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MARSRADIO Procedure And SELCAL
NOTE: Propagation is down during the lower part of the eleven year solar cycle and is affecting global communications. The primary frequency is 13.927 MHz. In adddition, an alternate frequency is 7.6335 MHz and is also monitored. Try the alternate frequency if there is no response on the primary frequency especially at night (CONUS). Try again 15 - 30 minutes later if there is still no response.
Operators are often monitoring but may not hear the call due to current propagation.
The USAF MARSRADIO provides worldwide 24 / 7 / 365* telephone service to US military aircraft via HF radio.
All US Air Force, Army, Navy, Marines and Coast Guard Aircraft are supported. The net is staffed by Amateur Radio (Ham) volunteers who are members of MARS (Military Auxiliary Radio System). US Air Force MARS is authorized by the Department of Defense and sponsored by the Air Force 38th Cyberspace Readiness Squadron (AFSPC) at Scott AFB, Illinois. There is no charge for using the Phone Patch Net. Only DOD aircraft or units are authorized to use the net.
Contacting A MARSRADIO Station
Use the primary frequency first and call MARSRADIO. All stations monitor the primary frequency both day and night. Call on the alternate frequency if there is no answer on the primary. The alternate frequency is normally better a night.
Often the MARS station can improve reception if the operator knows which way to aim the antenna. At times, having the antenna pointed correctly can make the difference between Loud and Clear and Weak, Barely Readable.
Call multiple times. To avoid confusion, the only station that will answer you on the first call is the Net Control station. If Net Control does not hear you, other stations will respond after your second radio call. If you are answered by an operator other than the net control, he will contact the NCS to see who will handle your patch.
EXAMPLE RADIO CALL: MARSRADIO REACH 123 NORTH ATLANTIC OVER
If after calling several times you do not get any response try the alternate frequency. Try again in 20 - 30 minutes when propagation may be different due to the time of day, and/or your location if still unable to raise an operator.
Another station may be asked to run the patch. Operators are volunteer and every attempt is made to spread out the phone patches so all stations can be involved.
Running A Phone Patch
Once initial contact has been established, the MARSRADIO station will ask you for your phone patch request. Give the operator the phone number to be dialed, and if making a morale call, YOUR first name. The net normally does not need the name of the party being called unless you feel that is important. Keep in mind that the phone call is NOT secure, as it does go out over short-wave radio. This is the reason that last names are not normally used.
Morale calls are made courtesy of the individual operator who normally has unlimited dialing within the US. Some stations can do international calls. Official calls can be made to a DSN or commercial number.
Your phone call may be picked up by an answering machine. Normally, the MARSRADIO operator will give you the option of leaving a message on the machine. If you know that you do not wish to leave a message, you should advise the operator of this when placing the call.
Since this is a radio phone call, each party must take turns talking. You cannot both talk and listen at the same time, as you do over a regular telephone. It is proper procedure for both parties to say the word OVER at the end of each transmission so that the MARSRADIO operator knows when to key the transmitter.
Morale calls should be limited to 5 minutes. Official calls do not have a time limit, and have at times been known to run several hours.
When you are finished with your patch, you should advise the MARS operator to TERMINATE THE PHONE PATCH so that the end point of the patch is clear to the operator.
Advise the operator if you have another request. As MARSRADIO operators take turns running patches, you may be routed to a second operator. If the reception of the second operator is not satisfactory, you may request net control to assign you a different operator. The Phone Patch Net wants to provide the highest quality patch possible.
MARSRADIO has started using a PBX telephone system that offers advantages to its customers. About half of the stations have this capability with more
being added.
MARSRADIO has started using a PBX telephone system that offers advantages to its customers. About half of the stations have this capability with more
being added.
- Easily transfer a patch in progress if propagation conditions changes
- Coordination among net operators
- Callback system that allows Operations to get back in touch with an aircraft or
a missed morale call**
a missed morale call**
The net is monitored by volunteer operators. Coverage is for the majority of a 24 hour period. Notify us using the
contact
form if you have expected or special operations. The operators will be updated concerning possible request. Operation times and location do not need to be specific.
Operational Callbacks can be handled by MARSRADIO. Units will be provided with the callback number that can put them in touch with net operators. Aircraft with SELCAL can use that to "monitor" the frequency and be notified when there is communciation for them.
Selective Calling (SELCAL)
The phone patch net has limited capability of broadcasting a SELCAL but is improving every day with more stations soon.
HF SELCAL is used by ATC for international flights however it is available for any flight on the MARSRADIO primary frequency. An aircraft must be tuned to the MARSRADIO's primary frequency to receive the alert.
"SELCAL operates on the high frequency (HF) or very high frequency (VHF) radio frequency bands used for aircraft communications. HF radio often has extremely high levels of background noise and can be difficult or distracting to listen to for long periods of time. As a result, it is common practice for crews to keep the radio volume low unless the radio is immediately needed. A SELCAL notification activates a signal to the crew that they are about to receive a voice transmission, so that the crew has time to raise the volume.
An individual aircraft has its own assigned SELCAL code. To initiate a SELCAL transmission, a ground station radio operator enters an aircraft's SELCAL code into a SELCAL encoder. The encoder converts the four-letter code into four designated audio tones. The radio operator's transmitter then broadcasts the audio tones on the aircraft's company radio frequency channel in sequence: the first pair of tones are transmitted simultaneously, lasting about one second; a silence of about 0.2 seconds; followed by the second pair of tones, lasting about one second.
The code is received by any aircraft receiver monitoring the radio frequency on which the SELCAL code is broadcast. A SELCAL decoder is connected to each aircraft's radio receiver. When a SELCAL decoder on an aircraft receives a signal containing its own assigned SELCAL code, it alerts the aircraft's crew by sounding a chime, activating a light, or both.
The crew next turns up the volume on the aircraft radio to hear the incoming voice transmission. Using ICAO radio protocol, they must verify with the transmitting operator that they are the intended message recipients. The crew then uses the received information."
(https://en.wikipedia.org/wiki/SELCAL
)
An aircraft may request that they be notified via SELCAL on the MARSRADIO primary frequency if they do not want to listen to the background static. Aircrew should contact MARSRADIO within an agreed time period if no SELCAL has been received in case propagation has changed from the broadcast site to the aircraft.
Base operations may request a SELCAL attempt with an aircraft via the net's PBX system. The aircraft will need to have their radio tuned to the MARSRADIO primary frequency and be within range of the broadcast site.
Further information may be obtained by emailing us through the
contact page
.