For several years, they were Motorola's, and before that, a GE or two. Looking at the latest press release pictures, there isn't ANY shown. However, the ones from Clinton's era show what appears to be Larsen's and from their appearance I'd say two of them are cellphone antennas, and one a UHF. The fourth one is anyone's guess, but it is definitely a SHF satellite antenna.
Alan, KØBG
www.k0bg.com