ALE On-The-Air Week
05-15 October AOTAW-2007
START:
0001 UTC 05 October 2007 Friday
END:
2359 UTC 15 October 2007 Monday
HFLINK sponsors this annual International Amateur Radio event.
All ham radio operators worldwide are invited to participate in 10 days of HF Automatic Link Establishment activity on the air. “AOTAW” is an open operating event for hams to explore ALE communications and equipment. The experience gained by operator participation in this readiness exercise is useful for HF Emergency/Disaster Relief communications.
Using ALE Under USA’s FCC Rules
USA hams can legally use ALE’s Selective Calling and Alerting features in the phone subbands, and all of the features of ALE in the data subbands. One of the aspects of operation using “new technology” in Amateur Radio is navigating the complexities of arcane, and sometimes contradictory FCC rules regarding modes, bauds, and subbands. Currently, many countries of the world have reasonable, easily understood bandwidth-based Amateur Radio rules where most of the protocol and features of ALE can be utilized freely. The USA Amateur Radio Service has been somewhat hamstrung in this respect, due to our more antiquated mode-based rules. There are several rule-changing proposals in progress which seek to take the USA Amateur Radio Service from its present mode-based rules to the more modern bandwidth-based rules. So, US operators might someday in the future, enjoy the freedom that other hams of the world already have to explore communications technology.
ALE as a Phone Mode
Currently, USA Amateur Radio Service operators are legally utilizing ALE and SELCAL in the “phone bands”. Transmissions fall under the FCC rule’s statement: “Incidental tones for the purpose of selective calling or alerting or to control the level of a demodulated signal may also be considered phone.”
ALE controller units use handshake signals to set up communication links between stations… The 1st station initiates the calling, the 2nd station ACKs (acknowledges) the reception of the call, and the 1st station ACKs the 2nd station’s ACK… in other words, it is a 3-way exchange of signalling to set up the communication to be in a linked status. Within this 3-way linking signal exchange, there are parts of the ALE protocol that can include “incidental” types of very limited text/status sequences and Link Quality signals, AMDs, or MOTDs.
The question then is:
“Where do we draw the line between Automatic Link Establishment operation as a PHONE mode, and make the conceptual jump to DATA mode under the FCC rules?”
The complex language of FCC rules are attempts at drawing clear lines between what is allowed and not allowed, but technology often turns these clear lines fuzzy. If the “spirit of the rules” are to be our guide for clarification, once the selective call or ALE exchange happens, and the LINKED status is established, the use of the ALE or selcall modem should cease and the voice or image QSO should commence.
Limiting Procedures for Operation as a Phone Mode
When the ALE or Selcall system is used as a “PHONE” emission under the selective calling FCC rules, (in the “phone bands”), operators need to limit the transmissions to:
1. ANYCALLS or NETCALLS (the ALE selective calling equivalent of CQ or a call for a group of stations)
2. ALLCALLS (the ALE alerting equivalent of a QST)
3. INDIVIDUAL CALLS (ALE direct call to another station)
4. Selective calling signals to set up a voice or image contact for QSO with other station(s).
5. Alerting another station to talk on voice.
6. Alerting another station to QSY.
7. Sending an alerting or selective calling signal to break the link.
Linked in the Phone SubBands
The ALE protocol and features provide an easy way for operators to make the fuzzy line between PHONE and DATA a little clearer! In the ALE protocol, there is a point during the “handshake” between two stations when the ALE software or the ALE controller tells the user that the station is LINKED. It means that you have succeeded with Selective Calling of the other station(s). We can use this LINKED status indicator as a dividing line between what the FCC defines as PHONE and DATA operation. If we use the AMD or data modem after the indicator says we are LINKED, we are probably stepping out of the PHONE mode and into DATA mode.
The possible allowable exceptions to this are:
1. An AMD to alert the other station to QSY or start scanning for a selective call on another channel.
2. An AMD or CALL to attempt to call yet another station.
3. An AMD to alert another station to talk on voice.
4. The limited orderwire that gets a free ride as part of the selective calling and alerting signalling.
5. Some bands such as 160 meters which do not have phone subbands.
FCC Rules for ALE in the Phone Bands
Here are some excerpts of present Amateur Radio Service FCC rules permitting the use of ALE and SELCALL for Selective Calling and Alerting in the PHONE sub-bands. Please note the last sentence in §97.3(c)(5) which is the definition of Phone mode. At the bottom are the URLs for §2.201 of FCC Rules which define emission type designators.
Ҥ97.3 Definitions.
…[extraneous text deleted]
(c) The following terms are used in this Part to indicate emission types. Refer to §2.201 of the FCC Rules, Emission,
modulation and transmission characteristics, for information on emission type designators.
….[extraneous text deleted](5) Phone. Speech and other sound emissions havingdesignators with A, C, D, F, G, H, J or R as the firstsymbol; 1, 2 or 3 as the second symbol; E as the thirdsymbol. Also speech emissions having B as the first symbol; 7, 8 or 9 as the second symbol; E as the third symbol. MCW for the purpose of performing the station identification procedure, or for providing telegraphy practice interspersed with speech. Incidental tones for the purpose of selective calling or alerting or to control the level of a demodulated signal may also be considered phone.”
[---emphasis added]
Does the ALE RF Signal Meet the FCC “300 Baud Rule” for Data mode?
Yes. The ALE (MIL-STD 188-141B or FED-STD-1045) signal is transmitted at
125 symbols per second. It is legal under FCC Rules for use in the Amateur Radio
Service for DATA MODE transmission on HF in the DATA sub-bands. Current FCC Rules in USA allow DATA modes up to 300 baud (300 symbols per second) in HF data subbands. Symbol rate (baud) is the number of state changes the transmitted signal makes per second. The ALE signal is 8FSK (8 Frequency Shift Keyed). 8 discrete tone frequencies are spaced 250 Hz apart from 750 Hz to 2500 Hz at audio baseband. A single tone is being transmitted at any given instant on any one of these 8 frequencies. No more than one tone is transmitted at a time. Each symbol represents three bits of data, resulting in an over-the-air data rate of 375 bits per second (375bps) using “125 baud”.
What is the Bandwidth of the ALE Signal? Does it meet FCC specifications?
The FCC does not currently specify an occupied bandwidth limitation for DATA emission, other than the stipulation that bandwidths must not be excessive for the data rate used. In this case, the bandwith is not excessive, since the objective is to provide a robust, fast selective calling signal with texting.
The ALE modem using MIL-STD 188-141B or FED-STD-1045 does not use excessive bandwidth to obtain sufficient signal quality error rates to establish linking through difficult HF noise conditions. The bandwidth is similar to PACTOR-III, SSB voice, SSTVand many of the other waveforms in current use in the Amateur Service. The ALE signal bandwidth is suitable for transmission via HF transceivers through a standard SSB audio/RF chain with an IF bandwidth of about 2.5 kHz. The 8aryFSK tones take up about 1750 Hz, but when the FSK is keyed, the bandwidth spreads out slightly, to an occupied bandwidth (-23dBc) of approximately 2kHz. In practice, for demodulating, amateurs have been able to use receive IF filters as narrow as about 1800 Hz with the passband centered at 1625 Hz.
The signal is somewhat resistant to noise, QRM, passband tilt, group delay, and phase distortion. It can be run through typical SSB transceivers with speech compressors on transmit and various AGC characteristics on receive. However, the use of DSP Noise Reduction receive circuits and transmit audio EQ tends to be counterproductive. A flat audio and IF response is best.
What subbands should be used with ALE for DATA mode?
Current FCC Rules specify that the 8FSK data signal may be transmitted anywhere in the allocated DATA mode sub-bands. According to the IARU Region 2 Bandplan, there are sub-bands dedicated to automatic digital modes. There is an ALE pilot channel frequency within the automatic sub-band of each ham band. The ALE channel list includes these as PILOT channels, and all of the repetitive sounding (station ID) activity for hams occurs on these Pilot Channels. Additional data channels are available in the channel list for texting, keyboarding, and digital messaging. It is important that operators follow the guidelines for use and to avoid interference.
For more information visit HFLINK http://hflink.com/alehamradiousa/
