Cooling the LNB

hexah

hexah

Specialist Contributor
Messages
2,388
Likes
491
My Satellite Setup
motorized Gibertini 85cm, fixed dishes from 1m to 64cm, generic FTA HD RX, TBS DVB-S2 PC card, a pile of bits and pieces
My Location
Hadrians Wall
#61
BombedOne said:
Hehe :)

Let me share my achievement in this area:

Liquid nitrogen: Does not worked
Reason: I applied it too rapidly, LNB cracked in middle and cable went into dust-like condition in about 4 seconds. Then I ran out of liquid nitrogen.
Did you make a video of this? :cool: O-Ha
 
Analoguesat

Analoguesat

Administrator
Staff member
Messages
46,028
Likes
8,550
Location
Scottish Borders
My Satellite Setup
TM 5402HD
Skybox F3
Sky+ UK.
My Location
Scottish Borders
#62
The liquid nittrogen idea is interesting. However rather than full immersion I would think that with a suitably insulated enclosure you would be better off with a pool of nitrogen under the lnb. You will get lots of cooling without full the thermal shock of immersion
 
D

dreadnutz

Member
Messages
7
Likes
23
My Satellite Setup
Directv DVR
My Location
Kingston
#63
I know I am bumping a very old thread but I just wanted to make sure this info is archived for the future experimenters out there.

First of all let me start out by saying I tried cooling of the LNB and it does work!
Unfortunately it is totally impractical to try this on the hobby level! And ended up costing me about 50 hours of work over a two week period and was one of the most frustrating endeavors of my life.

About 5 years ago I dumped about $1000 USD into this DIY project based on this threads info in order to see if I could bring up the signal on some transponders that would drop out in the summer months.

My first test involved cooling the LNB with DRY ice and I had some really good results. QC levels on those dead transponders rose up from zero to levels that made them usable, but of course the joy only lasted for a short period and as the ice went down the signals went, but it was proof of concept that gave me a lot of excitement and made me go to unbelievable lengths to make something that would work on demand.

I started by ripping off the plastic shroud around an LNB and wrapping the metal body with copper tubing used in AC work, I also used thermal paste to enhance the contact of the metals. I installed a small temperature probe near the coil and ran the wire out. I then covered the whole thing over with insulation tape so as to keep the cold in. I was actually able to Dremel out enough of the plastic LNB case holder bits that I could get the case back on and close it back to it's original form and sealed it with epoxy. The two copper tubes came out of the LNB, one was the full size tubing and the other was the very fine tubing used as an expansion valve to carry the liquid in an let it expand into a gas in the tubing wound around the LNB.

The next thing was to build an AC compressor system and using I think it was a 1/4 HP compressor designed for R22 gas and bought the condenser assembly along with a cooling fan and wiring, dryer etc. I made a case out of sheet steel and the platform base was drilled and brackets etc installed. I then welded everything together and then using about 20ft of copper tubing sheathed in insulation I welded it onto the tubes coming out of the LNB.

First test resulted in mixed results. I could only get down the temperature to about -5C deg with an outside ambient temp of about 29C. I consulted a friend in the AC business and he said the evaporator coil was way to small in the LNB and that I would need either much more tubing or I could use a "expansion tank" at least I think that's what it was called. Basically a canister that held about a quart in volume that was inline with the gas to hold more of the gas.

I added the tank into the system and was able to get down to about -15 deg and started to see some of the better transponders start to tickle the receivers meter, but still no real success. and I aborted after 15 -20 minutes.

I talked to my friend again and he said that I could use a hotter AC gas but it would damage the compressor in a few weeks as it was not designed for that Gas. I do not remember the number of the gas but at the time I thought why not, if it works I will just buy the right compressor for the job.

The third test:
I fired up the unit with the new AC Gas and the temperature came down to -30C and the transponders all started to kick in! Myself and a friend who was helping got out the beers and started to celebrate. Then about 20 minutes into the operation the signal started to drop even though the temperature was still at -30C !! We shut her down and and started to check a few transponders that normally had a good signal and we saw Zeros across the board!

The Autopsy:
During the time the LNB was operating we did see water dripping off of the case but figured that all was well as the LNB's electronics were sealed tight. So I pulled apart the LNB and noticed removed the insulation, the tubing and cracked her open only to find water condensed all over the circuit board.

The Fourth test:
Using a brand new LNB I modified the hell out of the sealing system. I then packed drying bead pouches into any free space I could find and then I buttoned her up and wrapped back the coil and put everything else back into place.
We fired her up and we got a signal and it lasted for about 30 minutes and then it slowly collapsed again.

The Fifth test:
I decided to go Nuclear with solving this condensation problem. My first thought was filling the LNB with nitrogen gas and having a line that kept some positive pressure from a small nitrogen cylinder on the LNB so as small amounts of gas escaped over time the tank would keep a small amount of pressure to keep air from getting in.

I drilled a hole into a new LNB's metal case and threaded it and added a line connector that could be run to with a very thin 2mm tube to a regulator on a gas cylinder. This all ended up being for naught as it was impossible for me to regulate the pressure down that small. I kept blowing off the LNB's front cap and eventually abandoned the idea.

I moved onto phase two which was to use an expensive variable fish tank pump to move air through about a quart of drying beads in a clear plastic cylinder. I used a very accurate electronic pressure switch to turn on/off the pump. The output from the drying beads would go to the same Nitrogen line and push dry air into the LNB as small amounts of air leaked out. I left the pump system running and every 30 minutes or so the pump would click on for a second or two. I left this going for about 2 days to make sure the air inside the LNB was as dry as a bone!

The Sixth test:
I fired up the system and low and behold with a few minutes the signal came up as expected. I sat there watching a small TV next to the dish monitoring all the parameters. I got past the 30 minute mark and things were looking good, I got to the one hour mark and I was ecstatic! Then I started to notice that water was dripping off the LNB's body at an accelerated rate. Soon water was all over the front dome and at the same time I watched in horror as the signal just started to drop and drop. I would wipe the front and the signal would come back up but within minutes condensation was everywhere and the signal would drop again.

The Seventh and final Test:
At this point I came up with the idea of using a hooded 2" high speed muffin fan to blow air over the LNB's plastic dome in order to keep the water from condensing and to hopefully blow it off and dry it off faster than it could gather.

I fired her up again and it worked :) One hour passed then two and she kept on going. Then after about 4 hours the signal slowly started to go down :( After about 15 more minutes it winked out of existence and my heart sank.

The Final Autopsy:
I pulled the LNB apart and as expected I found small amounts of water had condensed on the circuit board. At this point I gave up and shelved the project

Conclusion:
Anybody who is going to try this I want you to know that it can work but your going to have to use a Nitrogen filled LNB and your going to have to make sure that there is no way for the gas to escape or your going to have to keep it pressurized with a much more complicated system than I used. Also the humidity is going to cause a crap load of water appear everywhere, even things like the RG6 connectors need to be properly sealed with silicone etc.

I know they have commercial units that do this kind of thing but they use wave guides and the LNB's are indoors in sealed compartments. I hope this helps someone out there that might want to try this, you can learn from my mistakes and hopefully get around the problems.

RJG
 
D

dreadnutz

Member
Messages
7
Likes
23
My Satellite Setup
Directv DVR
My Location
Kingston
#64
BTW I should add that the dish I was using at the time was a Prodelin 1251 (2.4M) offset feed dish.
I could never afford the price to move up to a Prodelin 3.8M dish so this cooling method was the best option at the time.
I finally acquired a 3.8M Prodelin for a very low price about 4 Months ago.

The 3.8M offset had been sitting for 5 years in pieces on the ground in a guys backyard. He had bought it from a commercial property and in the dismantling stage they dropped one of the petals from 15ft up and cracked it badly. This on top of other fiberglass damage plus his surprise at the 1500lb weight and bulk of the beast made him give up on installing it so he just left it where the truck had dropped it off on his property. I came along got it for cheap and spent almost 60 hours over a 2 month period restoring it to almost brand new condition. Now I am happy to say that I am picking up all the channels that I have been missing for years.
 
PaulR

PaulR

Dazed and Confused Admin
Staff member
Messages
15,918
Likes
3,162
My Satellite Setup
-----------See sig-----------
My Location
Wirral, NW UK and Vaucluse, France.
#65
That's a fantastic story; thank you for taking the time to post it.
 
M

moonbase

Mini Dish Man
Messages
1,921
Likes
1,724
My Satellite Setup
1.25m Unicorn
My Location
UK
#66
BTW I should add that the dish I was using at the time was a Prodelin 1251 (2.4M) offset feed dish.
I could never afford the price to move up to a Prodelin 3.8M dish so this cooling method was the best option at the time.
I finally acquired a 3.8M Prodelin for a very low price about 4 Months ago.

The 3.8M offset had been sitting for 5 years in pieces on the ground in a guys backyard. He had bought it from a commercial property and in the dismantling stage they dropped one of the petals from 15ft up and cracked it badly. This on top of other fiberglass damage plus his surprise at the 1500lb weight and bulk of the beast made him give up on installing it so he just left it where the truck had dropped it off on his property. I came along got it for cheap and spent almost 60 hours over a 2 month period restoring it to almost brand new condition. Now I am happy to say that I am picking up all the channels that I have been missing for years.

Well done, both with the LNB cooling project and with the 3.8m Prodelin dish restoration project.
If you have any pictures you feel OK with sharing that show your Prodelin 3.8m installation they would be very welcome?
 
D

dreadnutz

Member
Messages
7
Likes
23
My Satellite Setup
Directv DVR
My Location
Kingston
#67
I have very little left from the cooling project. Most if it got dumped. I know I have the air drying system as I left the utility box it was in on the pole and even transferred it to the 3.8m dish in case I needed an extra electrical box.

I will try to take some pictures of the drying system and the dish on the weekend.
 
D

dreadnutz

Member
Messages
7
Likes
23
My Satellite Setup
Directv DVR
My Location
Kingston
#68
OK folks I took some pictures. I looked around to see if I still had the LNB and found nothing. I must have dumped it when I dumped the compressor unit. Both had been sitting outside under some plastic covers and had taken a real beating from the weather. Funny enough I just dumped them four months ago when I was trying to make space for the 3.8M dish project. I am now really upset that I did not at least take some pictures.

So here is where the Drying unit is today, on the pole of my new 3.8M dish. It is inside my second utility box which I put up in case I ever needed space for more equipment. I took these pictures today in case it ever gets gutted and the parts thrown out.

Keep in mind this was a PROTOTYPE! If something works I typically rebuild it to fix issues and make it more Durable.
The box at the back is the drying system

Cooling the LNB_1063403


Cover removed! Excuse the mess but this has not been touched in 5 years.
Cooling the LNB_1063403


Inside the Unit:
Cooling the LNB_1063403
Operation is fairly simple.
The Aquarium pump I bought has variable output. At top of the drying beads is a T connection, One side goes to a solenoid to shut off any air from escaping and then it goes to the pump. The other side goes to a tunable pressure switch at the bottom right. It that can detect small changes in air pressure. The pressure value is done using the knob in the front of it and allowed very small amounts of positive pressure to be set and detected.

The output of the drying bead cylinder goes directly to the thin hose that connects to the LNBs internal case. If pressure drops in the hose as in the LNB leaks out small amounts of air, typically over a 30 minute period the pressure sensors diaphragm flattens and activates the internal switch which then turns on the pump and solenoid and blows air into the drying bead chamber and out to the LNB. Once the pressure is correct (1-2 seconds of pumping) the pressure switch shuts off the pump and solenoid.

Another Angle:
Cooling the LNB_1063403


Dry Air Output and Cooling system exhaust
Cooling the LNB_1063403


Cooling Fan:
I had originally made my first prototype used two high powered Peltier devices. So I used a Power supply I had lying around. Peltier cooling was a complete waste of time as I could never get the LNB even near 0c on my bench desk. So it was ditched but I used the same power supply and had already built a cooling tower to pull out the hot air that rose to the top.

Cooling the LNB_1063403

I wish i had more parts of the whole system to show you guys. Had this worked the next step would have been a much larger air drying cylinder which I had already built and still have. The power supply would have been removed in favor of a smaller unit.

I took a lot of pictures of the 3.8M Prodelin restoration. I am going to create a separate thread for that in the coming days.

RJG
 
Channel Hopper

Channel Hopper

Suffering fools, so you don't have to.
Staff member
Messages
25,969
Likes
5,881
My Satellite Setup
A little less analogue, and a lot more crap.
My Location
UK South
#69
Very nicely done, nothing I created was designed to be housed in its own bespoke case.

The problem with peltier devices these days are the false claims by the suppliers. One of my business contacts ran up quite a few imported samples recently and found the power/temperature curves were as much as 200% off, meaning his project (for the cooling of DC motors in scale model vehicles) was a non-starter.
 
D

dreadnutz

Member
Messages
7
Likes
23
My Satellite Setup
Directv DVR
My Location
Kingston
#70
Very nicely done, nothing I created was designed to be housed in its own bespoke case.

The problem with peltier devices these days are the false claims by the suppliers. One of my business contacts ran up quite a few imported samples recently and found the power/temperature curves were as much as 200% off, meaning his project (for the cooling of DC motors in scale model vehicles) was a non-starter.

Yes they are certainly not the miracle device so many people think they are. The best application I seen them used for is water coolers for drinking water. Their power usage plus their lack of ability to sink any serious amount of heat makes them pretty much a disappointment for most applications. I also checked mine against the manufacturers graphs and found them to also not be as efficient as stated, but they were cheap enough to give it a try.
 
Channel Hopper

Channel Hopper

Suffering fools, so you don't have to.
Staff member
Messages
25,969
Likes
5,881
My Satellite Setup
A little less analogue, and a lot more crap.
My Location
UK South
#71
I have a storage box using peltier strips down the side of the compartment. Designed for transporting hot or cold food in a vehicle (12 and 240V sockets) it works better than I expected, but it is around ten years old. Quality control and unbranded supply from the Far East is probably to blame for the indifferent performance with today's devices.

I didn't experiment with peltier when I was testing cooling of head end equipment since I already had the fridge compressor and radiator, but I would certainly look at ripping out an older component rather than a modern mail order item.

The Vapochill link I provided a decade ago is still accessible using the wayback machine, though it does look like the company is no longer selling them

http://www.asetek.com - VapoChill LightSpeed [LS]
 
Top