Sat TV dish - Field of View and trees

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Gordy7

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#74581 2-Jan-2011 22:38

I have a 450mm portable satellite TV dish with my motor home which I mount on the ground.

I had a situation recently where there were 2 trees, either side of the view to the satellite.

The trees were about 20m away with a 5m gap.

As part of the dish alignment, I could peak up the satellite signal very well with a meter but could not display any TV signal.

I am wondering about various issues that would cause the problem.

- Dish field of view many times wider than the dish diameter?
- Tree leaf signal scatter from the wanted and unwanted satellites?
- Various signal phase changes due to scatter.

Anyone throw some light on this?

I have assumed the LNB is probably okay since I got a good meter peak.
I have not done any subsequent unobstructed tests.
Normally I get a good solid signal and solid picture display.

TIA

Gordy

My first ever AM radio network connection was with a 1MHz AM crystal(OA91) radio receiver.

Etacovda

31 posts

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#423578 3-Jan-2011 00:05

sounds like you're locking onto 156 or 152 if you're getting a 'good strong signal'; course, that all depends on what you define as a good strong signal, because if you're using a beep-o-meter then you really have no idea on how good the signal is until you look at your tv...

sat signal is a very small spot to aim at. There will be no 'phased signal' due to the trees - you aim at a spot in the sky, and either you have straight LOS to the sat, or you do not.

20m away, but how high? remember you're shooting anywhere between 36 and 50 degrees depending on where you are in the country...

Gordy7

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#424178 5-Jan-2011 10:12

The sat dish etc worked ok on a clear site since the problem I had.

The 2 trees were poplars, probably about 40m high.
I was aiming the dish thru the 5m gap about 20m away and about half height thru the trees.

As I did not get any TV decoding I was using a beep-o-meter.
This was showing about 10% of scale on background and full scale on the satellite I peaked on.

My set up reference was a compass (which normally gives a good heading) and other nearby satellite dishes.

It remains a mystery.

Gordy

My first ever AM radio network connection was with a 1MHz AM crystal(OA91) radio receiver.

Etacovda

31 posts

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#425317 8-Jan-2011 22:11

sounds very much like you were pointed at 152 or 156 rather than 160.

Juicytree

141 posts

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#425321 8-Jan-2011 22:17

Try Dishpointer - it may help

SCUBADOO

192 posts

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#425339 8-Jan-2011 23:11

Gordy

FWIW

I use a similar sized suction cup mounted satellite dish on my campervan.

It works well in most locations but if I have any CLOSE and almost inline obstructions e.g. trees, rocks, poles etc. I will often have problems tuning into the correct signal. I can obtain meter deflection simply by pointing directly at any of these objects or even the ground!

With my setup, D1 is usually the only signal that peaks the meter over the usual very narrow beam. ALL the other obstacles produce meter deflection over a much wider arc.

Occasionally I have to either move location or simply sacrifice TV for the night.

Nev