Useing an old or new scalar with an new BSC 422 LNBF ?

[johann12]

I ordered a BSC 422 LNBF and it comes with an scalar.
MY 10 foot channel master dish has an 15 year old scalar on it.
The old scalar ribs are way deeper than the scalar for my BSC 621 for example.

Should I use the old scalar or should I use the scalar that comes with the new BSC 422 LNB ?
What could happen if I use the old scalar with the new LNBF?

 

[Magic Static]

I would go with the old one myself. Mine held the new LNBF better than the new one, straighter, tighter fit.

 

[KE4EST]

That is what I recommend. I am using an old one and it works good, and has a tighter fit.

 

[johann12]

Thank you for the information.
That would make it a lot easier.

 

[wallyhts]

Yup I agree use the old one.

 

[Anole]

I'd like to see a technical discussion on the matter.
But baring that, I'd go old school, too.

Of course, that doesn't relieve you of responsibility of guaranteeing it's in the right place.
The massive Birdview scalar is a case in point.
It needs to be moved more than an inch further from the dish for maximum performance with new feedhorns.

 

[FaT Air]

If there's more ridges, or deeper, comparing one to the other. Check the length of the original feed horn "out the front" at a particular setting. Then place the new feed horn at the same length "out the front". Compare the F/D setting marks.
I say this because somewhere BITD, I think it was the big BV scalars, more feed was "out the front" compared to a chaparral, for the same F/D. Don't remember it being much, somewhere around 3/8 to a half inch. I think its because a scalar is actually an RF Choke. More choke = tighter pattern.

In the attached, F/D (d) = the F/D of the dish, F/D (s) = the F/D setting of the scalar on feed horn.
I theorize that setting the F/D of the scalar/feed below the calculated F/D ratio, as shown in #1, (But not to an extreme) may help an undersized dish get some signals as the illumination of the dish is increased. But may encounter increased interference from terrestrial sources.
#4 would be desirable if the dish exhibits excess gain, with normal F/D settings, but terrestrial noise is excessive.
(I think my theories are correct as I remember someone, a while back, taking my suggestion and trying reducing the scalar F/D setting and having success in a particular case. I believe it was a 5 ft prime focus )

Example 4 would also encompass a Ku LNBF intended for an offset dish (F/D ~.6) on a BUD.
Only illuminates a very small area of the dish.

 

[Anole]

Using the scalar to mount the feedhorn is THE worst, most lazy way to make a dish!
Some buttonhooks and a few other BUDs hold onto the feedhorn, and let the user slide the free-floating scalar in 'n out, tuning for maximum smoke.

One of the better examples has three legs holding a short section of stove pipe.
The feed is on a sliding bracket inside the pipe.
The scalar fits onto the feed which sticks out of the pipe, toward the dish.

Very clean 4-step process, with no interaction:
- remove scalar
- focus feed for best signal
- install scalar & slide for best quality
- you're done; there is no step four

 

[Babadem]

If there's more ridges, or deeper, comparing one to the other. Check the length of the original feed horn "out the front" at a particular setting. Then place the new feed horn at the same length "out the front". Compare the F/D setting marks.
I say this because somewhere BITD, I think it was the big BV scalars, more feed was "out the front" compared to a chaparral, for the same F/D. Don't remember it being much, somewhere around 3/8 to a half inch. I think its because a scalar is actually an RF Choke. More choke = tighter pattern.

In the attached, F/D (d) = the F/D of the dish, F/D (s) = the F/D setting of the scalar on feed horn.
I theorize that setting the F/D of the scalar/feed below the calculated F/D ratio, as shown in #1, (But not to an extreme) may help an undersized dish get some signals as the illumination of the dish is increased. But may encounter increased interference from terrestrial sources.
#4 would be desirable if the dish exhibits excess gain, with normal F/D settings, but terrestrial noise is excessive.
(I think my theories are correct as I remember someone, a while back, taking my suggestion and trying reducing the scalar F/D setting and having success in a particular case. I believe it was a 5 ft prime focus )

Example 4 would also encompass a Ku LNBF intended for an offset dish (F/D ~.6) on a BUD.
Only illuminates a very small area of the dish.

Nice permutations up there, FaT Air. I'll have to read this a few times to totally grasp it all.

 

[stogie5150]

I always used the old ones. They are built better, anyway, FWIW.

 

[johann12]

If there's more ridges, or deeper, comparing one to the other. Check the length of the original feed horn "out the front" at a particular setting. Then place the new feed horn at the same length "out the front". Compare the F/D setting marks.
I say this because somewhere BITD, I think it was the big BV scalars, more feed was "out the front" compared to a chaparral, for the same F/D. Don't remember it being much, somewhere around 3/8 to a half inch. I think its because a scalar is actually an RF Choke. More choke = tighter pattern.

In the attached, F/D (d) = the F/D of the dish, F/D (s) = the F/D setting of the scalar on feed horn.
I theorize that setting the F/D of the scalar/feed below the calculated F/D ratio, as shown in #1, (But not to an extreme) may help an undersized dish get some signals as the illumination of the dish is increased. But may encounter increased interference from terrestrial sources.
#4 would be desirable if the dish exhibits excess gain, with normal F/D settings, but terrestrial noise is excessive.
(I think my theories are correct as I remember someone, a while back, taking my suggestion and trying reducing the scalar F/D setting and having success in a particular case. I believe it was a 5 ft prime focus )

Example 4 would also encompass a Ku LNBF intended for an offset dish (F/D ~.6) on a BUD.
Only illuminates a very small area of the dish.

I rebuild and set up 2 c-band dishes so far and every-time I calculated the distance for the scalar and I always trying to get it within 1/32 of an inch or better. I measure to the center of the dish and also along the 4 ( 7 1/2 footer ) or the 3 ( 10 footer) support arms to make sure that the scalar is sqare.
I found out that the new thinner scalar is doing a terible job holding the LNBF quare in place which could give you problems in making adjustments if needed and may create problems also in tracking the arc.
I also noticed that the older thicker scalars are doing a better job in holding an LNBF in place and makes it easier to finetune an LNBF.

Technical electronic vise, I do not know if it would hurt to use an old scalar with an new LNBF.

 

[FaT Air]

By all means, use the old scalar if it does a better job of centering the feed horn.
I gotta agree with Anole. The feed horn should be held by the mount, not the scalar. Then one could adjust the focal length first, as it should be, then adjust the scalar for optimum performance. But WE didn't have input to the designers. Most went with the simplest design. We're forced to 'comply'.
BTW: don't think the 'mismatch', if any, between old and new would be of a magnitude to be detectable with anything less than laboratory equipment. Use the old scalar.

 

[johann12]

Well. I got the BSC 422 LNBF installed which is a c-band LNBF only.
I used the old scalar with it.
I am very very pleased how everything is working with this new c-band only LNBF and the old scalar.
I get stronger signals and more channels compare with the BSC 621 D 2 LNBF. I do not have to worry about getting a happy median between c and Ku band anymore.

Thank you all for your replies.