91W Eclipse of the Sun

[equant]

I'm sure this has been discussed before, but I found it interesting. I was watching 91W, everything is great. Then the signal starts to fade, and I lose lock. I look outside, no wind... I check Arts NTSC, it's still there, but getting worse. I try adjusting the satellite a bit west, then east, Arts goes out completely. I decide to see if there's a pigeon on my LNBF and when outside I notice that the shadow of the lnbf is in the very center of my dish.

By the time I'd figured out what was going on, and went back inside, the signal was starting to work its way back up.

I'll forgive the sun this time.

 

[i4tas]

your title says Eclipse which got me thinking...

has there ever been a solar eclipse around the equinox time of year. If so, then the area inside the eclipse would avoid the solar outage for that period of time?

 

[AcWxRadar]

Equant,

Oh yes, this is a reocurring phenomenon in both the spring and fall. It is actually a very useful tool, in fact. As you can easily detect if there is any obstruction in your LOS by following the sun at the appropriate date and time and can aim or locate your dish accordingly.

There are calculators which will tell you when the sun is in perfect alignment with the satellite in question.

For your location in Tuscon, in a few days, you won't notice the signal loss as the suns arc will move out of the way of the satellites arc. You will see this again next spring, in March between the 3rd and the 10th right about 11:03/11:04 am MST or right about 12:03/12:04 noon MDT. These are when it should be a peak outage, but your signal will begin fading out about 6 minutes before this.

Folks with offset dishes won't normally notice this signal outage as bad as you will with a Prime-Focus dish.

Pretty cool, eh?

RADAR

P.S. Ensure that if you have a solid panel C-Band dish, that you don't paint it white or silver. The dish can reflect enough solar radiation (infrared heat) and other radiation to actually melt your LNA/LNB

 

[FaT Air]

There are calculators which will tell you when the sun is in perfect alignment with the satellite in question.

Sun Outage Calculator
My solar effects will be seen Starting 10/07/2010 @ 8:21:15 am (30W)
and Ending on 10/14/2010 - 4:12:11 pm (137w)

 

[geekt]

Equant,

P.S. Ensure that if you have a solid panel C-Band dish, that you don't paint it white or silver. The dish can reflect enough solar radiation (infrared heat) and other radiation to actually melt your LNA/LNB

I wonder if there's any type of paint that won't reflect most solar radiation as much as the sat signals. That would be cool.

 

[Vorg]

Just a thought, while most think black is the hotest color absorbing the most, it's not. Green is.

 

[stanleyjohn]

This has been the week where the sun follows the arc where im located and YES!!! looks like it will be many years before any trees will be blocking my LOS from 30w to 137.

 

[Mikhel]

Just a thought, while most think black is the hotest color absorbing the most, it's not. Green is.

Cool... so Kirchhoff's law is wrong and now we should say "greenbodies" instead of "blackbodies" while talking about albedo and all that stuff =)

M.

 

[geekt]

Has anyone noticed if there is a signal increase with painting a dish a color that is less reflective? I would think logically, if a color reflects less sunlight, it should have less solar interference. This would of course not be true if the paint also absorbs more radiation from the spectrum you are trying to receive.

 

[B.J.]

Has anyone noticed if there is a signal increase with painting a dish a color that is less reflective? I would think logically, if a color reflects less sunlight, it should have less solar interference. This would of course not be true if the paint also absorbs more radiation from the spectrum you are trying to receive.

Just my opinion, but I don't think the "sunlight" is the issue, or at least it's a minor component of the issue. The solar outages are mainly caused by interference from the same freqs as your sat signals. Solar radiation basically includes ALL freqs, not just visible light, so it's hitting your dish with freqs in the sat bands. So if you did make the dish less reflective to those freqs, you'd also make it less reflective to the signal you want. Of course, the sunlight portion of the spectrum could be an issue if the dish was reflective enough to heat up the LNB, but as mentioned, unless you paint your dish with a mirror finish, that's unlikely to happen.

 

[geekt]

Yeah, I know sunlight's more than just visible light. Ever notice how sometimes you can still get a sun burn on a cloudy day? I would just think the less radiation bombarding the LNB outside the spectrum you are trying to receive, the better.

 

[AcWxRadar]

Just my opinion, but I don't think the "sunlight" is the issue, or at least it's a minor component of the issue. The solar outages are mainly caused by interference from the same freqs as your sat signals. Solar radiation basically includes ALL freqs, not just visible light, so it's hitting your dish with freqs in the sat bands. So if you did make the dish less reflective to those freqs, you'd also make it less reflective to the signal you want. Of course, the sunlight portion of the spectrum could be an issue if the dish was reflective enough to heat up the LNB, but as mentioned, unless you paint your dish with a mirror finish, that's unlikely to happen.

As I understand it, expressly with a prime focus dish, the background noise from the suns radiation simply overpowers the signal from the satellite and drowns it out. Just as you have stated, B.J. It raises the noise floor and the signal cannot emerge or be detected.

Painting the dish with a color that reduces the infrared spectrum will reduce the heat build up at the LNA/LNB, but won't necessarily reduce any other signal reception.

My older brother did a lot of C-Band (BUD) installations many years ago (in the 70's), and he told me about this phenomenon regarding people painting their dish to match their home (usually picking white) and then complained about their equipment failing twice a year.

I doubt that the paint color has anything much to do regarding the actual radio signals from the satellite being stronger or weaker. It is more related to how much heat is reflected and focused from the dish to the equipment.

Obviously there is something here as you can make aircraft paint to absorb or reflect RADAR waves, but I don't think that has so much to do with pigment as with other things in the paint.

RADAR

 

[geekt]

I also read that when an LNB is colder, it can increase the signal. This might not be effected much by the feed aperture, but rather the electronics, however it would still be interesting if anyone has ever looked into it.
Mentioning that radar paint. That might be something else to look into, as I believe some of the Ka band is used in RADAR. Correct me if I'm wrong.

 

[pedrogarcia]

I have a 3.8m prime focus in Cyprus and I can confirm it is related to heat. In fact I have a 3mm water feed from the irrigation system that drenches the LNB casing to prevent this. This might seem overkill but when it happens 6/7 minutes at a time during the world cup soccer series it became more important.

 

[hd fan]

Pedro García, your Satellite Highness LOL, after being a firm and devote beleiver of every single post of yours on this forum shortly after I started reading daily here, this morning after I read your last post those set of beleives were shaken heavily but being a mixed of an atheist-blind follower of your ideas I decided to put them to the test myself since coincidently we are on sun outage season. So at 11:10 am this morning I parked the dish on 55.5W and waited for RTS or Canal 4 or RTPi to fade away and they did as expected. So I went outside and using the garden hose with if not the coldest water at least one of the most cold ones you could find on this lands (I name it Sun Outage-Holy water lol) I literally flooded the Dish and the LNB for a few minutes expecting a miracle (that the signal (C Band) would comeback) but as predicted by the Satellite Communications theory it did not. It is not the heat per se, it is thermal noise or if you prefer frecuencies on the same C band coming in from the Solar activity or within the Solar Radiation. It does not only have to come from the sun to interfere with the sat signals though, the perfect example was my Hispasat dish installed on the ground just inches away and looking very low as you know. Guess what?, last summer as a result of intense heat during 1 or maybe 2 consecutive weeks, I lost all H signals on that bird while all the V worked fine. At the beginning I thought it was related to the LNB or something else but it turned out to be the extreme heat those days creates a heat wave on the sorrounding grass and surfaces (kind of the ones a road creates on its surface so it distorts images in the background) so it effectively generates thermal noise in the ku band in the H polarisation only apparently. When the heat went away the signal came back by itself with good CNR and quality numbers as before on the birdog.

I had nothing better to do and the garden needed water anyways but now that I think about it , woudn't the thin water layer on top of the dish surface reflect more visible light and therefore heating up the LNB even more? If so, good thing the cold water was also on the LNB then.

 

[Mikhel]

I doubt that the paint color has anything much to do regarding the actual radio signals from the satellite being stronger or weaker. It is more related to how much heat is reflected and focused from the dish to the equipment.

Yup, something i've seen in Mexicali, Baja California (México) where temperatures range in the 115°F-120°F in any given summer afternoon. Infrared radiation gets so high that equipment fails, i mean i've also retired coax cable toasted, literally toasted, after just a year exposed above roofs (those times the roof had shingles that get mighty hot).

M.

 

[geekt]

LOL! I think he was confirming that keeping the LNB cool can increase signal. If you REALLY wanna prove this, get any cheap LNB you got laying around, take off the cover, mount it, point it at a sat, and then spray a can of compressed air on it. Watch the signal rise as the LNB cools.

I fantasize about modding an LNB with a custom enclosure, a peltier cooler, and a heatsink.

 

[pedrogarcia]

HD I am only cooling the LNB, around solar outage ( used to be around 9 minutes on 26E for me) there is little you can do against solar radiation. however at this time when using large dishes and the ambient is around 110f at outage in direct and reflected solar heat the LNB goes out of manufacturers range specification. A temperature probe showed my Invacom QDH 31 metal case to be 174f at that time. I found that cooling the LNB allows me signal with virtually no outage but some degredation.
There is no measurable signal gain to be achieved in cooling. I can't imagine your location would suffer these temperatures so you are right just water the garden. LOL

 

[hd fan]

Ok, back to the praying position then , lol. I completely and foolishly misunderstood your last post then since I thought that you had found a solution for the Sun outages that I had never heard of before and obviously being in good humour that morning I decided funninly to challenge your theory in my last posts. Obviously the use of religious content or words was not and will never be intended as an offensive means rather than just a way to fool around or joke about something else.

I will try though , with the birdog SA today, to see how much the noise floor raises during the Solar Outage and see how rapidly the CNR degrades as well as making sure the shadow of the LNB is dead center and other stuff but without looking at the sun this time!!!, lol.

 

[pedrogarcia]

Obviously the use of religious content or words was not and will never be intended as an offensive means rather than just a way to fool around or joke about something else.

I will try though , with the birdog SA today, to see how much the noise floor raises during the Solar Outage and see how rapidly the CNR degrades as well as making sure the shadow of the LNB is dead center and other stuff but without looking at the sun this time!!!, lol.

No offense taken I enjoyed your post.
I think I made the mistake of inferring I had found a solution to sun outage when actually I was found a solution to solar heat not solar radiation.
Interesting you have a birdog 4 or USB, I think do you use the Spec analyser for fior tuning. Reason forthe question got one this year to save me carting my Satlook to and thro and I've just got used to it but am unhappy with the SA.