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Old 16-11-2013, 09:07   #16
tpreitzel
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Quote:
Originally Posted by DRM-OM
Note that total DRM power is limited to max. 40% if analog CARRIER only power for technical reasons. So don't expect more power.
This is a feature.
DRM is "sold" to transmitter operators with the arguement to save energy = money!

I'm aware of that artificial limitation, but it's precisely that technicality that needs review in scenarios consisting of less than favorable atmospheric conditions. Is it possible with modern detection systems to dynamically allow transmitters to adjust output power along their targeted path under adverse conditions? I don't know, but the current situation certainly is far from optimum as the sun doesn't allocate power statically.

Last edited by tpreitzel : 16-11-2013 at 10:01.
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Old 16-11-2013, 11:04   #17
Linux-DRM
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DRM Power

Yes, this is true, it is a selling point of DRM to operators, saying that you can run less power with the same listener impact (in theory) and I understand the technical reasons (interference etc).
In reality it does not translate to that unless good receivers/antennas are used with an excellent signal to noise ratio but this unfortunately is only afforded by enthusiasts...like us...consumers struggle to receive low power DRM transmissions which has been proved on a number of occasions (by me and others). When I had the DR111 (and currently test using the MR 27024) I can/could only receive AIR, REE and RRI consistently using the whip under stable propagation conditions, all these stations use power >50kW.
Sure, run lower power but not so low that the signal can't be received by the listener. DRM is either there or it isn't, people are not going to sit and listen for 10% audio (where 90% is silent).

Cap

Quote:
Originally Posted by DRM-OM
Note that total DRM power is limited to max. 40% if analog CARRIER only power for technical reasons. So don't expect more power.
This is a feature.
DRM is "sold" to transmitter operators with the arguement to save energy = money!
__________________
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Radios: MR 27024, 2 x Tecsun PL-660, Eton G3 & E5, Tecsun PL-365
Antenna: Homebrew Magnetic Loop (3-30MHz)
Software: Dream v2.2 (svn924) on Ubuntu 14.04 LTS

Last edited by Linux-DRM : 16-11-2013 at 11:15.
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Old 16-11-2013, 11:23   #18
DRM-OM
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Quote:
Originally Posted by Linux-DRM
Sure, run lower power but not so low that the signal can't be received by the listener. DRM is either there or it isn't, people are not going to sit and listen for 10% audio (where 90% is silent).
A former staff member of the frequency management of a big broadcaster once told me that if there is a minimum field strength for undesturbed conditions you have to add an overhead of >20dB (which translates to a factor of 100 in power) to cope with atmospheric conditions like flares and fading etc. to ensure a reliability of 98% or above - "that's a minimum, otherwise people will switch off"
If these days 50kW is not enough for satisfactory reception - noone will ever run up to 5MW DRM on shortwave!!!

Last edited by DRM-OM : 16-11-2013 at 11:35.
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Old 16-11-2013, 16:34   #19
Linux-DRM
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I never said 50kW was not enough power to satisfactorily receive DRM, it was a value based on the reception of a very limited number of DRM stations in a consumer environment using a whip antenna (not the best antenna in the world, but one used on nearly every portable radio and probably the only antenna used by a non-enthusiast consumer).
Maybe living in the northern latitudes is not the best place to be, I am sure tests further south would be more fruitful

Cap

Quote:
Originally Posted by DRM-OM
A former staff member of the frequency management of a big broadcaster once told me that if there is a minimum field strength for undesturbed conditions you have to add an overhead of >20dB (which translates to a factor of 100 in power) to cope with atmospheric conditions like flares and fading etc. to ensure a reliability of 98% or above - "that's a minimum, otherwise people will switch off"
If these days 50kW is not enough for satisfactory reception - noone will ever run up to 5MW DRM on shortwave!!!
__________________
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Radios: MR 27024, 2 x Tecsun PL-660, Eton G3 & E5, Tecsun PL-365
Antenna: Homebrew Magnetic Loop (3-30MHz)
Software: Dream v2.2 (svn924) on Ubuntu 14.04 LTS
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Old 16-11-2013, 17:59   #20
DRM-OM
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Quote:
Originally Posted by Linux-DRM
Maybe living in the northern latitudes is not the best place to be, I am sure tests further south would be more fruitful
If "UK" means "United Kingdom" - is that such far north?

But in any case these facts from the BBC Devon MW report apply to any DRM transmission:
Quote:
Second, whilst the night‐time coverage of DRM is greater than the equivalent ‘clean’
AM coverage, it is apparent that the technical limit of AM coverage is not the same
as the limit at which listeners will stop listening to it. Thus, listeners will tolerate
much more cross‐talk from interfering sources than is catered for in international
planning standards, even more so if it is content that they especially wish to hear.
Similarly, listeners will listen to field‐strengths well below the international limits
even if the result is audio which is covered in static and noise.(...)

Third, the failure mode of DRM is – as with all digital systems – dramatic. The
transition from working perfectly to not working at all is fairly sudden, even
considering that DRM is designed to provide a measure of graceful degradation for
longer than some other digital systems. Thus, listeners who previously received a
degraded, interfered‐with AM service at night now received nothing. At other times,
given the dramatic fluctuation in interfering signal strength, listeners found the radio
services dropping out – or burbling, or becoming ‘metallic’ in sound3 – and taking
some while to restore, despite any actions they took.
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Old 16-11-2013, 19:08   #21
Linux-DRM
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Yes, it is, far north of the UK.
I am very familiar with Project Mayflower.

Quote:
Conclusions

The Plymouth trial tested a particular situation: a one‐for‐one conversion of an
existing service on an existing assignment from AM to DRM, subject to the required
international parameters. As a result, it turned up a number of issues for DRM’s use
in the UK if deployed in this manner. It is clear, though, that all of the problems
experienced from a technical perspective can be overcome if there was a willingness
to increase the power of the transmissions, add more medium‐wave transmitting
stations to the network, and re‐plan the use of frequencies.

__________________
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Radios: MR 27024, 2 x Tecsun PL-660, Eton G3 & E5, Tecsun PL-365
Antenna: Homebrew Magnetic Loop (3-30MHz)
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Old 14-02-2014, 15:26   #22
tpreitzel
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To simplify receiving DRM broadcasts for listeners new to digital shortwave, install equipment for a location which allows one to meet these basic requirements for decoding audio:

A broadcast with a Main Service Channel (MSC) of 64 QAM:
1. With some minor variance, receiving equipment must maintain a Signal-To-Noise Ratio (SNR) of at least 16 dB for consistent decoding.

A broadcast with a Main Service Channel (MSC) of 16 QAM:
1. With some minor variance, receiving equipment must maintain a SNR of at least 10 dB for consistent decoding.

Unfortunately, most current broadcasters use 64 QAM with the AAC+ codec for the MSC. Some potential broadcasters of DRM then have the gall to complain about the ineffectiveness of DRM. Why not employ a configuration, i.e. 16 QAM for the MSC, suitable for noisier conditions since most digital broadcasts on the shortwave bands are underpowered? Naturally, these SNR's depend on usage of Mode B. With Mode A, add 6 dB to the minimum SNR.

Last edited by tpreitzel : 16-03-2014 at 07:31.
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Old 17-03-2014, 04:46   #23
tpreitzel
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Cost

As an aid in de-hamifying DRM, let's specify the overall cost to the SWL for listening to digital broadcasts. Most potential listeners won't object to paying ~ $200 (current value and exchange) total for the necessary equipment to receive digital broadcasts on the shortwave bands. Erecting artificially high standards for reception will continue to relegate DRM to a limited group of people, e.g. licensed "hams". Although we're not quite to the point of reducing the total financial outlay to $200 for listening to digital broadcasts on the shortwave bands, it's a reasonable and attainable goal in my opinion. When the total financial outlay to the SWL is ~ $200 for the necessary equipment and broadcasters start using robust configurations employing a MSC of 16 QAM or the power levels are increased to 60% of analog for digital broadcasts on the shortwave bands, then and only then will the potential of digital broadcasts be realized on the shortwave bands. Thankfully, DRM now has a sufficient codec in xHE-AAC and a few broadcasters like VOR, Vatican, and VON are employing sane configurations to fully realize the potential of DRM on shortwave. Given the current limitations on power, I'm convinced that more digital broadcasters on the shortwave bands will soon follow the leads of the aforementioned broadcasters.

Last edited by tpreitzel : 17-03-2014 at 05:12.
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Old 09-04-2014, 04:25   #24
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Another barrier to popularizing the use of the shortwave bands is KNOWLEDGE. Frankly, if potential listeners have to first learn vast amounts of technical information to use a technology, it will NOT be used by the average person. Shortwave NEEDS the average person with non-technical skills, not another licensed "ham" spouting esoteric and largely irrelevant information. Shortwave NEEDS diverse content produced by a diverse audience. Confine the SWL's technical knowledge to primarily learning a radio's interface. The rest of the burden should primarily fall into the laps of the manufacturers and broadcasters.

Last edited by tpreitzel : 09-04-2014 at 04:28.
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Old 28-03-2015, 02:33   #25
tpreitzel
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While testing coverage of my LPDRM broadcast today, I meet a lady along the route. She was genuinely interested in my project. As I was walking along the fringe area, my DR111 wasn't decoding audio at the point of our initial meeting. We decided to walk together for a few blocks as I discussed DRM in relation to my DR111. Eventually, my DR111 started to decode audio from my broadcast shortly before we departed. She appreciated the experience. This lady is a typical consumer with little technical skill beyond operating a radio. Our discussion focused on the capability of digital radio and she left impressed, but somewhat overwhelmed by the apparent complexity. Digital radio, including DRM, should strive to reach such a potential customer, but the interface of the radio must be radically simplified and robustness of broadcasts improved. The DRM standards are sufficient, but deployment for the typical consumer still requires much work.

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Old 28-03-2015, 21:28   #26
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Quote:
Originally Posted by tpreitzel
.... she left impressed, but somewhat overwhelmed by the apparent complexity. Digital radio, including DRM, should strive to reach such a potential customer, but the interface of the radio must be radically simplified and robustness of broadcasts improved. The DRM standards are sufficient, but deployment for the typical consumer still requires much work.

Sort of covered in earlier posts on this thread, robustness of broadcasts is entirely controlled by power levels and frequency planning. It can be done, but broadcasters dont see any money in it and the reality is the transmitters need to be provisioned at 10x existing capabilities of analog levels. Its all in the fine print of the DRM trials and papers hosted on the consortium website. one doesnt get that impression reading the 'public' sections, though.

I think you are right, its deployment for the typical consumer that needed the work. Probably too late now. Consumers expect that the radio in their new car or cellphone / tablet / DroidTV stick will get the signals they want to hear. Despite best efforts and encouragement (by the Consortium) nothing has become available for a consumer to happen upon that capability. The only manufacturers that were capable of crafting a consumer - useable product have abandoned their plans, although still listed as DRM members.

That leaves the Avion as possibly the only consumer radio to be sold now.
http://drmnainfo.blogspot.co.nz/2015...nstration.html

But this one is never going get consumer traction. doesnt look simple to use. If AIR ever accept it for their tender, it will be because of the AM stereo requirement. They have that capability in their new transmitters - NX series.
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Old 12-05-2015, 20:20   #27
tpreitzel
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A significant number of broadcasters suggest that most media will eventually be streamed on demand from users. Personally, I think the future of broadcasting isn't nearly so clear. Ubiquitous, illegal spying will play a significant role in limiting the appeal of duplex communication. Notice how governments promote projects such as "Big Whoop" which smacks of former fascist tactics that employed Brownshirts to snoop for the regime in power. Simplex communication will continue to provide users some privacy amidst such technological abuse. Media viewed on demand will affect video more than audio anyway.

In the frenzied pace of today's world, the influence of websites like the Drudge Report demonstrate the power of brief and current sources of information. A broadcast via radio which utilizes DRM can effectively duplicate the format of the Drudge Report. Global24 should take notes. Although broadcasts via radio in the future will eventually become more specific and briefer than historical broadcasts, simplex radio is just too robust and private to succumb to sources of media delivered on demand and therefore susceptible to ubiquitous spying. The future for simplex digital radio as delivered both domestically and internationally is bright indeed. As I've stated previously, the main problem with the adoption of DRM lies squarely with the unimaginative thinking and poor configuration of broadcasts by broadcasters, not the standards.

Last edited by tpreitzel : 14-05-2015 at 22:20.
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Old 02-06-2015, 20:44   #28
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I was listening to a fairly strong, analog shortwave broadcast with minor fading on my SDR-4+ last evening. In quieter environments, e.g. sleeping, loudness plays a significant role in the clarity of reception. Even with a strong signal, the minor fading of an analog shortwave signal is problematic. Digital Radio Mondiale (DRM) has no such problem. If a listener values retention of his hearing, I don't recommend headphones on analog shortwave broadcasts at all. Shortwave broadcasters need to adopt DRM now!

As for shortwave broadcasters insisting on the availability of dedicated DRM receivers before starting regular DRM broadcasts, such insistence is basically a poor excuse for not doing so. True, dedicated receivers would help widen the potential audience, but nearly everyone has a personal computer or access to one with freely available software such as DReaM for decoding of the digital signal. Except for some remote villages, probably most African listeners even have access to a computer where a digital broadcast could be received, decoded, and disseminated locally. Again, shortwave broadcasters need to adopt DRM now!

Last edited by tpreitzel : 02-06-2015 at 21:02.
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Old 03-06-2015, 09:15   #29
F1BJB
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Quote:
Originally Posted by tpreitzel
I don't recommend headphones on analog shortwave broadcasts at all.
I made the same observation.
I think 2 factors are involved:
SDR are totally flat between 10Hz and 300 Hz it is not the case of a classic BCL
Broadcasters try to compensate for the BCL case.
Some HIFI SSB signals even try to compensate for the roll off of the crystal
filter by concentrating 90% of the power below 300 Hz
A tip I use is that I listen on a TV set fed by HDMI and there is an equaliser
in the TV set .
And no headphone connector
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Old 04-06-2015, 21:49   #30
tpreitzel
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Quote:
Originally Posted by F1BJB
A tip I use is that I listen on a TV set fed by HDMI and there is an equaliser
in the TV set .
And no headphone connector

Although not as flexible, your method is much operationally simpler than my current method involving several pieces of software. Your method is in keeping with the spirit of this thread and I recommend it. Few potential listeners to broadcasts on shortwave will adopt a method as complex as mine. If only broadcasters would use robust configurations of DRM on shortwave and thereby remove such temptation. DRM solves very important problems with analog shortwave.

Good suggestion!

In the following link, none of the software is calibrated as I was merely demonstrating the complexity of listening to analog shortwave with sufficient fidelity. If you look closely, you'll notice that I should have swapped the I/Q in DReaM. I used DReaM for the noise reduction. I used Jamin' for the equalization. I used Quisk for the tuning. The developers of Quisk need to remove the requirement to install Pulseaudio. I literally stripped the Pulseaudio code from the source so it would compile on Slackware. In DReaM, I selected the cleanest sideband to increase clarity since the 10 kHz signal was weak and low in volume. The results were very good, but complicated. In all honesty, I wouldn't listen to analog shortwave for any length of time if DReaM hadn't included the Speex noise reduction.

http://tinypic.com/view.php?pic=2d7y7pj&s=8

Can the maximum file size for attached images be slightly increased please? 100 kB is too low for modern displays. A maximum of 150 kB would be much better.

Last edited by tpreitzel : 07-06-2015 at 02:50.
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