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Re: Offical AMC 8 Transition Thread (was Sat. AMC-8)

Posted: Fri May 19, 2017 8:51 am
by mbrockm
My five XDS receivers range 11.5 to 12.5 EB. AG is ranging from 45 to 50.Yesterday, I could watch one of my westwoods EB bouncing to and from zero. Today with all the rain solid at 11.5 EB. Royals is 13.5 C/N.

Re: Offical AMC 8 Transition Thread (was Sat. AMC-8)

Posted: Fri May 19, 2017 1:32 pm
by awsherrill
Yesterday I made an attempt to repoint one of those crappy old black mesh dishes at AMC-18. It was an utter goat rodeo.

I had TWO spectrum analyzers, a fresh LNB, and pictures of all the relevant transponder pictograms. I could not see anything on either instrument that matched the pictures, at any time during the attempt.

The dish in question is a "spare" that was not in use. It has an equatorial mount and a screw-jack azimuth adjustment, so that part was relatively easy.

Adjusting LNB polarity was another thing entirely. Whoever put the dish up was evidently missing part of the feed horn, and what was left was bolted directly to the support arms. So you had to unbolt the whole thing to rotate the LNB.

I had another feed horn that had a rudimentary skew adjustment and I swapped that in. It helped a little, but I still couldn't find the bird. I finally gave up after about three hours. Probably didn't help that it was a solo effort, and I didn't have a clear view of the spec-an (and the sun was in my face the whole time).

Re: Offical AMC 8 Transition Thread (was Sat. AMC-8)

Posted: Sat May 20, 2017 6:04 pm
by mbrockm
We borrowed a sat meter which would tell us which bird we were on. Then marked the various positions on the pole. Once we found some some nearby birds it was fairly simple to find the one we wanted. Highly recommend borrowing one.

Re: Offical AMC 8 Transition Thread (was Sat. AMC-8)

Posted: Sun May 21, 2017 5:46 am
by kkiddkkidd
Sorry it has taken so long to get back to you. I am working on an AM ground system project that is taking all my time.

What scale (db/division) are these plots? 6db/div? If so, I think that is a little too low.

It isn't surprising that you didn't see much change in the AG but would have expected to see a good improvement in the EB.

I do see a little cross pol interference in your first plot. In your first plot of Transponder 1, the region immediately to the left of the Skyview XDS carrier slightly "humps" up. That is a Horizontal signal leaking thru. Adjust your LNB for minimum 'humpage"... Notice that the amc8migration plot is almost perfectly flat at the noise floor from the Skyview XDS carrier downward. I have a few dishes that were as flat as the published plot but most do have a small hump below (actually above since the LNB output is inverted) Xponder1.

You aren't necessarly looking for a peak on the desired carriers but a null of the undesired cross polarity carriers.

I have also occasionally seen the carrier that you are noting and have no idea what it is nor where it comes from. It _could_ be a cross pole carrier from an adjacent bird. I will try to look closer at the next one that I move. It will be a couple of weeks.

Refresh my memory... What size dish are you using? Where are you located?

Regards,

wtcmeng wrote:
Thu May 18, 2017 2:44 pm
Kevin,

I installed a new LNB as you suggested. This one was manufactured by Norsat and sold under the Dawnco label. It has + or - 2Khz LOL stability.
http://www.dawnco.com/site_html/***Show ... =All_.html

I only saw a slight improvement in signal level. Signal quality improved some. I was getting numerous Reed- Solomon errors on the tuner status page of the orbital receiver before the swap out. This has improved but has not gone away. I re-peaked the dish and polarity yesterday. I am concerned my LNB driven element is almost vertical instead of the calculated 18.5 degree skew for my area. I have heard of some in my area having the skew set straight vertical for peak but others have it set at 18.5 degrees to achieve peak .
Drivenelement.JPG


I borrowed a spectrum analyzer and I am concerned about a few things.

There is an carrier at 1412 Mhz not seen in the plot provided by the AMC8 Migration website.
AMC18 TP1.JPG

http://www.amc8migration.com/docs/AMC18 ... 17-T21.pdf

The 80 MHz span of the TP 17 plot may indicate cross pol interference.
AMC18 TP17 80MHZ.JPG
http://www.amc8migration.com/docs/NOTIC ... 17v2.1.pdf

Here are the other plots

WW1
AMC18 TP17 .JPG

Orbital
Notice the carrier at 1012 Mhz
AMC18 TP21.JPG

Any thoughts?

Re: Offical AMC 8 Transition Thread (was Sat. AMC-8)

Posted: Sun May 21, 2017 10:53 am
by wtcmeng
Kevin Thanks for the reply. The dish is a 3.8 meter Patroit dish. It's located in Traverse City, Michigan.

I contacted Orbital and they had me null the cross pol they were seeing on the plot I sent them.
I wasn't able to fully null it and also tried realigning the dish to make sure i wasn't on the side lobe of the transponder or an adjacent satellite.

TP21 after null
IMG_9828.JPG
You can see a slight improvement. I should note the SA is set for 5db per division.

TP 17 WW1 looks good.
IMG_9831.JPG
Orbital is scratching their head as to why there carrier
has such low signal and the other carriers are good.
They want me to try another LNB. I have confirmed that another station in our area is getting 13 to 14 ebno from a 12 ft dish on the Orbital carrier. Do you have any suggestions? My hair is starting to turn grey trying to resolve this issue :x Could you PM me with your contact info as I would like to chat you off board if possible?

Regards,

Eric

Re: Offical AMC 8 Transition Thread (was Sat. AMC-8)

Posted: Sun May 21, 2017 3:22 pm
by TPT
Old trick--if you have a spare LNB & either power out of S/A or can free up a receiver just to power it (with a T & DC block):

Take the LNB & swing it around while looking at the S/A See if you see a signal. You may have something generating TI--but just on the transponder channel the Orbital receiver uses.

We presently have a 12 foot Comtech dish (soon to be retired). We were using it for what was then the ABC satellite radio feeds several years ago. Then tried to add Delilah from Premier. No dice. Seems that we were looking directly at an MCI microwave tower some 20 miles away--aimed directly at another tower 1/4 mile east of us. Only a few active carriers, but one just adjacent to the transponder Premier used. The terrestrial microwave carriers are interspersed between the satellite downlink transponder frequencies. Most of this terrestrial stuff has gone away, but there is still some around. And cell equipment has been known to generate birdies that can get into the downlink channels or even in L band--interfering with your LNB output. So if you see something with that "naked" LNB, you might have something locally de-sensing your receiver.

Re: Offical AMC 8 Transition Thread (was Sat. AMC-8)

Posted: Sun May 21, 2017 5:33 pm
by kkiddkkidd
Allen,

We may have a high tech version of Segal's Law...

Typically a polar dish is the easiest to reaim. Not necessary that they work very well but if the polar adjustments were setup correctly, just crank it around, optomize and your done. I have had to physically tie down a number of old polar mounts that were too floppy to stay aimed in the wind.

Some of those old polar feed mounts were meant to be turned by a small rotator looking device that spun the entire feed assembly.

Also make sure that you aren't looking at the east side of the arc. I just ran across an az/el dish that someone had tried to move with a simple signal strength meter and found that it was in fact at about the correct elevation but was looking at a bird on the other side of the arc. I messed with it for a few minutes all the while thinking that something didn't look quite right and then just swung it back to the west about 45 degrees and AMC18 magically appeared. I very seldom ever use a compass or worry abt looking at AZ.

Also, make sure that you are looking at the specan at the exact same span and center freq as the downloaded plots. A small change in either can make the carrier groups look completely different.

Good luck,
awsherrill wrote:
Fri May 19, 2017 1:32 pm
Yesterday I made an attempt to repoint one of those crappy old black mesh dishes at AMC-18. It was an utter goat rodeo.

I had TWO spectrum analyzers, a fresh LNB, and pictures of all the relevant transponder pictograms. I could not see anything on either instrument that matched the pictures, at any time during the attempt.

The dish in question is a "spare" that was not in use. It has an equatorial mount and a screw-jack azimuth adjustment, so that part was relatively easy.

Adjusting LNB polarity was another thing entirely. Whoever put the dish up was evidently missing part of the feed horn, and what was left was bolted directly to the support arms. So you had to unbolt the whole thing to rotate the LNB.

I had another feed horn that had a rudimentary skew adjustment and I swapped that in. It helped a little, but I still couldn't find the bird. I finally gave up after about three hours. Probably didn't help that it was a solo effort, and I didn't have a clear view of the spec-an (and the sun was in my face the whole time).

Re: Offical AMC 8 Transition Thread (was Sat. AMC-8)

Posted: Mon May 22, 2017 6:00 am
by kkiddkkidd
Yeah.... There is definitely something there below the Orbital AND WW1 Carriers.

It certainly could be interference (use TPT's bare LNB suggestion to take a "look" around). It looks like cross pol but it should null much, much better than that. You are losing about half of your C/N on the Orbital XDS carrier.

If you rotate the pol thru V to H, does the junk there below 1017mhz go up or down?

I will PM you in a bit. I am working on an AM project in Little Rock this week and the site has very poor cell service.


wtcmeng wrote:
Sun May 21, 2017 10:53 am
Kevin Thanks for the reply. The dish is a 3.8 meter Patroit dish. It's located in Traverse City, Michigan.

I contacted Orbital and they had me null the cross pol they were seeing on the plot I sent them.
I wasn't able to fully null it and also tried realigning the dish to make sure i wasn't on the side lobe of the transponder or an adjacent satellite.

TP21 after null
IMG_9828.JPG
You can see a slight improvement. I should note the SA is set for 5db per division.

TP 17 WW1 looks good.
IMG_9831.JPG

Orbital is scratching their head as to why there carrier
has such low signal and the other carriers are good.
They want me to try another LNB. I have confirmed that another station in our area is getting 13 to 14 ebno from a 12 ft dish on the Orbital carrier. Do you have any suggestions? My hair is starting to turn grey trying to resolve this issue :x Could you PM me with your contact info as I would like to chat you off board if possible?

Regards,

Eric

Re: Offical AMC 8 Transition Thread (was Sat. AMC-8)

Posted: Mon May 22, 2017 5:25 pm
by Jim Sofonia
Hi all,

In helping "wtcmeng" we are still looking at a on site solution to his problem. Our latest tests suggest it may be interference from a cell site just across the road from the dish.
Should we have to move to a new location, what options would we have for bringing in control as well as audio received from a few miles away? Anybody doing this?

Re: Offical AMC 8 Transition Thread (was Sat. AMC-8)

Posted: Mon May 22, 2017 5:31 pm
by NECRAT
Jim Sofonia wrote:
Mon May 22, 2017 5:25 pm
Hi all,

In helping "wtcmeng" we are still looking at a on site solution to his problem. Our latest tests suggest it may be interference from a cell site just across the road from the dish.
Should we have to move to a new location, what options would we have for bringing in control as well as audio received from a few miles away? Anybody doing this?
Have you tried using a TI filter for the satellite?

Re: Offical AMC 8 Transition Thread (was Sat. AMC-8)

Posted: Mon May 22, 2017 5:44 pm
by Shane
A pair of "fly swatters" might fix you right up. Just have to find out where to position them.

Once had TI that was bouncing off a nearby tall building that messed with, I think it was, the CRC carrier on AMC-3. The fly swatters fixed that. If I had a picture I'd post it but I don't.

Concerning backhauling audio from a remote dish, such as from a transmitter site where you might already have some two-way connectivity, like a T-1, you could probably send at least two channels back.

We have some big-city stations where a dish at the studios would be useless, that do just this. They can also send and receive closures.

Re: Offical AMC 8 Transition Thread (was Sat. AMC-8)

Posted: Tue May 23, 2017 6:23 am
by TPT
We had an MCI tower behind our dish giving us interference. Two solutions were tried:

First, we put up a screen of hardware cloth behind the dish, which helped on many transponders. Hardware cloth (a Midwestern term) looks like heavy window screen material, made of metal--folks use it to keep rabbits out of gardens.

Second, on one particular transponder (Premier) we got a filter to trap out the adjacent signal from the microwave path. Kind of worked, but eventually saw a work crew at the MCI site & got an engineering contact number for MCI from them. Regional guy killed that carrier, eliminating the problem. I still have the filter, in case you are interested--L band, stuck it between LNB feed and that sat receiver.

You should be able to figure out on the spectrum analyzer the approximate frequency of the TI...if you can find who takes care of the cell site they may be able to kill that piece of equipment. If it is out of L band, just causing de-sense; the hardware cloth solution may be the best.