Reshaping aluminum mesh

[colbec]

I picked up my first C-Band dish this morning. It is a used:

10 foot Channel Master dish, aluminum with al. mesh covering
Chapparal Eagle Aspen Turbo 120 LNBF
Superjack ZX H8 which I guess moves the dish
the whole thing was on a 4.5" OD post.

One of the 4 panels seems to be slightly sprung, with one broken alum. weld where a crosspiece joins one of the radial arms, not at the corners. I have tried a bit of repair work on this, but the mesh seems to have a mind of its own, springing back after I push it. I guess I don't know the right technique. I removed some of the screws that hold the mesh in place and got quite a bit done, but overall it is still not as smooth as I would like it to be.

Am I wasting my time on this? I want to get the experience at least of trying to put it together to prepare for next time. From other posts I guess my Coolsat will have a hard time controlling the LNBF?

I suppose it's better than a slap in the belly with a wet fish.

 

[starman345]

hehe, gotta be a fellow canuck Nothing to lose by trying. If its not warped its worth putting some effort into. Strngline the face of the dish, lip to lip with two strings that cross in the middle, that will give you a good idea, they should just touch.
No receiver came with it? You will need a receiver that puts out 36v to move the actuator. Lots of fun playing around with older stuff. I have a Coolsat 5000 too, I haven't looked but I think it has polaity control on the back, if you had a Vbox you could drive the dish with that but really an older c/ku receiver would be the cheap way to get started. You could probaby pick one up for free.

 

[colbec]

Thanks Starman, will do as you suggest. No box came with the dish, but I will check around. I was thinking I would set it up as a fixed dish first to check out whether I can get a signal from it.

The Coolsat 6000 does not seem to have a polarity outlet on the back of the box.

I am wondering if the Chapparal LNB will deliver a signal if there is no voltage applied to the polarity switch? I can get a DGC-223 LNB for about $35 which I think would be compatible with the Coolsat since it uses the 13/18V switching same as the Ku LNB.

 

[starman345]

I just checked my Coolsat 5000, no polarity control on that either, don't know what made me think it did Did you get the ribbon cable to connect the dish to the receiver? You can do without it but it is a handy all in one cable. There are two separate wires that send voltage to the polarotor, all it does is switch it from vertical to horizontal. You can still tune a channel without voltage to the polarotor, but you will be on one polarity only. Look down the feedhorn throat and you should be able to see a probe, the polarotor moves that probe 90 degrees when it switches. If its up straight, it will tune vertical signals, over sideways, horizontal. You can then choose a transponder to tune that is the same polarity as the probe is tuning. Have a look here for some good info on setting up a prime focus dish:
http://www.geo-orbit.org/sizepgs/tuningp4.html#anchor797917
Have fun and let us know how you are doing.

 

[colbec]

Polarotor has three wires, black-white-red, no ribbon cable. I'm guessing that the black is common wire (-) and red and white wires apply (+) voltage to move either V or H. I will see if I can find what voltage is expected and see if I can get it to move.

Looked down the feedhorn throat, I see a shiny U-shaped hook which I guess is the probe. With the blue cover of the polarotor straight up the probe is over at an angle of about 75 deg from vertical, so it is more horizontal than vertical but I would prefer to see it at 90 deg or 0 deg. Does not look good.

I'm now thankful for all that time playing with Meccano as a kid. Is this not a wonderful learning experience?

 

[turbosat]

Ive heard of taking out the mesh panel and putting it on a flat surface like concrete floor, and using a rolling pin or piece of pipe to roll over it, to straighten it out. That's if you can take the panel completely off I suppose. Some dishes have it screwed down, others just slide the panel into grooves in the dish's 'ribs' so its only fasten at the ends.

 

[starman345]

The black wire is gnd, red is +5V, white is pulse, just looked at mine. I think the red +5 moves the probe and the pulse tells it how far to move.
LIke Turbosat said, you can pound or roll out most panels, I've seen some people years ago who watched their system with panels missing and saying they didn't notice any difference, thats probably an exaggeration but having a few bumps, dips on the surface of your dish probably won't matter too much.

 

[colbec]

Thanks Turbosat and Starman, I will be trying the roller on the floor technique, it annoys me to see the rolling countryside on the dish as it is.

I tried to take the polarotor apart, looks like it has had a water attack, rusty bolts that are impossible to remove. I think it is toast. I will be dreaming up an alternative method of rotating the probe, even if I have to do it by hand. I assume that skew applies to C-Band just as Ku?

The rest of the lnb looks ok, reasonably dry inside, but quite a bit of white salty looking deposits that can be cleaned off with a toothbrush.

I am hopeful, will let you know what success but I think I will hedge my bets by ordering a new LNBF.

 

[dfergie]

Take the servo motor off (after tapping on the back of the screwdriver a few times to maybe help bread loose the screws) and see if the probe moves (should be what looks like a big standard screw head about dime sized underneath)

 

[linuxman]

Be careful not to touch the probe in the feedhorn or the probes on the LNBs with your fingers. The acid on your hands can corrode them and cause them to malfunction.

The white powder won't affect the performance, but you can clean it off if you like.

Dfergie's suggestion is a good one. The servo motor is pretty inexpensive. Should be able to get a new one for around $10.00, but you have to get that one off without twisting off the screws.

 

[dfergie]

The servo motor is pretty inexpensive. Should be able to get a new one for around $10.00, but you have to get that one off without twisting off the screws.

Did that to a co-rotorII last fall...

 

[colbec]

dfergie: It was easy to remove the motor from the lnb, and I can move the button (which is connected to the probe) that the servo motor is intended to move very easily. No problem there.

It is the tiny screws in the servo motor that are the problem. There were drops of water inside when I removed the motor from the lnb, and two of the tiny screws will not yield. You can only put so much pressure and twist on them. One that I did manage to get out was extremely long for its diameter and very stiff right up to the last millimetre of extraction.

What is perhaps more to the point with the servo motor is that I don't have a ird which can send it intelligent signals. So at this point anyway I am better off without it, and perhaps should find a manual way of setting V and H.

linuxman: spring has failed to arrive up here; the last time my fingers saw a drop of sweat was about 6 months ago... but thank you for the sage advice...

 

[dfergie]

My first BUD came with and still has (unhooked) an OTA antenna rotator, that was how I changed polaritys with my first system...

 

[linuxman]

spring has failed to arrive up here; the last time my fingers saw a drop of sweat was about 6 months ago...

I know how that is. We had spring once here. In the 70's and 80' for two weeks in March. The first of April we have had several nights down in the lower 20's and highs in the 30 - 40 range. It has been colder on us the last two weeks than all winter because we had already had gotten used to the warmth. Supposed to come back tomorrow.

Defergie. I hadn't ever thought of doing something like that. Anything that turns the probe will get the job done.

 

[dfergie]

Yeah I have a handcrank (should have stored as I could use it now) the antenna rotor a 120k LNA and the receiver had a Knobs to tune signal and audio and a signal meter ...