OuterEast Posted April 20, 2007 Share Posted April 20, 2007 I have two antennas on my mast. One is a VHF/UHF antenna pointed at Mount Dandenong(VIC) and the other is a UHF antenna pointed at Mount Tassie (Latrobe Valley - VIC). At present they are mixed such that the VHF/UHF antenna only gets VHF from Mt Dandenong and the UHF antenna gets its UHF from Mt Tassie. Is it possible to diplex the two such that I can get VHF and UHF from the VHF/UHF antenna, and also get UHF from the UHF antenna? Any help is appreciated. Link to comment Share on other sites More sharing options...
mtv Posted April 20, 2007 Share Posted April 20, 2007 OuterEast Could you clarify what antennas you have and how they are mixed and the reason you want to combine them, also if you are using any amplifiers? From your description, I take it you have a single VHF/UHF combination antenna pointing to Mt Dandenong, diplexed with a UHF antenna pointed at Mt Tassie. The diplexer only passing the VHF signals from your combi antenna and combining them with the signals from the UHF (Mt Tassie) antenna. If this is your setup, you should be receiving ABC, Seven, Nine and Ten from Mt Dandenong plus ABC, Prime, WIN, SC TEN and SBS from Mt Tassie? It can be done, but the method of achieving it will vary depending on what UHF frequncies/channels you are trying to combine. I see little point in changing your existing setup by trying to add UHF from Mt Dandenong, as the only UHF channel is SBS, which you would already be receiving from Mt Tassie. The program content is identical on SBS from Mt Dandenong and Mt Tassie. (Just as you will currently be receiving ABC from Mt Dandenong & Mt Tassie, the program content on both is identical) Link to comment Share on other sites More sharing options...
OuterEast Posted April 20, 2007 Author Share Posted April 20, 2007 Mtv I'm not sure exactly whether it's a masthead amplifier or diplexer up the mast. I had an installer place both these antennas up there (6 metres above the roof ridge) a few months ago. There is also an injector in the roof cavity below the mast. The aim was to replace an old antenna that was failing. I also wanted WIN and Prime, and to be able to choose both analog and digital. The combi antenna looks like the common type with a number of different length elements (horizontal), and the UHF antenna has a larger number of short elements. The channel allocation you describe is exactly how I am receiving them. All services are quite good on digital, however the SBS service from Mt Tassie has been plagued with pixellation/sound chirps. When watching SBS and WIN on analog from Mt Tassie, the signal is often quite poor. I was wondering if I could elect to receive SBS29 digital (and also MGV31 analog) from Mt Dandenong, as perhaps the signal might be better than that from Mt Tassie. Thanks again. Link to comment Share on other sites More sharing options...
mtv Posted April 20, 2007 Share Posted April 20, 2007 OuterEast Where are you located? If you have a power injector, then you have an amplifier (which probably has an integrated diplexer). This presents more questions. Which make/model? Is it amplifiying VHF only and passing UHF? Is it amplifiying UHF only and passing VHF? Is it ampifying both VHF and UHF? Does it incorporate an FM filter? If you want UHF from Mt Dandenong and Mt Tassie, you will probably require three separate antennas, VHF and UHF for Melb and UHF for Latrobe Valley. This will outperform a combi antenna anyway and what should probably have been installed in the first place. If you didn't need UHF from Melb at the time, which obviously you didn't, because the UHF signals from your combi antenna are filtered out, then a high-gain VHF-only antenna would have been a far superior choice. The three antennas will ned to be combined in a triplexer/amp. The problem here is the clash of close/adjacent channels. VHF... no problems. UHF... messy. Channel 31 (analogue) from Mt Dandenong would be adjacent to SBS channel 30 from Mt Tassie. Channel 29 from Melb for the same reason. The diplexer/amp may have difficulty with this arrangement. The setup you have now (minus Ch 31 analogue) should provide a more stable result. For the sake of only adding community channel 31, could seriously compromise your other channels. Without knowing actual signal level and BER measurements from all the channels at your location, prior to amplification, it's impossible to advise exactly what's needed. From your description, it's only a couple of UHF channels from Mt Tassie that have a few glitches, otherwise everything else is fine? Ensuring you have the correct UHF antenna for Mt Tassie and it's mounted in the optimum position, perhaps a change of amp, or adjustment to the existing one to help the Mt Tassie signals may be all that is needed. Considering you had an installer do this work only recently, I'd recommend you have him return and rectify the problems. Ask him for the digital channel power and BER measurements for each of the channels you require and post the answers here. If he can't provide those measurements, you need an installer who can, as your installation may not be performing as well as it could be. Link to comment Share on other sites More sharing options...
OuterEast Posted April 20, 2007 Author Share Posted April 20, 2007 mtv I am located in Pakenham. Thanks for your extensive advice. I will follow up with your suggestions re identifying amplifier/diplexer, and then try the installer again for power and BER data. I had suspected that what I have is a compromise, but wasn't sure. Channel 31 is not really a big issue if it's going to mess things up. Yes, all digital channels perform well with the exception of SBS. I can't understand it, but for the last week or so, SBS30 from Mt Tassie is performing well....it may be weather conditions, I don't know. I'll post later when I get some further results. Cheers. Link to comment Share on other sites More sharing options...
Grampus Posted April 20, 2007 Share Posted April 20, 2007 See my signature, that'll show what I use for just that. I have a Kingray amp for the Mt Dandenong leg. I dont worry about SBS from Mt Dandenong. But you may need a better aerial than I have for Packenham to Mt Tassie, as I have line of sight over the 70 odd k's to the txmitter. Link to comment Share on other sites More sharing options...
beeblebrox Posted April 21, 2007 Share Posted April 21, 2007 You can get Diplexors/mixers that mix uhf channels together ie Mix VHF and Band 4 UHF on one leg with Band 5 o nthe other leg... You may need a differen combination of amplifiers and of course there maybe issues as MTV has intimated Link to comment Share on other sites More sharing options...
mtv Posted April 21, 2007 Share Posted April 21, 2007 Grampus, That's a pretty good effort for a little (low-gain) antenna (PL10) Link to comment Share on other sites More sharing options...
Grampus Posted April 21, 2007 Share Posted April 21, 2007 Grampus,That's a pretty good effort for a little (low-gain) antenna (PL10) It did surprise, but as said b4, line of sight, no hills, roofs, or trees in the road. I can see the tower with binoculars. Pity I haven't got the same going the other way, I have a hill right behind me. The amp just doesn't quite cut it on some occasions. Link to comment Share on other sites More sharing options...
Recommended Posts