerial but both aerial wires lead into the diplex box then do I simply disconnect the E Mids wire from the diplex box so effectively the diplex box is just a join in the Sandy Heath wire?
Have I understood what needs to be done correctly and how easy is it? Is there any source of info to refer to?
If on the other hand the aerial isn't the right one then I have no choice except to call in an aerial installer who presumably can install the new Log 40 aerial and remove the E Mids Yagi aerial and lead a brand new wire into the house.
Incidentally why is it that connection via the HDD box and the SCART option give me all those extra channels except of course the illusive ITV3?
Mike O'Pray: If I could just further add for purposes of explaining / emphasising why the diplexer presently installed will be detrimental to your reception and likewise has to be removed.
Diplexers are simply twin input dual band filters that only allows two sets of channels within a defined frequency range to pass through, and the type that's installed in your aerial system will be allowing channels from Ch21 - 37 to pass through on its No1 input and with anything above that range being attenuated, whereas the diplexers No2 input will only be allowing channels from Ch39 upwards to pass through and will attenuate anything under that.
As you will probably gather, that as your Sandy aerial is on the diplexers No1 input then anything above Ch37 will be attenuated, which of course includes all of Sandy's commercials, namely Ch48 / Ch51 / Ch52 and the very ones you are having trouble with.
That said, these channels will of course be allowed to pass through the diplexers No2 input which starts at Ch39, this being why Dave Lindsay had mentioned about turning the Waltham facing aerial around to face Sandy, which of course would improve the situation but only in a second best fashion, as diplexers have insertion loses plus a signal level tapering off effect near to the crossover points between the two frequency ranges covered, and so its always better without anything being installed except possibly a booster, but only should this prove as being necessary.
Taking the explanation of how a diplexer works into consideration you can maybe understand why this device is totally unsuitable for receiving signals from Sandy because of its channel span range of Ch21 - Ch52.
What you have said with regards to your plan of action is correct, insomuch try and check the colour of the square plug on the end of the aerial cross member and if its red then another aerial of a wideband type is called for.
All you require to do in a diplexer is prise off its plastic cover and disconnect the coax from the Waltham facing aerial and tape the ends up out of the road, then take the coax connection from the Sandy facing aerial off the the diplexers input tags and join it onto the diplexers output tags where the feed to the house will already be joined onto, in other words the two coax leads joined in parallel.
By the way the only reason for you receiving more channels via the scart from the DVD will be because of either (1) the Panasonic has a more sensitive tuner, or (2) because when the signal is looping through the Panasonic then into the TV its being attenuated slightly, this effect always noticed more in weak signal areas.
Mike O'Pray: TV is broadcast on (UHF) channel numbers and these go from 21 to 69. They equate to frequencies. So 21 is a lower frequency than 41, for example.
The channel numbers are divided up into three Groups "A", "B" and "C/D" which are roughly the first third, middle third and top third of the band used for TV. For a table of which channel ranges relate to which Group, see here:
Back in the day of four-channel analogue, each transmitter broadcast on four channels that were all within the same Group. Sandy Heath used four channels in Group A (21, 24, 27, 31) and Waltham used four channels in Group C/D (54, 58, 61, 64).
In order to join the two leads from your aerials together a diplexer was needed; they can't just be connected together. A diplexer filters the feed from each aerial. See here for some examples:
Suppose that your diplexer "splits" at channel 36 (C36); therefore it allows C21 to C35 through from your Sandy aerial and C37 to C69 from your Waltham aerial. This worked fine with the former analogue channels mentioned above.
Due to the channel allocations of Sandy Heath and Waltham now, such a setup will mean that some are unreceivable.
I'll come on to which carries what in a moment. But hopefully you can now appreciate that if your diplexer is as suggested, you will be unable to receive 51, 52 and 48 from Sandy and 29 from Waltham. All the other channels would be expected to come through.
For some transmitters, including these two, "out of group" channels have had to be used for Freeview. That is, some channels are outside that of the Group used by the former analogue. This is because there aren't enough spare ones, now that six are needed instead of four.
Digital channels carry a number of services whereas previously one analogue service occupied one UHF channel. See the graphic under the heading "After switchover configuration" on this page (you may need to refresh by pressing F5 to get the graphic to show):
The six UHF channel numbers that I gave above for Sandy and Waltham those which these six multiplexes broadcast on in that respective order.
If your aerial diplexer is as I suggested, then you could theoretically receive the three PSBs from Sandy and the three PSBs from Waltham. You could only receive COM5 and COM6 from Waltham, but you won't be able to receive COM4 from either because they are outside of the range of channels that the diplexer allows through for each respective aerial.
On the 9th May there was a change to the channel used by one multiplex at Sandy Heath and that was COM4 which was on C31 up to that date. This was within the channel range allowed from your Sandy aerial which probably explains why you could pick it up then.
Receivers usually give the UHF channel number that they are tuned to on the signal strength screen. You may be able to ascertain what transmitter(s) the Panasonic is tuned to for which multiplexes. I suggest that you focus on the first service from each multiplex, i.e. BBC One, ITV1, BBC One HD (if applicable), ITV3, Pick TV and Yesterday.
My guess is that Pick TV and Yesterday will be coming in on 56 and 57 respectively, which means that you are receiving them from Waltham.
If there are duplicates, then you will find them in the 800s. So you will probably have duplicate PSBx services. The signal strength screen should allow you to identify which is which.
Perhaps you are receiving the PSBs from Sandy and COM5 and COM6 from Waltham (with Waltham's PSBs being in the 800s). Therefore your regional programming will be BBC East/ITV Anglia.
As for why the Goodmans hasn't tuned-in as many services, perhaps it doesn't cope too well with signals from different transmitters or perhaps during its automatic tuning sequence it stores channels from only one transmitter. This is speculation on my part and a clearer picture of what's happened may be gained through some investigation. If the Goodmans gives the tuned UHF channel number on the signal strength screen you will be able to piece together what it is picking up. Perhaps it only has the two (standard definition) PSBs from Sandy tuned.
If it has manual tuning, you may be able to add missing channels. However, before you do this, I suggest that you use the Panasonic to find out what it is that you are receiving; are COM5 and COM6 coming from Waltham? If they are and the Goodmans has a manual tune function, then you need to try and manually tune C56 and C57.
I suggested in an earlier posting that a possible solution may be to turn your Waltham aerial to face Sandy Heath. Obviously you will no longer be able to receive BBC East Midlands/ITV Central from Waltham, but the UHF channel spacings (if you wish to receive COM4) have probably put paid to that anyway.
My reason for making this suggestion is down to the likelihood that your aerials will be "Group" ones rather than widebands. That is, they will be designed with maximum sensitivity on channels within their respective Groups only. I think that we can safely say that this is so as they are 20 years old.
This is why I think that using one or the other may not work satisfactorily. For example, if removed the diplexer (and therefore Waltham aerial) from the equation by connecting the Sandy aerial directly to your downlead, then being a Group A aerial, it may not be sensitive enough for the high Group C/D channels that Sandy's COMs operate at.
There will be many people who will only have a single Group A aerial and who will now have to replace it with a wideband one in order to receive the COMs.
However, as you have another aerial that works at the desired channels (48, 51 and 52), I suggest that the cheapest solution may be to turn the C/D (Waltham) aerial to face Sandy.
Whether this will work hinges on what channel the diplexer splits at. If it is as I suggested above (36), then it should work. If, however, it splits at C51 (for example), then obviously it's not going to work. It needs to split below C48.
It is also to be hoped that the securing bolts can be undone!
I respect jb38's comments as he's a professional and I'm not. However, I suggest this as being a possibility, primarily because it seems to be the cheapest option.
Whilst there is signal loss with using the diplexer (and I couldn't say to what degree), it would appear that you picked up COM4 (via your diplexer) prior to 9th May when it was on C31 and radiated at a transmission power of 20kW. Now it is at 170kW, so you have a much stronger signal to play with.
Mike O'Pray: If I could just add a qualification to the plan of action insomuch that if its found that you do have an original group A (red end) aerial, then even without changing it you would most likely find that you could receive the missing channels by simply disconnecting the Waltham facing aerial and by-passing the diplexer, as that device alone will be killing off the reception of the commercial channels far more than the fact of the aerial operating out of band, as aerials out of band will still work but with their efficiency dropping off the further out of band they are required to operating in, although with the commercial channels upping their power to 170Kw that would more than compensate for the out of band deficiency.
Should I have known that your two aerials were linked together I would have mentioned right from the start that the system had to be changed, albeit of course that you were unaware of why it would be having such a detrimental effect on reception of the commercials.
In other words, to make life easy if you know someone with a ladder that can access the diplexer then maybe you could get them to by-pass it, even if its just done by taking the coax connections off the terminals (usually always screwed) and joining the coax from the Sandy facing aerial onto the coax feeding the house using a small terminal block, because as long as the terminal block is inside the casing for protection against water then its perfectly OK.
All my bbc programmes on freeview are poor reception.
We have the Waltham transmitter and prior to switch-over very good reception, and for 3 months AFTER switch-over reception on bbc reasonable. Now hopeless, in both TV and radio channels Scan shows 35% strength 26% quality. All other channels 100%
Ariel (type 2) on mast
John: Have you confirmed that it is Waltham that you are tuned to for the BBC services? The signal strength screen should tell you what UHF channel you are tuned to and for BBC One etc it should be C61.
Thanks for the info. sorry for not coming back sooner but not been able to mess about with the aerial until today.
1. i have removed 4 of the elements from my aerial but signal was poorer whether vert. or horz. Put them back one by one no improvement this was using the labgear signal strength meter.
2. signal strength at tv whether by-passing the 8 way splitter or not was the same.
3. I have a hitachi digi box recorder and the signal out of that was still two leds lit.
4. With regard to the transmitter being 27 miles away I hung a piece of aerial out the window and with it attached to tv got super pictures and sound on beb 1 and 2 but no other channels were available. when the aerial is attached to the digi box, the picture is broken up on beb 1 and 2 and no other channels available.
5. With the agro I am having would you advise getting rid of this new aerial and changing it for a XB10K or ????
Thanking you for your time
nigel: Thanks for the update / info regarding tests carry out, and in particular the result of your wire aerialtest somewhat proving that a good signal does exist at your location but one that most likely requires some experimenting with the aerial position to achieve a satisfactory balance over the six muxes, as if that test had been carried out using a length of coax connected to a DM log you would most likely have discovered that moving the log to the left or right as well as at various vertical heights (not necessarily meaning higher) could well have resulted in the other muxes being picked up.
With regards to the test you made on the aerial by removing some of the elements, this should really have been carried out using the TV's signal checking facility as any differences seen in signal level when this sort of thing is done in a non line-of-site location would be so marginal that your Labgear tester would not really show it, as proven when you replaced them one by one and no difference was noticed, not of course that there would have been that much of a difference if viewed on the TV either, as its only in line-of-site (or very near) conditions that this is noticed, and only "if" the aerial has been aligned bang on the signal source in the first place.
Regarding your present aerial which as was aforementioned is not really suitable for use in situations such as yours even with some elements removed, and although I did previously mention that a Log 40 would suffice, however going by the result of your wire aerial test I now feel that even the shorter DM log would be more than adequate in your circumstances as well as being easier to move around within a loft environment, and so even although the Log 40 is still OK for the job I would be inclined to use the DM log, that also being shown in the link previously sent.
A little tip though, for successful results when anyone is trying an aerial in different positions and not in possession of a professional meter, then they really require some other form of instant feedback on any actions taken, and this to be perfectly frank is where your Labgear tester is not really good enough for that purpose, because in most cases the best "quality" signal is not achieved when accompanied by a maximum signal strength reading, and indeed can be quite the reverse! this being where your Labgear can be misleading! and so if at all possible you should try to borrow a small portable TV to use in the loft with the aerial connected directly into it and leaving the TV sitting on its signal checking screen, as this would enable you to peak the reception quality irrespective of signal strength as well testing the reception across all the muxes after every movement of the aerial position.
Nigel I am no expert but IIUC the various elements of your aerial are intended to work as pairs at different frequencies, so unless you know what you are doing just removing some is unlikely to get results.
There is a lot to be said for paying a LOCAL installer for his local knowledge.
Stephen P: It all boils down to techniques of the trade and experience gained over many years of dealing with RF equipment whether it be for TX or RX purposes and likewise knowing where theory and practice part company, something which it very frequently does and why RF engineering is classed as a "black art", as the whole idea of the test was to slightly increase the beam width acceptance angle of the aerial irrespective of any upset to the dubious gain figures claimed for it, which in real life situations bear very little semblance to the figures published and especially so in a non line-of-site situation.
Slight widening of an aerials beam width by removing a number of the directors (or lenses) that focus the signal towards the active element can in some circumstances help even out the large differences in signal strength that an aerial of that type is prone to being responsible for when used in situations where a signal can deviate from straight line reception, this caused by the signal being reflected from objects such as trees etc, drifting signal strengths being a very common symptom of this situation applying, although reception across a large expanse of water can also be responsible for this type of problem and likewise cannot completely be discounted.
This technique can be used in any aerial except a log, as in that type of aerial all elements are active and with that being why logs have such an even response across all bands, i.e: its a series of dipoles that can all resonate at various points across the total range dependant on what frequency they might be receiving.
If you care to have a look at a range of aerials of the same type but which come in different lengths / gain ratings you will no doubt see that the longer the aerial the sharper its beam width is, as that's the penalty that has to be paid when using a higher gain type of aerial and why they should not be used in situations such as Nigel's.
Or to put it another way, the best wide angle aerial you can get is a simple dipole set top aerial, especially if its orientated vertically.
Nigel: The overall lengths of these log aerials are /
Log 40 is 4'4" (131cm)
DM log is 3'6" (107cm)
DM18 log is 2'6" (76cm)
I would suggest that the DM log would be best in your situation, although to be quite honest about it any of them would do as the gain figures aren't that terribly important for any aerial that's intended to be used in a location where a signal capable of resolving a picture can be achieved with nothing more than a piece of wire in the aerial socket of a TV or box, remember though that when trying experiments with the aerial in different positions it should initially be done with it vertically mounted, although tilting it to the left or right should also be tried at every good spot found.
I have an elderly JVC tv which has been receiving free view digital services through my top box.
I have not been watching telly for some months and missed half of the switchover as I was away. My friend tried to perform a "factory re set" but to no avail. Please can you give me some guidance about how to reset my telly?
Martin Raven: And just to confirm that it is the "Freeview boxes" model number that has been requested and not the TV's, as you are obviously only using it as a monitor and so it plays no part in reception.
Stuart Mcfarlane Tuesday 12 June 2012 9:51PM Haverhill
Hi, I have 4 TV's in the house all running from one digitalloft arial connected to a booster.Two of the TV's can pick up all the freeview channels but the other two are missing some of the channels and will not pick them up even after re-tuning. Do you know of a reason this is happenning and can you tell me a way of resolving the problem.
Hi, can anyone help?
BBC channels on my television (I.e. 1,2,7,70?,bbc news etc) have all disappeared off my tv since yesterday. The tv has free view? I've tried retuning and also carried out a factory reset, checked ariel connection, unplugged everything and started from scratch, all to no avail. Any ideas please.