issues with 6 foot dish aiming

[Mr Tony]

OK guys this is been bugging me for a while and hopefully someone knows

Why is it if I aim the C-Band dish to a satellite (say T6/IA6/G26) I get AMGTV really good (say 60-70 quality) but PBS (15 max) not so good. If I move the dish west then I get PBS excellent (75 quality) but AMGTV is crap (18-20)

same with G4....gets the nets locked in but KCHF is non existent...move it a little bit east and boom comes in great

The big one is G11...for same reasons

Is it due to the smaller dish size (6 footer)?? I guess what doesn't make sence is same sat same polarity but 2 different "channel lists" (where some channels come in if dish is at X but different ones on same satellite come in if dish is at X+an inch west)

 

[truckracer]

Hey Ice, what lnbf are you using? When I had the BSC-621 that's exactly how my 10' dish was behaving.

Now that I have the corotor II C and ku is exactly in the same place in the sky on all sats.
We know that theoretically when KU is peaked on a hybrid sat the c should be right there.

If the conflicting tp's are both c band, then what is probably happening is the smaller 6' reflector is taking in interference from a neigboring sat. One tp is probably getting it from the east (interference) and the other from the west.

Just a theory.

 

[jayelem]

Why is it if I aim the C-Band dish to a satellite (say T6/IA6/G26) I get AMGTV really good (say 60-70 quality) but PBS (15 max) not so good. If I move the dish west then I get PBS excellent (75 quality) but AMGTV is crap (18-20)

I had similar issues with Ku band in the past , in fact I once posted a Hockey feed in the WUT area from SBS6 and somepeople only could lock the signal if they adjusted their dish.

I have peaked signals on certain weak TP's only to find stronger TP's losing quality.

I have also blind scanned unknown space with no documented birds just hoping to find something someone missed , I found a channel on Intelsat 1R doing just that .

I hope someone sheds light on this , pretty Damn interesting IMO .

 

[truckracer]

I figured the beamwidth on my 10' on ku being 1/2 degree was to blame almost zoning in on individual transponders on the sat. I can do it on G25 ku where I can peak certain ku tp's while hurting others. Nature of the beast I guess.

 

[linuxman]

Hey Iceberg.

I have experienced the same thing on motorized dishes before, and found that I didn't have the elevation set just right which allows for the possibility of reception off-center so to speak.

I would try raising or lowering the dish and then re-peak and see if it doesn't get the whole satellite at the same signal quality in one position.

I have actually received signal in two separate elevations on the same satellite. One had acceptable signal, and the other had great signal.

It happens more often on a smaller flat f/d ratio dish than on a bigger deep f/d ratio dish.

 

[Mr Tony]

Hey Ice, what lnbf are you using? When I had the BSC-621 that's exactly how my 10' dish was behaving.

both that and the BSC-421

If the conflicting tp's are both c band, then what is probably happening is the smaller 6' reflector is taking in interference from a neigboring sat. One tp is probably getting it from the east (interference) and the other from the west.

Just a theory.

thats what I'm thinking too. Since T6 is my true south theres a few sat around it

 

[Mr Tony]

I would try raising or lowering the dish and then re-peak and see if it doesn't get the whole satellite at the same signal quality in one position.

I've tried that and nothing. I know I'm on the sweet spot for the elevation.

It happens more often on a smaller flat f/d ratio dish than on a bigger deep f/d ratio dish.

that's what I figured.....oh well

 

[tvropro]

Ice, it's because of the beamwidth is too wide on the 6 foot for the satellite spacing. You have a sidelobe interfering on some transponders from the adjacent bird. When you move the dish to get those channels better (null out the sidelobe) you get off the main beam of the satellite and loose signal on the other channels. I used to have problems like that on close satellites way back when when I had my 10 footer that was a bit out of round. You may want to do a string test and make sure that puppy is as true at parabolic as possible. On a 6 footer every little bit helps.

 

[tdti1]

Ice, it's because of the beamwidth is too wide on the 6 foot for the satellite spacing. You have a sidelobe interfering on some transponders from the adjacent bird. .

This is true, most probably even if the undersized reflector was not warped it will probably still have issues, plus it is not a quality reflector, of course a warp will not help.

 

[photoman76]

It's because of your dish size. When you are pointed at Galaxy 26, your dish is actually seeing signals from Galaxy 11 and Galaxy 3C also. I can see the same effects on my 7 1/2 footer, but to a lesser extent.

Attached are Broadlogic Spectrum Analyzer scans of Galaxy 26 dead on and with the dish moved east and west.

In the center scan both AMGTV and PBS signals are maximized. In the top scan, the dish has been moved east. The PBS signal has been totally wiped out by the adjacent signal on Galaxy 11, but AMGTV is still quite strong. In the bottom scan, the dish has been moved west. The PBS signal is still there, but now the AMGTV signal has been wiped out by the adjacent signal on Galaxy 3C.

Because smaller dishes see more than one satellite at a time, each signal is affected by signals on the adjacent satellites. Moving the dish east or west slightly will increase or decrease the effects of the adjacent signals on the channel you are trying to watch.

Larger dishes don't have much of a problem, because they only see the intended satellite and are mostly blind to the adjacent satellites.

 

[tvropro]

Larger dishes don't have much of a problem, because they only see the intended satellite and are mostly blind to the adjacent satellites.

My 12 is tight... but I wish I had a 30 footer

 

[Mr Tony]

You may want to do a string test and make sure that puppy is as true at parabolic as possible. On a 6 footer every little bit helps.

hee hee....this is the one that fell off the table 3 times so I don't need a string test

Oh well....had the dish on T6 for AMGTV (wrestling) and now back to 121W

 

[Mr Tony]

Thanks photoman for the scans....now it makes sence

 

[tvropro]

hee hee....this is the one that fell off the table 3 times so I don't need a string test

Oh I thought it was the good one. Your lucky your not seeing G-15 and AMC-3 at the same time on that thing

 

[Mr Tony]

amazingly the signals come in almost as good as the "good one"

the Pansat 1500 jumps alot but its stable

 

[Anole]

Let's get Iceberg one of those 6' Prodelin offset transmit dishes.
The fiberglass reinforced molded dish only weighs about 100 lbs.
I'm thinking the LNB arm and bracketry on the rear of the dish may weigh another 80.
As for the mount post, and NPRM, I couldn't say.
Actually, that one appears to use lighter hardware...this is the one with the beefy hardware.

At least it'd hold it's shape!

Plus, it'd give another data point with that flatter dish and longer focal length.

. . . and then we could get him to experiment with conical scalars for us, too!
I'd hoped Linuxman would, but he's way too busy with his six-pack of Birdviews, and other assorted toys, too numerous to behold! -

 

[truckracer]

I had one of those 6 foot prodelins. That thing weighed more than my 10' mesh!

I had two astrotel offset lnbf's with conical scalar rings. I had mine setup for 123W and 127W c-band. (remember the free ppv's that used to be on G10R).

I still have a 1.2 M prodelin out back that is not set up. I have the mount, feed arms, and dish.

I thought about playing "micro-bud" with it.