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-   -   De-Hamifying DRM (http://www.drmrx.org/forum/showthread.php?t=2480)

tpreitzel 10-02-2018 19:24


Thanks for posting this news. I especially like the promotion of the non-audio aspects of DRM as this aspect is precisely the component that has the most potential for informing the "listener". I, too, would like to see DIVEEMO both standardized and promoted.

Now, if AIR would only restart DRM broadcasting on shortwave with 16 QAM modulation and the xHE-AAC codec from their transmitter in Bangalore!


tpreitzel 10-02-2018 19:25


Originally Posted by Aetheradio
The main problem with DRM is nobody can buy or build a receiver that complies fully with the current standard.
It must have both DRM30 and DRM+
It must have all codecs and rates including xHEAAC

The modulation doesnt matter much between 64QUAM and 16QUAM on shortwave. I did enough practical on air tests to show there was maybe a half dB in it. Once your reception gets in the noise below minimum thats it. When things are this bad, only AM works.
The BBC tests on MW went to lower constellation at night due to adjacent channel interference. This is no longer a problem on SW because most everybody has left.



Logs on this forum and the experience of other members including myself clearly demonstrate otherwise. The threshold for decoding 16 QAM is MUCH lower at the receiver than 64 QAM even on the MW band. I should know as I have tested it with my DRMAX-1 transmitter. Furthermore, I don't have access to your tests so I can't and won't comment on them specifically. Regardless, ANY lowering of the threshold for decoding a DRM signal on shortwave is an improvement so, again, the use of 16 QAM on shortwave is absolutely necessary to MAXIMIZE decoding for the listener and supported by the thousands of logs on this forum. Therefore, we'll have to agree to disagree.

The inclusion of other codecs isn't really necessary in the DRM standard as xHE-AAC finally realized DRM's potential on shortwave when used in conjunction with 16 QAM ONLY modulation. Opus might be nice, but it certainly isn't necessary now with the advent of xHE-AAC.

As far as including DRM+ capability in receivers, it's not really necessary either, but would probably improve the market for a DRM receiver.

In conclusion, I'll agree partly with your comments that shortwave listening is currently declining because of both ignorance and convenience. Both of these latter factors can and will likely be overcome when more desperate times arise for an individual or even country ... Life isn't always rosy or cozy.

tpreitzel 23-04-2018 03:30

"Old" Analog Concept of Targeting Nations
With the multiple service capability of DRM, the old analog idea of narrowly targeting nations should be dying, but won't until those analog broadcasters die as well unfortunately. It's an awful thought, but apparently true. Engineers are so conditioned by ideology and practice, it'll be difficult to change the situation until new engineers arrive on the SW scene along with further refinements in low bit-rate compression. This latter process is already occurring, but will require more time. I'm NOT saying there will NEVER be a need to target a nation, but that the general practice will decline as multiple service capability is properly employed.

Even with 16 QAM modulation, the current DRM xHE-AAC codec can readily accommodate multiple audio streams and languages with decent quality. Even now, the perceived need for narrowly targeting nations via shortwave is rapidly disappearing and SW broadcast engineers need to rethink their old habits.

tpreitzel 21-06-2018 16:42

If it's possible, the DRM standard will soon have to incorporate 4 QAM modulation into the standard which will be a boon for digital shortwave. Then, digital shortwave broadcasters should be restricted to either 4 or 16 QAM modulation. The continuing research of incorporating AI techniques into codecs will allow audio from ultra low bit-rates below 3 kbps. Essentially, we're already there. Dolby has purchased Coding Technologies and released AC4. Opus will be following the others into the lower end a la Codec2 and its variants. All of this research will be a boon for digital shortwave and its listeners.

tpreitzel 28-06-2018 01:28

Video ports, e.g. HDMI, should be a standard component on digital radios as well as COMPACT IR remote controls on desktop units. When I'm working on various tasks, I don't want to have to stop and twiddle knobs or walk to a radio with a small screen to read data. An HDMI port will allow me to connect a micro projector. Although radio on VHF, HF, and MW bands will probably always remain a primarily audible experience, I can definitely foresee visual data increasing its share of that experience. Hence, designers and manufacturers need to prepare now. Radio data is primarily an attachment to an old analog paradigm. Purely digital technologies like HD, DRM, and DAB haven't been properly deployed since their inception. Again, the old analog paradigm has been replaced so stop thinking within the boundaries of its mental cage.

User-friendly digital radio is flexible and anonymous which are the main reasons for my continued involvement with DRM.

tpreitzel 31-07-2018 14:00

Digital IS the way forward on broadcasted bands. I was listening to Ted Randall of WTWW who was promoting his advertisers on shortwave and wondered about his effectiveness. Since the advent of the Spynet, listeners want comparative information before buying products which can only be done digitally. It's possible to promote SERVICES adequately on analog platforms, but I'm not so sure about PRODUCTS. Today, people expect reviews, both pro and con, on products before purchasing. Asking those potential buyers to access the Spynet is both cumbersome and unnecessary. Why not just use a digital platform such as DRM and broadcast that extended information so a buyer can decide without having to access the Spynet?

Digital broadcasters need to update their ancient analog thinking again, in this case, the promotion of their advertisers' products.

tpreitzel 04-09-2018 21:50

Congratulations to this Indian radio club for their educational program featuring DRM. Hopefully, Indians will conduct more such informal sessions. I'd like to see other nations conduct similar sessions, but the limited availability of broadcasts is problematic.


tpreitzel 12-10-2018 21:45

This thread is generally about simplifying digital reception on the broadcasted bands, primarily shortwave, for the masses. I've already discussed rational and robust configurations for digital shortwave. If broadcasters want to be heard with reasonable quality on shortwave, they should heed my recommendations. Now, let's look at content briefly.

The masses want the truth, but aren't generally willing to expend the effort to find it. Hence, unscrupulous broadcasters have lead to the rise of the mass media, or propaganda for the lazy masses.

With the aforementioned said, scrupulous broadcasters will attempt to provide those lazy masses with the truth. However, the truth will likely NOT be found in regurgitating one's biases over the air. Truth is found by diligently searching for all possible facts, incidental or direct, regarding a topic. For example, Dr. Michael S. Heiser, a biblical scholar with a different view than many in his field, has the ability and sufficient training to adequately interpret ancient texts. Michael's views on the paranormal can be found in his work, "The Facade", as well as more recent publications. I use Dr. Heiser as an illustration of someone who would serve as a counterpoint to some of the traditional interpretations found in ancient texts which should be broadcasted over the air. In EVERY field of human endeavor, a scrupulous broadcaster should monitor his own biases before selecting content to air.

Remember, the masses WANT the truth, but aren't willing to expend much effort to do so which is a weakness that unscrupulous broadcasters exploit.

tpreitzel 09-04-2019 04:46

Another Reason Why SW Broadcasters Need Digital
Limited bandwidth which SBR can effectively overcome. Most analog SW broadcasters don't equalize their broadcasts for the limited bandwidth of SW and the audio just sounds terrible, i.e. muffled and boomy, as a result. Non-equalized audio especially music on analog SW sounds awful unless broadcasted with at least 30 kHz of bandwidth. Personally, I can't listen to non-equalized WTWW on 5085 kHz for more than 5 minutes without getting a headache.

I've attached a sample recording of an analog SW transmission, Radio Marti, on 7355 kHz, after applying a steady roll-off of lower frequencies from ~ 800 Hz to 50 Hz (cutoff). The mid-range frequencies are largely flat and unaltered while the high frequencies are less steeply rolled-off beyond 6 kHz in case Cuba decides to broadcast 30 kHz, distorted analog... LoL I don't really alter this configuration much at all even though audio frequencies beyond 6 kHz are largely non-existent on SW. A multi-band parametric equalizer, qpaeq, was applied to the 7335 kHz transmission received via an SDRPlay RSP-1A and CubicSDR along with Speex NR from DReaM at -9 dB.

A properly equalized broadcast will sound progressively better with better audio equipment while retaining its balance.


tpreitzel 16-04-2019 02:16

A continuation of post #69 to illustrate the magnitude of processing required to produce adequate analog audio on shortwave:


This screenshot is busy and requires some explanation. First, a SOAPY RTL-SDR driver was used instead of a SOAPY RSP-1A driver since I was using an RTL-SDR V3 SDR on the Q-channel, i.e. no upconverter. The audio was managed by PulseAudio's Loopback device and routed to the I/Q Neg Split channel on DReaM's input. DReaM's output was via the FFT of the multi-band equalizer, qpaeq, on PulseAudio's default output device.

The reception and sound quality are quite good considering the use of a $20 dongle and 30' of wire antenna (MMDs-31). All of the rest of the processing was handled via software. Granted, the listener to these larger SW stations shouldn't NEED to equalize their unbalanced broadcasts on limited bandwidths as it's the transmitting station's responsibility. Furthermore, some limitations of analog just can't be overcome without digital.

tpreitzel 17-04-2019 05:16

Maybe I'm dreaming, but WTWW on 5085 kHz actually sounded much better tonight, April 16, 2019. Has Ted actually equalized WTWW tonight? If so, the sound is sooooo much better balanced than normal, Ted. If you want at least 10 kHz of audio bandwidth, Ted, please consider robust, i.e. 16 QAM, DRM with SBR. It CAN be done, Ted, and the quality will be vastly superior to anything you can broadcast in analog in 12 kHz of RF bandwidth. I actually enjoyed WTWW tonight from my higher quality audio system even with WTWW's limited 6 kHz of audio spectrum. Talk radio can be adequately done in analog on SW, but music is definitely hard to do and must be equalized to retain balance in RF bandwidths under 30 kHz.

tpreitzel 29-04-2019 00:28

As I hinted when I first joined the DRM Software Forum years ago, more is happening with the atmosphere than natural phenomena. I'll even add that anthropomorphic geoengineering isn't helping the continuance of shortwave and its digital counterpart one iota either. Yes, geoengineering consists of various technologies, but all of them need much closer scrutiny. At the very least, more attention needs to be focused on geoengineering and its potential effects on radio propagation.

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