混信 as you mentioned literally means 異なる信号が混じること, or when two signals emitted from two different locations "mix". This happens when the signals are at the same or very similar frequencies. 混信 generally refers to 電波, or wavelengths longer than infrared light. So, you will see its use when talking about wireless communications, radio and television broadcasting, etc.
干渉 has a much broader meaning. In physics, it is the when two waves superimpose to form a resultant wave of greater or lower amplitude (reference). Note that this is not restricted to radio waves as 混信 is.
Also, 干渉 can refer to noise(electronics) but 混信 cannot.
So, 干渉 can refer to any type of interference (in other words it is not restricted to signals).
So, in your example sentence, I think that both 干渉 and 混信 can be used, but depending on the context they are not necessarily interchangeable. Also, I believe 干渉 is much more common because it has a more general meaning than 混信.