All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Chris Merrill: Terrain plot to Rowridge:
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
Terrain plot to Hannington:
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
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Chris Merrill: I should add that Rowridge got a taller mast at switchover. If the current, Hannington, aerial was fitted before switchover because it was the best (or least worst) of the two that things may have changed with the taller Rowridge mast.
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Tony: Failing that, try taking the box to another aerial socket and seeing if you get any joy there.
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Tony: I don't know then. The UHF channel numbers and frequencies are given above, in the light green box with the text in slightly darker green.
The frequency of COM7 is 562MHz. The frequency of PSB3 (BBC One HD etc) is 618.2MHz, the +0.2MHz owing to the positive offset on the channel.
Things like HDMI leads and USB leads can interfere with RF signals carried in cables when they are run together. Try removing HDMI, USB, ethernet and other digital communications cables from the mix, if possible, in order to test this possibility. See if things improve. If it turns out to be the issue then use an aerial lead that is better screened, using the solid core stuff if necessary.
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Stephen Prince: This sounds like trees blowing about. If so then maybe resiting your aerial. If there are trees that you can see as possibly being the issue then you can try moving it to somewhere else, if such a spot is available.
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Stephen Prince: I should point out that the trees aren't forced to be within a few hundred metres of you they could be anywhere between you and the transmitter.
Here is a plot of the terrain:
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
The signal path runs low to the ground and is even blocked at 2 miles out, so anything on the ground which moves when the wind blows could be your culprit.
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m.whitbrook: On the basis that you are 5 miles from the transmitter, and with clear line-of-sight, too high a signal level would seem the most likely possibility!
Freeview signals: too much of a good thing is bad for you
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m.whitbrook: I wouldn't expect retuning to make any difference as, providing that the correct signals (i.e. those of the desired transmitter) are tuned, then the receiver will give the best picture from the signal provided from the aerial lead.
Perhaps it is local interference, an AM radio may locate. It might be worth trying the set-top aerial on the lounge TV to see if the same poor reception ensues.
Also, what is the strength and quality like? Some devices give more away than others so it's worth looking at the all to see which might be most helpful.
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Saturday 10 January 2015 9:43PM
Chris Merrill: There are never any exact answers here, but you would appear to have nearly clear line-of-sight to Rowridge but not Hannington. The Digital UK predictor suggests the same thing -- that Rowridge is quite a bit better than Hannington.
If you go for Rowridge then your Hannington aerial may not be suitable, or otherwise might not be the best for Rowridge.
If you're using a log periodic then go ahead and point it to Rowridge. If it's a Group B yagi aerial then it's not the right group and if it's a wideband yagi then it's inferior on Group A channels and so you might benefit from either a Group A yagi or wideband log.
See here for more information (other retailers are available):
Rowridge Transmitter
One other thing to be aware of is that Rowridge broadcasts horizontally and vertically. The COM channels aren't as powerful horizontally, therefore vertically may be preferred. However, the quasi-national COM7 HD multiplex only broadcasts horizontally, although on lower power than the other channels. So, you might wish to try horizontal polarisation first. If the COMs aren't reliable try switching to vertical polarisation but be aware that this may sacrifice COM7 (and COM8 when it comes on air).