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Thread: RF Modulator headache

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    Thumbs up RF Modulator headache

    This is a new experiment for me so I'm no expert, so I hope somebody can help...

    I have connected an RF Modulator to a CCTV camera system via HDMI and want to display to all TV's. So the setup I have tried is:
    I have a 4 port splitter from FTA with masthead amplifier;
    I have the modulator and FTA connected to a combiner (reverse 2 port splitter with all port power pass), connected to the input of the 4 port splitter, making sure the cable connection to the
    masthead amplifier power supply is in correct port.

    I just want to know if this is a correct setup? As I lose all TV channels when connected like this (I have tried 3 different combiners)
    The two splitters are from different manufacturers, does this matter?
    The modulator is working as if I connect it direct to a TV it works

    Any suggestions or tips/tricks and don't do's would be appreciated.
    thanks..



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    the modulator is getting up the masthead amp and squashing it

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    More info needed.

    What frequencies are your TV channels and your modulator?

    What type of modulator.. analogue or digital? Make/model or specs would be helpful.

    What signal levels are each of your off air channels and the modulated signal (at the amp input?)

    Make/model of amp... or specifications?

    The connection method you are using is OK, however it's essential that signal levels are balanced... eg: all around the same level.

    If not balanced, the modulated signal may be overloading the amp, or causing errors in the digital data stream.

    Make of splitter/combiner doesn't matter, providing they cover the frequencies used.

    If possible, keep the modulated signal on a different frequency band than your FTA signals with an amp that has separate inputs for those different bands with adjustable attenuation on each band.

    Eg. use separate UHF bands 4 & 5, or UHF and VHF.

    Some modulators have the ability of combining and balancing signal levels, which then get fed to a distribution amp.

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    Quote Originally Posted by ozsec View Post
    I'm no expert
    Neither am I.


    Quote Originally Posted by ozsec View Post
    (reverse 2 port splitter with all port power pass)
    I suspect that is the problem. If both ports of the 2 way splitter used as a combiner pass power, it's possible the static protection sink on the output of the modulator is shorting out the masthead amplifier power supply.

    I would use a 2 way one port power pass splitter like this:



    and connect the modulator to the non power pass port.

    I would also set the modulator output to 70dBµV if that is possible.
    Never stand under a shadow that's getting bigger

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    Quote Originally Posted by ozsec View Post
    (reverse 2 port splitter with all port power pass)
    I missed the important bit of ALL port PP, which as Antennaman has pointed out, may be an issue.

    It can also make a difference at which point in the chain you are injecting power to the amp.

    In addition to the questions I asked in the earlier post, are you using the MH amp due to poor FTA signals, or just to overcome losses associated with splitting?

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    Thanks to all whom replied. All great information. MTV I am using the MH amp due to poor signal strength on FTA. It would seem helpful if I get myself a signal strength meter to do some more in-depth testing. I am using the Blauhaus HD1090 Digital modulator, as far as the MH amp is concerned I'm not sure right now, I'm guessing it's your stock standard Matchmaster. I did try connecting the modulator to a non PP port on another splitter, but that didn't work. I'll test again to see if the Modulator is shorting out the MH power supply as suggested by Antennaman (i guess that is easy enough, just see if the power supply LED goes out??) In terms of balancing the signals, would I be correct in assuming this is done by adjusting the gain at the MH and modulator??
    thanks again all for your input.
    ozsec

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    I've looked at the manual for your modulator and it does have provision for combining signals.

    In this instance, the best way to combine FTA with the modulated signal is to configure the modulator as the combiner.

    Eg: FTA antenna signals go through the modulator before splitting/distribution.

    If the FTA signals rely on the MH amp to work sufficiently, then you need to take the output of the MH amp directly to the modulator antenna input, then the output of the modulator (now with combined FTA and DVB-T modulated HDMI input) into the splitter going to the TV's.

    Yes, level balancing is adjusted via the amp and modulator.

    When balancing digital signals, you not only need to ensure signal levels are within the operating margin (DCP) typically 65-75dBuV is ideal, but you also need to ensure BER/MER is also at acceptable levels, so you would need a meter capable of reading and displaying BER and MER.

    A common mistake may people make with digital is using an amp with too high output level, noise level, or both.

    Try connecting your system up using the modulator to combine the signals, as per the instructions in the manual.

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    Quote Originally Posted by mtv View Post
    I've looked at the manual for your modulator and it does have provision for combining signals.

    In this instance, the best way to combine FTA with the modulated signal is to configure the modulator as the combiner.

    Eg: FTA antenna signals go through the modulator before splitting/distribution.

    If the FTA signals rely on the MH amp to work sufficiently, then you need to take the output of the MH amp directly to the modulator antenna input, then the output of the modulator (now with combined FTA and DVB-T modulated HDMI input) into the splitter going to the TV's.

    Yes, level balancing is adjusted via the amp and modulator.

    When balancing digital signals, you not only need to ensure signal levels are within the operating margin (DCP) typically 65-75dBuV is ideal, but you also need to ensure BER/MER is also at acceptable levels, so you would need a meter capable of reading and displaying BER and MER.

    A common mistake may people make with digital is using an amp with too high output level, noise level, or both.

    Try connecting your system up using the modulator to combine the signals, as per the instructions in the manual.
    Thanks MTV, I did also see this in the manual and contemplated that scenario, however as the modulator is at one end of the house and the splitter at the other end with no ceiling space in between I was looking at avoiding running extra cables; or moving the modulator to the splitter and wiring in a power supply. But more interesting to me is WHY it isn't working right now. I have ordered a good quality meter that will give me Db and Mer/Ber readings so when that arrives I will be able to narrow down where the problem is. Do you practice terminating any unused ports on your splitters?
    thanks.

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    Quote Originally Posted by ozsec View Post
    Do you practice terminating any unused ports on your splitters?
    I rarely have a situation where there are unused splitter ports, but where there are I usually do in commercial installations, but rarely in homes.

    Commercial jobs, like hotels, apartment complexes etc, usually have a TV connected, so there is a constant impedance load present.

    In homes, often not every outlet has a TV/load plugged in, but it's usually not a problem.

    Commercial installations mostly use taps, rather than splitters.

    How many outlets are you using?

    You say you have a 4-way splitter, but are you using all 4 ports?

    Once you can take some signal measurements, will will have a better idea of what's happening but I highly suspect your issue is your modulator is overloading the amp.

    Have you tried reducing the output level of the modulator?

    Were you using this MH amp for analogue prior to digital, or purely for digital FTA?

    You haven't answered my question on what your FTA and modulator RF frequencies are.

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    mtv standing back!!!! it looks to me as if the mod is analog and mixing to fta frequs totally over loading it ???no answers seem to make sense to me ???

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    Quote Originally Posted by ozsec View Post
    I have ordered a good quality meter
    If this device has a spectrum display it should be easy to narrow your problem down very quickly.
    Never stand under a shadow that's getting bigger

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    Quote Originally Posted by hinekadon View Post
    mtv standing back!!!! it looks to me as if the mod is analog and mixing to fta frequs totally over loading it ???no answers seem to make sense to me ???
    Quote Originally Posted by ozsec View Post
    I am using the Blauhaus HD1090 Digital modulator, ...
    As the OP said, it's a digital modulator, but seems to be the common opinion without actual signal measurements, overloading of the MH amp from the modulator is highly probable.

    The OP hasn't provided any info about the amp or the output level of the modulator.

    Accurate signal readings will fill in a lot of blanks, but we need to know the amp specs, FTA and modulator frequencies as well.

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    agreed time to apply patience see what floats to the surface regards don

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    [IMG]C:\Users\ozsec\Pictures\meterreading3.jpg[/IMG]
    Picture of output levels of the modulator (it's a local image not URL so I appologize if it doesn't appear). Further testing seems to point that the modulator is in fact overloading the FTA as everthing drops out as soon as I connect the modulator into the network, but independently they work ÖK. I don't pretend to know anything about these readings so I'll just list below in case the image attached doesn't work.

    From modulator****
    PWR: -32 dBm @ 78%
    CN: 30.9 db @ 92%
    BER: 1.0E-9 @ 99%
    MER: 33.9dB @ 99%
    RF Lev: -32 dBm

    The FTA readings on one of the tuned channels I looked at is about 1/3 the strength of the above. The frequency I am using for the modulated signal is 585.500mHz and there are no conflicting FTA channels.
    I'll have a look at the settings on the modulator to see how to reduce the power?? is this correct?. I am also using a 20dB attenuator as there are 4 TV points but only 2 are used.
    cheers.

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    thats better something to work!!!! with -32db from the mod is the problem as you cant increase the fta sig level so to counteract the fta sig has to be in excess of the mod level then you have a good chance of it working for you ,have you got a heap of coax ?you could try putting a plug on each end and applying it as a antenuator to the output of the mod ,the fta amp must be a fair way from the mod as well to give yourself any chance of success the next thing is to make sure that you cant stuff a signal up its own arse no one likes this and so applys to rf ensure that you have a clear picture of what you want to have as a final result the splitters are only used as necessary and not just in case you mite want to later the more of these the more losses you intro into the system start with a plan to get a fta sig of good level and quality then progress to the desired step , i assume you are using rg6 and not rg59 coax if your using rg59 forget it completely as you are wasting your and my time regards don

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    Can't see your pic... we'd need access to your computer to see it at the location you've given.

    Upload pics to then copy and paste the link in your post.

    A 4-way splitter has the same insertion loss, regardless of the number of ports used.

    If you have need to reduce the amp output by 20dB, then you likely don't need an amp at all. (or it's way too powerful/wrong type for your purpose)

    What are your FTA signal readings at the antenna (before the amp) after the amp (at the splitter input) and at the wall outlets?

    We still need the make & model of the amp.... or the specifications of it.

    Instructions on adjusting the modulator output level are in the manual.

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    Quote Originally Posted by ozsec View Post
    RF Lev: -32 dBm
    If that is the reading with the supplied 20dB attenuator in line with the output port of the modulator that's fine.

    MTV has asked questions regarding your masthead amplifier type & FTA channel frequencies that have not been responded to. I would suggest drawing a mud map to show how you have connected the whole shebang together, as on re-reading your posts, it is not obvious how everything has been configured. (otherwise take a photograph & post it here.)

    Quote Originally Posted by ozsec View Post
    The FTA readings on one of the tuned channels I looked at is about 1/3 the strength of the above.
    Which is? -10dBm? -36dBm?

    Quote Originally Posted by ozsec View Post
    I'll have a look at the settings on the modulator to see how to reduce the power?? is this correct?
    I wouldn't worry, the 20dB attenuator is supplied because the minimum output of this modulator would most likely overload most TV front ends.
    Never stand under a shadow that's getting bigger

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    Thumbs up Solved!

    Just thought I'd keep you updated. It is working now, thanks to all of your input and feedback. It was a great experience learning something new like this. In the end, I just moved the modulator from default CH36 to CH40 and during all the previous testing (mucking around) I had replaced the combiner from a 2-way power port to a one-way power port, so I swapped this back, and re-tuned and is working great. I must say it does make things easier with the right tools (I'm very impressed with the SatKing 2500 tester)
    So thanks again all for your input.
    cheers
    OzSec.

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    Quote Originally Posted by ozsec View Post
    In the end, I just moved the modulator from default CH36 to CH40 and during all the previous testing (mucking around) I had replaced the combiner from a 2-way power port to a one-way power port, so I swapped this back, and re-tuned and is working great.
    You said:

    Quote Originally Posted by ozsec View Post
    The frequency I am using for the modulated signal is 585.500mHz and there are no conflicting FTA channels.
    Obviously, there were conflicting frequencies, if changing the modulator frequency solved the issue.

    Several times you were asked to provide your FTA frequencies which would have quickly identified an issue.

    I'm pleased you got it sorted, but you could have been a bit more helpful helping those of us trying to help you.

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    Well part of the problem was that on the main TV I was tuning originally, there were no conflicting channels, at least they didn't appear in the channel list on tuning. But what I did find was that on a separate TV in the house there was a conflicting channel. This to me says that different TV's have different tolerances when it comes to saving channels. As I mentioned at the very beginning, it was a new project of which I know very little about and I tried to assist by giving as much information as I could with some intelligent accuracy.

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