MFJ-1278 & MFJ-1278T Fast-Start Manual
9
2400 really shows its place in the packet world when used to pass large ASCII, BINARY and PIC-
TURE files. It is always good to use clear frequency and/or use direct connects to the target sta-
tion rather than going thru a node or digipeater. The reason is obvious. There are few 2400 nodes
at the present time. However, it should be pointed out that implementation of a 2400 node is just
as easy as building and using a 1200 node.
To select 2400 packet operation, under the CMD: command prompt, type:
MODE VP,2400
MFJ-1278 will be set to 2400 packet operation. TURBO LED will light. 2400 packet can be operated
with Radio Port 1 or Radio Port 2 on the MFJ-1278. Note that if your MFJ-1278 is not equipped
with the 2400 modem, TURBO LED will not function and you will not be able to operate 2400 pac-
ket.
B.
Receive Audio Setting
The MFJ 2400 modem employs automatic gain control (AGC) for its receive audio. The receive
audio level is preset for proper 2400 operation; no adjustment is necessary in most cases. If you
set the receive audio of your radio properly for 1200 operation, then it will be suitable for the 2400
operation also. No adjustment for the receiver audio on the 2400 modem board is needed.
C.
Transmit Audio Setting
Transmit audio on the 2400 board is set by adjusting R38 (next to T2) on the 2400 modem board.
Transmit audio for the 1278T is preset at the factory to match the audio level of the 1200 modem
on the MFJ-1278 mother board. Once the 1200 and the 2400 transmit audio are set to the same
level, then you may adjust the audio level going into your radio by using the "Transmit Audio" con-
trols on the left side of the MFJ-1278. Note that these controls set the transmit audio levels for all
the Operation modes of the MFJ-1278, including the 2400 packet operation.
When adjusting the transmit audio level please note that the range of R38 is preset by CN-6 head-
er. The shorting jumper on CN-6 header sets range as follows:
CN-6 Jumper Position
Transmit Audio Range (no load)
no jumper
50 mV - 60 mV p-p
1 & 2 (default)
100 mV - 200 mV p-p
2 & 3
250 mV - 3 V p-p
VI. AUTOMATIC SIGNAL ANALYSIS (ASA)
The latest firmware (Release 3.4) is installed in your MFJ-1278. A major feature, Automatic Signal
Analysis (ASA) is installed in this firmware release. ASA can analyze received Signals such as RTTY,
ASCII, AMTOR and HF Packet. It will tell you the speed, data bits and whether or not the Signal is
inverted. ASA automatically switches the MFJ-1278 to the correct mode once you accept the re-
sults of the signal analysis by typing OK and <CR>. As you see ASA is extremely helpful when tun-
ing across the Amateur or the Short wave bands. Let ASA help you determine what kind of Signals
you are listening to.