There were many factors leading up to the Radio,but two are very clear:
Early mechanization in the 1400s due to a lack of slave power from slaves, the Industrial revolution in the 1850s due to new ideas of mass production.
The earlier mechanization was because of the Bubonic plague, which crippled Europe because of a severe lack of manpower, and a need for mechanization.
Any massive plague would result in a similar need for manpower. Hence, being channeled towards religion, after the hell their supposed diety had put the masses through, this could likely invoke something like the Reformation in Europe.
The Industrial revolution would be tougher to predict, as it was dependant upon mostly human decisions.
But that will likely follow such a route as OTL. Radio communication could be seen as early as 50 years after the ATL Industrial Revolution.
As long as there is a plague, a printing press, and an ensueing Industrial revolution, you could see radio communication. If a POD affects wither of those three things, radios will be less likely.