[P12] What's up?

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For some reason we suddenly have solid reception of all the weak channels. Instead of the low 50s. Quality is now in the high 60s. Even as high as 70% on one channel! Signal strength S remains at about 78.

The weather is almost totally overcast but bright. With only occasional sunny periods. After a completely still start and an overnight frost, the wind is picking up to a breeze.

I have no explanation for this sudden change in signal quality. The wind cannot affect the dish very much even when it is blowing hard. Otherwise the stronger channels would disappear along with the weak ones. A large dish demands a much stricter pointing accuracy with its acceptance beam width of less than 1 degree.

I have found a second hand galvanised pipe to get rid of the ugly concrete fence posts which I use to load down the present iron and steel base. A simple pole will be much neater and allow the grass to be mown tighter to the dish.

By the time the new pole is cast in concrete it should provide a much more stable base for the new dish. A flange on the bottom will ensure the pole (and mounted dish) cannot rotate under wind loads. Normally one would have to add rods or fins to stop pole rotation in the concrete base.

A pole set in bare earth, even with added rocks or boulders in the excavation is not nearly stable enough. The concrete greatly increases the surface area of the pole. Thus avoiding the localised pressure a simple pole is able to exert on the soil. An "elephants foot" excavation will avoid the pole lifting due to frost heave or wind storm effects on the large dish. Channel Master recommend a cubic meter of concrete for their 1.8m dishes!

Yesterday's improved reception excitement was short lived. Q had dropped to 53% by 14.30 on most Spot Beam channels without a safe lock possible. Nothing pm, overnight or early morning.

Today the higher signal strength had returned by about 10.30am. S was back up to 80 with Q up to 70%. By 2.30 many channels were becoming only borderline watchable with low 50s% Q. Though some channels were still fine at 17.30pm! A very strange variation in Q across the range of transponders on the UK Spot Beam. 

I found this YT video on checking satellite dish focus using the sun and some small mirrors:

http://youtu.be/TTXvpES1_ZA

Provided the reflections are all equal and all overlap on the face of the LNB (or feedhorn) they must be centred and in focus. I believe the spoken language is an Indian dialect.

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