DMX741 C/KU LNB mod to fix drifting Ku

[. Raine]

Got bees into the C1WPLL on my 9' dish again, about a week ago. This time I didn't want to take the time moving them and just sprayed them and for whatever reason, it killed the C1, dead, no signal on nothing. I took it off the dish and couldn't see anything wrong with it, so I rinsed the barrel of it out, set it aside to dry out and try at a later date. I did pop a plastic plug into that stupid center hole on the C1's cap, so if it does work again, I won't get bees in it again!

So, I threw on a old DMX741 [I think it's a DMX741, there's no label on it] C/Ku combo LNBF that I have here and within the last week or so I'd noticed that the Ku side was drifting badly when it'd get hot out. The Ku part is held onto the back of the C section with three screws, so today I went out and removed the Ku part and strapped a Amiko Premium L-104 LNB over the hole where the original mounted and it worked pretty good, better than the drifting original did.

I then stripped the plastic housing and front cover off of the Amiko and mounted it back onto the DMX741 C section and wow, it works really good. Locked Cozi on 103W at 72% [MicroHD receiver] and the LPB stations on 87W that have a Q jumping from thirties to forties on my 30'' dish lock at 70%. Right now I just have the Amiko strapped to the DMX with wire, but I'm going to make a permanent mount for it sometime this week. Will take some pictures too, the batteries for my camera are MIA again, when I find and charge them, I'll take some pictures.

I didn't take my meter out and adjust it to optimum either, just strapped it on and made sure the skew of the Amiko was near zero, after I make a permanent mount for it I'll take the meter out to the dish and adjust it.

When I had the Ku section off of the DMX, I taped two strings across the hole on the C section in a cross-hairs and sighted down the barrel of the C section, looked like it was aimed right at the center of the dish. This made me think that maybe if LNBF's had a removable back cover, or a metal mesh with a dot in the center instead of a solid back, it might help with alignment of the LNBF? It also would help with cleaning out damn bees.

Although, a metal mesh might let the damn bees in, it'd have to be small mesh!

If the C1 does work again once I get around to trying it, I may cut a hole in the back of it and mount a Ku LNB onto it and see how it works. Worse case scenario would be I'd just have to cover the hole up if it doesn't work, which wouldn't be too bad.

 

[Titanium]

Very innovative idea to have a small hole in the casting for crosshair sighting the center of the dish! Insert a cap to seal the hole when finished.

 

[Lone Gunman]

For those of us who are "electronically challenged", would you please define what you mean by "the Ku side was drifting badly" in terms that we can understand? Reason I ask is because I own several of those LNBFs.

Thanks

 

[Titanium]

As DRO type LNBs and LNBFs age or during high or low temperatures, the LO frequency often drifts. A satellite receiver can usually tune into a frequency that is +/- 3 to 5Mhz higher or lower than the inputted transponder frequency and this drift may not be easily noticed. The LO drift is usually caused by electronic/hardware failures inside the housing such as distortion of the tuning slug housing, delamination or corrosion.

What happens if the LO starts drifting? The receiver no longer finds the transponder on the frequency that it is saved in the list. If it has drifted a few MHz, the receiver will probably find it and lock onto the transponder. If the frequency has drifted too far, the receiver may not be able to tune it and the transponder will not lock.

How do you know that the LNB(f) LO is drifting? If the receiver takes a long time to lock onto transponders or channels are lost during the heat of the day or the cool of the night. Another sign that the LO freqency is drifting is that blindscans logs the transponder frequencies which are different than the actual downlink frequencies (for example the downlink frequency is published as 11700, but the receiver logs the transponder frequency at 11705) and this is repeated for every transponder that is found during a blindscan.

 

[. Raine]

For those of us who are "electronically challenged", would you please define what you mean by "the Ku side was drifting badly" in terms that we can understand? Reason I ask is because I own several of those LNBFs.

Thanks

In the morning and at night, when it was cool out, channels would come in fine but when it started getting warmer outside in the afternoon, I would slowly lose Q and then channels throughout the day and have to do a re-scan to get them back, or bumping the dish over a few clicks would take care of it sometimes. Then at night time, I'd have to rescan or bump the satellite positions a few clicks again. With a re-scan, the transponder freq would scan in differently than what was scanned in previously, so the Ku LNB was drifting off frequency when it got hot out. Like the 1st scan might be one number scanned in and then the later scan different.

At first I'd thought it was the worm gear block on that dish because it was a little sloppy and I could wiggle the whole dish back and forth a 1/2'' or so. I took the block off and cleaned it, pumped new grease into it and adjusted it, dish was nice and tight, thought I had it until the next day. On one of the re-scans of a sat I noticed the difference in transponder freq compared to what I'd written down earlier and then realized what the problem was.

This is actually the LNBF that I sent pictures of to you a while back, which back then when I'd tried it on the same dish to see if it worked or not, the Ku was like I said then, it worked but not all that great, probably because the Ku part was crapping out. I didn't leave it on the dish for more than a few hours back then so I didn't realize this problem with it.

If you have an old one that's crapped out on the Ku side, or doesn't work real well, this would be worth trying. Especially as you don't have to ruin the LNBF to try it, if it's made like mine is and the Ku section is held on with three screws. This thing is working great and once I bring the meter out and adjust it I'll be able to skew the Ku and C separately, rather than having them both fixed in the same orientation. Not to mention the ability to upgrade the Ku section to PLL is a plus!

 

[Lone Gunman]

Thanks guys. That helps a lot, and, I do have one that seems to be doing something like that on that Unimesh system. And I thought the dish was off and needed tweaking? I see SR numbers that are off a good bit also along with the TP numbers being 1 or 2 numbers low. At times I've been able to move the dish a couple of clicks East or West and then it will lock, but not always. I've also had it to sit there for 5 minutes or so then all of a sudden it would lock.

I'd be interested in what you come up with on this and please keep in mind that there are those among us that are electronically challenged when you explain how you modify it!

Thanks

 

[. Raine]

I finally found the batteries for my camera, but it's pouring out here so I can't take any pictures of the dish itself right now. Well, suppose I could....don't want to get soaked though.

Here's some pictures of the Ku section that I removed and replaced with the Amiko LNB.



The Ku housing fits onto the C section of the LNBF only one way, but the actual Ku LNB fits into it's housing in two different positions, in the last picture you can see two slots for the two different positions that the LNB can put into.

A couple of pictures before I took it apart:



Will post some more pictures when weather and time permits, soon!

 

[. Raine]

Raining again today, but I did manage to get a few pictures. It's messy looking because I have the Amiko Ku LNB just temporarily wired onto the C section, but it works good. I almost cut the bottom of the Ku housing off today to use as a permanent mount but then changed my mind, just in case I come across another of these C/Ku LNBFs with a broken housing or something, never know. I probably will make a flange out of sheet metal that locks down with the three existing screw holes on the C section.



And of course, one of my supervisors was trying to figure out what I was doing out there in the rain....



I have some aluminum platter spacer rings out of some old hard drives of different thickness that are just the right diameter to insert in between the C section and the Amiko LNB to play around with the focal depth/length? Once I have a mount made, I will mess with them some. I may change out the scalar too, originally I had a Chap scalar on it, but I was messing with it one day and dropped one of the set screws and couldn't find it, one other screw was already frozen up in the scalar, so I'd swapped it with the C1WPLL scalar because I didn't have time to mess with finding a screw to fit the Chap. The C1 scalar works good, but the chap was a little better. As it was, it didn't really save me much time probably, because the C1 scalar didn't quite fit the button hook on this dish and I ended up having to drill a new hole for it to fit right.

Have to go through and set it all up right too, when I put it on I pretty much just quickly threw it on, not knowing whether it'd work or not!

 

[Lone Gunman]

That Amiko Premium L-104 LNB is a Universal LO LNB not a Standard 10750, correct?

 

[. Raine]

That Amiko Premium L-104 LNB is a Universal LO LNB not a Standard 10750, correct?

Yup! 9750/10600.

 

[Lone Gunman]

Ok , but do they make one like that in a Standard 10750 LO?

 

[. Raine]

Ok , but do they make one like that in a Standard 10750 LO?

Amiko doesn't, at least, not that I've seen. But, the GeosatPro SL1PLL is phase lock loop and does have a standard 10750 Lo. I don't have one of them myself, but it looks pretty much the same size physically as the Amiko and I would assume that the feed throat must be the same, or almost the same size as the Amiko. I would think it should work just as well as the Amiko LNB does. The SL1PLL is the only PLL that I know of with a 10750 Lo, but there may be others that I haven't seen.

Why do you want one with a 10750 Lo? Is it just so it will scan a bit faster, or is there another reason? I ask because all my Ku LNBs that are in use are universal 9750/10600 PLL's except for one standard LNB that I have on my 121W dish, that one has a 10750 Lo.

I've actually been wanting to get a SL1PLL just to try it out, but it's one of those deals where I don't need a LNB right now so I've been holding off on it until I actually need one. If there's another advantage to having the 10750 Lo other than a little faster scanning, I might pick one up sooner to try out.

I know some of my universal LNBs will work fine with the Lo set to just 10600, but a couple of them won't work right unless they're set to universal 9750/10600, they'll miss a lot on scans when set to just 10600, for what ever reason, I don't know.

 

[Jason S]

Amiko doesn't, at least, not that I've seen. But, the GeosatPro SL1PLL is phase lock loop and does have a standard 10750 Lo. I don't have one of them myself, but it looks pretty much the same size physically as the Amiko and I would assume that the feed throat must be the same, or almost the same size as the Amiko. I would think it should work just as well as the Amiko LNB does. The SL1PLL is the only PLL that I know of with a 10750 Lo, but there may be others that I haven't seen.

Why do you want one with a 10750 Lo? Is it just so it will scan a bit faster, or is there another reason? I ask because all my Ku LNBs that are in use are universal 9750/10600 PLL's except for one standard LNB that I have on my 121W dish, that one has a 10750 Lo.

I've actually been wanting to get a SL1PLL just to try it out, but it's one of those deals where I don't need a LNB right now so I've been holding off on it until I actually need one. If there's another advantage to having the 10750 Lo other than a little faster scanning, I might pick one up sooner to try out.

I know some of my universal LNBs will work fine with the Lo set to just 10600, but a couple of them won't work right unless they're set to universal 9750/10600, they'll miss a lot on scans when set to just 10600, for what ever reason, I don't know.

Another Standard PLL Ku LNBF is the Titanium PLL-1KS.

 

[Lone Gunman]

Why do you want one with a 10750 Lo? Is it just so it will scan a bit faster, or is there another reason? I ask because all my Ku LNBs that are in use are universal 9750/10600 PLL's except for one standard LNB that I have on my 121W dish, that one has a 10750 Lo.

All my systems (3) have standard LO LNBFs on them and all my receivers (6) are setup for that LO. If I go to changing stuff around then it will screw up my entire system. The way it is now I can take any receiver I have and put it on any dish I have and it will work fine without changing anything.

I've got a Titanium PLL-1KS that I got a few months ago when I was looking into a Ku only system. That thing has a plastic cover over it that I "assume" has to come off before it can be used but I've been somewhat reluctant to cut it up without knowing if it will work or not. Most of the Ku dishes I've seen advertised come with a LNBF so if/when I go that route I'll probably butcher up the one that comes with a new dish and use the Titanium one on the Ku dish instead.

 

[. Raine]

All my systems (3) have standard LO LNBFs on them and all my receivers (6) are setup for that LO. If I go to changing stuff around then it will screw up my entire system. The way it is now I can take any receiver I have and put it on any dish I have and it will work fine without changing anything.
I've got a Titanium PLL-1KS that I got a few months ago when I was looking into a Ku only system. That thing has a plastic cover over it that I "assume" has to come off before it can be used but I've been somewhat reluctant to cut it up without knowing if it will work or not. Most of the Ku dishes I've seen advertised come with a LNBF so if/when I go that route I'll probably butcher up the one that comes with a new dish and use the Titanium one on the Ku dish instead.

That makes sense to want to keep it the same, if everything else is 10750. When I first tried the Amiko, I tried it as it was, without removing the plastic cover or front cap and it worked fairly well, better than the original did. I was hesitant too to hack up a brand new LNB but once I saw how well it worked in it's original state without hacking it up, I figured I'd go for it. Try the PLL-1KS complete as it is, it'll probably work, the Amiko did.

 

[Lone Gunman]

Well, I did hold up that Ti one to the end of a "non-working" 741 without the Ku end on it but the plastic housing hits the F connector terminals and it wont' center up even without the cable connected, which I assume is required.

 

[. Raine]

Well, I did hold up that Ti one to the end of a "non-working" 741 without the Ku end on it but the plastic housing hits the F connector terminals and it wont' center up even without the cable connected, which I assume is required.

The Ti must be bigger than the Amiko then.
The Amiko was right up against the F connector for the C section with it complete, but pretty sure I was able to center it. Really close, if not. The cap on the Amiko is 2.40''.

Maybe try the Ti off-center, if it isn't way far off?

 

[KE4EST]

 

[. Raine]

View attachment 108449

I don't think he means those connectors, but the one sticking up vertically on the C section. In this picture you can see how close it is to the Ku LNB:



But, the front plastic cover of the Amiko and the PLL-1KS in your picture look to be pretty close in size. Do you by chance happen to know the O.D. of the front plastic cover of the PLL-1KS?

 

[KE4EST]

60mm