BSC621 modification

[scottc98]

I was at Sadoun today to pick up another switch. I mentioned the experience that I had with the BSC621 on my 120cm dish. Good for Cband (as good as a 4 footer can be ) but poor KU signal. I recently motorized the 4footer in the back yard. Being that AMC9 is my true sat, I tried setting up the dish with the BSC621. On the data transponders (listed in the strong Tps thread) I was only getting 45-53 signal on the BSC. replaced it with the invacom (without moving the dish) and same tps jumped up to 73-80!. No mater how I adjusted the the BSC, I could go higher than 45-53.

The rep (who I wished i remembered his name cause he is alway helping me out when I stop in; GREAT REP nevertheless!!) stated that he has heard that some people have improved the KU signal by cutting off some of the tube. This would put the KU and C focal point more inline. He stated that the length of the tube was mainly that long to insert the dialectic plate for circular signals (which I have no desire to use).

Before I go modifying my LNB, has anyone performed or heard of this modification? If so, do you mind sharing some notes/pictures.
'
Thanks in advance!

 

[voomvoom]

If that would work, I can see where getting the lnbf closer might make the ku work and ruin the C-band, so cutting the tube back could possibly keep the C-band working. In other words, maybe because the lnbf is back so far, is why the ku doesn't work, and if you move it closer to get the ku to work, the way the tube is made, you lose the C-band because the angle of signal is lost. So, cutting the tube might work. But, I'll let someone else give it a try? And Good Luck, if anyone tries!

Al

 

[scottc98]

Voomvoom,

I think that you are right about the actual ku LNBF being so far back.

My understanding with the conversation I had this afternoon was that you had to move the lnb closer to the dish in order to get KU signal ( which is what I had to do with mine). But with the tube so long, it actually cutting some of the KU signal since the signal is only entering at the end of the tube. Cutting the tube would allow the extra signal through that was gained by moving the KU portion closer to its true focal point.

I was told that people who performed the mod didn't affect the Cband signal but greatly improved the KU.

I'd hate to waste a $50 lnb on something I heard (even though I feel that the people at Sadoun are a great resource). Would feel a lot more comfortable with some feedback before I make an attempt

 

[Anole]

I'm all for it if it works!

But, let those who've done it post their pictures as well as before and after signals on the Sadoun forum, ... or better yet, here.

And to be proper, it'd be useful to have some representative C-band numbers in the crowded part of the belt, both before and after, to make sure C-band performance wasn't degraded.

Running the tests on a Fortec 180 would probably satisfy the most users.
(because a lot of people might buy the 180 if they know the LNB will perform)

Frankly, I'm still waiting on a review of the other guy's C/Ku LNB, since I know this one has problems.

 

[scottc98]

Anole,

Agree on all account! I tried looking at the Sadoun forums first before posting here but didn't find anything. Hoping Sadoun will pop in on this thread for some input. Otherwise, I might stop back in later this week for some more info (5min drive )

The only measuring stick that I had for Cband on my 120 was for Anik F2. I was able to get MCHD at about 53 quality w/o using any high tech gear (just small tv and receiver). It did include some pretty strong bleedover from SatMex that resulted in about 5 strong (50+) channels. Of course, I didn't experiement with the KU at the time since the dish was stationary. Since its been motored, I ditched the LNB for the invacom just for some reliable KU surfing.

The only other Minibud cband experiments I did was with a old Chapprel C/KU that I manually skewed. Was able to get some channels on PAS9 with the flat scaler ring (this is before I got the conial ring and the BSC621). On a funny note, I make my own conial scaler ring that actually increase my signal from the flat ring. (totally ghetto; funny what you can do with a modified oil filter and some foil )

To be honest, if I can just get the LNB to get a strong KU signal and still keep MCHD, i'd be happy .

Its been nice out the last few days so maybe I'll switch out the LNB back to the BSC to get some more Cband readings while I wait for some more feedback here.

 

[caddata]

This conversation about shortening the waveguide indicates that the diameters are wrong. If the diameters were correct it wouldn't matter how long the waveguide was, the loss would be very small.

Waveguide dimensions, whether round, square, or rectangular, are proportioned to a harmonic of the frequency. Once inside a proper sized waveguide, the signal can be made to go around 90 degree corners and long distances without loss. The 90 degree ells shipped with Coroter feedhorns are examples of the ability to force the singal around a corner without loss.

The electronic portion of the BSC621 seems to be well designed, in that they produce lots of gain and very little noise, while the mechanical portion of the feed seems to be lacking in optimization.

Harold

 

[bill190]

I installed a BSC621-2 on my 12 ft. wire mesh dish.

When adjusting it, I got a better signal with the LNBF almost all the way out (or away) from the dish. I adjusted it for best Ku, so was connected to Ku while doing this.

With the best sats on a clear day, I can get signal meter readings around 90 and quality up in the 70's/80's. This is with C and Ku.

My 12 ft. dish is a prime focus. I've read that some dishes are more "deep" and others less "deep". I don't know if that has anything to do with it? Or if the size of the dish would make a difference?

I don't know the specs on my dish as I bought it used, but it looks like all the new wire mesh dishes I've seen for sale.

Anyway in my case, I would not want to cut off any portion of the feedhorn. It is just right for my dish.

 

[scottc98]

Bill,

It does seem that this lnb was intended for a prime focus dish. The fact that it comes with a flat scaler ring and the diameter of the lng is not the standard size that you would see on a offset dish.
I think that is one of the reasons that you get a great reading as it, while others like myself don't.

So, I think that the lnb serves its intended purpose: C/ku together on a BUD.
If a modification can me made to get similar results on a offset dish, then that would be great. Maybe will see a BSC621-3

 

[bill190]

...If a modification can me made to get similar results on a offset dish, then that would be great. Maybe will see a BSC621-3

Well the manufacturer of this LNBF has done a great service for me and many other people. That is finally being able to receive C/Ku on my FTA receiver. Building a better mousetrap if you will.

Plus a Universal Ku LNB and extended C-band LNB to boot!

I'm sure they are being rewarded by plenty of sales. And they should be.

Anyway I think these folks listen to their customers and give us what we want. I think the following link is the manufacturer? (Or at least distributor) Might want to email them and suggest a BSC621-3...

http://www.dmsiusa.com/contact.htm

 

[Anole]

It does seem that this lnb was intended for a prime focus dish. The fact that it comes with a flat scaler ring and the diameter of the lng is not the standard size that you would see on a offset dish.

So, I think that the lnb serves its intended purpose: C/ku together on a BUD.
If a modification can me made to get similar results on a offset dish, then that would be great. Maybe will see a BSC621-3

I've been reading about this device here on SatGuys since before it every hit the market.
So far as I can tell, it was never intended for anything but prime focus.
It was all the guys with little offset dishes who were doing lots of experiments and making a lot of noise, though.
Sadoun was supposed to carry a deep scaler for use on offset dishes, lists one as "coming soon", but still doesn't have it.

In all my reading about the LNBF, I've never found it attractive for offset feed dishes, and wouldn't consider trying one.
On the other hand, the one attraction (for me) was to use it on a low-cost 6' prime feed dish.
There, it is lacking. By all reports, it never peaked on C and Ku for any given bird, at the same point in the sky.
I've brainstormed with an old TV engineer about how that could be, but we didn't have enough facts to come to an intelligent conclusion.

If the change proposed in this thread cures the LNBF for use on a prime-focus dish, I'd consider that a 100% improvement.
As to use with off-set feed dishes, that's a whole 'nother discussion.

 

[Sadoun]

Hi scottc98
It was me, yours truly, that you met and talked to at the Sadoun showroom.

If you want to try it, go ahead. I will make you this deal: If cutting the tube as I told you will not improve your KU receiption and will ruin your receiption, bring the LNBF back to us and I will be happy to replace it for you with a BRAND NEW one. I am making this special offer for you only since you are willing to experiment with it.

So good luck and share your results here and on our forum at: http://www.sadoun.net/forums/4dtv-c-band/8859-c-band-1-0m-1-2m-dish-yes.html

 

[scottc98]

Well....how can anyone turn down a deal like that!

I'll start working on that the next few days and post results on both forums. I figure that I'll start cutting the tube a little at a time with a dremel tool until I can get a similar ku signal gain as my other lnbs (invacom, sadoun dual standard, and fortec universal)

I, and I'm sure others here, appreciate this! You've always been great eveytime I stop in!

I'll keep everyone posted.

 

[Anole]

tubing cutter - if and why

Since I've never seen the unit, this idea may be totally useless, but . . .
Is it possible to use a tubing cutter to trim a bit off the end?
If so, it would make the job super-easy.

If it looks like a possibility, practice on something else to get familiar with the tool, before applying it to the expensive LNB


edit: If you grind, saw, or file the tube, there'll be metal filings.
Make sure you contain them and don't let 'em get down the throat of the unit.
Doubtful the tubing cutter will work, but if it does, it's filing-free.

 

[scottc98]

Most definately will

 

[voomvoom]

I like this idea and opportunity for scottc98 to do this. I eagerly await your conclusions! Good Luck! And thanks Sadoun for letting this happen!

Al

 

[scottc98]

Well.....Got a update and its not good

I attempted the modification today and didn't get positive results. I tested everything out on G11 and using two tps as benchmarks (12060 V 26700, and an H data tp). Using my existing Invacom LNB, I was able to get 76 on the V and 86 on the H. The BSC621 (pre mod; no scaler ring) measured 46-53(V) and 53-59 (H). For those readings, the LNB was barely on the LNB holder (same holder for the 120 from Sadoun). More on those reading later...... I started by cutting 1/2 in at a time. The first 1/2 cut my signal down to zero. When I added my conical scaler ring, signal jumped to 33-39, still less than before. Took another 1/2 off and now I get no signal at all. Even added back my invacom to ensure that I didn't bump the dish.

My test results found that cutting the LNB back produced a negative result. I didn't bother testing out the Cband portion since the KU was now non-useable.

I'm going to take the LNB back to sadoun to have it replaced......but I am not done experimenting

One thing that I did notice before I started moding was the fact that the LNB had to be sooo far back to get a peak KU reading. I even pulled the lnb out of the holder and I was able to increase the signal (hard to get a exact measurement since i was hovering it by hand ) That got me thinking that maybe the LNB holder is not at a ideal position for this LNB. When I get the new LNB, I'm thinking about modifying the LNB holder, so that it is farther back, yet at the same focal level. This should allow me to move the LNB a little farther back and actually be able to secure it down where it needs to be for optimal KU signal. In addition, it should provide some room for me to attach the scaler ring, that is needed for any positive (viewable) C band singals. I am also curious if the scaler ring will have any positive effect on the KU. Don't think it will, but I was kinda shocked that it helped earlier when I was cutting the LNB back.

Wife had the camera in the car, so I wasn't able to take any pics. I'll be sure to when I mod the LNB holder.

Thanks everyone for your patience. A special thanks to Sadoun for allowing me to test out this mod. I'll be sure to post these results in your forum when I am done with the LNB holder testing.

 

[voomvoom]

That's sad to hear, but I'm glad I heard it before I tried it. Not that I would? Thanks scott for trying and Thanks Sadoun for your proposal for scott to try this!

Al

 

[Anole]

how 'bout duct--taping the missing rings back on?
or maybe just finding some other material to use to remount the unit farther from the focal point, as you've suggested?
It may not be dead... just sleeping.

 

[scottc98]

or maybe just finding some other material to use to remount the unit farther from the focal point, as you've suggested?
It may not be dead... just sleeping.

Not dead

Definately looking into the remount solution. Duct tape is any man's friend Prob is that the current LNB may not hold up if the duct tape area is where I need to use to mount to the holder or for the scaler ring.

Thats why I may wait for the new LNB.

Wife is out of town this weekend so I 'll have plenty of time to tweak around

 

[gabshere]

yes i was going to suggest maybe a paper roll and extend it out a bit more
i have a paper & plastic roll that might be able to use if you need them...
you could probably use these extentions with the altered lnb and and scaler ring

or maybe some thinwall pvc to extend it that would give it enough support but would also keep it from fitting the scaler without modifing the scaler.