Splitters, diplexers, power inserters, tap couplers, attenuators, in-line amps

[zamar23]

If you must live with one coax downlead, there are hacks and tricks, but they can get ugly, complicated and expensive. Multiswitches are the better way to go 98% of the time. Learn to love a hole saw and use it.

What physics adversely affects use of F-tees to split LNB signal?

Sure, many FTA fans would be interested to learn some techniques and workarounds on splitting signal from a single coax downlead when unavoidable.

If you could articulate what you are trying to do, even with constraints we don't like, we could probably help you a lot more rather than trying to foresee all the things that might go right or wrong.

I'm trying to promote knowledge based FTA system setup by an average Joe. : And learn from what gets revealed (the guts) along the way. That affects future plans a lot - knowledge usually does. I think, we're all trying to do the same thing here, each by own means. This site gets a lot richer in content every day - don't you think? Aren't some politicians prefer to play underachiever - why would they?

 

[AcWxRadar]

Radar

Would you agree that most systems discussed on this forum are quite specific in terms of often unique combo of the equipment used, hence its hard to develop a universal recipe good for everyone, and basic signal distro blocks like splitters should be given fare consideration, including in FAQ?

Zamar,

I would agree and I also disagree. This is what I was trying to present in my two previous posts. I am pondering Sadoun's thread about how best to help promote FTA to the masses. We truly need to boil everything down to a convenient level for everyone and for all equipment. There is too much diversity that flies in the face of making the whole scope of FTA convenient for all and not so "taboo" or uncertain.

I am all for implementing the use of splitters and combiners with FTA equipment, but we need to ensure that we start refining the practice and the instructions of all the equipment that we may use.

This thread is extremely important to that cause. Basically, we need to do a great deal of digging and clarifying and refining it all in order to translate it into useable and reliable information for everyone.

Therefore, everyone here is playing an advocate on one side of every fence. This is good, because if we did not haggle and argue and debate this subject, we would not learn what is correct and what does and does not work.

I am presenting the information as best that I know, but I am also listening to what the opposing arguments are as well. Therefore, you are correct that all equipment and the discussion of such, should be given equal consideration, but we still need to discuss all the pros and cons from all directions.

I think we will eventually boil it all down to a consistency that we can all chew on.

My ancestors were from Missouri at one point, and they have a motto... Show me! LOL So, if we are going to try some bold experiments, let's do it right and get all the information as if we were doing a scientific research program.

Basically, you started a really excellent topic here and one which could provide a great deal of useful information. Now, we need to take the subject further and into the realm of actual applications. So, we should start anew with specific examples of when and when not to use these splitters and combiners.

Surely you identify with my direction, and I see yours also. We just need to start gathering actual facts rather than surmises and assumptions. I mean to say, let's get some actual real-world applications (schematics or block diagrams) to help explain what applications are actually viable.

I must close my post here with a note of thanks to everyone who has contributed to it. You have me thinking and pondering now, and if we all do the same, we will obtain results and information.

An excellent thread indeed!

RADAR

 

[Mr Tony]

Zamar - we've talked a lot of hypotheticals, and you've opened a number of threads to get people to spill their knowledge and guts on their own systems. If you could articulate what you are trying to do, even with constraints we don't like, we could probably help you a lot more rather than trying to foresee all the things that might go right or wrong.

I agree :up

Everybody has different setups and even if they are different there may be a common ground. Thats why in alot of posts we ask what someone has for a setup already so we know what we're working with

Iceberg - evil minds think alike.

I agree

 

[zamar23]

In-line Amplifier

I found a few interesting threads on this forum directly relevant to the discussion, and addressing general device applications rather than a particular setup:

Inline Amps
What good are all-port power-passing splitters?
What's the proper DC Block to buy?

Regarding in-line amps, it seems that member opinions were divided not only on the usefulness of in-line amps for a typical FTA install, but also on where to put these amps. Some say they're better suited in the middle of cable run to amplify the decreased by distance signal (and noise) levels. Others suggest to put an amp next to each LNB where SNR is higher at high freqs than in the middle of cable run, despite LNB itself amplifies the signal well enough, and the amp saturation risk is high.

Attached is the Spec Sheet of 13dB Channel Master Single and Dual in-line amps, both reported to be good quality models. It says in particular:

"Care should be taken not to overload the amplifier. Depending upon LNB gain, this would usually involve living a minimum distance of 100 feet of RG6U between the LNB and the line Amplifier."

I couldn't find any explanation given on the forum about inherent limitations on using F-tees instead of splitters to split LNB signal.

 

[pendragon]

What physics adversely affects use of F-tees to split LNB signal?

Ideally we want all of the LNB's output power that is sent down the coax to be absorbed by the receiver and zero power to be reflected back. For FTA we approximate this by using coax cable with a characteristic impedance of 75 ohms, and matching both ends by using a LNB with an output impedance of 75 ohms and a receiver with an input impedance of 75 ohms. If any of these has a different impedance, some of the energy will be reflected and not all of it absorbed by the load. This will lead to frequency-dependent gain, resonances and other unspeakable horrors.

Let's say we want to connect two receivers to the LNB. The proper way to do this is through a splitter, which will present a 75 ohm load to the LNB and act as two 75 ohm sources to the two receivers. It can only do this last part by splitting the power into two parts via a transformer so the impedance stays matched.

If you instead use a F-tee, to the LNB there will appear to be two 75 ohm loads in parallel at the end of the coax, or effectively 37.5 ohms. This is not 75 ohms and is a very bad impedance match. A lot of power will be reflected and you will have standing waves and nulls all over the place; this will compromise reception drastically if not completely. On the other hand if all the coax is passing is power and/or DiSEqC commands, the frequencies are so low that impedance matching is neither needed nor desirable. In this case F-tees are fine and preferable to splitters.

Sure, many FTA fans would be interested to learn some techniques and workarounds on splitting signal from a single coax downlead when unavoidable.

The obvious way to do this is via bandstacking. If you only have one dish and one LNB, a bandstacking LNB is the practical solution. It is also possible to to stack and destack more than one LNB, perhaps on more than one dish. But things start getting complicated and possibly expensive.

As an example, Dish Network's Dish Pro Plus technology has a switch that can connect four bandstacked LNBs to four dual-tuner receivers (eight independent inputs) using only four coax lines. Let's suppose we hook up the 110, 118.75, 119 and 129W sats to such a switch as follows:

LNB1:

950- 1450 MHz - 110W RHCP
1650-2150 MHz - 110W LHCP

LNB2:

950- 1450 MHz - 118.75W RHCP
1650-2150 MHz - 118.75W LHCP

LNB3:

950- 1450 MHz - 119W RHCP
1650-2150 MHz - 119W LHCP

LNB4:

950- 1450 MHz - 129W RHCP
1650-2150 MHz - 129W LHCP

We connect four dual-tuner receivers A-D to the four switch output ports using DN's special separator to split the signals for each dual tuner input. Let's follow this example:

Receiver A, Tuner 1 wants 119W RHCP
Receiver A, Tuner 2 wants 110W LHCP
Receiver B, Tuner 1 wants 119W LHCP
Receiver B, Tuner 2 wants 129W RHCP

This is what the switch sends down the two cables:

Receiver A:

950- 1450 MHz - 119W RHCP
1650-2150 MHz - 110W LHCP

Receiver B:

950- 1450 MHz - 119W LHCP
1650-2150 MHz - 129W RHCP

For Receiver A, the switch simply picks off the lower band of the 119W LNB and the upper band of the 110W LNB and combines them at the switch output. For Receiver B, the switch has to downconvert the upper band of the 119W LNB to the lower band and the reverse for the 129W LNB. Straightforward, but a nifty trick.

This is a theoretical solution to your problem, but there is a catch: you would have to figure out how DN commands the switch and replicate this somehow. You would also have to use something like Superdish FSS LNBs that follow DN's DSS stacking schemes. Both of these issues could be overcome with skills and/or money. The basic parts are cheap and readily available.

Another choice would be to set up at least one 4x4 or 4x8 multiswitch on the roof plus additional DiSEqC switches if you had more LNBs than the multiswitch could accommodate. This would interface to a stacker on the roof and a destacker inside the house with one coax cable connecting the two. The twist is you would have to engineer a commanding interface to take polarization/22 kHz and DiSEqC commands from two receivers and mux these onto the coax in the house, split them off and recombine them with the signal lines on the LNB side of the stacker on the roof. This is doable and could be overcome with skills and money. Some of these parts are costly and the interfaces would require custom electronics.

Technically either approach could be made to work with sufficient investment. They are not something a novice should ever consider on their own. In most cases extolling the virtues of a hole saw to the proper authorities would be the easiest path to take. But sometimes the highest courts offer no further appeal and one is left with a Hobson's choice. That is what I have described. Do not consider this an endorsement.

 

[pendragon]

Attached is the Spec Sheet of 13dB Channel Master Single and Dual in-line amps, both reported to be good quality models. It says in particular:

"Care should be taken not to overload the amplifier. Depending upon LNB gain, this would usually involve living a minimum distance of 100 feet of RG6U between the LNB and the line Amplifier."

The specs show some differences between the single and dual CM amps, and my testing and operational experience indicates the dual is considerably better than the specs indicate. I only use the duals in my FTA system. The singles sit in my parts box for test and quick-and-dirty setups only. You definitely want to power either with at least 18V, which may be why I am seeing somewhat better performance. I tried them at 13V when I first got them and the performance wasn't anywhere near as good.

My goal at the end of the cable is to have about a -30 to -40 dBm level per channel (transponder). Not everything has enough gain to make it this high, though. Factoring in cable and switch losses, this keeps me well below the saturation point of the CM amps, which measure better than the sheet with 18V power. As I've said before, the Trunklines are much more vulnerable to saturation, but work fine with lower output LNBs. Theory and practice has always shown either brand works best at the LNB.

If I ran into a case where the LNB output was too high, I would sooner put a pad on the amplifier input rather than move the amp farther down the cable. Some of the advice given on this sheet is misleading in this respect, but it may be targeted at installers who might not have something as exotic as a power passing attenuator. But if you've designed and managed signal distros before, you'll know pads are your friends, rather than mortal enemies to those who see any loss as heresy.

 

[B.J.]

......

Let's say we want to connect two receivers to the LNB. The proper way to do this is through a splitter, which will present a 75 ohm load to the LNB and act as two 75 ohm sources to the two receivers. It can only do this last part by splitting the power into two parts via a transformer so the impedance stays matched.

If you instead use a F-tee, to the LNB there will appear to be two 75 ohm loads in parallel at the end of the coax, or effectively 37.5 ohms. This is not 75 ohms and is a very bad impedance match. .....

I am not at all convinced that the impedance at the input of these FTA receivers are really 75 ohm. I have never tried to actually measure it, but I really suspect that it's much higher, to the extent that we shouldn't really be talking about power here. I also seriously doubt that the impedances presented by any of these consumer splitters we use is very close to 75 ohms either. Part of my skepticism is due to the cost of these things, and part of the skepticism is since these things need to cover a very wide band of frequencies, and it's next to impossible to keep the impedance constant over such a wide bandwidth.

Matching impedances is real important when you're dealing with power, such as when transmitting, but for cheap receive only equipment, it's not nearly so important, so I really think that cheap consumer receivers have higher impedance inputs that aren't degraded so much by impedance mis-matches.

I have seen several instances where mismatches would result in the high quality tranceivers, which have been carefully matched to the impedance of the cable being nearly deaf, while a cheaper receive only scanner isn't affected by the mis-match. When you are careful to match the inputs, the tranceiver outperformed the scanner. I attribute this to the cheap equipment not truely being 50 ohm in that case, and I'm guessing that the FTA receivers aren't the 70-75 ohms that they're supposed to be, but are much higher, and if by chance they ARE close to 75 ohms, then I'd bet that they are only 75 ohms over a very narrow freq range, not over the whole 950-2100 band.

I've opened some of these cheap devices, and don't see anything that would suggest that there is impedance matching going on.

 

[zamar23]

Impedance

Great, now its clear when one should use F-Tees and when splitters are preferred. I found a few sites offering F-tee coax adapters: Rackmount Devices seems to be a goody, and EBay is everyone's spare parts source.

As a newbie in splitter affairs, I'm having a hard time with this "impedance" term, which when mismatched can apparently result in "unspeakable horrors"! That's what I found so far:

"http://en.wikipedia.org/wiki/Electrical_impedance"][I]Electrical impedance[/, or simply impedance, describes a measure of opposition to alternating current (AC). Electrical impedance extends the concept of resistance to AC circuits, describing not only the relative amplitudes of the voltage and current, but also the relative phases. When the circuit is driven with direct current (DC), there is no distinction between impedance and resistance; the latter can be thought of as impedance with zero phase angle."

"The http://en.wikipedia.org/wiki/Characteristic_impedance"][I]characteristic impedance[/ or surge impedance of a uniform transmission line, usually written Z0, is the ratio of the amplitudes of a single pair of voltage and current waves propagating along the line in the absence of reflections. The SI unit of characteristic impedance is the ohm. The characteristic impedance of a lossless transmission line is purely real, that is, there is no imaginary component (Z0 = | Z0 | + j0). Characteristic impedance appears like a resistance in this case, such that power generated by a source on one end of an infinitely long lossless transmission line is transmited through the line but is not dissipated in the line itself. A transmission line of finite length (lossless or lossy) that is terminated at one end with a resistor equal to the characteristic impedance (ZL = Z0) appears to the source like an infinitely long transmission line."

When it comes to impedance matching, there is interesting explanation as well:

"http://en.wikipedia.org/wiki/Impedance_matching"][I]Impedance matching[/ is the electronics design practice of setting the input impedance (ZS) of an electrical load equal to the fixed output impedance (ZL) of the signal source to which it is ultimately connected, usually in order to maximize the power transfer and minimize reflections from the load. This only applies when both are linear devices."

OK, it may be too much for my head, but it seems like something really important, I better follow in my FTA system setup just making sure to use splitters or F-Tee adapters in the right places. :up

 

[zamar23]

Power Passing Attenuator

My goal at the end of the cable is to have about a -30 to -40 dBm level per channel (transponder)...If I ran into a case where the LNB output was too high, I would sooner put a pad on the amplifier input rather than move the amp farther down the cable.

Here we go again - another goody: Power Passing Attenuator. I even found some sources of these pads, like TechToolSupply. I have several LNBs of different makes and models mounted on my dishes. Presumably, each LNB amplifies the received from dish signal and sends it to my receiver, but the amplification levels vary between these LNB models. Ideally, I want to get about the same signal level from each LNB at my receiver. That's were a combo of in-line amplifier and power passing attenuator (extra resistor) comes handy. The amp would help to compensate signal loss in long cable runs, especially notable for high frequency signals. And the attenuator would lower signal level a bit from a hot LNB right before the amp to prevent its saturation. But how would I find out, where to put these amps and where attenuators, on what lines? Is it wise to put them only on the LNB coax lines, or any other lines like these between several receivers connected via splitters - are these places good to put an amp or attenuator if required?

 

[pendragon]

I am not at all convinced that the impedance at the input of these FTA receivers are really 75 ohm. I have never tried to actually measure it, but I really suspect that it's much higher, to the extent that we shouldn't really be talking about power here. I also seriously doubt that the impedances presented by any of these consumer splitters we use is very close to 75 ohms either. Part of my skepticism is due to the cost of these things, and part of the skepticism is since these things need to cover a very wide band of frequencies, and it's next to impossible to keep the impedance constant over such a wide bandwidth.

Matching impedances is real important when you're dealing with power, such as when transmitting, but for cheap receive only equipment, it's not nearly so important, so I really think that cheap consumer receivers have higher impedance inputs that aren't degraded so much by impedance mis-matches.

I'm not going to argue that cheap FTA receivers present a perfect 75 ohm impedance over the entire L-band range. They don't need to. For transmitters a mismatch can indeed be a critical problem because you do not want a lot of power reflected back from the antenna. The case for receivers is less critical, but impedance mismatches can cause serious problems with reception, particularly for 8PSK (most of S2 at the moment) and higher order modulations. Standing waves will form at different frequencies and this can cause disastrous phase shifts.

Without a network analyzer, I can't easily provide direct evidence, but I've run into FTA mismatch cases that were obvious on a spectrum analyzer. In the most severe I had just installed a new LNB on my toroid and a normally very high CNR DVB-S signal was nearly impossible to lock. The others on that bird were also not as good as typical, but they were usable. I originally didn't suspect an impedance mismatch problem and tried to fix it on the roof rather than looking on the spectrum analyzer. When I did, the frequency band had all sorts of local dips and peaks. Swapping the inline tap with and identical part number fixed this immediately. I wish I could have saved that image, but I hadn't splurged on a GPIB computer interface at that time. The same kind of thing happened with a diplexer on another occasion, but this was more isolated to a smaller portion of L-band. What initially clued me in was the receiver performance was very much affected by swapping cables of slightly different lengths. The cables themselves were fine.

I know I haven't put any numbers on this, but I suspect that using a F-tee instead of a splitter would cause some very interesting standing waves. All my receivers are tied up today, but if I get some time perhaps I can run a curve on the spectrum analyzer comparing the two.

 

[pendragon]

Here we go again - another goody: Power Passing Attenuator. I even found some sources of these pads, like TechToolSupply. I have several LNBs of different makes and models mounted on my dishes. Presumably, each LNB amplifies the received from dish signal and sends it to my receiver, but the amplification levels vary between these LNB models. Ideally, I want to get about the same signal level from each LNB at my receiver. That's were a combo of in-line amplifier and power passing attenuator (extra resistor) comes handy. But how would I find out, where to put these amps and where attenuators, on what lines? Is it wise to put them only on the LNB coax lines, or any other lines like those between several receivers connected via splitters are good places to put an amp or attenuator if required?

It's a bit odd, but Tech Tool Supply is a great source for a oddball FTA parts.

FTA receivers have AGCs (automatic gain controls) to compensate for very large variations in LNB output levels. I have not measured typical ranges, but I would guess they could handle 30-50 dB variations. Some are better than others, but one tends to see performance deterioration at the extremes of the AGC range. I've found my receivers perform best when their AGC gains are low, but not at the point of saturation. Keeping the output level within 10-15 dB works just as well as keeping it within 1 dB, which wouldn't be feasible because transponders can vary by a lot more than that.

FTA amplifiers tend to be only available at certain gain levels, nominally around 10-15 dB. Attenuators can be used to fine tune this a bit, but in most cases there is no need. However if a LNB has a very high output level, I may back it down a bit with one. I also use pads on the input of my signal meter because the internal attenuator is a pain to switch in and out, and doesn't provide a small enough step to be useful. I think most people can easily live without attenuators except for unusual cases. Without the right equipment, choosing the correct value can be difficult.

 

[zamar23]

Cheap Splitters

I have found very little difference between the cheap splitters that are used for TV, and only rated up to 1000MHz, and the more expensive splitters that are rated up thru 2000 MHz. There may be some small differences, but I've never noticed anything I couldn't receive using the cheap splitters that I could receive using the more expensive ones.

One of our friends subscribes to Cable TV and internet. He recently moved his cable modem upstairs and added a few extra TV outlets in his house, then suddenly started complaining that internet speed seemingly dropped, and people now have problem hearing him over a VoIP phone, plus Cable Interactive Services also become painfully slow. When I looked at what he's done, the reason become clear: he added a few cheap splitters from a Dollar Store rated at 5 - 2300 Mhz (based on their sticker) to the existing distribution such a way that affected both cable modem and HD Cable STB performance. SNR on his Motorola cable modem web interface was showing 32 dB which is the lower spec limit, while Downstream and Upstream Power Levels were well within the spec. As he didn't want to move the modem and router back to basement close to a multimedia drop-amp, I simply replaced his splitter on the Modem - STB cable split with Antronix CMC2002H-A rated at 5-1000 MHz. SNR on the modem immediately went to 39.2 dB, and download & upload speeds skyrocketed, as also ordering speed of Cable-on-Demand services. Just for demo purposes I replaced the Antronix with another no-name splitter rated at 5-1000 MHz, and SNR went down to 36 dB. Since I didn't have more Antronix splitters, I gave him a few Regals for the rest of his project. No complains so far, despite his distro is far from ideal.

I think it would be wise to recommend using high quality brand name splitters designed and rated for the intended application, and stay away from cheap Dollar store stuff to avoid notable signal and performance degradation. It was mentioned on this site that Perfect Vision, Holland, Regal, Eagle Aspen and some other splitter and diplexer brands perform consistently well in FTA applications.

 

[pendragon]

I know I haven't put any numbers on this, but I suspect that using a F-tee instead of a splitter would cause some very interesting standing waves. All my receivers are tied up today, but if I get some time perhaps I can run a curve on the spectrum analyzer comparing the two.

Here it is. I805 C-band, H pol on the spectrum analyzer as a reference and a badly matched termination (see plots). The reference uses the SA's internal 75 ohm terminator and for the mismatched spectrum, I used a F-tee, a high quality 75 ohm terminator and a 21 cm stub of cable to connect the tee to the SA. I cranked the video averaging so there is a miniscule plot-to-plot variation.

If everything was ideal (DC, pure resistive source and loads), one would expect a 3.5 dB loss vs. the reference. The slight extra loss is because the lower termination impedance causes more power to be dissipated in the source. The vertical scales are identical (5 dB per division) and comparing frequency point to frequency point, I see relative changes from around 2-8 dB. Even over narrow frequency ranges, there are significant differences. This means there will be multiple phase shifts across a high SR, high modulation index signal, that may not be readily equalized.

I didn't take the pic, but a different length stub changed the plot as would be expected. And it should be noted the SA and additional terminator are likely more resistive than a typical FTA receiver. This is a fairly best-case comparison.

 

[guapoharry]

I don't understand what the difference is between a splitter and a diplexer.

Could somebody please explain?

 

[Mr Tony]

a diplexer combines two inputs that run on different frequencies (like satellite and antenna).

You use them in tandem and it allows you to use one cable
example

antenna-----ant input on diplexer---------------------------ant output on diplexer----ant in on receiver
sat------------sat input on diplexer..................................sat output on diplexer--sat in on receiver

disadvantage is there is a loss of signal so weaker signals may not come in

 

[B.J.]

a diplexer combines two inputs that run on different frequencies (like satellite and antenna).

You use them in tandem and it allows you to use one cable
example

antenna-----ant input on diplexer---------------------------ant output on diplexer----ant in on receiver
sat------------sat input on diplexer..................................sat output on diplexer--sat in on receiver

disadvantage is there is a loss of signal so weaker signals may not come in

I've never used one of the sat/TV type diplexers, but used to use ham radio diplexers that would separate 2M from 70cm band, to feed a dual band tranceiver from a single dual band antenna. They worked pretty well, and I didn't notice much in the way of signal loss, although I guess there is always signal loss whenever you put anything in line. Of course consumer TV devices probably aren't of the same quality as the ham radio diplexers, plus the ham bands are narrower and further apart, so I guess it's easier to separate the bands.

I wonder though, if the filters in these diplexers might even improve a sat signal by filtering out noise, even if you weren't using the TV part of it? Ie you might lose some signal, but it might clean up the S/N by removing some noise?
Just something that occurred to me while viewing your post.

 

[zamar23]

More Diplexers

Another example of using diplexers in FTA was suggested by Anole and Pendragon in the following threads:

Naughty Mods I: DG-380 Separate Drive Power
Satellite System Structure Optimization
Two receivers - one motor: possible?

Shown in the above threads diagrams depicted using a diplexer in a single or multi-motor installation to separate motor commands from main signal coax and switch commands transmitted over it, thus eliminating usually associated with cable split satellite signal losses. Separated motor commands are then combined using a power passing on both ports combiner (splitter in reverse), and directed towards the motor. Its presumed, motor commands from different receivers to be sent one at a time, not simultaneously.

"You need to get a diplexer that passes power to both ports. This way the DiSEqC commands will appear on both the SAT and OTA ports. DiSEqC is modulated 22 kHz, so it looks like DC to most everything inline."

 

[zamar23]

Power Inserter

Pendragon

The above motor control solution is based on powering a modded motor by a separate extra coax that might not always be possible in one's circumstances. That brings to light another basic creature: In-line Power Inserter - another kind of diplexer. Is it possible to insert power to the line running from the combiner to motor using a 18V Power Inserter? Would the power coax line need to be then separated at the motor from its command line with another power inserter (acting in reverse as a power separator) and connected to the modded second motor port, or it can be delivered as in standard motor control solution to the motor command port, thus requiring no motor modification affecting its warranty? Advantages & drawbacks of such solution? What power inserter make and model will suite the best? Would it require to also add a DC Block and where exactly, or such Block is usually incorporated into a Power Inserter and /or power passing Diplexer to block power passing in reverse? A hand drawn schematics would help.

As an example, show below Channel Master 8001IFD Power Inserter incorporates a DC Block and can supply power to LNBs, TV Line Amplifiers, Boosters and Preamplifiers. The Channel Master 8001IFD general purpose power inserter supplies a max of 60 Volts and 2 amps. Required voltage and power determines choice of a proper Power Adapter. Summit Source offers a good choice of Power Inserters and DC Voltage Block Coax Adapters.

 

[zamar23]

Without the right equipment, choosing the correct attenuator value can be difficult.

Still, can you explain how exactly you derive the required pad resistance? You mentioned in another thread that a BLSA type device can possibly be modeled with a PC Card tuner. Would it help to analyze one's signal distribution system irregularities and compensators required without a Spectrum Analyzer?

 

[pendragon]

PendragonThe above motor control solution is based on powering a modded motor by a separate extra coax that might not always be possible in one's circumstances. That brings to light another basic creature: In-line Power Inserter - another kind of diplexer. Is it possible to insert power to the line running from the combiner to motor using a 18V Power Inserter? Would the power coax line need to be then separated at the motor from its command line with another power inserter (acting in reverse as a power separator) and connected to the modded second motor port, or it can be delivered as in standard motor control solution to the motor command port, thus requiring no motor modification affecting its warranty? Advantages & drawbacks of such solution? What power inserter make and model will suite the best? Would it require to also add a DC Block and where exactly, or such Block is usually incorporated into a Power Inserter and /or power passing Diplexer to block power passing in reverse? A hand drawn schematics would help.

The mod is only necessary if you want to supply motor power independent of the commanding line. If you only want to separate DiSEqC commanding from the LNB connection, there is no reason to do it. Regardless, a power-passing diplexer is arguably the best way to do this split with off-the-shelf components. One can do it with power inserters as you have pointed out, but one has to be more careful to avoid impedance mismatching. I see no compensating advantage with power inserters. Are you trying to use the power inserter to supply the motor power? If so you need to make sure the DiSEqC commands have some path to the motor. That can easily be done, but might require a little extra engineering. Hence the mod.