alanh

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About alanh

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  1. ABC now promoting DAB+

    James, Firstly the signals are identical except for the field strength at the receiving site. So your modulation argument is irrelevant because it is unchanged. I don't care what TV does we are talking of DAB+ radio. As I have already checked the ACMA has licenced all the Artarmon transmitters both TV and DAB+ to be omnidirectional which means equal power in all directions. Hawkesbury is a repeater. It contains no modulator only frequency shifters, filters reshift back to the original frequency and a power amplifier. There is no demodulated signals at all. Where is your signal strength map from the Hawkesbury transmitter site? Considering that the distance to Blacktown is 25.7 km and from Hawkesbury is 28.4 km and her complaint was closer to Artarmon than Hawkesbury makes the Hawkesbury even weaker than the 22 dB I calculated added to this the path from Hawkesbury is blocked by the terrain making it undetectable. Your diagram shows both signals at equal level which is far from the actuality. As I have already stated, if she was driving North with a truck on her right (ie East of her) then the Artarmon signal is blocked, then the Hawkesbury signal should have taken over but it is almost non-existent which is why it did not. You have not heard the machine analogy before because what you have is wrong. Firstly the diagram does not show the guard interval secondly all reflections have some absorptions making the signals weaker. Thirdly if the repeater is stronger than the main transmitter the receiver will resynchronise and make the repeater signal on the left instead of the main transmitter. If the delayed signal arrives less than 1.297 ms after the stronger of the signals it will be ignored and there will be no errors produced. The path length from Artarmon to Hawkesbury is 53.7 km. The distance back to Blacktown is 28.4 km which is a total of 82.1 km taking 274 microseconds. The path length from Artarmon to Blacktown is 25.7 km taking 86 microseconds. The difference is 188 microseconds which is well under 1297 microseconds gap even allowing for some delays in the repeater. As I have said the problem is insufficient signals which makes a repeater in the Blacktown and probably in the Hills region and maybe others in the SW suburbs a requirement for automotive reception and indoor reception particularly in blocks of units and in metal roofed houses. Alanh
  2. Sound quality

    MLXXX, This is a bit better, but now go and listen on a receiver designed to produce high quality sound. These tuners have digital outputs so that they can be fed into decent sound systems with good speakers adequately spaced. Why do you rarely talk of directional effects of the sound in broadcasts? Examples http://www.altronics.com.au/p/a2698a-opus-one-dab+-fm-digital-tuner-receiver-with-bluetooth/ optical digital output https://www.jaycar.com.au/dab-fm-hi-fi-component-tuner/p/AR1753 Optical digital output https://www.rotel.com.au/products/rotel-t14-digital-gateway-and-tuner Coax digital output http://www.ambertech.com.au/content/upload/files/Onkyo Brochures/T-4030 Aust NPR.pdf but you really need to listen to https://au.yamaha.com/en/products/audio_visual/hifi/t-d500/specs.html#product-tabs connected to one of their hifi amplifiers and speakers. Note their measured Signal to noise ratio and total harmonic distortion DAB+ and FM stereo! Remember also the sound quality is also affected by the digital to analog converter, because after decompression it is still a linear digital signal. Also remember that FM has high frequency boost prior to transmission which is reduced for high level high frequency sounds such as the snare or high hat. This is required to prevent distortion and interference to other radio users. When did you last hear such sounds in a live concert? because you cannot hear the original sound prior to broadcast. It would normally be a bright sound. Alanh
  3. Sound quality

    MLXXX, I am still waiting for you to describe the DAB+ distortions, the type of sound, along with which national program you hear it on, and what time so that we can all listen. This eliminates resampling as used above and we can use different receivers. Alanh
  4. ABC now promoting DAB+

    Malich, You would agree that DVB-T also uses gaps for the same reason that they are used in DAB+ Inhttp://www.roverinstruments.com/prodotti.php?idprod=211 catalog the Rover brand Digital Field Strength meter HD Pro Tab model in the catalog on page 16 shows the measurement of the Gap with the green background to show what is allowable for delayed signals whether from an SFN/repeater transmitter or from reflected signals. I have used a previous model of this field strength meter to measure such a gap and it is definitely empty except for reflected signals because I pointed an antenna a large wall which produced reflected signals whilst the main signal was partially blocked by a building on the side of the antenna. When I rotated the directional antenna back to the main signal the display was empty. "14.3.1 Null symbol As previously described, the first OFDM symbol of the transmission frame is the null symbol. During the time interval T 0,TNULL , the main signal s(t) shall be equal to 0." En300401 You are yet to state what data is inserted into this gap by the modulator and what the receiver is supposed to do with this data. The EN300401 2016-10 states that it has a timing relationship with the data and if you read the latest standard you will find there is 2656 sample periods of Null symbol which means zero or no data which equals about 1.297 ms out of a total frame including all data of 196208 samples. In other words the gaps must be synchronised with the data frames. Sample duration is T = 1/2 048 000 seconds. This gap is used to optionally add transmitter identification signals which are useful in Single Frequency Networks to identify transmitters, They use unique frequencies from each transmitter for a form of identification. See EN300401 2016-10 paragraph14.8.0. This does not interfere because the main signal is not being transmitted because it is in the gap. The null symbol generator is multiplexed with the main signal. When the number 0 is Fourier analysed the answer is zero hence no output going coming from the modulator. As a result there is no interference between the main signal and the transmitter identification frequencies. In addition to any optional Transmitter identification, there is other Phase and frequency references which are used in the receiver for automatic fine tuning, so that the listener is not given a fine tuning control. They are a fixed amplitude and so can be used optimise the signal level going into the analog to digital converter by controlling the RF amplifier gain. ie an AGC reference, remember there is no huge carrier in this system like AM's carrier. Lastly in my above example of a car driving North with a truck on its eastern side, the reception should not have failed if the signal from Hawkesbury had been strong enough, remembering that near East of Blacktown is almost equidistant from the main transmitter and the repeater. After all the Hawkesbury transmitter is 1/166th of the power of the main transmitter. According to one of your references the gap is great enough to compensate for the additional approx. 50 km extra travelled by going via Hawkesbury. Alanh
  5. Sound quality

    MLXXX, To make valid comparisons you must do like with like. The Pure radio uses the same RF amplifier for DAB+ as FM and the same audio amplifier. A different receiver does not. In addition no additional editing is required, just push the band button. It is also pointless comparing systems on clock radios rather than radios designed for high quality sound and good RF performance. Alanh
  6. ABC now promoting DAB+

    Malich, Please quote the paragraph number from ETSI standard ES300401 what these signals in the guard band are and describe what the receiver does with them. The ABC/SBS transmitter in Hawkesbury is 10 W more than the commercial repeaters, and the main transmitter in Artarmon is the same power. See the latest ACMA transmitter list. If you wish to prove that the ABC/SBS transmitter in Hawkesbury is operating you need to do the experiment I did at Mindarie. You need a portable battery operated DAB+ receiver drive to a location close to the repeater, but has a near by hill between you and the main transmitter. When I did this the signal strength was maximum, but as you drive away from the site back towards the main transmitter the signal level drops back to the general strength for the region. This forum had said that the ABC repeaters when they first started were not operating on a number of sites, so I did the above test and proved that the Mindarie one was on air. Alanh
  7. Sound quality

    https://youtu.be/z8P7EFEw3OA At least all the sound came from the same receiver even if it had a very small speaker. Why didn't the maker of the video that J Smith linked to use the Pure radio for DAB+ and then switch it to FM? This is a much fairer comparison. Perhaps the hiss was worse on the Digitek receiver because it had a better audio high frequency response? Alanh
  8. Sound quality

    J smith, I noticed that you are using two different receivers for this demonstration. How was the audio fed into the computer? Alanh
  9. ABC now promoting DAB+

    Liz, Hawkesbury repeater of a tiny 300 W is the same distance as the Main 50,000 W transmitter at Artarmon. As a result the power of the Hawkesbury transmitter is so low by comparison it will not even be detected by any receiver in the Blacktown area. So the Hawkesbury transmitter is 22 dB less than the Artarmon. The type of modulation is irrelevant because the signal from both transmitters are identical except for a much lower power and a delay from the Hawkesbury transmitter. There is 3.8 million DAB+ listeners in total covering Brisbane, Sydney, Melbourne, Adelaide and Perth and rising. Since 1/3 of all new cars sold in the last 12 months contain DAB+ radios, many more listeners will hear the variety of programs increasing the number of listeners even more. I have checked the profile from Artarmon to Blacktown and there is a shadow valley east of Blacktown, and the profile does not include buildings, semi-trailers etc. As I have already stated there is probably a case for a repeater East of Blacktown, however if the ACMA/ABC/SBS/ Commercial Radio Australia are not alerted to holes in the coverage then nothing will be done. My complaint about the current coverage area maps is that they do not show any holes in coverage which you have demonstrated exist. Alanh
  10. The latest is that last year slightly over 400,000 cars were sold with DAB+ and total car sales were 1.2 million. That means 1 in every 3 cars sold in Australia last year had a DAB+ radio. With all cars being imported next year and with Norwegian sales with 98 % DAB+ the international car makers have got the message and the UK is around 70 % new car sales. Hardly the image MLXXX was trying to portray. Alanh
  11. DRM installed in cars

    There is some misguided posts here. The overseas strand is under Digital TV Discussion/Overseas There is no strand for DRM digital radio only DAB+, so I put it in the strand Television and Radio Off Topic described as "Off-topic posts of an uncategorised Television or Radio nature" Hrh, I used the term live radio to indicate I don't want podcasts which are pre-recorded and distributed by the mobile phone network. It also applies to streaming broadband. I want AM or FM. Telstra https://www.telstra.com.au/coverage-networks/our-coverage has put 3G cell transmitters along the Eyre Highway. The coverage however is not complete. I don't know how many cars within the coverage area of an individual tower can be supplied with program because whilst broadcasting feeds all listeners simultaneously, mobiles treat each phone as an individual user with their individual program. The most isolated part of the Eyre Highway radio wise is between Kalgoorlie/Esperance to Streaky Bay SA. In a straight line between ABC's 6GF Kalgoorlie 2 kW power (6KG (RadioWest) 2 kW) to the ABC's 5SY Streaky Bay 2kW, 1128 km and the line crosses the Eyre Highway just East of Madura, however this is not half way. In a straight line between ABC's 6ED Esperance 1kW, (6SE(RadioWest) 5 kW) to 5SY, 1152 km but the path is nowhere near the coast of the Bight. Outside of Kalgoorlie, Esperance and Streaky Bay, very low powered FM transmitters are in Salmon Gums, Norseman, Penong SA and Ceduna/Smoky Bay. So where is there no daytime radio coverage? Alanh
  12. Garry, Read http://www.acma.gov.au/Citizen/TV-Radio/Television/TV-reception/whats-wrong-with-my-tv-reception and the associated links. Just remember that the ACMA will do nothing if the mobile phone tower equipment is operating within its licence conditions. It will be up to the viewer to insert a 700 MHz filter as I mentioned above with no compensation. Alanh
  13. Garry, The times you quote are typical of using mobiles, however the weather also changes in this pattern as well. This why a digital field strength meter is required to isolate if the signal is fading from Mt Sugarloaf/ ducting from Illawarra which is weather related or if it is interference from the mobile phone tower. I should also add any corrosion in the antenna system will aggravate interference problems because it causes intermodulation. I assume being so close to the coast that salt laden air will cause antenna corrosion. Alanh
  14. ABC now promoting DAB+

    Liz, 4 DAB+ channels fit into a TV channel. The total power of the channel is being measured so one would expect that the total power of the 1.5 MHz of the DAB+ channel would be 4 times higher than for a 1.5 MHz portion of a TV channel. This is an increase of 6 dB. However this increase is drop in the ocean when compared to the losses introduced by buildings, blocking terrain etc. The question about the maps is why are they different? The pair of commercial transmitters and the repeaters are identical to the ABC/SBS transmitters and repeaters. The operating frequencies are very similar so the maps should be identical, however how were they produced? Was it driving selected routes measuring the signal strength, which means lots of areas are unmeasured. The myswitch website map is likely to be the most accurate because it is computed using a 3D map of the earth and well researched formulas which calculate the path losses. It does however assume the antenna is outside and up to 10 m above the ground. The map has no details about buildings and vegetation blocking paths. At 10 m above the ground it is less of a problem than 1 m above the ground as is the situation in cars. Are you using the telescopic antenna fully extended and vertical? What is the roof made of? I ask this because my next door neighbour used to have a concrete tile roof and her mobile phone was fine. The roof was replaced with a steel roof. Now she has to use the phone outside. Radio waves do not travel through metal. The reason why the AM radio has a wavelength around 300 m compared to DAB+ which is around 1.4 m. Metal blockages which are a wavelength or longer in size it will drastically reduce the signal strength. This is why you are having less problem with AM. In addition the path that your AM signal is from Prestons which is different to the one from Artarmon. http://www.acma.gov.au/licplan/defmaps/documents/maps/la_542.pdf is the licence area for commercial/community radio stations. The Licence area is to keep other competitors out. Please complain to the ABC reception site. Alanh
  15. ABC now promoting DAB+

    Liz, The DTV is relevant because the transmitted power is the same as DAB+ as is the transmission frequency is very similar and their transmitting antennas are on the same towers. Some FM transmitters are on the same towers but their power is higher and their frequency is roughly half meaning that it will go round obstructions better. DTV use the same modulation system as DAB+. The effect of multipath reception is distortion on FM if the DAB+ is subjected to the same multipath reception will cause errors. If the errors are sufficient then cannot be corrected and the receiver will mute. High levels of reflections occur in the CBDs because of the tall buildings which also block the original signal at ground level. This is why the first DAB+ repeater was installed in Collins St Melbourne CBD. Now there is repeaters in Sydney and Perth CBD for this reason. Parramatta has tall buildings so there may be a case for another repeater on the top of one of those buildings. You should put a complaint into http://www.abc.net.au/reception/contact/ and let us know their reply. This is what the ABC claims to be the coverage area https://www.google.com/maps/d/viewer?ll=-33.79740899999998%2C150.99609399999997&spn=0.798849%2C0.961304&hl=en&msa=0&z=9&source=embed&ie=UTF8&mid=1kNyJ8aqkP_HS4-IuHhTgrnl2JeA and the Commercials version of the coverage area http://www.digitalradioplus.com.au/DigitalRadioPlus/media/DRP_Media/Coverage-Maps_Sydney.pdf Neither of these maps have the repeater coverage and the level of detail used by the 3D computed coverage area maps on www.myswitch.digitalready.gov.au for DTV. What is your reception like at home? I particularly like the high frequencies and the stereo sound. It is a pity they don't use stereo sound during interviewing a guest. Alanh