Many thanks to SWLing Post contributor Mangosman, who shares this Rear Vision audio documentary from ABC Radio National. It explores the rise, influence, and eventual dismantling of the Voice of America, offering context on how international broadcasting shaped geopolitics during—and after—the Cold War:
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Very much enjoyed listening from ABC on this. Thanks for posting it!
A really wonderful documentary. Waves of nostalgia listening to the clips. Thanks for the tip.
https://ampegon.com/shortwave-transmitters/
The 100 kW DRM/AM model was installed for Radio New Zealand Pacific. They already have another operational DRM/AM transmitter of the same power and an existing antenna system.
https://www.rnz.co.nz/international/pacific-news/523864/rnz-goes-live-with-new-pacific-shortwave-transmitter
in 2022 Tonga had an undersea volcanic eruption. I broke the fibre submarine cable, satellite signals will not penetrate ash clouds ( or hurricanes which they also get) which is why they spent $US2.64 million to buy the above transmitter.
Now Papua New Guinea is planning to start HF (SW) broadcasting for their mountainous, jungle country. They know that neither FM or MF AM will work.
In DRM mode the electricity consumption drops by 40 % has excellent sound, emergency warnings, and education with sound, pictures and text. Many of these listeners often do not have mains electricity or the internet and LEO satellites are too expensive. for the listeners.
Also VOA , Radio Free Asia Radio Free Cuba and Radio Free Europe to only use the internet as well, but it can be stopped at the border of countries who’s Governments don’t want their citizens to know. Radio Free Europe is now being funded by the European Union. .
In DRM mode the sound quality is very bad due to lossy digital compression. The bitrates are abysmally low, less than 30 kbps, which is lower than a modern phone call. No actual receiver supports the emergency warning functionality. In fact, there are no readily available DRM receivers anywhere. Since the PNG’s network will not utilize DRM, I think there’s no point in bringing it into the discussion there, unless this is some sort of a campaign.
I don’t know any “Radio Free Cuba”, but as for Radio Free Europe (Radio Liberty), they’re relayed daily on mediumwave, covering big part of European Russia and the neighboring countries.
Qwertysnmfc,
You obviously ever listen to low bit rate audio?. You are following a pattern I have seen at other sites, where criticism is based purely on numbers for old compression systems. All new systems have been tested by using large groups of listeners including experts where the give side by side ratings not knowing shat bitrate and system is being used.
Australia has may digital radio stations using 32 kbit/s. There is a new one in my city which is HE AACv2 and plays 60’s music. This is when there is lots of separation of musicians in original analog recordings. The broadcaster has bought a huge compilation of those hits which are copied from the master analog tapes at the current industry standardised sample rate of 48 kHz (not CD’s 44.1 kHz). Since the sample rate of both HE AAC V2 and xHE AAC is 48 kHz, The encoder will synchronise to the original AES 48 kHz uncompressed encoding. This minimises errors because each sample represents the same point of time. Many songs have different musical instruments on the edge of the audio field with a singer in the centre, It sounds great in a car with the speakers at the left and right edges of the windscreen. It is easy to locate each instrument. Compare this with HF broadcasts which have thig pitched sounds limited to less than 5 kHz, lots of noise, interference and phasing caused by multiple reflections from the ionosphere.
I have listened to the provided podcast once again and I still fail to notice issues like the acquisition of new transmitters by RNZ, Tonga volcanic eruption, PNG’s plans to reinstate domestic shortwave broadcasts, DRM, digital audio compression, Australian DAB+, stereo effects etc. being mentioned there. So is it just me, or are these remarks indeed completely unrelated?
Ampegon had some fully solid-state SW transmitters available, although capable of only up to 25 kW of power. But on the other hand, lots of LW and MW stations use fully solid state TXs with gigantic powers up to 2000 kW. So from the technical viewpoint it seems possible, perhaps there was no market for the higher-power ones?
Like Ampegon, the USA manufacturer https://www.contelec.com/shortwave manufacture single tube HF transmitters. These manufacturers also make other high power equipment in scientific and military industries
The higher the transmission frequency the lower the efficiency of transmitters. Eg DAB+ and VHF and UHF TV stations. These transmitters have to be tunable from 2.3 up to 26 MHz which is much greater than 1.7 MHz for the the transmitters below.
Low Frequency (LW} broadcasting has never been legal in North America, It only existed in Europe and North Asia.. I have ever heard of a new LW transmitter installation instead many decommissionings In Europe Medium Frequency (MF or ‘AM’) is also dying with services going to digital or FM.
Canadian https://www.nautel.com/content/user_files/2018/07/NX-Series-brochure.pdf and French https://thomsonbroadcast.tv/product/long-medium-wave-transmitter-s7hp-neo/ make high power transmitters.
Since an individual power Field Effect Transistors individually are no where near 100 kW. A 2 MegaWatt transmitter https://www.nautel.com/resources/customer-stories/am-transmitters/building-the-biggest-2-megawatt-transmitter-for-antenna-hungaria/ is to use 5 x 400 kW transmitters into a combiner. There has been no mention of the losses in the combiner. Within each of the 400 kW transmitters are combiners for multiple modules containing a couple of output transistors per module because transistor cannot operate at 150 kW which is what happens in the transmitters mentioned at the beginning of this post. Losses in combining networks increase with frequency making a single tube a better option. It also means that companies which make high power electronics need to have manufacturers contained in glass eg x-ray tubes and only using one model makes it easier to supply over time.
Lastly I would like to point out that all of the high power transmitters mentioned above are switchable between DRM and AM. They would not make such transmitters if the sound quality is as bad as you claim remembering as I have asked you before to listen to the demo of xHE AAC https://www.youtube.com/watch?v=SGLBKz9Q_XQ
I still fail to see why you are continuing so hard (by repeating the same claims over and over) to convince me and others on this website that this technology is so great that it makes an audio stream compressed to less than 30 kbps (4 times less than an EVS VoLTE phone call can deliver) indistinguishable from what you can hear in a concert hall. For me, this is pure bollocks, but obviously others can disagree.
The thing is that this is, after all, a hobbyist site, we (mostly) don’t have any impact on the decisions made by the broadcasters, but we can see them, and the pattern is clear – these transmitters, obviously capable of operating in DRM, are not being used to transmit in this mode. Now we can only guess why it’s like this.
Personally, I think it may be due to the fact that the broadcasters can also see that DRM is now a total flop with no real receiver available anywhere (except, perhaps, some undisclosed location in India) since over 2 decades. In that light, the idea of transmitting a signal no one can actually receive may not seem particularly appealing for them. This may also be the reason why the absolute majority of DRM broadcasts that were in the air in the early 00s (when the system was actually a novelty) were converted back to AM or taken completely off-air.
They’ve been shutting down shortwave for decades. Please, people, this is nothing new. The equipment is old. Most companies that built SW transmitters are gone. There are NO high power solid state SW teansmitters. Even the engineers, like me, are aging out.
Keep the faith Bob. At least you are providing worthwhile air time. Rich. wr3v.