All posts by Michael Rogers
Below are all of Michael Rogers's postings, with the most recent are at the bottom of the page.
DRM+ is a vhf implementation of DRM. I assume it will need a modified Linux software implementation on the PC processing the signal from the vhf receiver. Details will presumably be available from the DRM Consortium. Reception on vhf will, of course, only be possible in the Edinburgh area. As Brian states, DRM is not going to overtake DRM now, but ongoing research suggests it is still considered a possible future option. I received a very informative response from a BBC engineer to an enquiry about DAB and FM options planned for Devon which included a mention of the former DRM trial conducted from Plymouth.
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Goddards free-to-read summary is of relevant interest, and would seem to reflect the current state of play. I would be happy to see DAB really equal FM, but a "coalition-compromise" may currently be a more realistic expectation, especially for local and commercial radio. DAB may have to settle for mainly national SFNs, at least for this decade.
Goddard: "In my opinion, the likely outcome is that fm radio (supplemented in the uk by am and Long Wave) will continue to be the dominant radio broadcast technology. For those consumers who seek more specialised content or time-shifted programmes, the internet will offer them what they require, delivered to a growing range of listening opportunities integrated into all sorts of communication devices. In this way, the future will continue to be fm radio for everyday consumer purposes, with personal consumer choice extended significantly by the internet."
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As a mature student, I had to do Fourier transforms and advanced calculus to get my professional qualification. It is all too evident that dumbing-down has now spread way beyond GCSE...
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Possibles:-
1. Signal overload. Remove any booster amplifier. Insert an attenuator at the receiver.
2. Substandard coax allowing interference to "leak in". Joints not a good idea. Replace with satellite-grade cable in one piece.
3. Metal shed roof? Reflection problems?
4. Correct, intact aerial for group C/D?
If in doubt, replace with a log-periodic to
cover all eventualities.
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Bruce is right. Exceptions "prove the rule" - such as when all muxes radiate final full power. Unless close to and within view of the mast, a good quality roof aerial, sat-quality cable and good connections are advisable.
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BBC WORLD-SERVICE : Nedbod, cheer up! Get a good analog shortwave radio and you will be able to hear powerful stations from the mid and far east instead ...
From nearer home, it will be ever more cheapo podcasting. The broadcasters, directors, stock-markets and our beloved leaders know so well what is good for us that they dont need to waste money asking us :-)
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Kilvey Hill : Brian, when you tinker, could you check why Kilvey Hill doesnt show on my predictor, whereas Preseli, Carmel, Wenvoe, Huntshaw, Ilfracombe and Caradon do - all of which I get signals from. Brilliant it is already, so not much room for further perfection! Thanks.
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This is a fundamental issue. It looks as if coverage maps will ultimately "demonstrate" meeting the target. De facto received signal strength would, however, be the criterion of choice. If reception on a portable or incar is not as good as "historical FM", it will be too late to riot in the streets ...
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DAB SIGNAL QUALITY is obviously more significant than signal strength. However just as with the DTT predictor maps, only signal strength predictions are feasible, not quality. For this reason I referred to signal strength. Given the unreliability of DAB reception on a portable (or car) radio where there is a reasonable signal, as here, coverage, theoretical and real, is a valid issue to discuss. Also, there must be good reasons for the current vhf DRM+ experiments to go ahead. Maybe as a future complementary option in view of the limitations of DAB? The electorate might be unenthusiastic to have to buy yet another radio, but maybe we are getting used to the idea...
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Friday 14 January 2011 9:21AM
DRM+ TRIAL IN THE UK -This is good news! If DRM were moribund, this would not be happening! Extract from drm.org below:-
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The DRM Digital Radio Mondiale standard was extended in 2009 to add an additional mode for operation in the VHF broadcasting bands (known as DRM+), enhancing the established capability of DRM for digital radio services in the bands below 30 MHz.
DRM provides many features to allow user-friendly, high quality radio to be broadcast, including use of station names rather than frequencies, consistent digital audio, additional text and visualisation, an EPG, alternate service signalling, and automatic service following to DRM, DAB, FM and AM services.
After the successful trial in Sri Lanka (November 2010) the DRM Consortium will mount a comprehensive DRM+ trial in the UK. The trial will take place in the Edinburgh area of Scotland in the first quarter of 2011. Its objectives are:
* To measure the coverage of DRM+ operating in various transmission modes (lower capacity, higher ruggedness; higher capacity, lower ruggedness);
* To compare the coverage of FM and DRM+ in terms of transmit power;
* To assess the impact of DRM+ on FM and vice-versa;
* To demonstrate the performance of DRM+ in a range of environments throughout the coverage area, for example, urban, suburban, rural, etc., and therefore provide an analysis of performance in the presence of multipath interference, terrain shielding, man-made obstructions, etc., in both strong and weak signal areas;
* To measure the pattern of the antenna in order to correlate performance in different directions with expected performance;
* To provide suitable measurement data to international regulatory bodies, such as CEPT and ITU.