Kenwood TM 455 A Owners Manual

Page 2

Models Covered by this Manual:

- TM-255A: 144 MHz All Mode Transceiver
(U.S.A./ Canada/ General)

. TM-255E: 144 MHz All Mode Transceiver
(Europe)

TM-455A: 430 MHz All Mode Transceiver
(U.S.A./ Canada)

. TM-4SSE: 430 MHz All Mode Transceiver
(Europe)

Notice to the user:

One or more at the following statements may be
applicable to this equipment.

FCC WARNING

This equipment generates or uses radio frequency energy.
Changes or modifications to this equipment may cause harmful
interference unless the modifications are expressly approved in
the instruction manual. The user could lose the authority to
operate this equipment if an unauthorized change or modification
is made.

INFORMATION TO THE DIGITAL DEVICE USER REQUIRED
BY THE FCC

This equipment has been tested and lound to comply wim the
limits fora Class B digital device, pursuant to Part 15 cf the FCC
Rules. These limits are designed to provide reasonable
protection againstharmtul interference in a residential installation.

This equipment generates, uses and can generate radio
frequency energy and. if not installed and used in accordance
with the instructions, may cause harmful interference to radio
communications. However, there is no guarantee that the
interference will not occur in a particular installation. If this
equtprnent does cause harmful interference to radio or television
reception, which can be determined by turning the equipment of!
and on. the user is encouraged to try to correct the intefierence
by one or more of the lot/owing measures:

. Heorient or relocate the receian antenna
. increase the separation between the equipment and receiver.

' Connect the equipment to an outlet on a circuit diltereht from
that to which the receiver is connected.

- Consult the dealer [or technical assistance.

Page 13

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Function"

1 PKD

Packet Data (input)
- Transmit data lrom TNC to transceiver

2 DE

Data Earth
- Ground tor TNC output

3 PKS 1

Packet Standby

~ TNC can use this pin to inhibit the transceiver microphone input while transmitting
packet signals.

4 PR9

FM Demodulator Output
- For 9600 bps Packet operation
- Output Level: 500 mVp.pI to kn

5 PR1

Demodulator Output

- For 1200 bps Packet and RTTY operation

- Audio output is taken before the VOL control
(VOL control has no effect on audio level)

° Output level: 300 mVp-p/ 10 kfl

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Squelch Control or Relay Output 2

Squelch Control
- Inhibits TNC data transmit while transceiver squelch is open. This prevents
interference to voice communications on the same lrequency and unwanted retries.
- Output level
Squelch open: +5 V (HIGH)
Squelch closed: 0 V (LOW)

Relay Output

- Alternatively, provides a relay output for accessories such as a linear amplifier.
' The output switches to GND during transmit.

- Current rating: 500 mA maximum

It is not necessary to disconnect the microphone it using the DATA connector The TNC drives this pin LOW which mutes

the microphone.

2 Switch selectable: Set internal switch to P80" for Squelch Control or 'FtL" tor Relay Output (page 47L

Personal computer/
dumb terminal

Transceiver
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Page 28

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iACKET OPERATION

One of the most exciting benefits of owning a VHF or
UHF transceiver nowadays is being able to use it for
data modes. Due to the ease of setting up a digital
station. even those inexperienced with this type of
operation can be on~the-air enjoying these new
modes quickly.

You can use almost any computer to control one of
the widely available Terminal Node Controllers (TNC)
since the computer primarily serves to input
commands and output received text data to its
display. Little real computing power is needed,
therefore a high-powered processor is not necessary,
and even a "dumb" terminal is satisfactory. at least to
start. As you become more experienced, you will
realize how well your interest in radio meshes with the
world of data communications.

Connecting to one of the many stations with gateways
to HF or satellite links can give you national and
worldwide messaging or conferencing capability with
other Amateurs with nothing more than your single
band VHF/UHF transceiver for the communications
link. Much reference material is available for getting
started in digital communications from any store that
handles Amateur Radio equipment. Or, if more
convenient, check the radio magazines for mail order
bookstores.

The most common mode used on VHF/UHF
frequencies for Packet operation is FM. However.
there is also some 888 PSK activity on the satellites.

Type of Modulation Model Transmis- Emission
Keying Menu B, No. 77 sion Rate Type
GMSK,
eanuj-L FM / ON 9600 bps F1D
etc.
FSK FM / ON or OFF 1200 bps F20
PSK SSB I OFF 1200 bps GZD
Menu 5 input Impedance Standard Modulator Input
No. 77
OFF 10 kg 40 mVp-p
ON 10 kg 2 Vp-p

Consider the following before setting Menu B, No. 77:

- OFF: Transmit data input (PKD) sensitivity is
40 mVp-p. This is suitable for a typical
1200 bps TNC or other data
communications equipment.

Transmit data input (PKD) sensitivity is

2 Vp-p. This is suitable for most 9600 bps
TNCs. Set Menu 8, No. 77 to ON if using a
TNC with dual speed capability that only has
a 2 vap output. However, in this case, FM
mode must be used.

22

sung a modulator Input level thati far different from
the optimum 40 mVp:p / 2 Vp-p specifications may
result in deterioration of SIN ratio or signal distortion.
This could result in increased errors or a complete
failure to connect with other stations.

if the modulator input level rises to approximately
4 Vp~p, the transceiver automatically switches to
Receive to prevent transmitting a distorted signal.
Transmission is not possible until the input level is
reduced by adjusting the TNC modulation level.

To receive after making the necessary connections as
explained in "PACKET EQUIPMENT" (page 5}. use
the following procedure and refer to your TNC manual
for further assistance.

1 Select the desired frequency.

2 Select the correct mode by pressing [AUTO/FM] or
[SSE/CW].

3 Select the correct Menu B, No. 77 {page 14}
selection based on the type of keying, transmission
speed, and TNC that you are using (see charts).

4 Turn the VOL control clockwise to set a
comfortable level if you plan to listen to the data
exchanges. Otherwise, leave the control fully
counterclockwise.

- The VOL control setting does not affect the
receive audio level from the DATA connector on
the Rear Panel.

5 Adjust the SQL control until the "BUSY" indicator
on the Display just disappears (threshold) while the
frequency is clear of any activity.

After beginning to receive stations, use the

Main Tuning control for minor frequency adjustments
to compensate for frequency drift while watching the
tuning indicator on your TNC. Do not use the RIT
control since it is important to keep your receive and
transmit frequencies equal.

To transmit, proceed to the subsequent steps.

6 Commands sent from your communications
terminal (either a computer keyboard or a "dumb"
terminal) to the TNC control your transceiver.

~ Refer to your TNC instruction manual.

- Be courteous. Although packet protocol can
handle multiple stations on a single frequency,
overall throughput decreases due to packet
collisions during busy times of the day. Keep
transmissions short at these times.

7 Adjust the output level from the TNC while
watching the RF meter to avoid output power
saturation. Adjust for a maximum meter reading of
10 with a steady mark or space.

Note:

9 lnputting 9600 bps GMSK signals at too high a level or inputting
significantly distorted signals into the transceiver can cause
errors and a wide transmit bandwidth that may interfere with
other stations.

0 Always tune your transceiver to the exact frequency at the
station you are contacting. Failure to do so will result in
inaccurate demodulation 0/ received packets and multiple
retries. Use the Main T unlng control {-5 kHz to +5 kHz) for
making fine adjustments as necessary.

Page 36

MEMORY SCAN

Memory Scan can be used to scan only a specific
channel group (Group Scan). or to scan all memory
channels containing data (All channel Scan).
Selection of the desired method Is via Menu A. No.05
{page 13}. The default Is Group Scan (OFF)

GROUP SCAN

There are 100 memory channels total, divided into
groups of 10 channels each (00 to 09, 10 to 19, 90
to 99). When Group Scan is selected, the transceiver
scans only memory channels that belong to the
specified group and contain data.

1 Press [MR] to select Memory Recall.
- The last memory channel selected appears.

2 Select any memory channel belonging to the
desired group using microphone [UP] or [DWN].

3 Adjust the SQL control while no signal is present.

4 Press [SCAN].

The scan speed appears with "SCAN", and
Sean starts.

- To change channel groups while scanning,
press microphone [UP]/[DWN].

- To change the scan direction, turn the
Alternate Tuning control clockwise or
counterclockwise.

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5 Press [SCAN], [CLR], or the microphone [PTT] to
stop Scan.
~ Memory Recall is restored.

6 To restore VFO mode, press [A/B].
Note: I! no data is stored in the memory channels 0/ the specified

group, or all memory channels are locked out. pressing [SCAN] will
scund the Morse code 'CHECK' reminder.

ALL-CHANNEL SCAN

The All-channel Scan function scans all memory
channels containing frequency data.

1 Press [MR] to select Memory Recall.
- The last memory channel selected appears.

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2 Adjust the SOL control while no signal is present.
~ Remember, Menu A, No.05 must be ON.
3 Press [SCAN].

- The scan speed appears with "SCAN", and
scan starts.

- To change the scan direction, turn the
Alternate Tuning control clockwise or
counterclockwise.

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4 Press [SCAN], [CLR], or the microphone [PTT] to
stop Scan.

0 Memory Recall is restored.
5 To restore VFO mode, press [A/B].
Note: I! no data is stored in the memory channels, or all memory

channels are locked out, pressing [SCAN] will sound the Morse
code "CHECK"rem/nder.

MEMORY CHANNEL LOCK-OUT

Memory channels that you prefer not to monitor while
scanning can be Iocked~out. Lock-out any memory
channel with the following procedure:

1 Press [MR] to select Memory Recall.

2 Select the memory channel to be locked-out using
the Alternate Tuning control or microphone
[UP]I[DWN].

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3 Press [CLR].

A dot appears beside the memory channel
number to indicate the channel has been
locked-out.

- Pressing [CLFl] for more than 2 seconds erases
the contents of the memory channel.

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4 To restore the VFO, press [NB].
The dot disappears.

Lockout for an individual channel can be canceled by
repeating the above procedure.

Page 51

Tone Alert provides an audible alarm to indicate when
someone is transmitting on the frequency you are
monitoring.

Tone Alert is an effective partner with CTCSS, Page.
or DTSS. When the correct signaling comes through,
your transceiver alerts you of an incoming call from a
specific station. If using any of these functions with
Tone Alert, the CTCSS/Tone frequency and the
DTSS/Page code must match those programmed in
your transceiver or else Tone Alert is not activated.

Tone Alert can only be used with FM mode.

ENABLING TONE ALERT

1 Tune to the prearranged frequency.

2 Activate CTCSS, Page. or DTSS if you want to use
these together with Tone Alert.

3 Press [F], [TONE].
- A "bell" icon appears.

- Each time this key combination is pressed:
Tone Alert toggles ON and OFF.

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4 When the correct signal is received, you hear 5
double beeps, the "bell" icon starts blinking, and
the Call Number increments.

- The Display shows the number of minutes and
seconds elapsed after the last signal was
received. After 59 minutes 59 seconds pass,
the Display changes to 01.00 and continues
counting After 59 hours 59 minutes pass.
counting stops. When the next signal is
received the time resets to 00.00 and counting
continues. Each time a new signal Is received,
the time resets to 00.00.

- The Call Number records the number of calls
received to a maximum of 99.

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5 Exit Tone Alert by pressing [PTT].

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APO turns OFF the power i! no key entry is made Iar 180
minutes even if Tone Alert is ON.

I! Tone Alert is ON, there is no speaker output except the alarm
tone when a signal is received. To hear activity on the
lrequency without disabling Tone Alert. program one 0! the
microphone PF keys or Front Panel [PH lor the Monitor
function [page 35}.

For Tone Alert to iunclion correctly with CTCSS, the incoming
signal must be present for approximately 1 second.

If you find Tone Alert does not work reliably, your receive signal
may contain distortion or a high level of ignition noise. One
remedy is to install a TSU-B CTCSS unit and select 3 Tone of
141.3 Hz or lower to act as a filler.