My high gain aerial can't get all the Freeview channels I expected
Brian Butterworth published on UK Free TV You need a "wideband" aerial rather than a high gain one (see all about aerials). Also, if you use a signal booster in the setup, this can cause problems with digital signals.
Can I suggest that you try the following:
1. Check that all the connectors are OK, in particular that there are no stray wires and that both the outer shield and inner wire are connected;
2. If you are using any signal boosters, turn them off;
3. Check to see if you have anything like a VCR connected via a UHF fly lead - sometimes these can changed to use channels such as 68.
4. If you have a wideband aerial, if you can try raising it up an additional metre;
See also all about aerials.
All questions
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Thursday, 29 January 2015
Dave Lindsay
1:25 PM
1:25 PM
G Dixon: One of the experts (who have experience of this) will be along shortly, no doubt.
However, purely as a technical bod I will point out the following: My understanding is that this booster unit uses a separate power supply. That is, the mains electric goes into a power supply which feeds up one of the aerial cables into the booster. It does this by utilising both conductors in the cable -- centre core and outer screen. Thus, if there were to be a short-circuit between the two -- a piece of the braid was touching the centre conductor, for example -- then the booster won't get any power. I therefore suggest that this could be one possibility.
What I suggest you do is take the power supply into the loft and connect it to the booster with a short piece of coax, then see what happens.
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J
jb386:46 PM
G Dixon: The 4 sockets fitted on the amplifier used on this aerial are of a "one way" input nature as far as DC voltage is concerned, meaning that no matter which socket you connect the power supply into on the amplifier the 12volts DC voltage from the power supply will "not" (or should not!) appear on any of the other three outputs, the only thing that will do is the boosted signal from the amplifier.
If the aerial you bought as a replacement is exactly the same model as the one you are using, then the problem is more inclined to be caused by something connected into one of the output feeds, like for instance a TV or PVR capable of supplying power via its aerial socket to operate such as a mast head amplifier, because if any are? and the facility is switched on, then this will feed voltage up the coax and into the amplifier in exactly the same way as from the power unit, something which could cause problems if (as would be expected) the voltages are at different levels.
Therefore try this test. Switch off the mains to the aerials power supply followed by connecting the 4 coax cables back into the amplifier, then disconnect the TV's or boxes coupled into the various outlet point locations in the rooms and switch the aerial amps power supply back on, if the power supplies LED is illuminated, this indicates that your wiring is OK.
The next stage is to reconnect each of the TV or boxes used in the various locations "one at a time", checking after connecting each of the devices that the indicator on the power supply is still illuminated, if its not, remove whatever you have just reconnected and move onto the next device until they are all coupled up, the device you have removed being the culprit, therefore check its set up menu and look for "antenna power" being mentioned, needless to say disabling this facility if its seen mentioned.
Further advice dependant on feedback.
PS. By the way, if your replacement aerial is exactly the same as the one presently used, its assumed that you have tried swapping the power units over?
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Friday, 30 January 2015
G
G Dixon10:25 AM
jb38: Thank you for your answer I have tried what you said and still the same problem what I cant understand is all the TV's and video's have all worked fine up until a few weeks ago it looks as though I will have to run new cables to them all
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Lynda11:59 AM
New tv/DVD combi will not pick up most tv channels. No such issues in any other room , could it be a faulty connection in the box on the wall.?
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MikeB1:48 PM
Lynda: Easiest way to find out - get a TV you know works fine and plug it into that wall socket. If its rubbish, then you know its the socket, the aerial lead orl the cable that goes down to the socket. Likewise, check the new TV on another feed - if its fine, then you know its the socket. I suspect that the lead coming off the aerial has a problem, and if its in the loft, have a look to make sure its not frayed, etc.
There is one other possibility - is it tuned to the same transmitter as all other others? I have to admit I simply dont recommend TV/DVD combi's any wmore - they are just not that great, and the software might be a bit basic. So its possible that the tuner is picking up the wrong transmitter first, hence your problems. Check that its tuned to the correct transmitter. You've not put your postcode into the system, so I cant check which one it should be, but you can check yourself.
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jb383:55 PM
G Dixon: The best way to look at the problem is from the angle that the LED on the power unit will "only" go out (but see undermentioned) if a short circuit occurs on the 12 volts that's connected into the aerials amplifier.
Secondly, as the 12 volt power fed into the amplifier is contained "within" said amplifier, it is not, or should not, be present on any of the other sockets used to feed the amplified signal into the various locations its required, therefore if any short circuit should occur on any of these outputs the LED should not be affected in any way.
However, leaving this aside for the minute I would like to know the result of the following test, the reason for the request being that if any short circuit occurs on these Labgear power units (the ones generally supplied with these aerials) the LED turns red but not actually go out, therefore with the aid of a small piece of wire I would like you to try shorting out the "in" socket on the power unit, i.e: the one that runs to the aerial, the easiest way being by holding one end of the wire onto the threaded part of the "in" socket and touching the inner part of the socket with the other end, does the LED turn red or go out altogether?
By the way, the power unit will not be harmed in any way by this test, as its protected against being damaged by a short circuit.
Also, if all the sockets on the aerial amp are coupled up but with nothing being connected into any of the outlet points located in the various rooms, is the LED illuminated or not?
As far as you not having changed anything is concerned, if any of your devices have carried out an automatic update at some point, (mostly occurring in the early hours of the morning) then this can in some cases result in various settings being altered.
As before, further assistance dependant on content of reply.
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jb389:27 PM
G Dixon: In addition to that said in my earlier posting, once you have tried the power unit test referred to, couple the power unit into the aerial amplifier (on your spare aerial) using a short "F" connector jumper lead, then try shorting out each of the three outlet ports on the amplifier whilst observing the power units LED.
Needless to say, if the Megaboost system is operating OK, the LED should not be affected in any way by creating a short circuit across the output ports.
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Saturday, 31 January 2015
G
G Dixon10:27 AM
jb38: I have tried what you said and the green LED goes out so there must be a short a short on the system which affects the 4 supplies to the tv's
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jb381:40 PM
G Dixon: Many thanks for the update, your findings indicating that the amplifier is indeed defective by allowing the 12 volts supplied by the power unit to appear on its output ports, whereas if working properly it should be isolated from them by only allowing the amplified signal to travel down to your various outlet point locations, the fact that its not, meaning that power is being fed into the aerial connector points in your rooms, likewise anything connected into them.
By the way, and although you may have already tried this, but as one of the four ports on your aerial amplifier is connected into the power unit, (whereby being "in-out") did you also try the short circuit test on the lead that comes from the TV socket on the power unit?, as in this case the DC isolator (a small ceramic capacitor) is located inside the power unit.
Although it probably will not make any difference to the situation, but as the lead from the power unit can be connected into any of the 4 ports located on the left of the actual "aerial input" port on the amp, (connected into the aerial elements) I would like you to check if the situation remains the same by changing the port being used by the power unit.
The reason for the request being, that I cant quite remember if the amplifier uses a single isolator capacitor to feed the amplified signal into all ports at the same time, or each port has its own isolated output, although I do believe its the former due to the "shorting the output" test being active on all three outlet ports, the fourth port obviously being used by the power supply.
I will say though, that if you have outlet plates or boxes fitted in any room that the Freeview signal is fed into and you were in any way electrically inclined, you could get over the problem by fitting a small ceramic capacitor inside each outlet plate or box to block the 12 volts, the coax middle core being loosened off and the capacitor being fitted in series between the middle core and the point it was just removed from.
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G
G Dixon4:29 PM
jb38: Thanks for your help when I use the spare aerial and link it up to each tv it works fine so it looks as though I will have put in new runs to the tv's
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