T90 Troubles

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crawfrdb

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SatelliteGuys Family
Jun 5, 2006
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Setup:
Pansat 3500sd
T90
LNBFs:
3 x M20R
3 x ExtremeII
1 x Invacom QPH-031
Southwest US

With a new Wave Frontier T90 on the ground with a great southern view for initial alignment, a novel temporary mount was constructed to provide a highly stable mount while swinging the antenna around and easy/rapid fine adjustment to plumb the tripod.

First, an attempt to receive G10R was made connected to the linear ports of a Invacom LNBF. Performance was disappointing, with the strongest transponder (T6) peaking at only 30% while blind scanning the entire satellite. The Equity Broadcasting channels at Tp 1 and 5 have yet to be received at all. I manage to occasionally find Tp1, peaks at only 20% after a blind scan but no channels are ever found on a transponder scan. The two Fort Smiths on Tp21 can be received OK.

Next, T5 was a success with the linear feed at the centre bar (0), with the strongest peaks at about 90%. A neighbor with a 76cm winegard can reach 99% peaks on the stronger transponders, leading me to wonder how these T90s stack up against standard parabolic Ku dishes in general.

The beacons on a DSS satellite was then used find a peak with a LNBF at dead centre (0) of the LNB bar. This was a great success, with most signals found in the 90% range if not a full 99%-100%. A second DSS was peaked with an LNBF placed at around 15 on the bar. These first two LNBFs were easy to align and peak, presumably because of the circular polarization of a DSS signal. For a third try, T5 was selected and could never be found with the linear LNBF set at around 15 on the LNBF bar.

The linear LNBF was next returned to dead centre (0) on the bar and the T5 signal was re-acquired. In this configuration the LNBF was slowly stepped across the bar to it's intended resting place, re-peaking the signal by re-aligning the antenna as it went. As the LNBF was moved away from centre, the signal peak obtainable decreased until it nearly disappears entirely at about the 10-mark on the LNB bar.

It seems that skew is very important with linear feeds but a peak in the signal with both the antenna and LNBF skew adjustment does not seem to bring a noticable improvement in signal quality.

Questions:
1. Is it normal to experience a degraded signal at the edges of the bar in this manner?

2. The LNB bar is to be mounted to match the concavity of the secondary reflector (i.e. concave outward), right?

3. I'm getting horrible performance with the Extreme IIs, by far the worst of any feed tried so far. Has anyone had success with this feed?

Thanks in advance for any comments.

B
 
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crawfrdb

Thread Starter
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Jun 5, 2006
106
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Ah, very helpful.

I was setting the LNBF with the connectors facing down, would appear to be 90° off the mark.

Thank you.
 
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crawfrdb

Thread Starter
SatelliteGuys Family
Jun 5, 2006
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Thanks.

Was hoping they would work, though I bought them before realizing they were singles. Need Duals.
 
SatAdam

SatAdam

SatelliteGuys Pro
May 2, 2006
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doesn't a T90 require "backwards" LNB's? Like the polarity reversed so it works correctly?
 
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crawfrdb

Thread Starter
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Jun 5, 2006
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Yes, it does for circular. I'm only using the linear ports on the Invacom.
 
SatAdam

SatAdam

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May 2, 2006
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I think they use something jazzed up for linear too... I always wanted a dish like that, but it's a PITA to set up correctly.
 
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Mr Tony

SatelliteGuys Pro
Supporting Founder
Nov 17, 2003
447
181
Mankato, MN
I always wanted a dish like that, but it's a PITA to set up correctly.
thats why I prefer a motorized (unless we're talking G10..then its a fixed dish) :)
 
PSB

PSB

On vacation
Nov 5, 2003
1
5
We all know what these dish are mainly used for :)

You just can't beat a regular motorized dish pointing to the satellite, even takes care of its own skew! (IMO)
 
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crawfrdb

Thread Starter
SatelliteGuys Family
Jun 5, 2006
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PSB said:
We all know what these dish are mainly used for :)

God, no. Please don't say that. I bought this thing because of how FTA is so spread out among several sats.

Hopefully the only thing that separates me from 'linear Nirvana' is a baptism of fire :devil:

spindoctor said:

The data set I received from Wave Frontier for my location for satellites T5 and
G10R were identical (Az/El/Skew) to satlex.de's computations except for the position on the bar.

Wave Frontier calculated LNBs to be positioned at +/- 15.something.
satelex.de computed 19.something.

Will be interesting to see where I end up (assuming I can get the damned thing to work at the calculated Az/El/Skew).
 
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crawfrdb

Thread Starter
SatelliteGuys Family
Jun 5, 2006
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G10R on a T90....Anyone?

OK, re-asking this again on it's own thread.

Has *anyone* with a *T90* antenna been able to receive all of G10R fully above threshold (clear pics)? Particuarly, the Equity channels?

Even with the feed dead centre on the LNBF bar and the antenna aimed straight at the sat, I'm lucky to get 3 or 4 channels in the clear.

Thanks,
B
 
Labgate

Labgate

SatelliteGuys Pro
Nov 9, 2004
182
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Hello

I'm very surprised that you are having problem. I have a T90 and a T55 and my t90 was very easy to setup.

However I did not point it to G10. However I'm getting sats from 61.5 to 111 perfectly.

It is very strong so I would suppose that getting G10 would be easy. Are you sure that your adjustment is right, the skew is very important on this dish.

Also I noticed that it is very important that the post be perfectly plumb to be able to follow the arc.

As far as lnbs, you need a reversed lnb if you want to connect it to a circular sat (like I do for 61.5), it is connected to my dish network 510 receiver and working great, like 110 and 119 with reversed lnbs coming from my t55.

I also have 82 and 91 on the t55 connected to my 9220 expressvu receiver, again working great.

Also insure that you did not invert a piece. It is not so easy to assemble.

Good luck. It took lot of time to align the 13 lnbs on the t90 so I won't move it to try to get G10 but I'm sure it should work.

Labgate
 
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