Problem receiving NASA on AMC 18 C band

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Robz

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Hi,

I have a 6 foot prime focus from Sadoun. I am trying to get better NASA reception from AMC 18. There was never a problem receiving NASA on AMC 3. However NASA is now on AMC 18 but seemingly with much lower signal. During heavy rain they fade.
Also, of the 20 (approx.) transponders only the NASA channels I can receive and the NASA transponder is nearly the weakest. I have attached a spectra graph of the transponders. I am using the DMX 741 C/Ku LNB.
The red is vertical and green the horizontal polarization. Picture one shows only the vertical polarization. Picture two shows a combined V and H polarization.
I have already aligned the dish for max signal, possibly a little more could be squeezed. Anyone with a 6 foot dish get more than the NASA channel on AMC 18? Is anyone getting more than NASA regardless of dish size?
Any suggestions welcome.

105.0W-RFScan VR.png 105.0W-RFScan.png
 

FaT Air

HOA Free Zone
Feb 27, 2010
6,668
914
97W 48N
Is anyone getting more than NASA regardless of dish size?
Got everything with the 10 ft. Could it be interference from 107.3 or 103 ? A 6 ft has a wider beam spread than a 10 ft. There was someone having problems getting (i think) DW. on 103, with a 6 ft dish a while back. 3740V29270 Might combat it with careful feed and dish tweaking.
 

Robz

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SatelliteGuys Family
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joshrr, Fatair,

Thank you for your reply. It does help knowing there is a chance with a six foot c band dish to get better reception. As previously mentioned I do get the NASA channels on AMC 18, but weaker than on AMC 3. Rain kills the C band signal on AMC 18, never a problem on AMC 3. Alignment has got to be a significant factor. I think I have good mechanical Clark Belt tracking, but cannot be sure where the dish is aimed based on actuator pulse count. For all I know, I might be actually aimed at 107 (ANIK F1_R) thinking I am aimed at 105 AMC-18. The spectrum plot does help identify, but subject to satellite cross talk. Obviously the larger the dish the higher gain and narrower the beam width; but is also more critical to alignment anomalies.
 

joshrr

SatelliteGuys Pro
Apr 19, 2010
237
22
Michigan's Upper Peninsula
Amc 18 is definitely weaker than amc3 feed was. I used to get amc3 at 76qual on the 6ft. I do continue to get nasa through bad weather still though. To tune in channels/satellites Ill get the signal well enough to scan in the channel hen while watching the channel ill go east till it completely freezes video then ill count over the clicks west until the picture freezes. Ill divide by two and count back towards the center of the signal by that many clicks/counts of my dish mover. That will zero in on the signal every time if your scew is dead on as well as your elevation. To adjust your skew go to your true south satellite and there your vertical scew should be straight up and down so adjust your skew there as its easiest to adjust it straight up and down.

You can use a similar trick to adjust skew as i do to zero the dish in on a satellite. Adjust your skew left till the picture goes out thne count the clicks right till the picture goes out again then divide by two and count back to the center. If your dish is tracking properly you should only have to mess with your skew once. Your dish tracking on the polar mount will naturally skew it after that.
 
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