HTX-252 2-Meter Amateur FM Mobile Transceiver
(190-1127)                 Special Features           Faxback Doc. # 60181

Continuous Tone Coded Squelch System Features

Your transceiver can transmit and receive a low-level, selectable 
subaudible tone at the same time as it transmits (TX) or receives (RX) a 
regular signal.  This special tone lets you listen only to other 
transceivers set to the same tone frequency when you use the transceiver 
in simplex operation.  It also lets you match your transceiver to the 
subaudible tone frequency used by a local repeater.

To enable the TX and RX tones for the transceiver, follow these steps. 

1.  Press F+T-SQ.  The current tone setting and T appear.  (T indicates
    that only the TX tone is enabled.)

2.  Rotate the tuning control or repeatedly press UP or DN to select a
    tone frequency from the list below.  About 5 seconds after your last
    change, the display exits the tone setting mode, stores your tone
    selection, and the current operating frequency appears again.

3.  To enable both the TX and RX tones, repeatedly press F+T-SQ until T-SQ
    appears.  To disable CTCSS operation, repeatedly press F+T-SQ until T
    and T-SQ disappear.

4.  Press PTT to store all the settings.

Temporarily Opening Squelch

If you use the Tone Squelch (CTCSS) feature, you might not hear a 
transmission on the current frequency.  To temporarily open the squelch so 
you can hear all transmissions on the frequency, hold down F.  To resume 
normal operation, release F.

Subaudible Tone Frequencies (Hz)

  67.0        88.5       110.9       136.5       167.9       210.7
  71.9        91.5       114.8       141.3       173.8       218.1
  74.4        94.8       118.8       146.2       179.9       225.7
  77.0        97.4       123.0       151.4       186.2       233.6
  79.7       100.0       127.3       156.7       192.8       241.8
  82.5       103.5       131.8       162.2       203.5       250.3
  85.4       107.2

Using DTMF Tones

DTMF (Dual-Tone, Multiple Frequency) is another term for touch-tones (the 
tones a telephone produces when you press a digit).  This standard set of 
tones is used by many different amateur transceiver systems for accessing 
programmable features and dialing through auto-patches to a standard 
telephone. 

Your transceiver produces all 16 standard DTMF tones (0-9,*,#,A,B,C,and D)

Follow these steps to use the DTMF feature.

1.  Set DTMF on the bottom of the microphone to ON.

2.  Enter the DTMF sequence using the alphanumeric keys.

3.  After you complete your transmission, set DTMF to the left position to
    turn off the feature.

Other Special Features

Using Priority Frequency Monitor

You can designate one frequency as primary (in either VFO or memory mode) 
and another frequency as secondary (VFO only).  Once you do that, the 
transceiver tunes the primary frequency or memory location for 5 seconds.
Then it checks the secondary frequency for 1/2 second.  If the transceiver 
finds a signal on the secondary frequency, it automatically remains there 
for 5 seconds before returning to the primary frequency.

Using VFO Priority

1.  Select the desired secondary frequency using the tuning control or
    UP/DN. 

2.  Press F + PRI (SCAN).

3.  Select the primary frequency using the tuning control or UP/DN.  The
    transceiver starts to monitor both selected frequencies.

4.  To disable priority monitor, press F + PRI (SCAN) again.

Using Memory Priority

1.  Select the desired secondary VFO frequency using the tuning control or
    UP/DN.

2.  Press F + PRI (SCAN).

3.  Press MR (MS) then select the desired memory location for your primary
    frequency. The transceiver starts to monitor both selected frequencies 

4.  To disable priority monitor, press F + PRI (SCAN) again.

Changing The Transmit Frequency Range

You can change the standard transmit frequency range from 144-148 MHz to 
an extended range of 142.000 - 149.885 MHz.

To set the transceiver to its extended range, turn it off.  Then while 
holding down F and LOCK, turn on the transceiver.

To return to the standard frequency range, repeat the above procedure. 

Selecting The Transmit Power Level

You can select either of two transmitting power levels: high (25 watts) 
for normal operation or low (10 watts).  Choose the lower level to reduce 
the possibility of overloading nearby receivers.  Choose the higher level 
when conditions warrant maximum transmitting power.  To switch levels, 
press F + PTT.  If low is selected, LOW appears.  If high is selected, LOW 
disappears. 

Locking The Keypad

To lock the transceiver's keypad so you do not accidentally change a 
setting, press LOCK (SHIFT). (key symbol) appears. This locks all controls
except PTT, F, VOL, SQ, and LOCK.

To unlock the keypad, press LOCK again.

Turning The Key Tone On and Off

The transceiver is preset to sound a beep each time you press a key.  To 
turn off the beep, hold down the PTT button while you turn on the 
transceiver's power.  To restore the key tone, repeat the procedure. 

Setting The Frequency Step

To change the frequency increment used during scanning and stepping to a 
frequency, press F + STEP (CALL). The current frequency step appears. Then 
repeatedly press UP or DN or rotate the tuning control to change the 
setting. The default is 5 kHz. You can change the frequency step to 5 kHz,
10 kHz, 12.5 kHz, 15 kHz, 20 kHz, or 25 kHz.

Reducing Interference

Because your transceiver is exceptionally quiet, any noise you hear 
probably originates from a source within your vehicle such as the 
alternator, the spark plugs, or unshielded wires.

To solve the problem, you must locate the noise's source.  You can
determine the noise's source by first turning off the engine and operating
the transceiver with your vehicle's ignition set to ACC.  If the noise
decreases or disappears completely, the problem is with your vehicle's
ignition or associated wiring.

Here are a few suggestions to help you reduce or eliminate such noise:

  Make all of the transceiver's power and antenna wires as short and as 
  direct as possible.

  Route the power wires away from the antenna wires.

  Be sure the chassis ground connection is secure.

  Replace old ignition wires with new, high-voltage, noise suppression 
  wires.

  Install noise suppressors on your spark plugs, or install new spark 
  plugs that have built-in noise suppressors.

  If problems persist, check to ensure your alternator and electrical 
  system are operating correctly. You can reduce any noise by using bypass 
  capacitors at the various output voltage points.

Your local RadioShack store carries a wide selection of capacitors and 
other appropriate noise reduction components.

(BR EB 6/14/00)

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