Answered Aerial and amplification

Discussion in 'Freeview & YouView' started by Durzel, Sep 3, 2017.

  1. Durzel

    Durzel
    Member

    Joined:
    Aug 9, 2013
    Messages:
    151
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    31
    Ratings:
    +27
    Ok, I've got a messed up setup here from what I can tell, I left it to a professional to install while the house was being renovated and didn't have a chance to question any of it at the time.

    Here's the setup:

    - TV aerial goes to Antiference MHK4LTE 4-channel Masthead Amplifier in the loft. It doesn't seem to have any power supply, even though it seems it's supposed to.

    - From that only one of the outputs is used, which goes down 2 floors to my media cupboard and plugs into a Triax SCS-4 4-way splitter.

    - The outputs from this go to the 4 coax points at various points in the house (1 on ground floor, 2 on first floor and 1 on top floor)

    If I plug the aerial directly into a TV using an F-type to Coax connector I get a perfect signal, with 175+ channels (TV & radio I guess) found.

    If I plug the TV into one of the wall sockets fed by the splitter in the cupboard, I get around 50 channels but they mostly break up.

    Not knowing anything about this it seems as if the Masthead Amplifier should be powered by a 12v PSU that takes the aerial feed and outputs the TV feed to the amplifier box. I can't find this PSU anywhere in the loft, and I can confirm that the aerial was directly connected to the input on the amplifier (this seems to be where the output from the PSU should go)

    I don't really know why I need a 4 channel amplifier at all when all the wall plates are wired to the splitter downstairs? Wouldn't I just need a 1 channel amplifier in the loft?

    Also - do I need a "set back" amplifier in place of the Triax SCS-4 passive splitter downstairs? Would amplifying the signal twice cause problems?

    (Don't ask why the 4 outputs on the Masthead Amplifier aren't the ones going to the wall plates around the house - I don't know why it was done this way, and I have to deal with it now)

    Thanks in advance!
     
    Last edited: Sep 3, 2017
  2. Best Answer:
    Post #11 by TJT1, Sep 4, 2017 (1 points)
  3. grahamlthompson

    grahamlthompson
    Distinguished Member

    Joined:
    Aug 3, 2006
    Messages:
    23,520
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Redditch
    Ratings:
    +3,947
    The PSU should be connected at the remote end of the coax from the masthead amp output before the input to the 4 way splitter. Virtually all such amps can be powered from any of the outputs. If you tried to connect one to the aerial in socket as many aerials will be a short circuit to DC it cannot possibly work. Without a power supply the masthead amp is in fact massively attenuating the signal from the aerial.
     
  4. Durzel

    Durzel
    Member

    Joined:
    Aug 9, 2013
    Messages:
    151
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    31
    Ratings:
    +27
    Thanks.

    If the PSU is downstairs (2 floors) isn't it going to struggle to send 12v/100ma or whatever it is all the way up?

    Also looking at the PSU (that I don't think I've got) it's got two F-type connectors - one marked Aerial and the other TV. Surely the outside aerial is supposed to plug into that?
     
  5. TJT1

    TJT1
    Member

    Joined:
    Jul 29, 2011
    Messages:
    3,946
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    East Sussex, UK
    Ratings:
    +778
    You could try just bypassing the masthead amp (MHA) and see what happens. Or is that what you effectively did when you say "...plug the aerial directly into a TV using an F-type to Coax connector"?
    12V 100mA will 'go up' the coax no problems providing any and all the joints are sound. Some TVs and boxes have a 5V/12V output to drive MHAs. Has yours? But the splitter might block the DC supply unless it has a DC pass path.
    The aerial plugs into the MHA UHF Input and the socket on the PSU marked Aerial goes to one of the outputs of the MHA via the downlead coax to power it and the other, marked TV goes to the TV. The other way, and what GLT is suggesting, is to disconnect the splitter from the MHA, connect the Ariel connector of the PSU to the to the coax from the MHA and the connector marked TV to the splitter input and the O/P of the splitter to the TV.
     
  6. Durzel

    Durzel
    Member

    Joined:
    Aug 9, 2013
    Messages:
    151
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    31
    Ratings:
    +27
    Thanks, that makes sense.

    Currently I have no PSU. I haven't been able to locate it anywhere in the circuit. I've been looking online at what it looks like and what ports it has on it. Sales pages for the Antiference MHK4LTE MHA show that it should be supplied, but I don't appear to have it/the installers didn't use it.

    It looks as if the splitter downstairs was connected directly to the output from the MHA in the loft. The MHA had two cables plugged into it (aerial and output to splitter)

    I should also say that until yesterday I hadn't actually tried to use these sockets, so as far as I know they've never worked.

    Here's what I've tried:

    1) "As is" - Aerial plugged into MHA, single output of MHA to splitter, splitter to 4 wall plate coaxial ports. Auto Tune on TV plugged into any of these ports gave no signal at all on any of them.

    2) Aerial plugged directly into portable TV coax port (MHA disconnected) using a F-type to Coax converter. 175+ channels found on Auto Tune.

    3) Aerial plugged directly into splitter cable by using an F-type to F-type connector (MHA disconnected). TV plugged into one of the wall sockets. Auto Tune found around 50 channels, some of which worked and others were blocky/intermittent.

    That's how things are at the moment.
     
    Last edited: Sep 3, 2017
  7. TJT1

    TJT1
    Member

    Joined:
    Jul 29, 2011
    Messages:
    3,946
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    East Sussex, UK
    Ratings:
    +778
    Plug portable into the cable that goes from the MHA to the splitter with the MHA bypassed so you have a 'direct' connection between aerial and TV. This will check out the aerial and downlead to the splitter. If that works OK, reconnect the splitter and check the signal at one or more of the wall plates. The MHA will not work without a PSU, and, as GLT said above, it will just kill most of the signal if left in circuit.
     
  8. Durzel

    Durzel
    Member

    Joined:
    Aug 9, 2013
    Messages:
    151
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    31
    Ratings:
    +27
    Yes, you're right - with the MHA in circuit there is no signal to any wall plates at all.

    With the MHA bypassed - i.e. so the aerial connects to the cable that runs down to the splitter input downstairs using a F-type coupler, I get around 50 channels found with the TV plugged into one of the wall sockets that come off of that splitter. Some of those channels barely work though, and drop in and out of signal.

    The only thing I haven't tried is connecting the TV to the splitter cable at the splitter input end (i.e. what you've suggested) to see if I still get 175+ channels then. That's because I only had 1 F-type coupler to hand.

    I don't entirely know why the wall plates weren't wired from the MHA outputs in the loft, rather than going down 2 floors to the media cupboard, into a redundant splitter, and then back up again. The MHA has four outputs but only one of them was ever used.

    The wall plate that gives ~50 channels is on the first floor, so in cabling terms that wire is going from the aerial, down two floors, then back up one floor again.
     
  9. TJT1

    TJT1
    Member

    Joined:
    Jul 29, 2011
    Messages:
    3,946
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    East Sussex, UK
    Ratings:
    +778
    I wondered that as well.
    So, if the signals at the splitter input are similar to a wall plate, it seems that the coax runs are OK and you just need to power the MHA to get any further.
     
  10. Rodders53

    Rodders53
    Well-known Member

    Joined:
    Dec 8, 2007
    Messages:
    4,664
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    Lowestoft
    Ratings:
    +795
    Call back the installers to do it right (i.e. supply and fit the power unit).

    Or buy one and install it yourself:
    1. in loft if mains readily available there,
    2. before the passive 4-way splitter input.

    Temporarily you could bypass both masthead and passive splitter to feed one room outlet... IF that gives perfect results, it may be possible to relocate the masthead amp-splitter to your cupboard to replace the passive splitter, but you'd still need a power supply for it.

    (Other solutions are available but won't be as cheap as a power supply unit... which ought to be supplied f..o.c. by the contractor under guarantee.)
     
  11. Durzel

    Durzel
    Member

    Joined:
    Aug 9, 2013
    Messages:
    151
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    31
    Ratings:
    +27
    MHA in the cupboard would mean it would be amplifying the signal from 2 floors up. I was under the impression the MHA had to be as close to the aerial as possible, since it would amplify both signal and noise?

    Getting power to the loft space where the MHA isn't wouldn't be impossible, but if I can just power it from downstairs without any performance loss I'd sooner do that.

    Getting the installers back isn't an option as this was all done a couple of years ago. I've been using Sky happily in several rooms for that time, and haven't really explored getting Freeview up and running as an alternative or replacement until now.

    Seems like the most logical option is for me to simply buy another PSU (they seem to run at ~£10 on Amazon) and get this MHA working. Is there any point in me replacing the 4-channel output MHA with a single channel one, if all it's doing is outputting to the splitter anyway? Do I lose signal from having 4 outputs?
     
  12. TJT1

    TJT1
    Member

    Joined:
    Jul 29, 2011
    Messages:
    3,946
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    East Sussex, UK
    Ratings:
    +778
    Best Answer
    That is absolutely correct. But unless the signal level is really low from the aerial, in practice it will make little difference. A MHA is really only there to overcome losses down the cable and the subsequent losses in the splitter whilst maintaining the Sig/Noise ratio.
    You can feed the 12V up the coax to it. It's pretty much the standard way of powering a MHA.
    Only a small amount. Certainly not enough to fret over and spend money on a single channel one. Get the one you have already working before shelling out on a single channel one.
     
  13. Rodders53

    Rodders53
    Well-known Member

    Joined:
    Dec 8, 2007
    Messages:
    4,664
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    Lowestoft
    Ratings:
    +795
    Masthead amps come in a variety of flavours. Those aimed at fringe reception are single output high gain low noise and must be within 1-2 metres of the antenna (aerial) to do their job.

    Others have variable/adjustable gain (often just an attenuator following the amplifier) an poorer noise performance plus passive splitting to supply additional outlets. Yours has variable 1-25 dB gain (so to make up for the 8dB splitter loss, will be 9 to 33dB internally :eek:). Effectively it is just a fancy weatherproof powered distribution amplifier with plenty of welly!

    If the aerial is man enough to provide a perfect signal to one set then a powered distribution amp downstairs could work fine... Using the amp you have rather than buying another. We know, however, that 8dB of splitter loss ruins the signal, so - after more thought it is probably not a good choice as the level is too close to the digital cliff edge.

    Unused ports on any splitter should be terminated with a 75 ohm load Television Aerial Boosters / Amplifiers, Splitters, Diplexers & Triplexers but you can probably get away without them.

    You should use your various TV signal meters to determine the setting for the gain control of the masthead amplifier. You will be looking to get 100% quality on all mux frequencies (you must check all separately). Max gain might not be the correct setting.
     
  14. Durzel

    Durzel
    Member

    Joined:
    Aug 9, 2013
    Messages:
    151
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    31
    Ratings:
    +27
    Thanks all.

    Will probably try and get the MHA up and running and go from there. The PSU is only a tenner so worth a punt, and it seems like I'm going to need the MHA at some point in the circuit whether it's in the loft or replacing the splitter (since I only get ~50 channels at one of the wall points off the splitter with no MHA in circuit, and I get 175+ directly connected to the aerial).

    It's a shame the wiring to the wall points wasn't done off the MHA in the first place. I have no idea why it terminates in the media cupboard downstairs only to branch out again to the various rooms. Can't do anything about that now though.
     
  15. TJT1

    TJT1
    Member

    Joined:
    Jul 29, 2011
    Messages:
    3,946
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    East Sussex, UK
    Ratings:
    +778
    Probably done that way so that it is then a bit more convenient to mix other signals in such as the RF output from a Sky box or another modulator of some sort. Going up into the loft etc. to do that would be a right pain.
     
  16. Durzel

    Durzel
    Member

    Joined:
    Aug 9, 2013
    Messages:
    151
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    31
    Ratings:
    +27
    Just to add some closure to this - bought a PSU (Antiference PF1), wired it in downstairs, and... no green LED on it.

    Turns out the coax wire going to the MHA from downstairs was a bit duff (the strands touching the middle pin), so I rewired that, connected it all up, green LED on PSU, green light on Masthead amp in the loft, and 177 channels on a TV off one of the wall sockets! :clap:

    Of course I've got that nagging feeling about whether the cable connection being iffy was part of the problem (although I did get 50+ channels before), but ah well - it's working now.

    Thanks for the help all. :smashin:
     
  17. TJT1

    TJT1
    Member

    Joined:
    Jul 29, 2011
    Messages:
    3,946
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    East Sussex, UK
    Ratings:
    +778
    It was! Along with no 12V to the MHA.:D
     
  18. Rodders53

    Rodders53
    Well-known Member

    Joined:
    Dec 8, 2007
    Messages:
    4,664
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    Lowestoft
    Ratings:
    +795
    :clap:
    Thanks for coming back and reporting the solution.

    :rotfl: the only way to find out is to remove amplifier and psu from the circuit...

    One for a day of boredom, perhaps :D
     
    • Agree Agree x 1
    • Funny Funny x 1
    • List

Share This Page

Loading...