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Letter: DRM Offers Advantages Over Hybrid Radio

A single-point system beats a system requiring multiple signal sources

The author is a broadcast technical author from Australia and has spent a lifetime in training technicians. Radio World welcomes opinion and points of view on important radio broadcast industry issues.

Having read “Hybrid Radio Making Strides,” I have a response. This article says that the receiver will switch to the internet when the HD Radio digital signal is poor. This will happen often for a large proportion of the audience because of the extremely low power of the HD Radio’s digital signal.

If a DRM or DAB+ radio is used instead, the only power limitations are the distance to another broadcaster on the same channel only and the cost of the transmitter. High-power DRM/DAB+ digital transmission eliminates the need to constantly switch to mobile internet. In addition, DRM and DAB+ can instruct the receiver to switch to another transmitter radiating the same program, as well as their ability to have multiple transmitters for single broadcaster for dead spot within the license area. High-power broadcasting produces much more even coverage than the mobile internet which uses many cellphone towers to try and produce even coverage

[Read: Where Is Terrestrial Radio Going?]

In addition, nothing has been said about the delay of the receiver switching between HD Radio and mobile internet and back again — there is a variable time it takes the signal to get to the receiver via the internet. It can require the radio to store an HD Radio signal buffer for multiple seconds while the internet signal is sought out and collected from the broadcast studios. Remember that the internet sound is sent in blocks which can take different paths including the receiver switching between different cellphone towers. As the automobile receiver travels around the relative delay between HD Radio receiver itself and the mobile internet will constantly change. If the same relative delays are not identical sections of sounds will be repeated or omitted.

Netcasting requires a path for each listener to their receiver as well as a return path back to the broadcaster. The return path is virtually unused except for a possible counting of the number of receivers switched to that broadcast, but it cannot tell how many listeners there are nor if they are even awake. The return path needs to also contain the location of the receiver particularly for mobile broadband routing of the signal to appropriate cell tower. All of which is not required in broadcast.

The telco has to buy identical spectrum bandwidth for the forward and the return path as well as using separate cables through the telco network to the broadcaster. To increase the capacity of mobile broadband the telcos are having to resort to 28 GHz 5G. These signals will not go through walls, roofs, and hills, so each building will need a 5G transceiver feeding a Wi-Fi modem. A view of this on broadcasters was described in “Will 5G Be Part of the Broadcasting Future.”

I have not seen a recent cost comparison in the U.S.A. of the price of transmitting a program using the internet for the broadcaster, particularly when there are millions of simultaneous listeners. Here is one made by the EBU for European broadcasters.

The cost of simulcasting of FM analog, adding HD Radio and mobile internet for large numbers of listeners is expensive. Large numbers of HD Radios receivers switching to the mobile internet to overcome the problems of very low-powered digital transmissions will see broadcast accountants asking why the broadcaster is running a transmitter at all. The telcos can then control the cost of delivery of a broadcaster’s program to their listeners.

In an emergency, the cellphone network in the emergency area can be overloaded by people call to find out what’s going on and, in those events, HD Radios switching to mobile broadband will aggravate that situation. An overloaded cellphone system prevents people in imminent danger from calling for help.

DRM-based radios can display maps of the affected areas and an indexed multipage text service for emergency instruction in multiple languages if required. All digital radio standards include a method of waking the radio and speaking an emergency announcement which can remove the need for calling all phones in the emergency area.

The best solution would be to convert all broadcasters to DRM for the lowest cost, highest reliability of delivery. There is no spectral space for DAB+ because those frequencies are used by television in the Americas.

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