There are seven drainage chambers and two sealed cisterns scattered around the Capital Wasteland. These are minor dungeons, and all are home to Fallout 3 radio stations broadcasting Morse code (except Oscar Zulu and Yankee Bravo). The particular message is explained at length on the page for signal Kilo Bravo. Many of the stations do not have a map marker but can be spotted by looking for the tower.
All have a transformer at the base of the tower with a switch to throw that starts the encoded broadcast, except Kilo Bravo, where the switch is inside WKML. The entry to the underground ham radio station will be nearby. It is possible to zero in on the broadcast, coming from the sewer grate or manhole cover, not the tower itself. They have a short broadcast distance of roughly 200 yards (183 meters).
At the edges of the broadcast, it is entirely static. At its source, there is no static and the signal can be heard clearly. Turning off the ham radio stops the transmission. It can be turned back on, in which case it needs to be selected in one's Pip-Boy again to hear it.
The numbers in [brackets] denote the drainage chamber's designation in the G.E.C.K. For example, signal Kilo Bravo is interior location FFRadioCache01 and its unique radio (with broadcasting script) is designated FFHamRadio01. The FFHamRadio records also show the signal names.
- Signal Kilo Bravo (KB)  - Also in northwest, from WKML Broadcast Station, a bit southeast of signal Alfa Lima and far south of Fort Constantine.
- Signal Oscar Zulu (OZ)  - In the northeast quadrant of the map, a bit southeast of relay tower KX-B8-11 and northeast of Temple of the Union. In the broadcast, Bob Anderstein sends a plea for medical help for his son.
- Signal Alfa Lima (AL)  - In the northwest quadrant of the Fallout 3 map, at broadcast tower KB5, just west of the deathclaw sanctuary.
- Signal Echo Foxtrot (EF)  - At broadcast tower LP8, near the north edge of the map, south of Oasis.
- Signal Oscar Tango (OT)  - South of Jury Street Metro station.
- Signal Sierra Romeo (SR)  - On the western edge of the map at broadcast tower KT8, due north of Little Lamplight and northeast of Vault 87.
- Signal Yankee Bravo (YB)  - In the northeast part of the map, north-northwest of the Corvega factory. Feral ghouls are broadcasting their heavy breathing.
- Signal Sierra Victor (SV)  - In the southwest quadrant of the map, southeast of Jocko's Pop & Gas stop.
- Signal Papa November (PN)  - Due west of Megaton, near the west edge of the map, at a tower just west of the Charnel House. Southwest of Fort Bannister and northwest of Evergreen Mills.
- Many signal chambers have at least some purified water, suggesting that they were initially inhabited when the bombs fell.
- Even if one kills off all the ghouls broadcasting over signal Yankee Bravo, the ghoul's heavy breathing can still be heard over the radio.
- The reasons for these signals are unknown. The variation in messages suggests that they did not all originate from the same group. The usage of the NATO phonetic alphabet is common for both military operations and ham radio operators, as well as anyone with training in radio communications protocol. There is no information regarding their previous use, aside from the content of the radio messages themselves and the equipment found along with the remains of the radio operators.