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<blockquote data-quote="PaulR" data-source="post: 863064" data-attributes="member: 176256">I suppose that the real question is - Why does the regular aerial give a lower signal quality?&nbsp;There a number of things that we don't know.&nbsp; What type and group aerial is fitted?&nbsp; Is it actually pointing at Rowridge?&nbsp; Is it aligned for horizontal or vertical (interesting this - see later) polarisation?&nbsp; Is there an amplifier involved anywhere?&nbsp;The first answer might be that the signal is so strong through the aerial that it's overloading the tuner causing an actual reduction in quality.&nbsp; This is relatively easy to test by putting an attenuator into the lead before it goes into the TV and seeing if the quality then goes up.&nbsp;Rowridge transmits on Channels 21, 22, 24, 25, 27 and 28.&nbsp; It is a unique main transmitter as it transmits in both horizontal and vertical polarisation - this is to help combat co-channel interference, you align the aerial to the polarity that gives the lowest interference.&nbsp; In V mode all channels are 200KW but in H mode only 21, 24 and 27 are 200KW the other thre are 50KW.&nbsp; These lower powers are so as to minimise inerference with Crystal Palace which also uses these channels.&nbsp; As to why channels 27 and 28 don't come in, perhaps answers to the questions above might help.&nbsp;I had vaguely remembered about the dual polarity transmitting but I gained most of my information from this very helpful web site <a href="http://www.aerialsandtv.com/rowridgetx.html#RowridgeChannels" target="_blank">http://www.aerialsandtv.com/rowridgetx.html#RowridgeChannels</a> for nerds like me it was a fascinating read.&nbsp;A final easy test - do you get any channels by putting a short length of wire by itself into the TV aerial socket? (the proverbial bent coat hanger test).</blockquote>

[QUOTE="PaulR, post: 863064, member: 176256"] I suppose that the real question is - Why does the regular aerial give a lower signal quality? There a number of things that we don't know. What type and group aerial is fitted? Is it actually pointing at Rowridge? Is it aligned for horizontal or vertical (interesting this - see later) polarisation? Is there an amplifier involved anywhere? The first answer might be that the signal is so strong through the aerial that it's overloading the tuner causing an actual reduction in quality. This is relatively easy to test by putting an attenuator into the lead before it goes into the TV and seeing if the quality then goes up. Rowridge transmits on Channels 21, 22, 24, 25, 27 and 28. It is a unique main transmitter as it transmits in both horizontal and vertical polarisation - this is to help combat co-channel interference, you align the aerial to the polarity that gives the lowest interference. In V mode all channels are 200KW but in H mode only 21, 24 and 27 are 200KW the other thre are 50KW. These lower powers are so as to minimise inerference with Crystal Palace which also uses these channels. As to why channels 27 and 28 don't come in, perhaps answers to the questions above might help. I had vaguely remembered about the dual polarity transmitting but I gained most of my information from this very helpful web site [url]http://www.aerialsandtv.com/rowridgetx.html#RowridgeChannels[/url] for nerds like me it was a fascinating read. A final easy test - do you get any channels by putting a short length of wire by itself into the TV aerial socket? (the proverbial bent coat hanger test). [/QUOTE]

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