Nationwide
The UHF NBFM system Harold Peach mentioned (on 415.7/407.85) is
code named "Echo Foxtrot", or "Nationwide" (the later name distinguishes
it from the "Washington Area" system used for communications with White House
limos and staff cars). It provides full duplex clear voice coverage
over most of the continental US to VIP aircraft in flight (SAM aircraft
- Special Air Missions - which fly out of Andrews AFB). It links them to a
console at the White House Switchboard ("Crown") in the Old Executive
Office building basement from which phone patch connections can be made
to telephones at the White House, on the commercial POTS/DDD network,
various other federal telephone systems, and occasionally the DSN
(Defense Switched Network - formally Autovon). (E/F is not an Autovon
system or just intended for Autovon patch use).
The system is operated by the White House Communications Agency
(WHCA), and AT&T. Ground sites (there are about 30 of them) for the E/F
system are located on AT&T microwave towers throughout the US and are
connected by leased lines to a tech control console ("Crown Control")
that is part of the White House Switchboard ("Crown" or "Signal"). Each
individual site can be separately keyed from the console and patched
into a call, thus the system is capable of handling several calls at
once although the aircraft involved have to be far enough apart not to
interfere with one another.
The E/F system is completely manual at both ends, call setup and
ground site selection is done by operators. On the ground the operators
are WHCA/White House switchboard operators, on the aircraft they are CSO
(Communication System Officers) who are military NCO's (tech sergeants
mostly).
The E/F system is in-the-clear UHF NBFM full duplex voice. The
aircraft often push-to-talk keys its transmitter, so it only transmits
when the party on board is talking. The ground site usually transmits
continuously for the duration of the call. The system has been recently
used with STU-III's for security, but apparently not too successfully.
There have been occasional attempts in the past to use other kinds of
secure voice but most calls are still in the clear. Recent White House
staff people who use the system have been made aware that listening to
it is quite popular amoung scanner hobbiests and have been fairly
careful about what they say, but when the system was first installed in
the late 60's and early 70's there were some very interesting
conversations on it.
E/F antennas on AT&T towers are small and not very conspicuous
but they can be recognized if one knows what they look like. They are
always mounted at the top of the tower near the Hogg horns. There are
usually three antennas, two small ground planes and a short vertical
pole mounted above them and three or four feet apart.
Air Force One mostly uses the E/F system for actual phone
connections when it is out of range of other systems or there is
extremely heavy traffic on them (but it always maintains contact via E/F
when in range of a ground site as backup anyway), and has in the past
sometimes used E/F as a communications order wire to set up calls on the
other systems. The Bush conversation with Senator Byrd refered to in
the summer 1992 Washington Post article (reproduced and discussed
extensively in these newsgroups) about scanner listeners tuning in to
the President was one of the relatively rare recent presidential calls
on this system (the call took place in August 1990). That call was
probably put on E/F due to very heavy traffic on the other lines.
Now the question: What frequencies are used once the calls are in place?
There are two main systems used for most of the actual traffic to AF-1:
Secure UHF satcom
The primary AF-1 high level voice link is the secure UHF military
tactical satellite voice system. This provides two (on the 747s 28000
and 29000) (and one on the Gulfstream C-20's favored for shorter flights
by Clinton) 16 kbs MSK CVSD secure digital voice circuits using Vinson
KY-58 crypto gear (or some interoperable equivalent). These duplex
voice circuits are relayed via the 500 khz wideband (NCA) transponder
(or used to be) on various of the military UHF Fleetsats/Leasesats; which
one depending on where the President is going. (A popular one is the
105 West bird at 262 mhz.). Just like the E/F system, the aircraft end
of the UHF secure voice link is run in push to talk mode and the carrier
only comes on when someone on the aircraft talks.
These two secure satellite phone links connect to the White House
via a ground station at Camp David (code named "Cactus") and are connected
to parties on the ground via the White House Secure Voice Switchboard
(code named "Royal Crown"). These circuits are the primary voice links
from the plane for the President and senior members of his staff, and
much (but not all) high level traffic is routed via these links. Calls
dispatched to these circuits are usually indicated by such phrases "put it on
Royal Crown". As far as I know, most or all of these calls are handled
by operators at both ends of the circuit and not directly dialed.
This system was only made operational in 1987, and before it it came
into use the previous secure satellite system (which dated in part from
the LBJ era - 1968 or so) provided such poor audio quality that it was
rarely used and calls from the President and his senior staff could be
overheard on the clear voice systems regularly. Now this is rare.
Most of the other SAM VIP aircraft used by high level government
officials also have this secure UHF satellite capability (one channel
mostly) and use it, either via Camp David or Andrews (Brandywine) to
handle high level secure traffic. The system is apparently being
converted to use narrowband (5 khz) channels and narrow band vocoded
voice (2.4 or 4.8 kbs) rather than the 16 kbs FSK CVSD voice in 25 khz
channels (this makes possible use of less transponder power and
more conversations on the satellite at once).
The UHF tactical system also provides a secure data/fax capability.
UHF LOS
The second system, the UHF-LOS (Line Of Sight) system, is used
to provide up to 12 in-the-clear full duplex voice grade telephone
circuits via a FM-FDM-SSB link in the 225-400 mhz band to Ground Entry
Points (GEPs). The GEPs are located on AT&T microwave towers at
hardened underground switching centers (nuclear bomb proof bunkers)
which are mostly located along the routes of the old hardened
transcontinental coaxial cables. There are also GEPs located at some
military bases and the various underground command and control bunkers
(such as site R). GEP coverage of the US is less extensive than the E/F
coverage but has been provided along most routes that AF-1 often
travels. There are GEPs in other places around the world outside of
the continental US as well.
The UHF-LOS system was first installed in 1963 and is very old.
Its primary function (in this capacity code named "Combat Ciders") was
providing communications for the PACCS flying command post aircraft
(Lookinglass, Scopelight and the like) which orbited various parts of
the US on 24 hour airborne alert to provide backup nuclear command and
control capability. It was their primary connection with the DSN
(Autovon) network. (The command post aircraft also had a 56 kbs FSK
single channel secure full duplex digital voice link in the 225-400 mhz
range to the GEP's (KY-3), but this capability has not been observed in
use from AF-1).
The UHF-LOS system was designed to provide air-to-air relay of
the 12 channel UHF FDM multiplex signal in addition to the air to ground
connectivity. This capability was extensively used for years by AF-1 as
it crossed the Midwest (Kansas/Nebraska area where Lookinglass orbited)
to provide UHF-LOS voice circuits via the Lookinglass flying command
post as a relay. It has also been used routinely when the President
travels abroad to link AF-1 to the Nightwatch nuclear command and
control plane that always accompanies him when he is outside the US; and
used to extend the range of GEPS by using the Nightwatch as a relay to
link to GEPs that are too far away for AF-1 to reach directly. It has
also been used to link AF-1 to the backup plane (usually 29000) that
also accompanies the President when he flies abroad. Sometimes both
AF-1 and the backup AF-1 have been simultaneously linked to a GEP via
the Nightwatch aircraft.
The White House version of the UHF-LOS system (called
"Nightwatch" and in the LBJ area "Chandelier Circuits") provides a group
of 12 voice grade circuits with full single frequency (2600 hz)
signalling and DTMF dialing. These circuits are carried on a full
duplex FM-FDM-SSB signal on various pairs of rf channels in the 225-400
mhz band (the channels are code named "RF-1" through "RF-9") (the
channels used for the PACCS aircraft are on different frequencies, but
otherwise similar). The SSB voice channels are located on alternating
upper and lower sideband pairs in the 12-60 khz range, and there is an
orderwire (called "admin") from 0-4 khz used to coordinate GEP
transitions as the plane flies from the coverage of one site to the
next.
The GEP UHF-LOS ground stations use manually operated radios run
by a telco tech located at the site who manually patches through the
multiplex gear to special hardened Nightwatch leased lines from the GEP
site that terminate at a tech control center colocated with a hardened
DSN switch near Andrews AFB. There are undoubtably also other routing
and patching options to provide nuclear survivablity. The GEP sites and
the tech control center use standard military rotating tactical call
signs (such as FIREPLUG or CALLIOPE) on the orderwire ("Admin") which
are changed every 24 hours. AF-1 always id's as "AF-1".
UHF LOS ground stations (GEPs) that are located on AT&T
microwave towers mostly use very characteristic thick black (or copper
colored) vertical pole antennas (actually some form of broadband
collinear array under a fiberglass radome) about 10-12 feet long and
maybe 6 inches in diameter. These are usually located in groups of 4 or
more arranged in a square and mounted well above the Hogg microwave
horns way at the top of the tower. They have little pointed lightning
rods on top. Some of these sites are also E/F sites, but GEP and E/F
sites serving an area are not always co-located. Some other GEPs use
smaller antennas mounted on telephone poles in the ground. Virtually
all GEP sites (but not all E/F sites) have hardened underground bunkers
and are manned 24 hours a day. Many are at the junctions of multiple
underground cable, fiber, and microwave routes.
AF-1 uses 2 of the UHF multiplex voice channels as direct
connections into the Andrews DSN switch and two into a backup DSN
(Autovon) switch. These provide outward and inward direct DTMF dialing
capability on the DSN to the CSO's on the plane. These channels are
sometimes refered to as the "circuits" or "Autovons", but much more
commonly called "Alpha" and "Bravo".
When placing a call from the plane it is customary for the CSO
on AF-1 (there are actually 3 of them on 28000) to dial the White House
Switchboard (called "Signal" in this context) on these DSN lines and ask
them to complete the call; if the party is not immediately available the
Switchboard dials back on one of the DSN lines when whoever is being
called is found and the CSO dials whoever was requesting the call back
on the aircraft's (clear voice) PBX to complete the connection. Often
this process takes a while and is coordinated over one of the other
voice circuits with messages such as "put the call on the Alpha". Calls
originated from the White House Switchboard are handled much the same
way.
The 4 DSN lines are also sometimes used by the flight crew and
radio operators (CSOs) to directly dial DSN numbers (not routing via
"Signal") such as the aviation weather forecast office and various
Andrews (Brandywine) communications facilities. They are rarely if ever
used for incoming DSN dial-in traffic from other than the White House
Switchboard.
In addition to these four lines, in 1989-1990 the Nightwatch
UHF-LOS system installed in the bigger SAM VIP aircraft was expanded to
include more lines (going from 4 channels at 12-28 khz to 12 channels at
12-60 khz which was already the PACCS standard used with the command
planes). Two of these additional lines provide a direct connection to the
commercial POTS/DDD network and are used only in the outgoing direction, and
two provide bi-directional ringdown connections directly to the White
House Switchboard ("Crown"). The others lines seem rarely used. The ringdown
lines are also used (in addition to the dial up DSN "Alpha" and "Bravo"
lines) to complete calls to the plane via the White House Switchboard.
The POTS/DDD lines are sometimes used by the CSO's and flight crew to
directly calls home to report the plane's arrival time.
The DSN lines have also been used recently to provide a secure high
speed data circuit using STU-II's. This circuit carries fax to and from
the plane and probably various other kinds of digital traffic. Both the
DSN lines and the direct White House ringdown lines have also occasionally been
used with STU-III's and AN/DVT secure digital voice terminals to provide
secure voice connections via the UHF-LOS system.
The primary current use of the AF-1 UHF-LOS voice circuits has
been to provide non-secure clear telephone connections for middle and
junior members of the White House Staff and the Secret Service and
military personel on the plane. These lines are occasionally also used
to relay news releases from the press office on the plane to the wire
services and networks on the ground. Years ago, before the secure UHF
satellite system was in full service, they were the primary channels
over which the senior White House staff and sometimes the President made
most calls. Obviously there were some interesting conversations on them in
that era. But more recently with the increased consciousness of the
insecurity of any kind of non encrypted radio communications system most of
the traffic is very routine.
The UHF LOS system is also used for AF-2 communications on
occasion and regularly for communications with the large 707 VIP (VC737B)
aircraft carrying the Secretaries of State and Defense on trips abroad.
The Gulfstream C-20 used by President Clinton for shorter hops
does not currently carry the UHF LOS system.
HF Backup Systems
In addition to these primary systems there are several backup systems.
The most important of these is the Mystic Star HF-SSB network,
which is a world wide network of remotely operated HF-SSB transmitter
and receiver sites linked by switched DSN lines and some leased lines to
a control center near Andrews (Brandywine Md.). All are located at or
near military bases (mostly Air Force), and can be tuned, keyed, and the
antennas selected and pointed from consoles at Andrews. Most of the
antennas are huge rotatable HF log periodics.
Andrews selects sites and frequencies to maintain continuous
HF-SSB voice contact (on the "primary") with AF-1 (also AF-2 and certain of
the other SAM VIP aircraft). Frequencies used come from a list of more
than a hundred throughout the HF spectrum. When the President is aboard
(and the plane is really called AF-1) this voice circuit is also patched
into the White House Switchboard to provide a backup link if other
channels are unavailable.
Most of the traffic on this HF circuit has to do with
coordinating the other HF-SSB circuit (the data circuit), but
occasionally it is used to coordinate other communications systems, and
when the plane is out of range of the VHF/UHF systems it is occasionally
also used to provide phone patches (usually on trips overseas). Back in
the 60's and early 70's before the all the UHF and Satellite systems
were fully deployed the HF-SSB systems were used for much greater
amounts of telephone traffic, and a second HF-SSB voice circuit was also
often used for additional telephone traffic. Now there is little traffic
on the HF voice link, and most of that extremely routine.
The HF-SSB voice circuit always carries departure and arrival
messages patched to the the Air Force Operations Center in the Pentagon
(presumably to test that such connections are possible in a war emergency).
The other HF-SSB circuit is a full duplex encrypted data circuit
code naned "India Oscar" that uses DSP based HF modems (MIL-188?) operating
over HF-SSB radios. This circuit is used with a KG-84 crypto and a GRID
laptop to provide secure message (email, etc) communications between
AF-1 and the White House Situation Room via its "Com Center". It is the
circuit refered to by comments such as "meet me on the keyboard". I
believe it may occasionally be used for secure fax, and possibly for
other data traffic. Until 1989 this circuit used lower speed 4 tone
anti-multipath modems (TE-204) and ran at 75 baud baudot with occasional
circuit testing and unclassified message traffic (propagation forecasts and
weather forecasts and the like) to and from Andrews and the plane in the
clear.
Other systems
In addition to the UHF radio systems, the aircraft is equiped to
communicate on the VHF federal hi band DES/DVP encrypted full duplex
secure voice system primarily used to provide a secure telephone circuit
to the presidential limo. This system, code named Yankee/Zulu after
the two White House frequencies it uses (Yankee and Zulu), is provided
by WHCA and permanently installed around Washington DC and presidential
vacation homes. It is usually installed on a temporary basis at
the site of a presidential visit (although there has been some recent
use of STU-III's over regular cellphones to provide an alternative).
Calls via this system are routed throgh the White House Secure Voice
Switchboard ("Royal Crown"). Portable units operating on this system
were confused with cellphones in the news media when President Bush
was photographed talking on them while golfing.
This system (Y/Z) is occasionally used from AF-1 to complete calls
during landing and takeoff. It is not used enroute.
AF-1 also carries a GOLAY paging transmitter, and no doubt various
cellphones (although these are not used from the air).
And needless to say the aircraft can communicate on most of the
standard Secret Service Presidential Protection VHF and UHF radio
channels. These are DES/DVP secured (with occasional nbfm clear voice
once and while). These are not normally used for telephone traffic.
And of course there is normal VHF and UHF AM air to ground capability.
WHCA may possibly have installed or intend to install INMARSAT
capability on AF-1 (INMARSAT has occasionally been used for Presidential
support), but my information is not definate one way or the other on
this.
Disclaimer
AF-1 is no doubt also equiped with classified ("black") radio
systems (such as perhaps a secure HF voice capability and Milstar), but
the ones I have described are to the best of my knowlage the ones that
can be received (or at least detected) on normal radio gear, and are
almost certainly the channels over which the calls refered to on
Nationwide flow.
There is much more specific detail I have omitted, some of it because
it not relevant to an overview, and some of it because it may in some
way be sensitive or not generally known. This post is meant to answer some
of the questions from scanner-type listeners that come up from time to
time in the radio newsgroups; actual information on the frequencies
used (somewhat accurate) and some of the site locations can be found
in various hobbiest publications.
