Feedhorn Adjustments

MikeO

Regular Member
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My Satellite Setup
3.2M Dish
Invacom C120 UNI Quad LNB QDF-031, NF 0.3dB
PACE DS430N
My Location
Limassol, CYPRUS
#1
Hi Guys,

I wonder if anyone can give me a bit of advise about fine tuning a feedhorn.
Basically, I had a small feedhorn on my quad, but due to pixating probs in Cyprus every evening, I was advised that a larger feedhorn may help. So I trundled off to the local supplier and bought one. The swap over was easier than I hoped, I only had to remove the smaller scaler ring and put the bigger one on as the screw threads were the same. The rest of the feed horn was identical, so I though I wouldnt need to replace that bit, and make my life easier.
But I have noticed that the reception is still poor, and if anything a bit worse now. I think maybe there needs to be a bit of fine tuning needed. Does the relative position of the scaler ring have a majour impact, ie if it is screwed on fully, partially, or just near to the aperture?
Also, I would guess just by changing the scaler ring, I wouldnt have to change the position of the LNB, ie its focal distance wouldnt have altered, nor the skew angle. I am at a bit of a loss. I also dont know if the reception change also just coincides with the bad time of the year here. I have noticed however that the default transponder at times almost entirely loses the signal quality (drops to zero), but this is early in the day, when 2D reception is great. I have also started to get a little breakup of C4 during the day which I didnt notice before.
Maybe I should stop tinkering and get someone in to check everything for me, but any advise would be greatly appreciated.

Cheers,

Mike
 

dxsat

Specialist Contributor
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My Satellite Setup
Snap's setup: (In Spain) Humax HDR, Prodelin 1.8m dish + Invacom QDF-031 + CM feed, (In UK) CallFlow VDSL + EE 4G, Sky Q, YouView HD, Mac OSX, iOS
My Location
UK: Tonbridge, Kent. Spain: Madrid.
#3
The first link is to c- band feedhorns, do not use one of these.
Read RD 100's advice on the third link in the dish set up thread, this is the accurate advice. Set the scalar ring back from the throat and adjust focus point and skew. The exact distance of the ring back from the throat is critical, follow the advice in the thread.
 

MikeO

Regular Member
Messages
72
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My Satellite Setup
3.2M Dish
Invacom C120 UNI Quad LNB QDF-031, NF 0.3dB
PACE DS430N
My Location
Limassol, CYPRUS
#4
Cheers guys,
Just one quick clarification: Adjust the rings as above, then the focal distance you say. I guess the focal distance must be from the center of the dish to the opening of the throat of the feedhorn. Since I didnt change the throat containing part of the feedhorn, just the ring, the focal point wouldnt have changed as I didnt move the lnb at all. I guess also the skew should still be correct as it wasnt touched. Is this right?
Thanks guys
 

dxsat

Specialist Contributor
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My Satellite Setup
Snap's setup: (In Spain) Humax HDR, Prodelin 1.8m dish + Invacom QDF-031 + CM feed, (In UK) CallFlow VDSL + EE 4G, Sky Q, YouView HD, Mac OSX, iOS
My Location
UK: Tonbridge, Kent. Spain: Madrid.
#5
If it was Ok before and you haven't touched it, sure. The problem must be in the ring adjustment.
It would still be a good idea to get someone along with a meter to make sure everything has been optimised.
You could fine tune it yourself without a meter if the dish is accessible and it is safe, with a bit of space to work on it.
We can give you instructions for this if you want.
 

MikeO

Regular Member
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72
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My Satellite Setup
3.2M Dish
Invacom C120 UNI Quad LNB QDF-031, NF 0.3dB
PACE DS430N
My Location
Limassol, CYPRUS
#6
Cheers snap, yes that would be really helpful. The location of my dish is safe and very accessable as it is mounted on a flat roof. I could bring a portable and digibox up there so that I could see what I was doing. So any tips would be greatly received.
Thanks again
 
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#7
snap said:
The first link is to c- band feedhorns, do not use one of these.
Read RD 100's advice on the third link in the dish set up thread, this is the accurate advice. Set the scalar ring back from the throat and adjust focus point and skew. The exact distance of the ring back from the throat is critical, follow the advice in the thread.

No, the first link is to Ku (and C) feedhorns and original docs etc were taken from this in thread----.. http://www.chaparral.net/support/trouble/feedhorn.html (from off that first link) is best info.
 

dxsat

Specialist Contributor
Messages
745
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My Satellite Setup
Snap's setup: (In Spain) Humax HDR, Prodelin 1.8m dish + Invacom QDF-031 + CM feed, (In UK) CallFlow VDSL + EE 4G, Sky Q, YouView HD, Mac OSX, iOS
My Location
UK: Tonbridge, Kent. Spain: Madrid.
#8
pedro2000uk said:
No, the first link is to Ku (and C) feedhorns and original docs etc were taken from this in thread----.. http://www.chaparral.net/support/trouble/feedhorn.html (from off that first link) is best info.
Sorry, does not make sense, only one of the Chaparral feeds -the Ku wideband polarator- is wide band and able to receive Astra 2D, but it is not suitable for the type of LNB Mike O is using, as it has a WR 75 fitting. All the others are either high band Ku, C band or for an offset dish, and not what he is looking for.
 
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#9
mornin snap, thanks for the info.... the link (1) was meant for info help etc. on the 'original' thread ...not product info... are you saying this is no good for the original question...? \(sub/ page links from the link 1 I supplied..>>>.)
Feedhorn installation tips - Focus on feeds from those feedhorn fanatics in Technical Support.
f/D ratio and scalar rings - Why it is important to set properly.
Formulas for calculating focal distance and f/D ratio for any dish*.
Feedhorn troubleshooting tips - How to section on recognizing and correcting feed\polarity problems.
 

trigger

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My Location
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#10
The loss of signal during the day is probably down to the Autumn equinox. This is when the sun is directly behind the satellites for a short time during the day. When the loss occurs look at your dish and see if there are any shadows indicating the sun is behind the sat. Prime focus dishes you will see the shadow of the lnb in the centre of the dish.
Triggs
 

MikeO

Regular Member
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72
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My Satellite Setup
3.2M Dish
Invacom C120 UNI Quad LNB QDF-031, NF 0.3dB
PACE DS430N
My Location
Limassol, CYPRUS
#11
Thanks Trigger, but my prob with 2D happens at night (9.30-10.30pm local time), so no shadows to look for unfortunately. Could hold true for the Ch4 breakup but it doesnt really concern me too much then as I dont watch during the day. You may well be right though. Ill have a look for interest though.
Cheers
 

dxsat

Specialist Contributor
Messages
745
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My Satellite Setup
Snap's setup: (In Spain) Humax HDR, Prodelin 1.8m dish + Invacom QDF-031 + CM feed, (In UK) CallFlow VDSL + EE 4G, Sky Q, YouView HD, Mac OSX, iOS
My Location
UK: Tonbridge, Kent. Spain: Madrid.
#12
Loss of signal owing to equinox will be about 11.55 AM CET for around 5-10 mins.
Pedro2000 - the info is extremely useful, thought you were recommending that he buy one of these Chaparral feeds.
 
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#13
cheers snap, that Chaparral link's a good one. Love the Autumn equinox info Trigger.., we used to get the same thing a few years ago on 26e at about 8:15 every morning for about 15 minutes..
 

bignick

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Back in the UK and missing Cyprus!!!
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Aylesbury
#14
Mike

For your dish, a 3.1m Famaval, the focal distance IE the distance from the end of the feed horn WITHOUT the scalar ring screwed on to the dish face should be 93cm dead! You then screw on the scalar ring so the ring is in line with the end of the end of the feed. IE No thread prodruding. Do not be surprised if you have to fine tune the dish once again after this.

Nick
 

MikeO

Regular Member
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72
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My Satellite Setup
3.2M Dish
Invacom C120 UNI Quad LNB QDF-031, NF 0.3dB
PACE DS430N
My Location
Limassol, CYPRUS
#15
Thanks Nick.
Sound very different to what I have got! I havent measured the focal distance, but for the best picture todate, I have to have the scalar rings screwed on all the way to the top of the feedhorn....sound a bit diff hey.
I will try your tip. If I have probs, I will PM you and maybe imploy your services(Next week as Im off to UK Wed for a week).
Thank alot.
Mike
 

bignick

Specialist Contributor
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Back in the UK and missing Cyprus!!!
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#16
MikeO said:
Thanks Nick.
Sound very different to what I have got! I havent measured the focal distance, but for the best picture todate, I have to have the scalar rings screwed on all the way to the top of the feedhorn....sound a bit diff hey.
I will try your tip. If I have probs, I will PM you and maybe imploy your services(Next week as Im off to UK Wed for a week).
Thank alot.
Mike
No probs m8. The rings screwed in that far will have a VERY negative effect on picture quality!

Nick
 

Zorba

aka Skyman
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My Location
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#17
The only way to get the most out of your dish is to call for an expert sat dish installer with a good sat meter. You may think its easy to change just the feedhorn but every millimetre makes a difference. Up down left right and the skew and focal distance,You might have moved the dish a bit when you stepped in to change the feed or maybe the lnb wasn't correctly aligned in the first place.You say you have a 3.2m dish. Do you mean the 2.4m with extensions or the 12 piece 3.2m ?
 

MikeO

Regular Member
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72
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My Satellite Setup
3.2M Dish
Invacom C120 UNI Quad LNB QDF-031, NF 0.3dB
PACE DS430N
My Location
Limassol, CYPRUS
#18
You are right Zorba,
Its the 2.4 with extensions, so as Big Nick says its probably 3.1M.
Dont understand exactly whats going on. I measured my focal distance yesterday and it was less than the 93cm Nick said. The scalar rings are fully tightened, but last night, not even a pixel out of place.
I think my time of tinkering is over. Ill get someone in to carefully check everything with a decent meter and finish the prob., hopefully once and for all. Without a meter or experience, there is only so much us amateurs and tinker with.
Thanks everyone for your comments and advice.
Mike
 

Zorba

aka Skyman
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3m(28.2E),1.5m(19.2E.13E,10E),1m (4W ,7W)1m (?).diseqc 10,sky plus,VU+,telergy iptv.
Satlook nit colour + Horizon hdsm.
My Location
Limassol, Sunny Cyprus
#19
Last night was one of my best nights so far since i got back from holiday on sept 5th. Looks like the equinox has finished and bbc/itv should get better.
 

bignick

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#20
It is still possible to fine tune even if the weak time is over. Just use a very marginal channel such as ITV Yorks on 10.891 H 22.0 5/6

Cheers

Nick
 
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