Inside surface of Feedhorn - Shiny or dull?

[tmbp]

Dear Feedhorn experts,

I am living in Hungary and have recently acquired a large sat dish, the original LNB was an SMW. I am now in the process of changing the LNB to the invacom, and I will use the original Feedhorn from the SMW.
Problem is, it seems to have oxidised, therefore I would like to ask if it makes any sense to polish it up? will it make any difference?
Many thanks in advance for your help and advice.
Thomas.

 

[Llew]

Hi Thomas, welcome to the forum.

You mean the inside or the diaphragm on the face?

If it's just the outside metal surface, it shouldn't affect the perfomance if you remove any oxidisation.

Llew

 

[Llew]

Sorry, I was distracted and didn't read your post header.

If the oxidised surface can be removable without any apparent disfigurement to the inside surface, it should be OK.

Regarding fitting an Invacom LNB to the feedhorn, the fixing holes won't align perfectly. You will probably only be able to use a couple of the screws, but as long as the O ring is giving a good seal it will be fine (that combination is what I have used for some time now).

 

[tmbp]

Thank you Llew.

I have attached a pic of the inside of the feedhorn. The cover was shattered, I suppose for a while now - it just crumbled away in my hand. Beneath the external cover the metal rings are looking very matt, and probably oxidized. I wondered if this would affect the signal before reaching the LNB? Should I polish it?
Many thanks for your reply,
T.

 

[Llew]

Yes I can see you might have a problem with the cover having perished. It's difficult to tell without inspecting at first hand. SMW feedhorns are made of diecast aluminium, so a polish suitable for aluminium should remove the oxidisation.

Are you sure that it is an SMW feedhorn? They usually have four holes for fixing to an SMW LNB.

Llew

 

[tmbp]

Llew,
I cannot say for sure that the feedhorn is an original SMW. The feedhorn was attached to the LNB. I will post some photos later this morning of the dish, and the LNB. Maybe the feedhorn was fitted onto the LNB when that was replaced, but that I don't know.
back later........
Thanks,
Thomas.

 

[tmbp]

here are the pics.

 

[Channel Hopper]

Picture 3 looks suspiciously like the back end of an Irte magnetic polariser, which should be discarded immediately.

As for corrosion on the feed, it's never bothered my system unless the oxidising retains moisture behind any cap you might fit. Polishing the dull bits is unlikely to improve your signal with the exception of the bore, where blistering can give losses at the odd frequency, but this is minimal.

An offset dish (when installed vertically/non-inverted mode), needs a completely waterproof cap, otherwise water will ingress down the feed to the sensitive parts.

 

[Llew]

That'll be the SMW ferotor if Pic 3 is of the one fixed on the LNB in Pic 1. As CH says, you won't need that if you are using an Invacom universal LNB.

 

[tmbp]

Thank you very much Llew for your help. I was going to throw out the SMW stuff that was attached to the feedhorn anyway, I think it is obsolete by now. I attached the pics, because it maybe that the feedhorn is not an original SMW one.
Any ideas about the dish? It is cast plastic, and oval in shape. Do you think that if I used the signal strength meter on my "strong" sat receiver, I can find the optimum focal point for the horn/ angle and azimuth of the dish?
Many thanks,
T.

 

[Llew]

Looks like an Andrews dish to me. 1.8M?

If you're using the original feedhorn and just swapping the LNBs it will already be correct for focus.

Don't bin the SMW stuff, you should get a good price on those on fleabay.

 

[tmbp]

Thanks. 1.8m wide and 2m high - in fact oval.
you're welcome to the SMW stuff if you pay the postage....
T.

 

[Llew]

Thanks for the offer Thomas, I can't use them now as my installation is not set up for that LNB/polariser now. Hold on to them though, maybe somebody here might be interested in them.

Llew

 

[Turok]

Hello!
i often recogneized,that the are many problems,to fix flange lnbs,for diffrent brands!
when you see,it does not hold good,you realy need a good weather protection!
alternativly you can try to make some more holes,to fix the flange lnb better,with more screws!

invacom offers a big plastic protection cape,that you can slide for there lnbs,iam not sure,is this conver separatly avalibe or not,i bought invacom circular linear quad lnb,in usa,and here,the rainpotection was included ,in europe i never see any!

with smw you have the better freqency stablity,then with the incacom,inverto also very good,i remove now all my incacoms from my dishes,because,when i look on the signal meter,the signal curve on my normal quad incacom,looks not very solid!
inverto lnbs,has like a plastic protection,that cover over the lnb,on my kathrein cas 180 ,this lnb was not working long,because also of the reason why some screws are not posible to install,then it works one month,after that it shows no signal,after that,i look on the lnb,that was installed with the protection ring,and see,that inside was accure,from outside i see no damage,was no problem to replace inside the warrenty!
also good to know is,that you have on the old gray incacoms only 2 year warrenty,and on the white newer ones,you have 5 years warrteny,the hotline told me!
on inverto you have always 5 years!
smw,i got confirmed from sweden,has stopped there lnb production on dec 31 -08
best thing you keep your lnb,and dont sell it,its very hard to find again,i have also to xline ftype here in reverse,when some emergency would happen!

 

[Channel Hopper]

Looks like an Andrews dish to me. 1.8M?

From memory it looks more like a Prodelin with those additional reinforcements on the edges, the double strut along the horizontal central line is a giveaway to a derivative of the 1194 series.

But the ribbing near the centre is far more concentrated than I recall from my time working with them.

 

[Turok]

Hi!
front and backside pictures of Prodelin 1,80 m dish,you will find currencly under this item nr


120467950550

 

[Channel Hopper]

Hi!
front and backside pictures of Prodelin 1,80 m dish,you will find currencly under this item nr


120467950550

I don't recognise that number .

A link to the manufacturer's site with a (poor)picture of the back panel

_http://www.gdsatcom.com/Antennas/Data_Sheets/5002-352.pdf

 

[tmbp]

Hello,
Well I connected the feedhorn to the LNB and fiited it to the mounts. One strange thing is that the feedhorn shaft is 27mm, but the holder is only 20mm diameter (see photos). This is probably why the signal strength is not as good as I would have like to get it. I suppose the real answer is to find out what make the dish is, in order to find out the type of original feedhorn, and also to get the focal lenght correct.
I did do the calculation, but for offset where is the point on the dish that you need to measure from??
Thanks,
Thomas.

 

[Channel Hopper]

The feed clamping system does not look like a Prodelin, but they did have feeds that went outside the 20/40mm clamping arrangement.

 

[tmbp]

Thanks for the info.
I was trying to find out exactly which dish I have. At prodelin, they say I have a 1183/1186 series, but the geometry drawing and the fixing arrangement for the feedholder are different. My ffedholders are screwed to the sides, unlike the 1183/1186 where they are fixed through the front. I looked at all the geometry drawings and found the nearest to my dish, which were the 2194/3180 series.
Please would someone kindly tell me what is the difference between these three dishes, as although they seem to be same, somehow they differ. If, assuming mine is of 2194/3180 series - will it be suitable for TV reception??
attached geometry pics of: 1183/1186 / 2194/3180
and photo of the rear of my dish, and the front with the LNB holder rods.
The reason I need to be sure which dish I have, is to have a correct setting of the focal point of the LNB - which I am assuming is presently incorrect.
Thanks for any help on this subject,

Thomas.