What is wrong with my new TV ariel Installation plz?

[ZeroZero]

I am in UK and have just built a summerhouse and inside is a large LG flatscreen TV. I purchased an aluminium pole, ran the cable out and up (within the pole, I hope this does not matter) and attached it to the ariel. It's only picking up three channels. The cable has preformed F type connectors on both ends and I have ensured they are firm. The ariel is pointing the same way as other houses. The site is free from obstruction - on the edge of a field.
The cable is standard co-axial cable and the ariel is also standard (link below)



What am i doing wrong? Really puzzled!

Thanks

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Z

 

[brianmoooore]

Possibly the signal you are receiving is strong enough, but not 'clean' enough.
On old analogue TVs, a weak signal would appear as a grainy picture, and a signal that was not 'clean' would give rise to ghosting - a faint second picture displaced sideways, caused by the TV signal being reflected from hills, tall buildings, or even trees.
Digital TVs are not so fussy about a weak signal, but won't function unless the signal is 'clean'.
Signals that are excessively strong will also upset a digital TV. I'm about 2 miles away from a 100kW/channel TV transmitter, and often have to fit attenuators to reduce the signal.
Most TVs have a built in signal quality and error rate function somewhere in the menu options. Check this on the channels you can receive.
May be useful to take the TV to somewhere you have an exiting aerial and 'pre tune' it, so you can check the quality of the missing channels.

 

[mhar]

If you are not lucky when adopting the 'just put it up and see what happens' approach then you will (ideally) need a uhf signal meter. As Brian correctly states above, it is not just strength that is required, the signal quality is paramount. Have you got the polarity correct (flat for main transmittersa, upright for relays)? In an area where reception is problematic you are a bit lost without a meter so your only other option is to keep trying different locations, 6" can make a difference.
Amplification is rarely the answer with digital signals, amplifiers can cause more problems than they solve.
The EIRP diagrams that you see are all for 15m above ground level so height is often a requirement