Test, Comparison, and Review WS International DMX741 C/Ku LNBF

[linuxman]

The Test:

The test was performed on my 10 foot perforated Unimesh Scanning/Testing Dish mounted on an AJAK H-H 180 mount using my tried and tested Pansat 3500SD. I ran a base set of numbers using my ADL patent infringing CoRotor (special Ku probe), a Chaparral 20K old style (built-in elbow) C-Band LNB, and an NJR .7db PLL Ku LNB. I chose a random set of satellites and transponders from the far West to the far East of my viewable arc. I next installed a Geosat Pro CK-1 (closest real apples to apples competitor of the DMX741) and ran the numbers on the same satellites and transponders across the arc. Finally, I installed the WS International DMX741 and ran the numbers on it.

Please keep in mind that the test was not all run on the same day. I started with the CoRotor and CK-1 on last Saturday, but due to circumstances beyond my control, I couldn't finish the test until today. Also keep in mind that I didn't spend my usual several hours tuning in the two LNBFs. The dish was already set, and I did make some adjustments to center, skew, and focal length. I also took advantage of the Chaparral scaler rather than re-doing the whole dish setup. To get maximum numbers, you need to spend some time with LNBFs. They are different than Co-Rotors and everything must be set perfectly to get best performance. I am sure I could get better numbers on both LNBFs in quesion if I were to spend a bit more time "fine tuning".

The Numbers Comparison:

Numbers on different receivers will yield different results depending on the receiver, but here they are as I recorded them.

Equipment------------------------------CoRotor-----------CK-1----------DMX741
131W - C 3747 H California Channel-------90%----------------75%---------------90%
129W - Ku 11963 H WSTV----------------89%----------------75%---------------90%
123W - Ku 11720 V WNGS----------------75%----------------45%---------------60%
101W - Ku 11856 H - AOC----------------60%-----------------45%---------------45%
95W - C 4041 H - Daystar----------------90%----------------89%---------------80%
91W - Ku 12050 V - test card------------75%----------------45%---------------45%
91W - C 3720 H - The CW---------------99%----------------99%---------------99%
83W - Ku 11735 H - RTN-----------------70%----------------45%---------------30%
72W - Ku 12053 V - NBC-----------------90%----------------90%---------------60%
72W - C 4040 V - NASA-------------------99%----------------90%---------------90%
43W - C 4152 H - Rural-------------------60%---------------45%---------------45%
30W - Ku 11883 V - Cubavision------------75%----------------45%---------------80%

The Review:

The DMX741 is a well designed C/Ku LNBF with a straight barrel shaped feed-horn. It fits very snugly into my Chaparral scaler which I like. The raised numbers were of no use to me because I had to grind them off to get it to fit inside my ancient scaler. It fits into it's oem scaler without having to "make it fit". In my opinion it is a little too loose in it's own scaler. The Co-Rotor II scaler has protrusions in the inside circle which allow it to fit in and can rotate the numbers past the protrusions without having to grind the numbers off. It could cause problems if that were the critical point of the skew.

The numbers above pretty much tell the tale and you can see for yourself. I have had the CK-1 for some time and have always liked it's performance and would have to say the DMX741 is equally as good a performer plus easier to install on the dish with the straight barrel feed-horn.

Pros:
Straight barrel feed-horn design
F/D numbers
Skew adjustment numbers
Great Performance on C-Band and Ku Band

Cons:
F/D numbers would be better recessed
Scaler could be a little snugger (goes with raised numbers)

All in all, it is a great addition to our choices for modern voltage controlled C/Ku LNBFs!!

I would encourage others who own this product to post their findings here as well.

 

[stogie5150]

Very Nice Linuxman!

:up

 

[phlatwound]

Nice review, linuxman, appreciated!

How does the CK-1 fit in a Chapparal scalar, compared to the DMX741 ?

 

[Anole]

Very thought-provoking! - :up - Thanks for the fine review.
Hope others run some comparison tests, too.
Like to see what a dozen DMX's do up against a random dozen other LNBFs.
More data is always more better.

Apparently these don't suffer from the Ku misalignment recently reported by some of the -621's.
Guess that was never a problem on the Ck-1's.

Hope the members test-driving the DMX's will ALSO give these a week or two and report back on long-term reliability, temperature drift (if detected), and saturation on hot birds.
There's nothing like living with one to find the little secrets.

Great news -

 

[Lak7]

Biggest improvement for me, is that the LPBS DVB-S2 feeds holds after the sun goes down.
Otherwise, I saw about an 8% overall Ku improvement.

 

[Anole]

Biggest improvement for me, is that the LPBS DVB-S2 feeds holds after the sun goes down.

Well... that's a make-it or break-it decision!
Kinda like getting a bigger dish to combat rain fade, huh?

Otherwise, I saw about an 8% overall Ku improvement.

Great news... but over what? -

 

[linuxman]

Nice review, linuxman, appreciated!

How does the CK-1 fit in a Chapparal scalar, compared to the DMX741 ?

Thanks!

The CK-1 has a slightly tapered feed-horn barrel which fits a little loose even in it's own scalar and very loose in the Chaparral scalar.

 

[Zorak]

Thanks for taking the time to post your review!

Do you think it is safe to assume a good co-rotor install will always beat these new products? Or do you think the data favors the co-rotor because the installation was optimized for it? Did all three products yield acceptable results from a picture quality perspective with your receiver?

Thanks again....

 

[linuxman]

Thanks for taking the time to post your review!

Do you think it is safe to assume a good co-rotor install will always beat these new products? Or do you think the data favors the co-rotor because the installation was optimized for it? Did all three products yield acceptable results from a picture quality perspective with your receiver?

Thanks again....

I was hoping one of the engineer types might answer your questions with a better response than I can give, but here goes.

The difference in design between the Co-Rotor and these new voltage controlled LNBFs is what makes the performance higher with the Co-Rotors. There is the obvious difference with adjustable skew, but beyond that, the probes are located in different places.

The evidence over the past couple of years have indicated that C-Band has not been a problem, and the products above indicate that very high results can be expected on C-Band with the newer LNBFs.

The problem arises with Ku Band. I have never owned a BSC621, but have read where the Ku performance was unsatisfactory. Both the products tested above show a pretty decent Ku performance.

So in my opinion, these newer products have come a long way towards filling a need in our hobby.

As the products are used, and more data is gathered, I think the manufacturers will continue to improve their products and the next generation will be even better. At least I hope so.

As far as picture quality, as long as the signal quality meets the threshold on your receiver, the picture quality is the same.

If others have answers, please put in your two cents worth.

 

[Babadem]

Well done Linuxman!!!!:up

 

[Zorak]

Thanks for the answer. I have been wondering if it is worth trying to set up a co-rotor for a small or mini-bud versus the one piece unit. Perhaps it will be worth experimenting and I'll give it a try. Thanks again!

 

[Desertnight]

I have noticed that some channels have better signal quality than others. So....once the polarities and best picture possible have been set at installation of the units, how does a person adjust the skew from the satellite receiver. Do you have to go back outside and make adjustments to the skew on the BSC or DMX while its on the dish..

Do you have to go back outside and readjust the skew? Whereas, the skew can be managed in the house with a Cororotor.

 

[Robert_W]

I recieved my DMX741, instead of the ordered DMX241. That was fustrating, since I wanted just the C-Band. The small dielectric plate was to come with the DMX741 was not in the package, and wonder if it is installed already?
I do not have scaler ring arms, so I e-mailed WSI about the usage of buttonhook, that was two days ago and no message reply.
They did not have instructions with the product, so I had to go to their web-site and see their PDF instructions.
Someone told another member that the scale on this product was in tenths. But it was from mouth to back,,,2, 0, 8, 6, 4, 2. Well Like stated b-4 I have a .278 F/D so where would I aprxx set it?
I thank this web-site for reviews and help generated from all the members.

 

[Mr Tony]

the dialectic plate is only used for circular polarity satellites which are over the Atlantic

 

[ZetaMale]

In this digital & 8PSK world, I'd like to see some numbers for the LNB LO freq stability.

 

[DRCars]

From looking at the numbers in the first post of this thread it appears that the DMX741 LNBF does not perform quite as well as the co-rotor feedhorn/LNB setup on C band and even worse on Ku band. Appears to lose about 10% quality on average on C-band.

I have a 7.5 ft. dish and need all the signal quality I can get to pull in the DVB-S2/8PSK feeds nowadays (still can't get all of them). Not only does 8PSK seem to require better/more signal but also the uplinkers seem to want to use the higher FECs (that hurts too - A double whammy). So I know I would do better if I had a 10 ft. dish.

That said, would it be a waste of time for me to try to use a DMX741 LNBF in place of my conventional feedhorn/LNB and hope to get at least what I do now? It sort of looks that way.

Is the DMX741 the best available LNBF for replacing a conventional feedhorn/LNB? Are there others that might do better even though they might be more expensive?

Your responses will be appreciated.

DRCars

 

[stone1150]

I have noticed that some channels have better signal quality than others. So....once the polarities and best picture possible have been set at installation of the units, how does a person adjust the skew from the satellite receiver. Do you have to go back outside and make adjustments to the skew on the BSC or DMX while its on the dish..

Do you have to go back outside and readjust the skew? Whereas, the skew can be managed in the house with a Cororotor.

Once the lnb skew is correctly set at the dish, you don't need to mess with it. As the dish moves across the arc, it rotates. That keeps the proper skew for all birds. Some birds seem to have wierd skew, or some have reported anyways. I myself have not had that problem. I run the DMX742 on a 10 foot dish. (Button hook mount.) I am very pleased with it however it was a little touchy when setting it up. I have marked improvements in both C and Ku signals over the Corotor that was replaced. Have a great day!

 

[stone1150]

I do not have scaler ring arms, so I e-mailed WSI about the usage of buttonhook, that was two days ago and no message reply.

I have a button hook mount. The scaler plate that comes with the lnbf is setup for either hook or arms as it has two sets of holes to mount it with. Have a great day!

 

[Cham]

I've been using a Corotor on my 10' solid for many years with great results, but now with a new receiver without skew control I find switching polarities to be a bit of a pain in the butt... I think the best option is replacing the feedhorn with the 741 as the reviews seem to show this as an acceptable unit, however for 8psk h.264 reception I am a bit concerned with the frequency stability.
Second option would be to use the (vaporware) G-box XX with skew built in as positioner. Would eliminate the analog receiver (positioner) which I hardly use these days. Suppose this might be a first option if it existed

Still on the fence here...

-C.