Button hook Q&A Time

[Long Hair]

As the title states I have a few ? about centering my lnb on a button hook. What is the best way to do this. As of now I can pick up my true south on C-band @ 99% but just a blimp on ku. I was able to go to W5 4dtv and signal was good but not as good as the 7.5 was.So I believe my skew may be off. ? what is the best way to set skew on a DMX 741 C/Ku LNB(f). one more thing the holes in the mesh are just under 1/4 of an inch,will I even be able to do ku ? Here's a few pics maybe it will help. Thanks Long hair

 

[Anole]

what I'd do:

I've never had a button hook, but from reading and thinking about the problem, I'd consider the following:
- install four stainless wires from the buttonhook pipe, to the edges of the dish.
- for easiest adjustment, I'd tie the guy wires well up the buttonhook pipe, near the LNBF
- measure from the edge of the dish in four places to the edge of the scalar (or to the rim of the feedhorn)
- make sure all four measurements are within 1/8th inch (?), by tuning the guy wires


AND, since you have the LNBF captured/held/mounted behind the scalar, I'd do one more thing:
- aim at a medium strong C-band satellite
- take off the scalar
- tune the LNBF toward and away from the dish for best signal
- now install the scalar, and move it toward and away from the dish for best signal (quality)
- try again by tweaking just the scalar on a weaker bird


Skew for DMX741 - as I recall it's 12 o'clock or 6 o'clock with the dish at true south... plus or minus 10°
(tune for maximum smoke) - - (best Quality, on your receiver)

Getting Ku on that lashup may be difficult, so get happy with your C-band first, then we can talk about Ku.

 

[ACRadio]

In addition to Anole's post...add some little turnbuckles to the guy wires...makes it real easy to adjust.

 

[DK_Sat]

No matter how good off adjustment you do the feedhorne always will be off center. Dishes with button hook are bad on receiving signal from Ku satellites ok on C-Band.

 

[Long Hair]

I have the lnb arms from my 7.5 dish. Would I be able to use them to support the button hook or even remove the button hook, assuming I can get my focal length . Would this even be a good idea? The Dish is 10ft x 21inch deep,so focal length is 42.8inches.

 

[B.J.]

Can I assume that you can adjust the focal length with that clamp that's about 10" up from the dish?
The dish mesh looks OK to me, that should work fine on Ku unless the dish is warped. The big question I have is getting the feedhorn at the proper FL. I would check to make sure that the feedhorn is centered fairly well, and if so, find a C-band sat, and try to peak that sat by moving the dish in all directions. THEN, try to peak the focal length adjustment by moving the whole buttonhook thing in and out. Once you're fairly close, try to peak the focal length on a Ku sat, again by first tweaking the aim in all directions, then by tweaking the focal length.
Reason for the 2 step process is that if the focal length is off quite a bit, that Ku won't focus at the same point that C-band does, so you need to get the focal length pretty close before trying to peak on Ku. The problem I see with this dish, is that it looks like there isn't any convenient way to change the focal length of that buttonhook except from that clamp you have 10" up from the dish, and that's hard to get to when you're aimed at a sat. Hopefully there is another way to adjust the FL that I"m not seeing.
If you try some of the previous suggestions related to centering the feedhorn, I would recommend getting the focal length set first, because if you start running cables to the feed, then you might not be able to adjust the focal length, as it doesn't look like you have much room for adjustment where that clamp attaches.
The advantage of a buttonhook like that is that you can usually adjust the feed in and out easily to get the proper FL without altering the F/D setting on the feedhorn. The feeds that are mounted on 3 or 4 arms are more stable relative to centering, however they really make it hard to change the focal length without changing the F/D setting on the feedhorn. I can't tell if your feedhorn has an F/D adjustment or not, but I assume that it must.

But anyway, unless you have that feed pretty close to the proper focal length, then C and Ku won't focus at the same point, because C will be a blurry spot, while Ku will be a donut, ie not peaking at the center. But as you correct the focal length, that donut focus turns into a spot that's centered at the same point that C band is focused. So if you intend to do both C and Ku, then you need to be pretty close to the proper focal length, and you really have to adjust C band first, then Ku. If you try aiming on Ku first, you'll be peaking on an off centered ring of the donut. (Hope that makes sense.) Hopefully there is some way to adjust focal length without getting all the way up to that clamp that's 10" from the dish surface.

 

[Long Hair]

Can I assume that you can adjust the focal length with that clamp that's about 10" up from the dish? Yes
Hopefully there is another way to adjust the FL that I"m not seeing. The U bolt holding the LNBF, it's not on the ring just the lnbf.
I can't tell if your feedhorn has an F/D adjustment or not, but I assume that it must. Yes,but it suck's,when you tighten the set screw the scaler moves cockeyed
If you try aiming on Ku first, you'll be peaking on an off centered ring of the donut. (Hope that makes sense.) Yes it does

I know now that the Button hook pole has a lot of play in it.So I will be needed the guy wires for sure,and the lnb poles off my 7.5 will not work(way to short). So It's time to go play.If anyone has more info good or bad please post it.
Thanks Long Hair

 

[GreatFTA]

I never had any issues with my button hook. Every time I replaced any LNBFs I just go in and out or twist around the LNBF to get best signal.
That button hook has been in the same position since 1986.

 

[Long Hair]

Well, I changed out the dmx with my ADL RP3 C-ku. It lines up better,so far so good. I haven't tweaked it yet,but I know its not skewed well,because when I move the servo from 45 to 35 the verticals come in better(on my true south).I had a dumb-ass moment when I installed the dish.The ADL RP3 C-ku would not change polarity,so I assumed the wiring was bad and replaced it with the Dmx741.Than this morning before I when to work I thought maybe I didn't have the servo wires wired up before it entered the house,well I was right. I think I'll have better luck with this lnb and scaler because they screw together,so I don't have to worry about it being cockeyed.:up

 

[Long Hair]

Well I put up some guy wires today.Here's some pics,what do you'all think. I haven't played with the dish yet to see if it helped,but I'm sure it didn't hurt it.

 

[DK_Sat]

Those guy wires need to be hooked at the scalar ring so you can adjust the center for the feedhorne

 

[Long Hair]

Those guy wires need to be hooked at the scalar ring so you can adjust the center for the feedhorne

I see what your saying,I thought this way would be better so I could adjust the focal length when tweaking,maybe not?

 

[Long Hair]

Played with the dish today and I'm able to get signals from 58west to 137west(c-band).I used the guy wires and was able to center the lnb(checked with tape measure from 4 points).So now I have a ? can you do a string test reliably on or with a button hook feed arm?Why I'm asking is when I got this dish I measured from the lnb to the button hook plate and read about 43inches. so I did some math (120x120)/16*21)=42.857.So the depth must be 21inches.With the dish apart I did the string test and came up with 21inches going (n to s) it was on uneven ground and 20inches going (e to w).I lifted the dish off the ground and the two strings came together,so I left it at 21inch depth.Yesterday I climbed up to the dish and tried the string test again this time fully assembled with botton hook in place, I get 20inches N to S,and E to W. I moved the lnb to 45inches and the signals seem to be ok, a little better than before. Can I trust the string test? By doing this I'm able to start seeing a little ku signal on my true south 95west,on CCTV reading about 20%.Before the signal was jumping from 0 to 99% it wouldn't even lock on to the signal.

 

[Long Hair]

So now I have a ? can you do a string test reliably on or with a button hook feed arm?

Anyone?

 

[phlatwound]

I'm not sure I understand your question but wouldn't the buttonhook arm interfere with the strings, if they were crossing in the exact center of the dish? Maybe if they were moved slightly (to avoid the arm) it would be "close enough"?

Sounds like whatever you did improved your signal, so that's a good thing.

 

[Long Hair]

I'm not sure I understand your question but wouldn't the buttonhook arm interfere with the strings, if they were crossing in the exact center of the dish?

Yes it interferes so I pulled the string tight above the button hook and followed the rim of the dish to the right spot,or (Straight across).

 

[Long Hair]

I was looking for more info today on the web about this dish of mine.And I found an old post by linuxman about a 10ft. perfect 10 dish.Reading the post I realized that my dish has the same f/d and Focal length as his. So I started looking at my old post about my 7.5 perfect10, to see the manual someone posted for me. It stated that the 10ft Focal dist. calculated to 45inches,but needs to be set to 44 and 5/8. I set this unknown dish to that and now I'm able to get ku on 95west(TS) @ 33% on CCTV and MacTv. I know this is low,but before I was barley able to get cctv @ 15-25%. So I'm happy that this bud will get ku.:up Now back to more tweaking.
(Side Note) I measured the center plate that the button hook connects to and I see that it isn't centered,off by about 1/4inch going east to west,and the same going North to south.My ?, is this common?

 

[FaT Air]

I've read somewhere, that the DMX 741 C/Ku LNB, would peak Ku at a different focal length than it does on C band. Enough to make a big difference in performance, C to Ku. Some experimentation was done where they removed the Ku portion, fabbed and inserted a spacer, then reinstalled the Ku portion. I believe the spacer was around an inch to an inch and a half. Can't remember where I saw this though. It was last winter/fall tho- May be worth a try.
I also have the ADL C Ku feed but couldn't get Q above 30 on Ku no mater what I tried. Don't really know if it is the feed or the mesh used on the dish. But with winter fast approaching, the 30 inch Ku I mounted to the bottom lip of the BUD(HD steel) by far out performs what I could get with my Bud. You may have better results, your mesh looks to be finer(smaller holes) then mine.
Buttonhook mounting on plate off 1/4 inch, shouldn't be a problem as lnb is aimed to within 1/4 inch of the bottom center of the dish, unless something further up is bent. Common, I wouldn't doubt it, but I've never measured that aspect in any dish.

 

[Long Hair]

I used the adl on my 7.5 perfect10 and was up in the high 80's on CCTV and MacTV,but the mesh on that was about 1/8 hole size,where this steel dish I have now is just under 1/4 of an inch. I like the little ku dish mounted on the bud.I had thought it would be fun to see if that would work.I guess I know the answer to that now.