All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
A report was published last month on reception issues in the Thanet area:
http://stakeholders.ofcom….pdf
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MikeP: Thanks. Impedance matching has always been one of those things I haven't got my head around.
Is it possible to buy 75 ohm load IEC male aerial plugs? I see F-connector ones are available, but this would require an adapter.
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MikeP: Yes, thanks, it does help.
I ask because I have an aerial which feeds one room and which I'll be fitting a splitter to in order to feed another room. If there is one room which doesn't have a TV in when the other does I can fit one of these terminators if the picture is affected.
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Jack Williams: The most obvious question is: is it tuned to the transmitter to which the aerial faces?
Are you tuned to Rosneath rather than Garelochhead? Bring up the signal strength screen on BBC One and observe the UHF channel tuned. Rosneath is on C49 and Garelochhead is on C42. Do the same for STV: Rosneath is on C58 and Garelochhead is on C45.
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rob: See the following terrain plots:
Crystal Palace:
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
Oxford:
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
Hannington:
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
As you probably know, none are sparkling owing to the fact that you are surrounded by high ground.
Due to the dog's dinner of aerial groupings from transmitters, using a diplexer to combine feeds from different transmitters is becoming increasingly impossible without loosing access to some channels.
However, Crystal Palace and Hannington are about the only pair whose channel groupings which aren't overlapping, almost.
I say "almost" because COM7 and the forthcoming COM8, if receivable by you, overlap from these two transmitters. "If" you can receive all channels from Crystal Palace you can add Hannington for BBC and ITV using a diplexer. This would mean you would only be able to receive COM7 and COM8 from CP.
The only warning is that PSB3 from Hannington is on C39, so a C38 diplexer would attenuate it a bit. If you use a C36 diplexer you would attenuate COM8 on C35, when is comes on air from CP. At the present time, however, BBC One HD on PSB3 is the same for all areas. ITV HD has about four or five regions nationwide.
Don't use your tri-boom for CP:
Crystal Palace Transmitter
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Ben C: The new HD services, which include BBC Four and BBC News, are essentially pre-switchover and introduced so as to encourage take-up of Freeview HD receivers. The lifespan of these multiplexes is likely to be very short, it being at least 5 years. At that point things are likely to change again, including selling more frequencies off to mobile phone operators.
The equipment used is that which was already in existence, and therefore didn't have to be purchased. The objective is to serve as many as possible.
The only thing you can do is consider whether you might be able to receive from Mendip or perhaps Wenvoe, and pick up the quasi-national HD channels from one of those. With Wenvoe you might be able to combine feeds with your Bristol Kings Western aerial so as to give you West regional ITV and BBC. This option may mean forfeiting of Made in Bristol.
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rob: I write on here as a technical bod rather than an aerial installer.
If you're going to use a C36 or C38 diplexer to combine the two feeds, then the LTE filter only need go on the Hannington aerial because by definition C61 to C69 (which are allocated to 4G) is filtered anyway. Or, feed the two aerials into the diplexer and fit the filter afterwards, I wouldn't think it matters. The main thing is to have as much as possible in the loft so as to facilitate easy access, should there be a fault or should you find that the solution you have enacted requires adjustment.
ATV in Sheffield's website gives lots of information www.aerialsandtv.com They sell stuff too obviously other retailers are available. ATV sells Blake stuff and from what I've read Blake produces very respectable products.
The saying is "if you can use a log, use a log". A log periodic is wideband and therefore will work on any transmitter and even so when the powers that be decide to play musical chairs with UHF channels and groupings.
The gain of an aerial is at the expense of acceptance angle. Or to put it another way, think of the aerial as if it were transmitting (rather than receiving). The higher gain aerial would be radiating a stronger and narrower beam. Thus, thinking back to the aerial being used for receiving, where you don't have line-of-sight to "see" you have no real beam from the transmitter so it could be said that a wider angle might be better. This is because the objective is to get good quality and the quality over a small angle could fluctuate whereas over a wider angle the average quality is more likely to be more stable. You can always increase strength with a signal amplifier, something which it is inevitable you will have to install anyway.
So, I'm not sure under what circumstances the Group A and Group B yagi aerials you mention might be better than two logs.
One possibility is to get one log and try it on each transmitter, in turn, giving a period of several days maybe for evaluation. That said, obviously where you don't have line-of-sight as is the case for all three transmitters, reception could vary at different times owing to things on the ground such as trees which have leaves on in summer but then you've got that irrespective of which aerial(s) you go for.
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SL: BBC One is carried on the same multiplex (same signal) as BBC Two and other standard definition BBC services. So, if you are missing them all then use the manual tuning function (if available) to tune to UHF channel 53.
If only BBC One is missing (and BBC Two, BBC Three etc) are present, see if BBC One is in the 800s. BBC One from Oxford is on UHF channel 53 and this information is usually given on the signal strength screen, so you can ensure that it is Oxford's BBC One and not a BBC One from another transmitter. If the set allows, move it to logical channel number 1. If not (many don't) try a manual tune of UHF channel 53 or else a full retune might be your only option.
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carol barrie: See:
Single frequency interference
It sounds like interference from an electrical appliance in your property or one nearby. The fact that it happens at the same time suggests it could be a timed one. A battery-powered AM radio tuned away from a station may help track down the source of the noise.
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Friday 30 January 2015 1:29PM
carol: You say you have attenuator(s) in place (which you refer to as "restrictors"). Perhaps you need to increase your level of attenuation further.
Go to the manual tuning page and enter/select UHF channel 44, but don't press the button to scan/add services. Observe it for a minute or two. If the strength is seen to be high one moment and keep jumping down to low then that could be because the signal level is OTT.
Try pulling the aerial lead out and holding the plug within a centimetre or two. This might "loose" some of the strength. If it stabilises then it could indicate too high a signal level.
If you are feeding 4 ways by a powered booster then attenuation should go before it and not after it. In any case, with such a strong signal you will probably be able to split it four ways with no powered booster (and still potentially require additional attenuation).