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Thread: Again Digital TV Aerial question

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    Question Again Digital TV Aerial question

    I have just installed a new digital aerial from Jaycar ($99 one).
    Compare to my previous aerial (old analog one) I have a very good signal for channels 7, 9, 10 and ABC. SBS signal I assume is much weaker as I can receive good picture on one of my HTPCs when the other HTPC reports no signal at all for the SBS. I measured ignals on the HTPC using one of the software utilities from DNTV (the PC has DNTV Live S3 tuner card) and SBS frequencies don't lock at all, with other channels locking between 30 to 80% quality. Compare to the previous setup I had SBS frequencies at ~ 40% and others at ~9% causing a lot of grief (which caused me change aerial).
    The new antenna as I understand has much better UHF and much weaker VHF sections, even though I still have good reception on my other HTPC (different tunner). I contribute this to probably higher tunner sensitivity.
    My question is: "Can I connect my old aerial VHF assembly to the new UHF/VHF aerial?" The old antena had separate UHF and VHF masts connected to some sort of signal combiner (it had two inputs for two aerials and one output). Can I reuse that combiner for this setup?



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    You can use a cheap Diplexer that is available at Jaycar or DSE for under $20. You just need some co-ax to go from both antennas into the diplexer, and then that goes into the splitter/distributor to feed all the outlets in your house.

    This is assuming that SBS is in fact on VHF, while the other channels are on UHF. Check in your set top box or the HTPC tuner utilities menu to see what frequencies the channels are on. I think SBS still uses a different FEC or coderate (can't remember which) and this means you need more signal for that than any of the other channel groups.

    The diplexer will have a VHF input, a UHF input, and a UHF/VHF outlet. Just connect your antennas respectively.
    Last edited by big mick000; 28-06-09 at 08:12 PM.

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    Thanks Mick,
    I think SBS is coming at 575000MHz frequency range in Melbourne or around that and therefore it needs VHS module operational.
    My old antennaes had two masts as I said before, with VHS being realy huge compare to the new aerial I just bought. I think this is the key to the problem I have.
    For whatever reason SBS is still using VHS range for their digital transmisiions, making our life a bit more difficult. It's just i never thought about the frequencies ranges associated with channels. For whatever reason I thought all digital transmissions are in the same range, which turns to be a silly assumption.

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    If SBS is at 575 MHz then it is UHF. With most combo antennas (which is what your description sounds like) the very long elements are the dipoles for VHF band I, which will get you ch2 ABC, the elements that are between 1 and 2 feet long are for VHF band III, which is between 170 MHz and 250 MHz (very roughly), and the elements that are typically less than a foot long are for UHF bands IV, V, and V+. I am not sure what the digital channels are for Melbourne, and what various translators/transmitters are around the area, but I would be inclined to have your combination antenna cabled straight to your splitter/distributor by itself, using RG-Q (quad shield) cable.

    I think that all FTA digital channels in Melbourne, from the main transmitter at i think, mt. Dandenong are on VHF band III, with the odd UHF digital translator here and there. I'm not 100% sure, though.

    Maybe post a picture, or a good description of the antenna, as I am a bit unclear as to what type of antenna it is.

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    I was amazed to find out some time ago that the Sydney Metro area was digital on VHF as I thought all this conversion was to clear the VHF spectrum for other useage.
    It seems its the regional areas that will be wholly UHF when analog is finally switched off
    As far as I know SBS has never broadcast on VHF (Channel 28) so I would suggest you get the frequencies of the FTA services for your area.
    Canberra and Lithgow were 2 places I know of that used both Vertical and Horizontal polarities for the then 2 channel (Commercial/ABC) services.
    Since aggregation, the commercial channel stayed on Vertical VHF (ch 6) and the ABC joined the other 2 commercial channels on Horizontal UHF.
    Another thing I noted in the listings is the Digital translators are not transmitting the same output power as the analog are/where for some areas.

    I cant help it but I get very annoyed by the advertising of these so called 'Digital' antennas.
    I wont deny some are better made and will work better and last longer but its suggesting that only these will receive a Digital signal and thats untrue.
    Same as those ads intimating you must have a 'FreeView' approved devise to receive all the Digital channels.
    A few years ago it was the labeling of TV's as being 'Cable/PayTV Ready'.

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    Out here we get all 5 FTA broadcasters' DVB signals on Band III VHF, from Mt. Baranduda. I think that it is the same deal for Melbourne, but then again, not 100% sure.

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    Here's the digital TV channel list & frequencies for Melbourne.

    All Band 3 VHF except SBS (UHF Band 4) from the main transmission site on Mt Dandenong. All Horizontal Polarisation:

    7 177.500 MHz

    9 191.625 MHz

    TEN 219.500 MHz

    ABC 226.500 MHz

    SBS 536.625 MHz

    There are also some translators around the Dandenong Ranges and the Mornington Peninsula which are on a UHF SFN (single frequency network) which means they share the same frequency for a particular channel.
    All UHF Band 5:

    Upwey (Vertical Pol), Ferntree Gully (Horizontal Pol), Selby (Horizontal Pol), Safety Beach (Horizontal Pol), Rosebud (Vertical Pol):


    7 620.500

    9 641.500

    TEN 711.500

    ABC 662.500

    SBS 683.500

    There are also translators in Sth Yarra (on the Como Building):
    All UHF Band 5 Vertical Polarisation:

    7 774.500

    9 690.500

    TEN 711.500

    ABC 753.500

    SBS 732.500

    As for regional areas around Australia, the majority or transmitters/translators are UHF, some in Band 4, some in Band 5 and some in both bands.

    Some regional areas are on VHF band 3 and some areas are a mix of Band 3 VHF and Bands 4 & 5 UHF.

    Polarisation also varies with different transmission sites.

    Only channels 6 - 12 VHF Band 3 and UHF channels 28 - 69 (Bands 4 & 5) are used for digital TV (DVB-T) in Australia.

    As someone mentioned SBS on VHF, they originally commenced broadcasting on channel 0 in the 1970's, after the 0/10 Network moved all transmissions to channel 10. SBS also simulcast on channel 28 UHF and was known at the time as SBS 0/28. A few years later, (after allowing time for people to add a UHF antenna) SBS ceased transmitting on channel 0.

    SBS now transmits solely on UHF across Australia with various channel/frequency assignments for various regions.

    Hope this helps.

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    Looks like I am all confused. I don't understand what is causing the problem as I can receive the SBS signal perfectly from another room using different HTPC and TV tunner. Could it be the tunner I have in the problem computer is faulty as it can't get the frequency for SBS? It's just very strange the tunner failed when I changed antenna. I actually didn't have both my HTPCs disconnected from the wall outlets while changing antennaes, and both were in S3 sleep mode.
    Anyway, the antenna I now have details are


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    The antenna in the pic is designed for areas with very high signal strength.

    It's not much better than rabbit ears.

    If you have two outlets connected to this antenna, the signal is halved at each outlet.

    Perhaps the signals are on the 'digital cliff' and one tuner is more sensitive than the other.

    Have you tried connecting the tuner that works to the other outlet and vice-versa?

    Which suburb are you in?

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    What confuses me I am receiving much stronger signals with this antenna compare to my old setup (see my earlier post). The whole reason for the antenna change was to get rid of constant freezups, especially on CH10 and the new antenna gave me the desired result. Everything except SBS .
    I live in Ormond area, BTW. I always thought we have good signal compare to other areas.
    As far as swapping PCs around, I kind of tried to avoid it as I have a lots of cables on both of them, also both PCs are siting in such areas that it won't be easy to pull them out. I'll do it this coming weekend, not before as it will take some time.

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    Ormond is generally ok for reception, but there are some areas which can suffer from impulse noise interference from trains & industrial areas etc.

    Buildings in the signal path will also affect reception, together with any multipath signals (seen as ghosting on analogue pictures).

    Your older VHF antenna was probably not designed to receive above channel 10 analogue and TEN and ABC digital are on channels 11 and 12 respectively.

    The new antenna is designed to receive VHF channels 6-12.

    The UHF section of the antenna is very low gain, where as your older UHF antenna probably had higher gain.

    You could use your old UHF antenna combined with the new antenna with a VHF/UHF diplexer (which you would have had with your old separate antenna setup).

    A much better combination antenna for your area would be a Fracarro LP34F or Hills SMX14B4+ and SMX24B4+

    Your coax cable should also be good quality, such as RG6 Quadshield and all connectors F type, together with outlet plates, splitters etc.

    Poor cable & connections will cause greater loss at UHF frequencies.

    Pic example SMX14B4+ antenna


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    So, can I simply connect my new antenna to the diplexer input 1 and my old UHF antenna to the second input, or I have to remove UHF elements from my new antenna first to avoid some signal unwanted interference?

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    Quote Originally Posted by fromaron View Post
    So, can I simply connect my new antenna to the diplexer input 1 and my old UHF antenna to the second input, or I have to remove UHF elements from my new antenna first to avoid some signal unwanted interference?
    Providing your old UHF/VHF diplexer is in good condition, otherwise replace it with a new one.

    You don't need to do anything with your new antenna elements.... just connect it to the VHF input of the diplexer and connect the old UHF antenna to the UHF input of the diplexer.

    The diplexer will filter out any UHF signals picked up from your new antenna, as it will only pass the VHF signals from it.

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    Some very good information here guys, is there a way to tell what type of antenna you will need from the suburb you live in without using any signal measuring apparatus ?

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    Quote Originally Posted by loanrangiel View Post
    Some very good information here guys, is there a way to tell what type of antenna you will need from the suburb you live in without using any signal measuring apparatus ?
    These need more than a good antenna, good cabling & connectors can be just as important.
    iam a bogan

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    Quote Originally Posted by mate View Post
    These need more than a good antenna, good cabling & connectors can be just as important.
    Too right. I have fixed many a problem by changine whatever old (sometimes new) cable that was there, for some nice new RG6.

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    Yes understand its all components that need to be up to scratch. I get good reception but i notice when i loop the antenna thru my pvr then to the tv i get signal loss, i will be replacing the cabling as i will be moving the tv location plus add a few sockets where you werent any before.

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    Quote Originally Posted by loanrangiel View Post
    is there a way to tell what type of antenna you will need from the suburb you live in without using any signal measuring apparatus ?
    Digital signals can vary greatly, even with antenna mounting location moving just a few centimetres in any direction, including up/down, so a site survey will provide the best possible resuly.

    Having said that, there are some areas known to installers that are good, not so good and very difficult.

    If you tell me your suburb and if your house is in an elevated position or down in a gully, blocked terrain etc, I can give you some recommendations of the type of antenna generally suitable for the area.

    As you are planning to add multiple outlets, you may also require a distribution amplifier. Once again, it all depends on available signal strength and quality.

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    Quote Originally Posted by mtv View Post
    Digital signals can vary greatly, even with antenna mounting location moving just a few centimetres in any direction, including up/down, so a site survey will provide the best possible resuly.

    Having said that, there are some areas known to installers that are good, not so good and very difficult.

    If you tell me your suburb and if your house is in an elevated position or down in a gully, blocked terrain etc, I can give you some recommendations of the type of antenna generally suitable for the area.

    As you are planning to add multiple outlets, you may also require a distribution amplifier. Once again, it all depends on available signal strength and quality.
    I'm in St Helena (Nth Greensborough) , in a very slight gully moderately treed and current antenna is in the roof space. Will be adding 2-3 outlets so 4 in total- 4th will be about 20m from main room.

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    I'd be inclined to go with separate Band 3 and Band 4 antennas, like a Hills DY6 and Fracarro PU4A or similar with a diplexer, all RG6 Quadshield cable, F connectors, F type 4-way splitter, or perhaps a Kingray amplified 4-way F splitter, especially due to to losses over a 20m cable run.

    Number one rule..... the antennas MUST be mounted ON the roof... not in it.

    This is a guide only and there may possibly be better antenna options, which without a site test, is impossible to make more-accurate recommendations.

    Mounting location and mast height can be critical for optimum digital reception in obscured signal paths such as yours. Once again, without accurate signal measurements, it's only an educated guess.

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