prime focus dish mount with off set dish ?

[seti]

I be downgrading dish from prime focus to offset and to a smaller 1m dish.

The problem is that I am using a H-H mount of a 1m prime focus dish with a 1m off set dish run by a acuter arm, can get it to work with 1w and 19e, + 13e but lose signal when I get all 3.(not tried any other as these are the main for me at this time)

If I set it up best on 1w then 89% signal, no 19e and about 50% on 13e.

To get it to work with 1w and 19e +13e I have to lower the elevation of dish and get about 51% on 1w and about 64% on 19e and 85% on 13e.

Am now using ground pole set in to the ground (solid) and definitely straight, H-H mount pointed dead south, have tried to offset this both ways by a few degrees but best results are above, using TM 6900 with a Diablo 2.3 cam.

Channels I using to set up are AXN on 1w, BBC world 13e, Film 1.3 on 19e.

I know how to use a compass but as to elevation angles no way..

Mainly want to know if I just need to keep tweaking it or am I using the wrong H-H mount ?

Any help most welcome.
thanks

[ratman]

try moving motor slightly off south make sure dish is plum to motor and also try ajusting scew on lnbhope this helps

[ian]

i think your mount will be ok.your problem sounds as though your dish isnt pointing correctly south.(you need to be a degree or two off from true south)

setup your dish for the strongest possible signal on 1w.
now move to 19e.if you get little or no signal,adjust the elevation untill you do.if you have to adjust it up to get signal,your dish is pointing too far to the west and if adjusting it down gets you signal then its pointing too far east.

go back to 1w again and adjust the elevation for the best signal,then this time swing the whole dish and mount on the pole a few degrees to the east or west depending on the results you obtained from 19e.

once you have both 1w and 19e,do the same with 30w.once you have all 3 repeat using the weakest transponders your dish size will pick up.
it all takes time my friend and is a case of trial,error and experiment.then you have to mess about with the skew(twisting the lnb left or right)and the focal length moving the lnb closer or futher from the centre of the dish to find the correct focal point.

im writing this from memory as it was over 20yrs ago i set mine up,but i do remember it took me a full week to align perfectly.a meter really helps shorten this time,but it can be done without one.ian.

[tr8.]

If iv'e read it right.
You are using a prime focus mount and ofset dish
If this is true that your problem.
It a long time ago i switched to offset dish's but the mount was different.
As the ofset dish twists to follow the arc differently to the older prime focus.

[ian]

@tr8

are you sure mate?
an arc is an arc.
thinking about it logically,i use an offset but if i were to bolt on a prime focus,what would stop me just raising the elevation to follow the arc at a much higher point as the prime focus dish does?
if you were situated on the equator all that would have to be adjusted for a prime focus would be to raise the mount high enough untill it was perfectly horizontal so the dish travelled from the floor to the floor in an arc.
any difference is corrected with declination angles.ian.

[chorleycat]

seti

prime focus dish mount with off set dish ?
I be downgrading dish from prime focus to offset and to a smaller 1m dish.

The problem is that I am using a H-H mount of a 1m prime focus dish with a 1m off set dish run by a acuter arm, can get it to work with 1w and 19e, + 13e but lose signal when I get all 3.(not tried any other as these are the main for me at this time)

If I set it up best on 1w then 89% signal, no 19e and about 50% on 13e.

To get it to work with 1w and 19e +13e I have to lower the elevation of dish and get about 51% on 1w and about 64% on 19e and 85% on 13e.

hi - seti

how- have you lowered the elevation enough to get a picture from 1 west etc -- ?

a mount built for prime focus is not likely to have enough forward adjustment capability , without being modified in some way -

if you have lowered the dish by adjusting it at the back of the dish where it fastens to the mount you will get 1 sat ok -- but the decline angle will be all wrong so it will not follow the arc

regards - c.c.

[ian]

what chorleycat says is perfectly true.
the elevation has to be adjusted from the mount.the declination(on the back of the dish)is only for minor corrections.ie using elevation alone the dish points out into space to infinity,but the sats are 26000 miles away so the direction needs to be adjusted slightly away from infinity by using the declination.
also the declination is used to provide a slight compromise at the very edge of the arc.this is because the world isnt completely circular(its a little bit squashed)so to get an excellent signal on sats very low on the horizon,ie 68e,you have to loose a little on the stronger sats at the top of the arc.but most peeps are not interested in this as 45e to 45w is enough.ian.

[seti]

Thanks for all the reply's.

Chorleycat i have only been adjusting the elevation on the mount not on the dish to the mount. will have another play with it.

Thanks again for all reply's.....


Had the dish set on 1w for a few months and I did Totally forgot I modified the mount, it now a prime focus mount with a off set base on it to adjust dish angle.

Sorry for not adding this in first post but did totally forget about the modifications