hh120 fs120 cm dish aiming question - like a c-band dish align???

[skysurfer]

It's been awhile since I installed my HH120 with a 90cm ku offset dish on it.

With the upgrade to a 120cm dish, I had to change elevation but I kept everything else (the dish mounting bracket alignment on the HH120 motor since I used the 90cm mounting bracket with the 120cm dish since they were identical) and I kept the hh120/dish to the mounting pole alignment since I didn't have to remove the motor.

I peaked elevation for center sat (0 position on HH120) and it's awesome (12 db signal/noise on my due south sat ku peaking reference dvb-s mux). On AMC-21, not so much (about 8.2 db on my reference PBS mux) so very disappointing. When I push up on the dish to increase elevation, signal level rises quit a bit so it tells me the arc falls off at least on the west end. I don't know where I stand on the east end yet as to whether I'm high or low of the arc on that end.

My HH120 motor elevation adjustment is correct for my latitude since I checked that setting. Can I pretend this is something like a big backyard dish alignment and assume my FS 120cm N/S axis is a little off and go to an extreme sat and loosen the bolts holding the dish to the HH120 tube and rotate it for maximum signal strength, and then go back and forth between 0 position and extreme sat position and work on getting the N/S axis set so that the arc has great signal throughout?

 

[Lak7]

Check an Eastern Sat first.
Is the Dish bolted through the Motor Tube?
Possible the Motor needs a North / South adjustment?

 

[skysurfer]

Check an Eastern Sat first.
Is the Dish bolted through the Motor Tube?
Possible the Motor needs a North / South adjustment?

the dish is bolted to the hh120 motor tube with u-bolts. the hh120 motor with dish attached is then bolted to a support pole so there are two places in theory that the N/S axis could not quite be right.

I can go check tomorrow to see if the indicator on the HH120 tube matches with the 0 mark on the main body of the motor, so if it's off a little bit I may need to see if my traxis 3500 can command a reset of the 0 position.

 

[SatPhreak]

Stab motor don't get lost since they use dual encoders so they don't need a reset to zero. It could be that the ubolts holding the dish to the motor shaft might be slightly off center (E or W), or the motor might need to be rotated slightly E or W.

 

[skysurfer]

It could be that the ubolts holding the dish to the motor shaft might be slightly off center (E or W), or the motor might need to be rotated slightly E or W.

that's what I am thinking. I'm not sure how to go about figuring it out other than pretend like it's a c-band dish, go to an extreme sat, and start with the dish to the motor shaft first (since that's the easiest to adjust) and then dish/motor to the mounting pole last, if necessary (since it's quite a bit harder to adjust) and just keep bouncing between 0 position and extreme sat and do the "dish lip" test and look at the signal level to see if I'm making any progress at the 0 position and extreme satellite positions.

 

[Lak7]

You need to make sure the Dish is "square" (for a lack of a better term) to the Tube first.
Usually there is a bolt that goes through the Tube, so the clamp can't slip.

 

[SatPhreak]

I was playing around with a homemade dish last spring, and I used a carpenters square to make sure the dish face was perpendicular to the line on the bottom of my hh90 tube. I then reinstalled the dish/tube combo back on the motor. This was done to eliminate one variable for aiming since elevation and focal distance were still imprecise.

 

[skysurfer]

You need to make sure the Dish is "square" (for a lack of a better term) to the Tube first.
Usually there is a bolt that goes through the Tube, so the clamp can't slip.

not on this one. A pair of U-bolts hold the dish (FS 120cm) to the HH120 tube.

When I originally installed the 90cm on that hh120, I used a weld line, mold mark, or whatever it is on the HH120 tube that was right along the 0 marking on the tube as a South centerline and put my 90cm FS bracket on the tube, lining up that centerline of the hh120 with something that looked to be centerline on the 90cm bracket.

Today, I did my East position - I had to push up on the dish from behind to get better signal. West was the same way the day before. Printing out the alignment troubleshooting page from the hh120 manual on this site, it told me I had to adjust the elevation of the HH120 motor (not of the dish) so I changed it from my correct latitude to the next latitude marking and tightened it down. I went back to 0 position, redid the elevation with my jig, took off the jig and E and W are still off (push up on the back of the dish to get better signal on both ends). I am beginning to wonder how accurate the elevation setup markings on the HH120 motor are and I guess I'll play with it degree by degree until I find where the arc is tracking right.

I also did the push/pull test with my dish at 0 postion and I"m trying to figure out something. I can push up on the dish from behind and get better signal than I did when my jig was on the dish and used the jig to maximize signal level. I am wondering that means the weight of the invacom qph-031 is slightly deforming my dish and when I do my dish push test, I'm relieving some of the weight of the invacom from the dish, bring the dish into better alignment and resulting in better signal. I may have to do my dish aiming with a light LNBF and then put the invacom back on it when I'm done getting the dish properly aligned. Yes, I'll probably lose signal with the invacom on it, but I should have a little bit more signal to begin with, I'd think, making that slight loss of signal while using the invacom not as significant.

 

[Lak7]

I'd leave the QPH on. Set the Motor Lat to where is should be, and set the Dish elevation for max Quality. Then try a East or West Sat.