Posted 06 August 2009 - 10:23 PM
I've had a good read of the information available on this site and done some fiddling with my antenna setup, but am hoping to get some advice before going any further. I don't own the house I'm in, nor the antenna system, but my landlord isn't interested in improving the reception I'm getting, so I'm on my own.
I'm in Jerrabomberra. The house and antenna installation are about 11 years old. It has a combination UHF(horizontal Yagi) and VHF (vertical 2 bay phased array) pointed at Black Mountain. The mast head diplexer and all antenna and wall plate connections use saddle clamps. There is one F-connector 2-way splitter in the roofspace and the cabling is all R59. I'm only using one wall plate, but unfortunately it is at the front of the house while the antenna is at the back, so there is probably 10-15m of coax and a two way splitter attenuating the signal.
When I first moved in, I had barely satisfactory analogue reception with only three watchable channels (ABC and ten were unwatchable). I bought a cheap set top box, not knowing anything about digital TV and found I could only receive the five or so SBS digital channels. I went through the whole antenna system from top to bottom, cleaning and re-terminating all connections, taking about an inch of coax out at each one. My analog reception improved dramatically - ABC and Ten are now watchable, but still not as good as SBS, Win and Prime, which are now good enough to be mistaken for digital channels. I also get most of the digital channels now, though the SNR (from STB display) is over 70 for SBS and only just over 40 for Win, Prime, ABC and GO! I still don't get ANY SC Ten digital channels (which is a little frustrating since motorsport on One HD was the whole point of the exercise) I also know from the experience of a couple of goes at cleaning up the antenna system that SNRs (from my STB) below 40 will not allow me to view the channel, even if the STB can tune it in. I'm therefore very close to the cliff edge for most of the digital channels I can receive. To clarify, the STB currently doesn't pick up any of the SC Ten channels in any way.
The things I have been contemplating next are re-cabling with RG6 quad shield coax direct to the single wall plate I am using (therefore bypassing the splitter). I have also considered moving the antenna closer to the wall plate I wish to use, but this would be a relatively major operation (tile roof, through-roof mast, etc) for a house I don't own.
Before I dive in and do any more, I'd like to be sure I'm on the right track and know if there are other things I should also do. eg: Will changing to RG6 quad shield be enough or will I be wasting my time without a masthead amplifier or shortening the cable length? Do I need a new diplexer with F-connectors? Should F-connectors be used at the connections to the dipoles and wall plates as well? Is the cable and connection type between the wall plate and STB important? Are the screw on F-connectors as good as crimp ones or should I pony up for a crimping tool?
My biggest questions relate to my VHF antenna, as it seems (assuming I have read the info on this site correctly) that I get good reception for all UHF channels (both analogue and digital ones) but relatively poor for all VHF ones...and don't get SC Ten digital channels at all. So I'm wondering if there is something wrong with my VHF antenna, though it looks fine. I've measured the total lengths of the dipole (1480mm) and reflector (1560) rods, which I think is right and with a few exceptions, the neighbours all seem to have similar setups anyway. Is there something special about SC Ten digital (even lower signal strength than other digital channnels?) or VHF digital signals that would make it harder / impossible for my antenna to receive or more susceptible to cable losses?
Appreciate any advice.