"Experts believe that while Iran may be unable to totally block the signals, they can beam so much noise over the city's grey-brown skyline that broadcasts suffer lengthy drop-outs.
"The main targets are around six channels run by sympathisers of the ousted monarchy. These stations, mostly based in Los Angeles, spend their time trying to convince Iranians that the rule of the late shah, Mohammad Reza Pahlavi, was a golden age, and that Islamic Iran is not.
"Other channels teasing the turbans include the MTV-inspired Persian Music Channel, which shows far too much flesh for the regime's liking.
"But there are also possible side effects of the battle of the frequencies.
"The local signals of state television, busy trying to drum up interest in the elections, have also suffered.
"The mobile telephone network, already subject to overcrowding and poor service, is another apparent victim, given that the coverage zone has reportedly shrunk in parts of the capital."
Judging from this story they appear to be targetting the exile opposition rather than reformist groups inside Iran, though I don't even know if the latter have TV stations. Because these foreign groups have little or no grassroots support in Iran, this shows how insecure the rulers there have gotten - any discussion of the system's legitimacy is a threat.