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Thread: Dish Paint and thermal noise

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    Junior Member hca's Avatar
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    Question Dish Paint and thermal noise

    Paint for dishes, so we all know a non reflective matt paint is required not to cook the LBS etc, and most paints like that go powdery and fail in the weather over time.

    I have been overhauling and respraying the dishes, I decided for weather protection to spray them with a thinner based coat of zinc chromate and thinner based gloss white metal paint as a weather proof base coat, then a sacrificial top coat of flat acrylic with a promise to self to maintain the paint this time so I don't have to do this rotten job again.

    Then I found an acrylic waterproof sealing paint called "no drop", a water based elastic flexible paint that dries matt, a bit like a thin latex skin which seemed an excellent weather solution. I have put it on a 2.4 and 1.8 solid to try it, but have one more 1.8 not yet coated with it.

    So having explained that lot, here's the issue. On Ku the 1.8 with the gloss coat out performs the 2.4 with the waterproofing coat. With both peaked up in every respect on a given weak Ku signal I get 43% on the 1.8 and 37% on the 2.4.

    Both have identical new from the box Fuji LNBs. Swapping them makes no difference. The dish string lines fine and no obstructions they are almost side by side.
    I need to check Ku the other 1.8 which is on C band and seemed ok and compare the result, but that involves moving household upper managements TV service to another dish first..

    As I cant fault the dish otherwise and it seems ok on C band, this leaves me with the possibility of the noise temp of this paint is upsetting things?



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    If you want a guess with experience , The are interfering with each other , caused by the lnbs local oscillators ,or reflections from one dish to the other . peak up one dish and remove the other away then put it back and see the difference in signal , over twenty wave lengths of the lowest freq . If its not a metal flake paint it wont affect the dish . you mention noise temp ? do you know what this is ? cheers Don
    are you a self appointed hypocrite sheriff or just a nasty person

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    Maybe the thin base layer of Zinc Chromate is reflecting better & outperforming the other dish.
    Cheers, Tiny
    "You can lead a person to knowledge, but you can't make them think? If you're not part of the solution, you're part of the problem.
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    Shit I always paint them in GLOSS Paint. I use normal house paint from bunnings and do them again (wet and dry them) ever 4 to 5 years. See they are GLOSS painted then semi gloss and after two year they are Saturn than MATT then after 3 to 4 years they become FLAT. The photos are about 2 years old so the dishes are Semi Gloss. LOL. Only had one year that they melted the LNB, LOL maybe I've been lucky



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    Cheers Guys,



    Thanks for your replies,

    I just wondered if there something to do with the elastizer in the paint, I doubt its natural latex. I can compare the two 1.8 Mt dishes, only one has the top coat but both are set up with dual LNBS so they can be compared just by swapping the C band LNB with the Ku. Unfortunately I don't have access to the test gear as I did in the work days.

    Don, I was not meaning so much noise as in the G/T of the dish more so the noise temp in the paint additive, as in the noise floor from an LNB when you point it at the sky then the ground. I had a dish near a fence back in the Aussat 1 days on the 12 watt epal transponders, I think the fence was well outside the fresnel zone. Anyway a creeper grew up the fence causing the signal to go down, ripping the creeper of the fence brought things back to normal.

    Likewise this 2.4mt, having the plate out of the hub makes no difference, but putting your face behind that hole has a noticeable effect on the signal.

    The fd is pretty similar with the 1.8 at .41 and the 2.4 at .38, the LNB has a 4 ring scalar so I don't think there's an illumination problem. Having said that I don't know how to work out what F/D the LNB scalar is designed for and its not mentioned on the spec, Any takers?
    Once a long time ago I had an ex link 3mt dish with and FD of .25? and it needed a special scalar which from memory had more rings and they were not quite so deep. A similar looking feed claims an F/D range of .335 to .425.

    In fact the 1.8 has a dual C band scalar in it with the Ku LNB mounted in it so effectively its a much bigger scalar and also more obstruction to the dish.


    I have an Invercom and a couple of Norsat LNBs with different feeds I can try but these are about stability with PLLs not high gain low noise, the Fuji "claims" 0.3. I had these same LNBs in the 3.5mt in the forum photo as well and they went very well.

    That 3.5mt dish is down right now as well, currently I am building a full precision computerized tracking hub for it and setting it up for moon bounce, Bit of a waste using it for TV!

    I don't think they would be interacting in this case, I have never had them both powered up at the same time, there is at least 3 meters between them and the 1.8 which is the better performer is setback a bit. But see what you think from the pix below. I can easily point the 1.8 the other way, and any suggestion is certainly worth trying.

    All in all why its under performing has me a bit miffed.

    Tiny, they all have the same base coats, just the 2.4 had the extra waterproofing coat, and I don't relish the idea of getting up there to remove it.

    Mr 672A that is a nice dish farm you have there, I doubt mine will every be that tidy but no one will know when they are 9mt off the ground on the back roof.

    I don't know what size the sun behind the satellite becomes an issue, but back when I had the ex link 3 mt mentioned it was pre Aussat days, we we using them on NBC from Intelsat with some sync recovery and a friend living in Wagga with one found if he pointed up at the link towers he could get TV from the Sydney/Melbourne links. He painted the dish with silver frost and came home one day to no signal, the LNA was a puddle of alloy on the bottom of the dish.








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    WOW.You must live on the very top of WA with that elevation.
    Not responsible for any post written after the 28/10/2014. My pet hate, Corrupt Politicians, Corrupt Legal System + a legal system Australia wide that does not allow you to sue a Solicitor or Barrister for Professional Negligence (as Stated by the Law Society and prominent Lawyers) and Corrupt Cops. Not necessarily in this order. Please Note Lawyers are PROTECTED SPECIES IN THIS COUNTRY, PROTECTED FROM THEIR F..K UPS

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    Nah, 100 points for observation but you don't have mangoes and roof tiles like that Nth WA. Polar mount declination is 1.2 degrees, read "was" not "west".

    BTW whats in your aviary?
    Last edited by hca; 03-06-20 at 06:09 AM.

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    Quote Originally Posted by hca View Post

    BTW whats in your aviary?
    We do Rescue birds from the RSPCA and Australia Zoo (Steve Irwin) and between October till April we get FLOODED with baby Magpies, Injured older magpies, baby Currawongs older injured ones and when they get older or better we let them go. Cost up around 3 to 4 thousand a year to do this and yet the Government give us pensioners NOTHING except a Bill for License each year to do this. We specialize in these two birds and every now and then we get a Special Magpie or a Currawong that is different that become humanised to a point that the bird finds its way back home after the bird has been released 5k- 10k up the road and come back. We have a Magpie that does this and 99% of the time it knocks on the kitchen window, we go to the sliding window and say "Emmy how was her day today" and she come inside the house and entertain herself in the kitchen whist she steels my lollies. at around 7.00pm at night when my Daugther does the washing in the Kitchen and my daughter goes to her bedroom the Magpie flys on her shoulder and she goes into the her bedroom and the Magpie plays in her room with the cat. We are all worries if we let her go like most morning that she wont come back because she is different and this is the reason why bird will pick on her and try to kill her.
    By the way, the Magpie rarely shit after 7.00pm, its in there DNA not to shit at night all because in the wild if a bird shits at night predators know this and find them and kill them
    Last edited by Mr 672A; 03-06-20 at 10:55 AM.
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    Good show, yes magpies are interesting birds, real characters some of them. On a couple of occasions in the past we have raised young ones that fell out of the nest, you know when ones down by they commotion the rest of the family make. I don't remember much trouble with local groups but they hung around the house for a while till they were older, a bit like the one you mention, in the house at any opportunity then I guess they found a mate and moved on. l seem to remember they were pretty good at painting things white but its rewarding activity when you see them succeed. A few injured Crimson Rosellas also but we never had any permits.

    Does not matter what you do there's always a permit and fee required, the agents of the Prime tax collector are everywhere and into everything.

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    So bit of a close out on this, I still don't know whats in this paint but its water based, elastic with polyester fibers. That makes it good on water proofing thin steel work like on the back of dishes. Seal up all the bolt holes ect to keep water out of tubulars and thin steel joints. On the surface, hopefully extend the paint life as well.

    After testing on 2 identical 1.8 mts solids with the same lnbs on the same birds, only one has the extra top coat of the water proof paint, I cant detect any performance difference on C or Ku bands.

    As for the 2.4 performance I am miffed, I can only assume its illumination and start making some test scalars for it.
    Last edited by hca; 25-06-20 at 06:44 PM.

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