ozadam Posted April 10, 2007 Posted April 10, 2007 Today I purchased one of those MTV SD stb's from Coles. I connected it to the antenna and performed an auto-scan for channels, not expecting any troubles as our analogue reception is pretty good and being at Redcliffe, I'm not too far from Mt Coot-tha. I was surprised when the only channels it found were the SBS and Channel 7 ones. I've performed the auto-scan several more times today, and the results are the same each time. SBS is fine, but Ch.7 varies between unwatchable to slightly glitchy. In the manual scan, I've noticed that the channels I do get have a very high signal strength (> 95%) but a low signal quality (< 50%). If I try to manually enter a channel, e.g. ABC (12 - 226.5 MHz) it shows > 90% strength, ~50% quality, but after I press OK it says "Warning: No Service". I'd appreciate if anyone could suggest where the problem here lies.
alanh Posted April 10, 2007 Posted April 10, 2007 ozadam, You have too much signal, got to an electronics shop and by an attenuator and put its output into the STB antenna in and the cable from the wall goes into the other end. Any further problems, read Get the Best Reception, Brisbane and read the links. AlanH
ozadam Posted April 11, 2007 Author Posted April 11, 2007 ozadam,You have too much signal, got to an electronics shop and by an attenuator and put its output into the STB antenna in and the cable from the wall goes into the other end. Any further problems, read Get the Best Reception, Brisbane and read the links. AlanH Thank you for the advice, I'll pick up one of those Jaycar variable attenuators and see how it goes!
mtv Posted April 11, 2007 Posted April 11, 2007 ozadam I also suspect your signal levels are too high. Have you read This Thread with similar problems?
ozadam Posted April 12, 2007 Author Posted April 12, 2007 Today I bought the variable attenuator and connected it between the antenna and STB, however this caused me to lose the few channels I was getting. From MIN to about 3/4 on the attenuator dial, I get 0 signal/0 quality, and then from 3/4 to MAX I get ~40-60 signal/0 quality. (does MAX refer to max attenuation or max gain? if it's the former then perhaps I need another attenuator in series?) So in summary, I suppose excessive signal is not the problem, as the attenuator greatly diminishes signal without giving me any quality boost. What would be worth trying next? Trying another set top box? Thanks
mtv Posted April 12, 2007 Posted April 12, 2007 ozadam as per my linked-post: Without accurate measurements of channel power and quality (Bit Error Rate) it's difficult to tell exactly what your problem is. There can be numerous reasons for your reception problems, too-high signal levels at your location in certainly one of them. Without being able to 'see' all of the signals present on a digital field strength meter/spectrum analyser, it's impossible to know exactly which signals are causing the problem, if in fact any of them are. It is very common to have frequencies other than the digital TV signals causing receivers to overload. The common offenders are analogue TV (especially Band 1 ABC), FM radio, AM radio, communications transmissions etc etc. IF you have some of these high-powered signals present, your digital TV signals may be comparatively lower. Using an attenuator will reduce all levels, but it won't discriminate between what you need to keep and what to remove. Attenuating filters for the problem frequencies may be required. This is why I keep stressing the importance of having reception problems checked by a pro installer with a digital meter. Once you KNOW what the problem is, then you can correct it. There may be a combination of problems. You can keep 'guessing' for months and experimenting, but it's much easier to solve a problem when you know for certain what the cause is, not just the symptoms. You haven't given any details of your antenna (type/model/mounting), cabling, splitters etc. All these things are factors. On the other hand, as you say, try another STB. At least if you knew your DTV signals were fine, it would give you a fair indication it was the box.
KismetKat Posted April 21, 2007 Posted April 21, 2007 apols for this - thread to post to with test is closed
datvman Posted April 22, 2007 Posted April 22, 2007 Have you tried a high pass filter? The 50kW cancer stick is only down the road from you at Bald Hills. I'd give that a go.
brisdigitaldan Posted April 23, 2007 Posted April 23, 2007 Have you tried a high pass filter? The 50kW cancer stick is only down the road from you at Bald Hills. I'd give that a go. What has an AM radio transmitter got to do with TV reception?
digitalj Posted April 23, 2007 Posted April 23, 2007 What has an AM radio transmitter got to do with TV reception? removed, refer to next post.
mtv Posted April 23, 2007 Posted April 23, 2007 Noise, AM Radio causes a lot of noise, aka Impulse interference. Incorrect, AM RF transmission is not impulse noise, which is typically caused by electrical arcing. However, any strong RF transmission can cause digital reception to 'break up' due to overloading the front-end of the receiver.
ozadam Posted April 24, 2007 Author Posted April 24, 2007 Just as an update, the problem ended up being with the set top box; new set top box and all channels are being received (even some from the Sunshine Coast transmitter)
mtv Posted April 24, 2007 Posted April 24, 2007 A good outcome for you then, ozadam. Just goes to prove that if you can compare reception with another STB, it can help solve a problem. (process of elimination)
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