Surplus SRI Discone info
There has been several of these unique ultra broad band Discones on Ebay recently and they could provide some very interesting monitoring capabilities. I'm posting this info that will hopefully show up in a Google search since the actual part # 26401/7447-1 does not link to any useful information.
This Discone antenna was designed for the US Gov't for RF surveillance and intended to mount above a false ceiling inside buildings. It can be oriented in a normal Discone fashion with the disc on top or inverted to make the antenna more sensitive to signals below. The frequency range is stated as 80MHz to 10GHz in the "antenna" mode and 0.1 to 80MHz in the "RF probe" mode. This is a passive antenna and can be used for transmitting in the 300MHz to 1GHz range at minimum.
The specific 26401/7447-1 is no longer made but the mfr SRI has graciously forwarded me specs on the AF-1000 replacement, which I am told has the same basic specs. Attached is the spec sheet for the newer antenna.