Max distance from dish question

[JosephB]

I'm looking to setup a new motorized FTA system. Close to the house we have plenty of trees, but a few hundred feet out there is a great place that I should be able to pick up the whole arc. What is the maximum distance I can have between the receiver and the dish, and if I'm over it, can I amplify it? If I can amplify it, how many times? I'm probably looking at a good 300 feet or so.

 

[Anole]

things to ponder:

I've never had to go that far, but I can tell you some things to consider.
We've undoubtedly got more experienced folks on the forum, and they can nail down the rest of the details.

- RG-11 coax and proper fittings (bigger than RG-6)
- 1 meter commercial dish
- possibly a bandstacked LNB (see below)
- NO amplifiers!

The larger coax will cost a lot more.
It'll have lower signal loss and lower voltage (power) drop.
Discuss the use of all copper core , not copper plated steel core.

Bandstacked LNB vs regular 'cause you only need one voltage on the coax.
Usually, 18 volts is sent.
Regular LNBs are voltage sensitive, so you'll have trouble changing polarity if there's a large voltage drop.
Bandstacked LNBs avoid that problem

The matter of amplifiers will be discussed by others.
See what they say.

.

 

[rv1pop]

Well said Anole! The only thing to add would be to get the best QUALITY connectors Broadcast grade and waterproof all connections. The cable is too expensive and the run is too long to skimp.
POP

AND repeat - NO AMPLIFIERS.

 

[JosephB]

Ok, no amps. So is there not a maximum distance like DBS? I'm only going to need to feed one receiver, this is definitely a hobby and I'm really in this to find feeds and not for regularly scheduled programming I'm just wondering if anyone knows of a setup that far out that has worked before? I'd hate to buy all the stuff and then not be able to use it.

This weekend I'll try to get a rough estimate of how far out it is.

 

[Cadsulfide]

Can you go North of the house 75' in order to see over it, and the trees? Dishpointer reports 35 degree elevation.

 

[jamestheman]

I doubt 75 feet will work too well with a motorized system, the most I ever went was 100 and I could tell a little difference from my normal 50 or so.

It might work, I doubt it will work as well as if you had it closer though.

 

[JosephB]

If 75 feet is the fringe, then where I need to go is definitely out of the question. It is over 150 feet, but maybe less than 300 feet.

 

[turbosat]

josephb , I'm about 25 min n of Trussville, and have a good sharp chain saw lol.

 

[pendragon]

Your best first step would be to use RG-11 with a solid copper center conductor and quad shielded. This will provide half the DC resistance and about half the high frequency rolloff of similar quality RG-6. The quad shield isn't as important as the all copper center conductor in terms of DC resistance, but it helps. At 300 feet such a cable would only drop about 0.5V with a typical motor load; that will be no problem. In fact the RG-6 would drop around 1V, which isn't a big deal either.

Bandstacking has good and bad points. It will allow you to run your motor at 18V all the time. However it will put a premium on your high-frequency performance, as the cable will have to carry signals up to about 2150 MHz, instead of 1450 MHz. There will be several dB of extra loss for the high frequencies. Again RG-11 will help some.

I strongly disagree about using an amplifier at this distance. The only times I have seen amplifiers measurably degrade signals at these frequencies were:

1. The amplifier was not needed.
2. The amplifier noise floor was close to or above the signal noise floor.
3. The amplifier gain was too high to support the required maximum output level.
4. The amplifier was simply crummy.

Admittedly without the right equipment, amplifiers can be easily misapplied. However a good amplifier, and in your case perhaps more than one, would likely make the result imperceptibly different than having the dish a few feet from the house. Good amplifiers will normally have the right specs and will provide slope compensation to offset the high frequency losses present in long cable runs.

The NF of the amp would ideally be around 2-3 dB, but certainly no more than 5 dB. With 300' of RG-11, you will need something around 15 dB of gain plus slope compensation. Less gain is better than more. Make sure the amplifier can take the maximum output of the LNB at full gain without more than say 1 dB of compression. Put the amp on the dish. If you need another, put it halfway down the line.

One of my motorized dishes has a 150' run to the house. I used RG-6 with a normal shield and measured some degradation using a non-bandstacked LNB on my spectrum analyzer, and by comparing signal quality with the receiver at the antenna vs. at the end of the line. A decent 10 dB amplifier on the dish erased all degradations. If I had used RG-11 quad shield, I could have gone out to 300' and would see basically the same results. Actually while it would require a little more effort, I'm sure I could handle your entire pull with RG-6.

I am uncomfortable disagreeing with my distinguished colleagues, but this is a problem that can be solved. It's the same basic approach cable providers have been employing for years.

 

[ACRadio]

All my dishes are no less than 250ft and the farthest is about 300ft...and I have a motorized oval Primestar at about 275ft. Use good quality RG11, forget the amps, and hook 'er up...you'll be just fine. I have about 4000 ft of RG11 in my runs...most was Commscope but I used one roll of Times...none is solid copper center conductor...just copper clad steel.

 

[pendragon]

All my dishes are no less than 250ft and the farthest is about 300ft...and I have a motorized oval Primestar at about 275ft. Use good quality RG11, forget the amps, and hook 'er up...you'll be just fine.

Probably, as long as the LNB and dish have enough gain, as long as the receiver isn't deaf, etc. Receivers normally specify a fairly broad dynamic range (30-40 dB), and will work well as long as the signal levels fall within it. LNBs are designed with a limited gain for economic purposes and to not overload a typical receiver or intervening components should the cable run be short. This puts limits on how far one can pipe the signal without amplification.

A few receivers, for example the Pansat 9200HD, have an optimistic sensitivity spec and are prone to losing signals at low input levels. A weak transponder, a small dish and a middling LNB will not generate booming outputs.

If one uses a non-bandstacking LNB on 300' of RG-11, you will lose around 14 dB at 950 MHz and 18 dB at 1450 MHz. Put in a bandstacking LNB and it will lose nearly 22 dB at 2150 MHz. Connections and switches may also contribute losses. In a hypothetical case where a receiver that degrades signals below -60 dBm is used with a bandstacking LNB, guaranteeing the LNB output is always above -38 dBm would be on the hopeful side for most FTA dishes. No doubt the typical scenario is not as bad.

There is no harm in first trying straight cable without an amplifier. If you end up with signal level problems, it's cheap and easy to add an amp. For me, roughly balancing levels on my LNBs and cable runs makes troubleshooting a lot simpler, and in every case has improved my reception margin on very weak signals. I am only offering the opinion that amplifiers are not always a bad thing.

 

[Anole]

Discussions are a good thing, here.
But often people ask question A, then ignore the "... but that requires you to consider X, Y, & Z".
They just want a simple answer.

Most don't have the test equipment to properly evaluate signal levels, and amplifier performance.
What I love, is someone asking, "can my old (too small) dish receive FTA?"
There are two answers:
- NO, it's not suitable for all the signals you will encounter.
- YES, it'll get that one hot bird you want.
Whichever answer you give, someone will contradict you! -

ACradio certainly doesn't spare the square inches on his dishes.
So, his results are positive.
Another user, skimping on dish size, accuracy, or LNB, might have a different result.
And, I'm darned sure he's using the right connectors, applied correctly, too! - :up

As for bandstacked LNBs, they are designed with a tilt to lessen the loss at higher frequencies.
Anyone using cable not rated for 3ghz, will be at a loss, of course. (pun intended)
But the point is still well taken that losses will increase in a bandstacked system!

One thing folks overlook, is the significant losses through each switch, and certainly the motor!
A troubleshooting technique for the test-equipment impaired, is to bypass both and see if it helps.

There are boxes for repowering the LNBs which are located at a distance.
I'm not endorsing such things, but someone uses them.
Also, there are procedures to remote power to the little HH motors, bypassing the coax entirely.

Not everyone will apply good engineering, but it's always appreciated. - :up

 

[JosephB]

I appreciate the discussion. This weekend I'm going to get a better handle on the distance. I have an old primestar dish as well in a location that is pretty much only able to see the old primestar slot, trees in every other direction. If I can move it and use it, great. If I need a larger or different dish no big deal.

This is probably going to be a long-term project into the summer. It's not cold here, but we're doing some work to the house so I don't have a ton of time or money to put into it immediately, however I wanted to get some info and during my down time at work I can do some planning and research.

 

[pedrogarcia]

The cost of cable in the US was a big surprise to me, for some reason it is still nearly twice the price of cable in Europe and there no-one would seriously consider using steel core. I always bring 100m back to the US, it doesn't have a use by date.
In this case I would definately use copper as the volts drop on steel over that distance would not allow polarity change unless your receiver can increase the LNB volts in the menu. R11 is the right way to go but the cost wow!
I am not a fan of amplifiers remember they also amplify noise. Dish size is more important

 

[pendragon]

I am not a fan of amplifiers remember they also amplify noise. Dish size is more important

Dish size is just about the whole ball game. Once the LNB spits out the signal, an amplifier cannot improve it. If we all watched TV next to our dishes, there would be no need for amplifiers. However long cable runs, connections, switches, high frequency roll-off, etc. will attenuate both signal and noise levels. As long as the effective noise floor of the receiver is enough below the noise level delivered at the end of the cable by the LNB, everything will be fine. Using an amplifier would be of no value.

However if there is enough attenuation, and the noise level at the end of the cable approaches the effective noise floor of the receiver, the CNR will be degraded. The right amplifier can fix this in an instant.

There are a few caveats: if you need an amp, use only the minimum gain necessary, and make sure everything in your signal chain can handle the output level. When I first installed my 3m, my spectrum analyzer made it clear I could use a little boost on the very weakest transponders. I tried installing an amp, but it didn't work very well. I measured levels all the way back to the house and everything was -30 dBm or lower, just where I wanted them. Stumped.

When I replaced my unpowered 4x4 switches with powered 4x8s plus DiSEqC switches, I tried the amp again. Worked perfectly. It turned out the 4x4s couldn't handle -30 dBm without some compression. I discovered the 4x4s had even been affecting straight LNB outputs on strong transponders. It would have been easy to blame the amp, but it wasn't the problem. Amplifiers are simply there to match signal levels to what you require, when you need them. If you want to design a good one, it's pretty straightforward nowadays.

A CD player can generate enough output to drive headphones, but not speakers. So we use an amplifier to match the output level to what is required. Too much gain can be as bad as too little in audio also. But I hear very few complaints about the need for audio amplifiers, and fundamentally a coax amp is only doing the same thing on a smaller scale.

 

[ACRadio]

R11 is the right way to go but the cost wow!

$150/1000ft shipped to my door isn't bad for Andrew RG11 in my opinion...15 cents a foot...

 

[B.J.]

All my dishes are no less than 250ft and the farthest is about 300ft...and I have a motorized oval Primestar at about 275ft. Use good quality RG11, forget the amps, and hook 'er up...you'll be just fine. I have about 4000 ft of RG11 in my runs...most was Commscope but I used one roll of Times...none is solid copper center conductor...just copper clad steel.

I agree. My BUD, two 3' dishes, and a DirecTV dish are all out about 225-250'. I don't use the expensive coax, just inexpensive RG6, and actually, when I first installed my BUD, I only had a 175' run, but I moved my receiver, and had to add 75', and I actually spliced 75' of RG59 to the RG6, and even that worked. I've since replaced the RG59. I do have a bit of roll-off at high freqs, but not enough to affect reception, and I think most of that comes from my diseqC switch. My biggest problem is getting enough power to the motor on my BUD. I thought I would have problems with power and diseqC signals to my SG2100 motor for my 3' dish, but it works fine.

Anyway 250' is no problem even with cheap cable, so 300' shouldn't be a problem. And I agree that amps would make things worse. Amps are requirred when you're dealing with weak signals, but these signals have already been amplified in the lnbs and are not weak signals.

 

[pendragon]

Amps are requirred when you're dealing with weak signals, but these signals have already been amplified in the lnbs and are not weak signals.

If what you have is working and you're happy, I would be the last to suggest you change it. However the above is a misconception. Dishes are the only part of our signal chain that give us real gain, as in an improvement in signal over noise. LNBs amplify like amplifiers, but not always enough. I'll try to illustrate an example.

A LNB block converts part of the spectrum and amplifies it by around 60 dB. It cannot improve the dish's CNR, but it will boost the signal level to something that can travel down a cable. Ideally this puts the signal and the noise floor within a window of roughly -30 to -65 dBm, which is the design range for most receivers. Some are better, some are worse. A fair number of receivers can accept more level on the high end, but fewer are designed for lower input levels. If the signal level into the receiver is too low, you'll compromise a weak signal. If it's too high, the receiver may go into compression and compromise a strong signal. Either way it's marginal engineering.

I'm going to take a few liberties, but let's say I want to receive a DVB-S2 8PSK signal at a respectable FEC. I'll need at least 10 dB of CNR.

-30 dBm - (-65 dBm) = 35 dB receiver window
35 dB - 10 dB = 25 dB of dynamic range

The dynamic range represents, at least spec-wise, the difference between the weakest and strongest signal I can receive with negligible degradation. 25 dB is plenty, but I'll likely have somewhat less because the fixed gain of the LNB will not perfectly center the 'output' of the dish.

Let's say I run 300' of RG-11 and use a normal LNB. At 950 MHz, I'll attenuate signal and noise by 14 dB, and at 1450 MHz, I will lose 18 dB. That means my maximum dynamic range could drop to 11 dB at 950 MHz and 7dB at 1450 MHz. I say 'could' because the LNB may output more than -30 dBm on boomers, in which case I might have problems with a shorter cable run, but I'll buy some dynamic range back on a longer run.

Regardless I might get by and not notice any problems, but I've lost a lot of margin. As long as most signals work, I'll probably not even realize I've lost reception potential. This is hardly the worst case, because there will be other losses in switches, connections, etc. and you could be using a bandstacking LNB.

If I were to insert an amplifier at the dish with 10 dB of gain and 4 dB of tilt, the dynamic range would be only be degraded to 21 dB. I'll take that any day for less than $20, but will try to shut up now.

 

[Wescopc]

I just did a install/service call - without a motor. In a nursing home pre wired with RG-6 for cable service. Home run wiring from all of the rooms to the head end with RG-6. Had a 90cm dish already installed (aimed@101W) with 250 foot run to the head end. Wanted to use existing wiring to three rooms for a receiver in each room. Furthermost room 350 feet from head end. Total footage 600 feet! I Installed a Sonora LA141 (14 dB gain) before a powered multi-switch and another one in the line going to the far room. This effectively reduced my cable run from 600 feet to ~ 300 feet. It worked fine. I'll see how well it does this summer with a hot attic and hot RG-6! The system(s) would not work at all without the amplifiers. So amps do work when you need to pull things up out of the basement.
Bob

 

[pedrogarcia]

$150/1000ft shipped to my door isn't bad for Andrew RG11 in my opinion...15 cents a foot...

Depends very much on the cable spec but is certainly a good deal for the US


Like Your Dish farm pictures!!!