359 ft run??

[red hazard]

Even with a possible typo as you mentioned, I still fail to see why the manufacturers (Belden, Andrew, Times) all seem quote loss per 100', AND the 100m numbers seem to be linear extensions (ie x3.28) of that.

Sure seems to me that your calculations must be off.

Please post a hot link. I find it very odd that Belden would make the same mistake by simply multiplying in db by 3.28 to get the loss for 100 meters. I've visited the Belden site many times and never even seen the losses posted for meters. You state that you agree that decibels are not linear yet you then seem to agree with TMR's linear conversion of db by a factor of 3.28 for meters(????). Before you claim someone's calculations are off, do the calculations yourself!

 

[SimpleSimon]

I have done the calculations using accepted and logical formulae. I don't understand why you are stuck - you yourself have said that you can directly add and subtract dB factors. If what you were saying is true, you could not state a loss factor for cable at all without knowing the power input, and we agree that you can do that. The conversion only needs to happen when you need the power value in different units.

Here's some links:

http://bwccat.belden.com/ecat/pdf/7731A.pdf
http://www.andrew.com/catalog38/LoadDocument.aspx?pagenum=664
http://www.timesmicrowave.com/telecom/pdf/400-75.pdf

Belden doesn't quote in meters, but the other 2 major suppliers do, and the loss sure looks linear to me. So, for you to be right, at least 2 major cable manufacturers have to be wrong - one of them in 2 places (spec sheet & online calculator). In addition, at least 3 different pros that I've worked with in the past would be wrong.

 

[red hazard]

Linear?

Apparently the assumption that a meter would have 3.28 times the loss because it's 3.28 times as long is not exactly true and I am not sure why. Looking at the second link in the 75Mhz row it shows a .5db for ft and 1.7db for M yet in the 150Mhz row it shows a .5db for ft and 1.8db for M. In the 450Mhz row it shows .8db for ft and 2.5db for M and in the 980Mhz row ir shows .8db for ft and 2.7 (vice 2.5db) for M. That indicates that the test results would not agree with any method one tried to calculate. Regarding power. One can, for the sake of simplicity, assume 0 dbm (1 milliwatt) is being inputted. The losses (convert to negative number in from the losses given) would hold true in dbm without any conversion. For say a 2.7 db loss, you would state a -2.7dbm. However, there DOES tend to be some linear relationship in those tables as you indicated. Back to the drawing board.

 

[red hazard]

DishPro LNBF

I
Maybe there's 2dB more loss, but the install specs say you can run it twice as far. To me that means more gain, and probably a considerably better SNR.

See http://www.microyal.com/dp-300sd.html
At least Microyal publishes their DishPro LNBF specs. A .7db noise factor is mediocre. My LNBF on my FSS Ku dish has .3db NF which is considerably better. Since I've seen a number of folks state that microyal products work well on Echostar systems, I would expect that Echostar's LNBFs would be similar to Microyal's. The typical conversion gain of 56db is not particularly great either. Many FSS LNBFs are rated at 60db (typical). According to DBSTALK the reason for allowing DishPro to go 200ft runs and not legacy was because of the DC voltage drop was so great on copper clad steel RG6 that polarization switching would not work so they went to band stacking. I would bet that 200ft runs coupled with the up conversion of half the transponders is going to make those systems very susceptible to ran fade. I was going to convert to DishPro but now have serious reservations.

 

[SimpleSimon]

I didn't drag out the calculator, but I think the differences could be nothing more than rounding error.

Remember that Dish is NOT FSS. FSS signals are weaker, and therefore require more umph in the LNA segment.

I don't know who posted the reason over @ DBStalk and would like to read it. I'm not sure just how DishPro controls the satellite switching. Maybe it still uses voltage switching. Maybe it's the 22kHz tone. Or maybe both.

I don't think they do an "up" conversion for the 2nd tp set - I think it's actually 2 separate LNA front-ends, so how much difference in loss is there in doing block-conversion from 12GHz to 950-1450MHz vs. 1650-2150MHz? I'll vote for insignifcant myself.

 

[red hazard]

Finis

The point I was making is that the DP LNBF specs. from Microyal does not seem indicate any advancement in LNBF performance. Those are mediocre LNBF specifications.

The dbstalk article I referenced is at http://ekb.dbstalk.com/217 Also see http://www.cvssystems.com/techservice/dishpro/DishProTechnology.pdf
It clearly states that even transponders are converted up to the 1650Mhz-2150Mhz (obviously using another LO in the LNBF). This is a form of FDM and negates the need for 14/18V polarization switching. Previously ALL transponders were in the 950Mhz-1450Mhz range and now only the odd transponders reside there. If one takes a gander at the frequency losses on RG6 they will note that a shift up in frequency by 700Mhz ROUGHLY will incur 2 db of additional loss; a downside of DP technology though I have not seen it discussed elsewhere. In my rain rate zone it's recommended to have at least 6db fade margin for 99.9% availability. I'll take every db I can get.

I would surmise that the DiSeqC 19 volts is to power the switches (those without their own PS) and the LNBFs. The 22Khz tone is used in FTA Ku FSS for switching to different LNBFs. DP uses it for that too.

And on the linear conversion of db I realize that it don't look good for two sites to both indicate straight multiplication is OK. But think about this. One number where the loss as a loss factor is the same as in db is the number 10. 10db loss is the same as 10 times the loss (or 1 tenth the original signal strength at the output). The formular for db is 10log(power ratio). The log of 10 over 1 or 10 obviously is 1. Multiplied by 10 of course yields 10. The LMR-400 figures at 2500Mhz shows an additional 14.8db loss for the length in meters. 14.8db is greater than 10db and it doesn't make sense that increasing the cable lenght by a factor of 3.28 would yield additional losses greater than ten times. If it was stated in a linear quantity such as milliwatts I would agree that its fine to straight multiply. I'm going to look into this at work with our engineers. Guess we've beat this subject to death.

 

[SimpleSimon]

They may be mediocre specs, but reality intrudes - they work!

I don't read that article the same way. They moved the target band up. It says nothing about down-converting to the low band and then upconverting it to the high band. Considering that there has to be two totally independent front-ends in the unit, it is much easier to simply have the second one not move the band down as far, instead of moving it all the way down and then back up. Think about it.

The TMR calculator shows approx. 6.8/100ft & 22.2/100m. That's linear. And it's right. You are misusing the calculation. I'll trust the FCC-lcensed pros that I've worked with, thank you.

 

[KKlare]

Split the switch stream?

Has anyone considered splitting/separating the low frequency switch signal from the high frequency satellite stream?

A simple breakout box could Y out the near-DC signal using an inductor (perhaps a few turns of wire around a pencil) and a optional capacitor for the satellite -- an LC divider. The near-DC would then be sent to an identical box on the other end by zip cord or the like -- watch the polarity. This way foam cable could be used for the satellite signal and have much less attenuation than RG-11's solid polyethylene dielectric. Optimize each wire for its signal type.

Just a thought.

 

[SimpleSimon]

Interesting thought. I don't know enough to know if it would help or even work. Will it pass pure DC current (about 750ma) to power the LNBs? The "near DC" as you say is a basic voltage switching of 13/18VDC - which also powers the LNBs. The other signal is 22kHz.

The cable I originally proposed before Red and I got sidetracked was LMR-400 which is a foam core, good DC (12 gauge center conductor), and rated to well above 2150MHz (I use it for 2.4GHz WiFi). His proposal of RG-11 should also work (14 gauge conductor) for the DC side.

 

[red hazard]

They may be mediocre specs, but reality intrudes - they work!


I don't read that article the same way. They moved the target band up. It says nothing about down-converting to the low band and then upconverting it to the high band. Considering that there has to be two totally independent front-ends in the unit, it is much easier to simply have the second one not move the band down as far, instead of moving it all the way down and then back up. Think about it.

The TMR calculator shows approx. 6.8/100ft & 22.2/100m. That's linear. And it's right. You are misusing the calculation. I'll trust the FCC-lcensed pros that I've worked with, thank you.

But do DP LNBFs have better specs. than legacy? Apparently not.

They separate The RHP from the LHP and use two different LOs to down convert the different polarizations to two different frequency bands which Echostar calls band stacking. There is not additional up converting. Universal FSS Ku LNFBs also use two LOs to down convert the satellite signal to two different bands (but they don't separate the polarizations before down converting). This is basic electronics. Ask you friends with FCC licenses; they might know.

Regarding linearity of decibels I found this site from a University of California: http://arts.ucsc.edu/EMS/Music/tech_background/TE-06/teces_06.html
They totally agree with me. In their example they calculate a ratio of 4.7 trillion to 23 and come up with 113db. According to your logic and that of the WEB sites you stick all your faith in, the answer would be 204,347,826,100db !! Here's another link from another University: http://hyperphysics.phy-astr.gsu.edu/hbase/sound/db.html
In their example they they calculate a ratio of 10,000 to 1 and give an answer of 40db. According to your logic and the two WEB sites you stick all you faith in the answer would have been 10,000db!!
Here's a link from Columbia University: http://www.columbia.edu/~fuat/cuarc/dB.html
In their example they show two cascaded amplifiers with a total gain of 15,125. They convert that figure to 41.79db. According to your simple logic it shoud be 15,125db!!
Here's a link from Rice University that shows a table comparing power ratios to decibels: http://cnx.rice.edu/content/m0082/latest/
It clearly shows for anyone with a limited background in mathematics that decibels are not linear. I'll keep my trust with the mathematicians and engineers with graduate degrees Thank You.

 

[SimpleSimon]

It's funny how you've contradicted yourself more than once in this conversation - such as in how DishPro LNBFs work.

What you have not taken into account, and which is the core of this whole issue, is the fact that the cable has a lower ABSOLUTE loss at lower power factors, and a higher ABSOLUTE loss at higher power factors. And guess what, it averages out to be 6Db per 100'

 

[red hazard]

In post #9 and #11 I answered "willagers" question with facts and figures. No one else did. I recommended a practical solution where the coax WOULD fit in the LNBF arm. I subsequently provided a link to a site selling F connectors. I also provided a site that sold Belden 7731A by the foot. No one else did.

In post #14 I did a detailed analysis of a working RG6 system and showed that the RG11 7731A at 350ft would have very similar losses. I explained my calculations in detail. When challenged I provided links to 4 respected Universities that showed my method of calculating decibels was correct. No one else did or even bothered to do the calculations themselves. Maybe they don't know how.

I provided data that "willager" could use to decide if going to DishPro would be a good idea including a link to DP LNBF specifications and demonstated that there would be about 2 db additional loss for the even transponders in the higher band. Only thing I saw from others was conjecture. I also provided two links that explained the distance limitation on legacy was related to the polarization switching voltage being dropped too much vice some other reason. No one else did.

In post #2 Simon stated, "You won't be able to find F-type connectors for cable that size" then in post #10 states "Oh - and TMR DOES have F-connectors for their LMR-400-75."

In post #18 Simon says, "still fail to see why the manufacturers (Belden, Andrew, Times) all seem quote loss per 100', AND the 100m numbers seem to be linear extensions (ie x3.28) of that" and in post #20 says "I saw that Andrews AND Belden make the same "mistake" that you say TMR does". In post #22 he says, "Belden doesn't quote in meters."

In post #20 Simon says, "I fully understand that dB is not linear.." and follows in post #27 "The TMR calculator shows approx. 6.8/100ft & 22.2/100m. That's linear. And it's right."

In post #31 Simon says, "It's funny how you've contradicted yourself more than once in this conversation..." HMMMMM?

In post #31 Simon Says, "What you have not taken into account, and which is the core of this whole issue, is the fact that the cable has a lower ABSOLUTE loss at lower power factors,..."

This is a distractor and totally false as the discussion on this thread applies to satellite receive systems which operate at very low power levels.

This is my last post on this thread. I'm sure the viewers have been entertained.
__________________

 

[SimpleSimon]

Well, in Post #10, I admitted I was wrong in what I stated in Post #2.

I'm big enough to do that.

In doing all my homework with definitive sources, I screwed up - thought I saw a Belden piece that supported me. So, I only have 2 out of 3 that do.

I think maybe that red doesn't know as much as he thinks he does. I myself know that I don't know a lot about RF theory (just have practical experience) and always look to others when I get out of my depth. They support me in my assertions here.

And I'm done.