Timewave DSP-232, Operating Manual, Page: 160 / 271

Chapter 9 AMTOR Operation
Chapter 9
AMTOR Operation
Overview
The DSP provides AMTOR operation in accordance with FCC Part 97.69 and CCIR Recommendations 476-2/476-
3 and 625 for mode A (ARQ) and mode B (FEC) modes. AMTOR is an adaptation of the SITOR system used in
high-seas ship telex, which provides error detection and correction.
AMTOR has two basic modes of operation, mode A (ARQ - Automatic ReQuest for reception) and mode B (FEC -
Forward Error Correction).
♦
AMTOR mode A (ARQ) is a handshaking protocol that allows only two stations to communicate in a near
error-free fashion. For years, this mode has been used by Amateurs as the best, error-free method of getting
messages through on HF when conditions were poor.
♦
Unlike ARQ, FEC AMTOR is similar to Baudot RTTY and is used to call CQ or to carry on “roundtable”
contacts. (No “link” is established between stations.)
In AMTOR, the transmitting station (ISS) “has the link” and requires a periodic
ack signal from the receiving (IRS)
station as part of its error-checking scheme. An analogy of this would be you reading off sequences of numbers to a
friend and having him
ack them back, then when you’re finished you’d switch roles with him and he’d call off his
set of numbers.
When you’re reading off your set of numbers (transmitting) you have control of the link since you’re the sending
station. Your friend, the “receiver,” answers back (
acks ) with either a quick “yes, I heard you okay” or a “no, I
missed something.” In the former case, you’ll “send” the next sequence of numbers; in the latter, you’ll repeat the
previous number sequence. After you’ve read all the numbers on your list, you’d hand the link over to your friend
and it’d be his turn to read numbers to you and for you to acknowledge them as “received okay” or “not received
okay.”
The
+?
character is a software changeover command that switches your system from being the ISS to the IRS.
When you’re linked, it switches the other system from being the IRS to the ISS. When the other operator sees the
+?
, he knows it’s his turn to type and the link will be in his control.
Before proceeding with the rest of this section, review the following commands that are directly applicable to the
AMTOR mode:
AAB , ALIST , ARQ , ARQTMO , ARQTOL , ARXTOR , CBELL , CODE ( 2,7,8 ), EAS , FEC ,
GUSERS
,
MHEARD
,
MID
,
MYIDENT
,
MYSELCALL
,
OVER
,
RXREV
,
TXREV
,
TMAIL
and
WORDOUT
.
The AMTOR commands are listed and explained at the end of this chapter. Terminal commands can be found in
Chapter 4.
Setting Up
September, 05 9-1