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USER'S GUIDE
3.2.2.
If tail-ending on a previous contact, and the intention is to call one station on ARQ and
his SELCAL code is not known, then there are two ways to proceed.
3.2.2.1.
There is a convention in operation amongst AMTOR operators in respect of the way to
choose the station SELCAL code from the station call sign. This is to choose the firm let-
ter of the call sign, followed by This is to choose the first letter of the call sign, followed
by the last three letters, ignoring completely any figures. In the case of call signs with
only three letters altogether, the first letter is repeated twice. This ruse breaks down for
call signs in which the prefix contains figures. However, if the call sign of the desired
station can be translated into a SELCAL code in this way, then use that SELCAL code to
call him after he signs off with the station he is working.
3.2.2.2.
If his call sign cannot be encoded in the above way, or his call sign is not known, or he
does not respond to the expected SELCAL code, then call him in FEC mode, giving him
the choice of calling you back on your SELCAL code, or asking him to tell you what SEL-
CAL code he is using. Note that some stations who may be using commercial SITOR-
type units, may not always be able to make ARQ calls to all possible combinations of
letters in a SELCAL, and thus may require that you call them, often with a SELCAL code
that bears no relationship to their call sign, being in fact a translation from a telex num-
ber associated with the commercial equipment.
3.2.3.
To make a CQ call to start an AMTOR QSO, do so on FEC mode, mentioning your own
SELCAL code so that, at the end of your call, a prospective QSO partner can call you back
directly with your SELCAL. If you are expecting replies only on FEC, for example for con-
tacts via a long path, mention this fact in the CQ call.
3.3.
Operating techniques whilst in contact in FEC
Whilst operation in FEC is very similar indeed to that of conventional RTTY, there are two
points to note, both related to the method by which the FEC receiver synchronizes to the
distant transmitter.
3.3.1.
Since the receiver can only synchronize to the transmitter when it is not sending traffic
(that is, idling) each transmission must start with a period of idling. Most AMTOR units will
ensure that a short period of idle precedes the typed message, but under poor conditions,
or where it may help the distant receiving station to tune in, extra periods of idle will help,
both at the beginning of the transmission, and also at periods during the transmission, in
case interference may have resulted in the distant receiver losing synchronization.
Note that the practice common on conventional RTTY of transmitting a line of test mes-
sage of RYRYRY to allow the distant station to tune in, is actually counterproductive on
FEC, since the distant receiver will not synchronize until the end of this test sequence,
and the idle-signal itself is quite suitable itself for tuning purposes.
3.3.2.
Some commercial SITOR-type units require a received FEC transmission to start with a
carriage return and/or a line feed signal. For this reason, and also to aid the formatting of
any distant printer copy, always start an FEC transmission on a new line.
PK232UG Rev. E 9/87
AMTOR OPERATING SUGGESTIONS FROM G3PLX
D-3
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