I realize and understand what you are saying about "written specifications" for different cables and what a person can prove with simple math. However, there are many nice advantages in doing things with passive devices, as opposed to powered and active components. Especially in regards to maintenance and compatibility issues.
I guess it depends on one's perspective. I prefer to employ amplifiers as needed, partly because of maintenance and compatibility issues. By tuning the gain for each cable run so the levels are about the same, I find it much easier to troubleshoot any problems that might occur. I have also found this minimizes the compatibility issues between different tuners and switches that may perform differently at low signal levels. I want the performance of any tuner to be as good in the house as if it's patched directly to the LNB with a 1' cable. That's the main reason I use amps.
Granted there may be a reduction in system reliability when amps are added, but I expect it to be close to negligible. I can't quantify this because MTBFs and/or failure rates are generally unavailable for FTA devices. However if one compares the circuitry in a FTA amplifier to what is inside LNBs, switches and receivers, one will see the component count in an amplifier is small compared to other devices. Reliabilities tend to scale inversely with circuit complexity.
From an anecdotal point of view, I have used amplifiers in satellite and OTA applications nearly 40 years. I am not aware of a single failure or loss of performance. In the case of a couple of OTA amps I put up 35 years ago for my parents, who live in a deep fringe area, I checked these a couple of weeks ago and they measure the same as when they were installed.
One thing for certain, a signal amp will not help you with DC line losses for operating a H-H motor or a voltage controlled LNBF or switch. The RG-11 cable improves this over the RG-6 cable. A signal amplifier won't assist in this aspect as it does not amplify the DC signal from the receiver.
I did say RG-11 is better cable, but as with signal attenuation, the improvement it offers in DC losses over RG-6 may be less than one might expect. If one compares apples to apples (similar construction), RG-6 has a DC resistance about twice that of RG-11. The question is how much this matters.
I'll consider a fairly extreme case of a 300' run with a LNB that draws 150 ma and a DiSEqC motor that draws 350 ma. Most LNBs draw considerably less and the DG-380 motor I looked up draws 200 ma under "normal" load. At this distance I would likely not use coax for motor power, but if I had to I would certainly go with copper-core and probably quad shield. For RG-6/RG-11 there will be a 0.5V/0.25V drop with the LNB only and a 1.65V/0.84V drop with the motor running. The improvement that RG-11 offers is 0.81V for LNB + motor running and 0.25V for LNB + motor off. This is well within the tolerances the LNB and motor are designed to operate within, and I don't think either will matter very much.
In your statement that I quoted above, remember, that the dB scale is a logarithmic scale and a difference in 3 dB is either 1/2X or 2X the power. So, if you compare a 200 foot run of RG-6 cable and a 200 foot run of RG-11 cable at 1 GHz, the result is 13 dB loss for RG-6 vs 10 dB loss for RG-11. This is a difference of 3 dB or 1/2 the effective power for the same distance of cable. Considerably worse at 2GHz.
I don't get your point. As I said in my original post the loss for either 1 or 2.25 GHz is about the same with 130' of RG-11 as with 100' of RG-6. The point is a properly placed amplifier can easily compensate for a loss of signal power with an almost immeasurable loss in CNR. In fact, a proper choice of amplifier with RG-6 will generally outperform unamplified RG-11 because it will compensate for tilt. With RG-11 alone you will have higher losses at the higher frequencies. Been there, done that a thousand times.
Actually calculating the differences out per foot is a bit too much for this time of my morning, but, for a real world scenario, I was able to compare the difference between 300 feet of RG-6 to 300 feet of RG-11 and I found a very substantial difference at the receiver. As well as with the motor and LNBF operation. Therefore, I found out first hand that RG-11 provided me with an extreme advantage over RG-6.
I will not argue against RG-11 being one option that can help with longer cable runs. If it works for you, I am not trying to convince you to change. But cable is one component that is easy to measure/spec, is manufactured to fairly close tolerances and performs very close to calculated values. I don't know what you mean by "substantial" and "extreme advantage", but I would not use the same adjectives. I have a 500' roll of RG-6 and a 500' roll of RG-11 and when I measure the DC losses and sweep them on my spectrum analyzer I see pretty close to the specified numbers. RG-11 is certainly better, but not by a lot. And if I insert an amplifier into the RG-6 line, it blows away RG-11 alone on attenuation and tilt, and when feeding even my most sensitive tuner I see a better CNR with the RG-6/amp combination vs. RG-11 alone.
My one concern is that if you see the drastic difference in performance you are reporting at only 300', there may be other issues that need to be solved in your system because it appears you might be near a threshold point.
I am a firm advocate of using the least possible powered or active devices in any system. All such devices do add some level of their own backgound or amplifier "noise" whereas a passive device like a better cable does not. Therefore, powered devices and amplifiers intrinsically diminish the CNR right off the bat whereas a passive component, such as a better quality cable, will not. Keeping the overall system as simplistic as possible is always the best policy and that is probably my biggest reason for avoiding amplifiers.
I think you are missing the point. LNBs and receivers are certainly not passive and have considerable gain built-in. If there's enough gain for the cable run, there is no reason to use an amplifier. However LNBs cannot be built with too much gain or there would be the potential to saturate the front-end of some receivers on a short cable run.
The demodulator sections of a receiver will generally only perform optimally in a very narrow range of input level. To compensate this, tuners have a variable gain stage, called an AGC, that automatically adjusts its gain so the signal drives the demod at its preferred level. As one increases the signal attenuation with longer cable runs, the tuner's AGC must necessarily increase its gain.
The problem with this approach is that it quickly leads to compromised CNR. A LNB should output the transponder signal level so the dish's noise level is well above the theoretical thermal noise of the characteristic impedance of the distribution coax. However with long cable runs, the dish noise level gets closer to the characteristic impedance's thermal noise. When the tuner's AGC kicks in, the additional gain is also applied to the latter's thermal noise.
Compare this to putting an amplifier right after the LNB. The difference between the transponder levels and the dish's inherent noise floor will be virtually the same coming out of the amp, but this will be at a much higher absolute level. The tuner's AGC will drop its amplification of the characteristic impedance's thermal noise by the amount of the amplifier's gain. This can result in very measurable improvements in CNR relative to the unamplified case. This is a classic example of "you can pay me now or you can pay me later".
I have omitted the example calculations I provided in earlier threads that quantify this. There are different approaches people take and I have no problem if someone gets something to work with a different technique than I would use. But no amount of ingenuity and wishing can overcome the laws of physics, which happen to apply extremely accurately to the domain of satellite signal reception. There is enough slop built into the systems we use to provide good reception even when the approach employed is not the best. In this case, one has a choice to put the gain at the tuner (with the AGC) or at the LNB (with an amp). Both will work, but one will always work better when properly implemented.
That was many years ago, but I do remember saturating the front end of my amplifiers on a cable system and having a horrid looking picture. I was just investigating the stuff without really knowing anything about it back then.
