Please Help with LNB / Feed Assembly / DMX241 or Original? - On the roof now...

[signal.quest]

Please help me answer the following questions:

-How can I set the skew on the DMX241 while the dish is not at the APEX? It is on my roof and not possible for me to access the LNB while the dish is at the APEX.

-Is the DMX241 better or easier to setup than the original Eagle Aspen General Instrument Feed Assembly? (See pics)

-I mixed and matched the ring from the original assemble and installed the DMX241 in it. Does this look correct as far as how the arms are attached?

Trying to get this project done so I can watch some stuff this weekend. Thanks!

 

[FaT Air]

pic is worth a thousand

 

[FaT Air]

Align the F/D mark to the flat surface of the scalar. the scalar should be on the dish side of the plastic cover ring. Use the 241 .

 

[signal.quest]

Thanks. Is it ok to use the scalar ring from the original assembly? Or should I use the one from the DMX? I see from the drawing and other pics that the arms from the dish should go on the outside of the scalar ring? Is that important?

 

[FaT Air]

That's the normal place for them, the arms. If the scalars are the same design and the dimensions are close, can't see why you couldn't use the original. But according to the pics, the bolts look pretty rusted, and disassembly may break some, may as well change it to the new. From dish side, scalar - arm -- cover ring. Use new bolts, and any furure work on it will be easier.

Edit: just saw your other post http://www.satelliteguys.us/c-band-...1-help-identifying-model-10-perfect-10-a.html Disassembly is required as the scalar is backwards and on the wrong side of the plastic ring.
Reassemble correctly, measure F and D, Set LNBF to F/D. Should see a big improvement.

 

[signal.quest]

Please let me know how this looks. I think I understand the skew and F/D now. I still want to make sure that I have the rest 100% correct. Please see the attached pics. I was going to use the nose cone. Is that a good or bad idea?

 

[FaT Air]

Turn the scalar and the plastic ring around. The dish should see the grooved side of the scalar with the plastic ring behind the scalar.

 

[signal.quest]

Ok. Thanks. In process of flipping it around. It looks like the arms need to go before the plastic ring for the cone. Is that correct? Is the nose cone worth putting on?

 

[Lak7]

Run it naked, loose the plastic ring too.
I cut up an empty clear 2 Liter bottle as cover.

 

[signal.quest]

Ok, here is where I am now. Please keep telling me how it looks. I used the outter holes on the scalar for the bolts and slid the arms as tight as they would go to ensure it was equal on all 4 sides. I tried to eyeball the skew mark on the LNB and line it up with the arms of the dish. Not sure if the arms are a good indication of top and bottom though. Please see pics. Thanks for the continued help. This forum is the best!

 

[Lak7]

I used the outter holes on the scalar for the bolts and slid the arms as tight as they would go to ensure it was equal on all 4 sides.

If it were only that easy.
You "must" measure, there is no easier way.

 

[signal.quest]

If it were only that easy.
You "must" measure, there is no easier way.

Measure from the screw holes to the edge of the dish? I also have a green laser pointer - will that help determine if the LNB is looking at the center of the plate?

 

[FaT Air]

Measure from the center bottom of the dish to the scalar(F), Then across the face of the dish, edge to edge. Calculate F/D, and set that mark to the rear flat surface of the scalar. It appears that the skew is very close. I think, it looks like, the polar axis is about 45 to the upper right, lower left, so mark should be half way between.

determine if the LNB is looking at the center of the plate?

Definitely! Give it a go, and see is that improved the performance.

 

[signal.quest]

Day 2 is over and I am still not up and going. I am now getting less channels than yesterday. I am hearing SATs on the ARC with my meter, and seeing some transponders, but I am not getting any channels to show up on the traxis 3500. I am doing an AUTO scan on the traxis for the SAT it thinks is 72W, however I am sweeping the ARC doing AUTO scans when I hear high pitch squeals from the meter. Please help. My wife is starting to ask me to how much more time will I be wasting on it...

 

[FaT Air]

I's Auto scan the same as BLIND scan? I don't know. What other options for scans are there?
Edit, found manual. Auto scan is Blind scan. The other question is : Now when you move the dish to zenith, will that skew mark be horizontal? What is your calculated F/D? Are the channels you do get, are they all the same polarity?

 

[signal.quest]

Thanks for hanging in there with me on this... On the DMX241, I made sharpie mark extending the 0 degree line across. I don't know if it is correct when at the zenith. I will try to look tomorrow. Here is what I calculated for the FD. The D is 121.5". The F is 40.25". The F/D is 0.33. I lined this up accordingly. I also measured each arm to be of equal length. I only got one channel and I don't recall the polarity. I moved the arm back to the west side before doing any of this. I noticed that when the dish is at it's zenith the arm is almost fully extended. Does this make sense?

 

[FaT Air]

The arm fully extended when at zenith, wow! Should have 18 or 24 inches of extension available(depending on Model) Mine measures 13 (of 24) at zenith. Might be the actuator is somehow mounted too far behind the pole. Did you adjust the actuator mounting, with it fully retracted?
I have another thought about the feed. Put a string across the face of the dish, across the center. Measure the distance fron the string to the bottom center of the dish. Calculate Focal Length, D(dish diameter) squared, divided by 16 times the measurement. This will be only close to ideal as there are variables we cannot control, but should be close enough to get C band fairly well. (Page 3 BUD Manual) Reasoning, Are the arms really original to that dish? Being the scalar was on backwards, what else was assembled wrong or with parts from another dish(?)
Pics ore worth thousands.

 

[signal.quest]

I will post a pic of the actuator and mount tomorrow. I did not adjust the actuator - is the adjustment on the actuator or the mount point? Maybe something is wrong with actuator... Back to the feed problem. Do you think it is skew, FD, or something silly like bad coax or LNB? I wish I did not have to remove the actuator to get to the LNB.

 

[FaT Air]

I think the skew adjustment is OK. I think it may be a focal length issue, putting the string across and measuring the depth below the string, Doing the math, will shed light on that.
There could also be an issue if you're only getting one polarity. My DMX241 likes a lower voltage than what my 2 Pansat's and the Openbox put out for the 13volts. The other polarity with 18v is fine. (This would be confirmed if a Blind Scan gets the same channels on both polarities and missing the known channels on the other polarity. I have a LOW TECH solution I'm using.)
The actuator-- it's where on the actuator tube mounts to the immovable pole or mount, You'll notice on mine, the actuator is mounted to the pole only about 2 inches from the end where the extensible part retracts into. that will allow the dish to go quite a bit east (55W is extended about 2 inches) and full extension(24 inches) will more than aim it at 140W. Another thing is if it's mounted too close to a line that extends from your true south through the pole. It should be offset from the pole, to the side you have the actuator on.
LightBulb-- Did you say you have a meter, and when you had an indication on the meter, a blind scan didn't get anything?? Scrambled or FTA? This suggests you may be loosing signal between the meter and the receiver(cables,splices,switches,connectors?) or might be something with the receiver.(programming?) Ku operation is OK ?
3 pics, just because i can.

 

[signal.quest]

Tomorrow I will send pics of the actuator and the mount. It looks different than yours. I am going to check for bad crimp and bad cables too. I will also do the string measurement. I need to return the scaffolding soon. I am paying like $25/day for it. My friend told me I should build a roof platform out of plywood to reach the LNB without taking the actuator arm off. I am going to try the east side again to see if the LNB is within reach when the actuator is fully retracted. If I have to remove the actuator - Is there something I can use (or make) to keep the dish from flopping over when I remove the actuator?