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Thread: Interferrence and how to block it.

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    Default Interferrence and how to block it.

    I have an annoying pulsing interferrence that seems to run 24 hours a day.
    It comes on for about 3 seconds, off for about the same then on again for 6 to 8 seconds.
    It causes a heavy herringbone pattern on analog and I am wondering if is interferring with the digital signal as I am in a marginal signal area.
    I did think it could be a hot water thermostat or even a radio channel marker, like a CB repeater ID but there is no morse.
    I found an old Tandy FM filter did reduce the effect somewhat.
    I have just bought one of those Aldi LCd's and when I tuned it in, it found a signal on 135Mhz, thats just under old channel 5A and that never existed in my area.
    I dont expect to locate the source even though it would be nice but I was wondering if any one can suggest how to filter it out.
    The TV is on Band 5 here, starting on ch 56 I think.
    I was thinking of trying to identify the frequency this noise is on using a scanner but unless I am already scanning within the frequency range, it would be pretty hit and miss.
    I dont think the noise is on the mains as we had a power failure one night that covered a large area and I fired up a small generator just on the TV/MHA's and it was still there.
    As I need boosters here, anything the antenna picks up the MHA's just make it worse so I need something before the MHA.
    I do have a railway communication pole only 300 metres away and every time certain trains pass it, it makes a mess of the analog channels for about 10 seconds, some kind of data exchange between the train and the location.
    Other than that there are no other transmitters within a 5 kilometre radius.
    There is the possibilty the noise is from this location, some kind of handshaking signal perhaps ?
    Any ideas and suggestions greatfully received.



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    Senior Member Farmsky's Avatar
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    Is it available and do you get reliable DVB-T reception?

    Rough locations can be helpful

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    Try another TV first......

    Yes you can filter out anything you want... some products you can buy to do this, others you may need to hand wind yourself (to make traps etc).

    Correct antenna selection is important (you don't want signal flooding in from the side of an antenna that is pointed at another translator etc).

    Sometimes... as i found yesterday, it can be a fault of a poorly set up Translator itself. The place i was yesterday suffered from cross modulation, causing diagonal lines to move across the screen on every channel (also Band 5 Vert)

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    added to original, the pulse occurs at about 3 minute intervals.
    It appears worse on a CRT than an LCD on analog.
    To answer Farmsky first, I have 4 of the 5 digital channels (no SBS) the signal is marginal, that is why I was buying another antenna, a PU16H (see other postings)but currently a Hills 97 element 'Super Fringe Yagi' on a 45 foot mast plus MHA's plus 80 metres of RG6 quad sheild.
    There are 2 translators within 15 kms of me.The one I am aiming at is vertical and over a 100 degrees turned away from the other. The other it is horizontal on UHF but does have ch 6 still vertical. Also there is a ridge and a fair mountain between it and me.
    What doesnt help is the translator I am using has a very directional signal path and I am NOT in the coverage area.. I still have the maps showing the coverage areas back when aggregation came in.
    This noise has been evident for a number of years to varying degrees otherwise I might wonder about the new Village water storage tank as it has an antenna on it which I think sends data to the council.
    Oceanboy, as for dodgy translators, One local whinged and bitched to the TV channel claiming it was not broadcastingly properly untill to shut him up they finaly got off their backside and found the bloody cable between the transmitter and antenna was either broken or a very bad joint.
    It was reported in the local paper so not just an urban myth in this case.
    Because this interferrence occurs at approx 3 minute intervals, about 3 seconds on,clear for about 3 seconds then a longer pulse of 6 to 10 seconds makes me think its either doing a handshake to another location or a vacant channel marker.
    This just causes herringbone as I havent seen diagonal lines for it so far.
    Bear with me on this but even on digital I feel my signal varies due to time of day (sun) and weather conditions and the way the topography between the translator and here reacts to those conditions.
    Which to me would explain why the interferrence is more noticable on one day to another because of either a strong or weaker signal. I think for the signal to move a db (or more) either way is enough to make or break the reception.
    Way back when I had Sydney reception, on a hot summers night shortly after sunset the signal used to go beserk for up to 3 hours untill the ionoshere cooled down.
    Great for Shortwave DX'ing and skip but a bummer trying to watch the TV.
    My antenna system is still only rough as I had planned on a new antenna, mast and I thought before I finaly lock it down, if it needs filtering at the antenna, now is the time to do it.
    Thanks fellers

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    I find the easiest way for problems like this is to do a search here,



    to determine where a likely interfering signal may be.

    You will need to look at the drop down menus to work out which parameters need to be entered for your particular location.

    If any of the frequencies you find close by are within the band of frequencies used for the reception of television, and you are using a masthead amplifier, then you may have an issue caused by the overloading of your masthead amplifier, which from your description, it sounds like you may be experiencing.

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    One thing about here is I know the location of most transmission points but then we also have very high voltage feeders from Wallerawang/Mt Piper criss crossing the scenery and I believe they may carry communications or data.
    One feeder is the main 500,000 volt for the south and it is between me and the TV translator.
    That is a failing of MHA's in that they cant tell rubbish from signal so just amp the lot. You should see the mess a two way radio does to the TV's if used within 700 metres of your TV aerial.
    I found an old inline Tandy High Pass filter, 5 to 900 Mhz but it didnt seem to do anything.

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    If it was from the train comms system the first thing I would try would be to contact the transport provider (see if they can either fix the problem) at their cost, which may be affecting other people in the area which often happens.
    This is not an uncommon scenario and if you put in a complaint with them it is not unreasonable to expect some sort of action (they might also be able to tell you what licensed spectrum they are using - helpful in designing a filter.

    Faulty radio equipment (potentially theirs) can cause all sorts of issues.
    Just a question - do you have a meter such as a spectrum analyser? This will show the interference and help you to dignose the problem.

    As for general filters GME Kingray make a huge range of filters, laceys.tv do stock filters. However get in touch with the transport authority first, because that won't cost you anything.

    DVB-t will only fix some types of interference. Also try contacting the ACMA (supposed to...) which should be able to help.

    A PU16H is a great antenna however it is not a filter, and they are very directional.

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    Talking High Gain Antennae.

    G'Day All,
    Just an observation, may or may not be useful.

    High gain antennae, in fact all antennae have major lobes and many minor lobes.
    In some instances, it is possible to keep your desired signal within the major lobe while getting the noise source in a null between minor lobes.
    Certainly worth a try, may be the easy answer.

    Kindest Regards, " The Druid ".....


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    Senior Member Farmsky's Avatar
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    TV antennas tend to be directional in one polarity only. See my diagram which roughly explains this.



    Yagis are very directional in horizontal mode, but very broad in vertical mode. This may well be a useful clue in this situation.

    So as a generalisation......

    Diffused /blocked reception:

    If your reception is vertical, yagis are good for diffused reception through trees etc. If it's horizontal, use a phased array for diffused reception.

    Directive high gain (fringe):

    Reverse the above

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    I can only repeat what I have said before that I am in a TOTAL Blackspot area. The signal I am chasing comes from a DIRECTIONAL Translator and my area is NOT even remotely in the intended coverage area.
    What I get is purely 'Fortuitous Reception' so its always been my understanding that as I am not in a reception area for the interferred signal, no complaint will be investigated.
    If it was affecting Austar or Aurora or any other authorised satelitte service thats a totaly different story.
    I have the origonal literature issued by the old Dept of 'whatever' in 1988 when aggregation was introduced and here is way outside their projected coverage. This coverage was NOT altered when they added the new tower and installed the panel antennas for the digital transmission.
    It is only because a radio signal doesnt know that when some 'expert' draws a line on the map, it isnt supposed to cross it but as we all know it does, sometimes with surprising results.
    I am painfully aware no antenna is a filter but my intention was to bung up as much metal in the sky as feasable to gather every single electron possible.
    Thanks for all the ideas and info, every little bit helps.

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    Gordon, Earth Leakage from your electricity supply can cause the symptoms you have mentioned. Resistance changes depending on the ground moisture content. If your house wiring is current and running from a digital meter box, please disregard.

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    Forgot too add that rural remote sensing stations could also be a possibility.

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    Thanks jack, wiring was down by either Edison or Tesla, meter is the old clock face with the spinning disc, no earth leakage fitted to the board except the M.E.N.S earth that goes to both a ground stake and the buried water pipe but the possibilities are endless arent they ? About 300 m to the East from me the council has a water reservoir with radio telemetry but I think the noise existed before that was built. About a km away south is a windspeed evaluation devise that according to the application was to transmit data via mobile phone but it too is only recent. To the west about 3 ks is a mountain some 400 m higher than me with all sorts of microwave and a commercial FM radio transmitter along with many other services.
    2 high voltage lines as well as our electricity supply run thru the valley as well.
    And I just remembered there is a Next to useless mobile phone tower about 6ks north. I have all sorts of possibilities surrounding me for interferrence. So much for living in the Bush, eh??

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    Since I made the last posting, the 'noise' appears to have gone.
    It stopped about the same time as a near house was vacated by the tenents 10 days ago.
    Being in a small village that you can damn near spit across, its not hard to keep track of the movements of people, particularly when they have a bit of a dummy spit during the process.
    This is NOT conclusive proof that the 'noise' was emmanating from this house, either from an external electric hotwater unit or other appliance inside or one owned by the departed tenants.
    I lean towards the 'noise' being created by the thermostat in the hot water unit but that is pure conjecture.
    All I can do now is wait and see if when it is re tenented again if the 'noise' returns.
    This house is in front of but to one side of the antenna so relocation of the antenna is not an option.

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    its only FTA TV, i tell you it's over rated

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