Online Users Guide for the PCX-250 HF Radio

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The PCX-250 HF transceiver is a compact, 10-Watt portable HF radio designed specifically for Northern climates. The PCX-250 is designed to replace the legendary Spilsbury SBX-11 radios, which have proven themselves over many years of operation throughout the North. The PCX-250 and SBX-11 have a similar front panel layout, and share many common features and controls. Personnel with experience operating the SBX-11 should have little trouble adapting to the PCX-250.

The PCX-250 was designed to be an all-new radio, and is substantially smaller than the SBX-11 that it replaces. It also has higher battery capacity, much lower "drift" at low temperature (which means that received signals sound natural, even during cold weather operation) and is designed for long life and trouble-free operation.


Front Panel Controls and Indicators

As mentioned earlier, the PCX-250 and the SBX-11 have very similar controls, and both radios operate in a similar manner. The photo below (Figure 1) shows the front-panel layout.

5. Battery / TX Meter

4. Tune Button

3. Clarifier

2. Channel Selector

1. On/Off & Volume

Figure 1 - PCX-250 Front Panel Controls

The PCX-250 has 5 different controls and indicators:

1) Volume Control / ON-OFF Power Switch
2) Channel Selector
3) Clarifier Up/Down Control Switch
4) "Tune" Pushbutton
5) Battery Level and Transmitter Output Meter

All of these controls are also present on the SBX-11, and perform similar functions.

The controls and indicators are described below.


1) Volume Control / ON-OFF Power Switch

This control is used to turn the radio ON or OFF, and to adjust the radio to a comfortable receive listening level.

To turn the radio ON, rotate the control in a clock-wise direction, until a "click" is heard. (The control has a firm feel, which prevents it from being turned on accidentally while inside the case). Continue to turn the control clockwise, until the receiver volume is at a comfortable listening level (usually around where the white knob stripe points straight up.

To turn the radio OFF, rotate the Volume Control fully counter-clockwise until a distinct "click" is heard.


2) Channel Selector

The channel selector is used to set the radio to the correct Channel or "frequency". Normally the channel use is identified on the channel decal (which is included with the radio), which should be placed on the side of the radio chassis. The name or usage of the channel should be on the decal, as well as the frequency (usually a 4 or 5 digit number, such as 5.0310 MHz ). See Figure 2, below.

Figure 2 - Decal placement showing Channel Frequencies

Technical Note:

Usually, the radio technicians set channel frequencies soon after the radios have been delivered. Radio frequencies are measured using the units MegaHertz or KiloHertz (MHz or kHz). 1 MHz is equal to 1000 kHz.

For the most part, higher frequency channels (4.5000 MHz to 8.0000 MHz) are used during the day, and lower frequencies (2.000 MHz to 4.500 MHz) are used during the night. There are no hard and fast rules, however, and the best frequency to use is dependent on many things, such as distance between stations, local terrain, time of day, and season of the year. The most common frequencies used in the North are between 4.400 MHz and 5.600 MHz for daytime use, and between 2.500 MHz and 3.500 MHz during the night. However, many users rely on frequencies in the 5.000 MHz range for round -the-clock communications.


3) Clarifier Up/Down Switch

The CLARIFIER switch is used to adjust the "pitch" or tone of the received voice signal.

Sometimes, when the radio is receiving a station that is slightly off-frequency, the received signal can sound "off-pitch" or un-natural. (A good example is if you hold your nose while speaking; an off-frequency signal can sound like this). The CLARIFIER is used to restore the natural tone to the received voice signal when this occurs.

The CLARIFIER toggle switch can be moved either UP (+) or DOWN (-), depending on the desired change in pitch. If the CLARIFIER switch is pressed DOWN, the pitch is made LOWER. If the CLARIFER switch is pressed UP (+), the pitch is made HIGHER.

Normally, this control is not required, but if you hear a signal that sounds un-natural (too high or too low in pitch), try using the CLARIFIER control to improve the received voice quality. Listen to some other stations on the radio and note the effect that the CLARIFER operation has on the quality of the received signals.

The CLARIFIER pitch can be changed in two steps, in either the UP or DOWN direction. Changing the channel resets the CLARIFIER to its normal (center) position.


4) "Tune" Pushbutton

When the TUNE push-button is pressed, the Transmitter puts out a constant, high-level signal to the antenna. Normally, the TUNE button is not used unless the radio is used with an electrically "tuneable" antenna. This TUNE signal is required for 3-5 seconds to allow these special antennas to adjust their electronics to work on a given channel. Normally, these types of antennas are found on ATVs, trucks, boats and other moving vehicles. These types of antennas are also known as "Tuneable Whip Antennas".

The TUNE push-button can also be used for two other functions. It can be used to test if the antenna is connected properly, and can be used to "load" the batteries so that their condition can be checked. More information is explained below.

After the antenna has been set up and connected to the radio, press the "TUNE" button, and observe the meter, located in the lower left hand corner of the front panel. If the antenna is functioning properly, the meter needle will move into the GREEN area of the meter face. Note that this test is not always necessary, but it gives an easy "go/no-go" check.

The TUNE button can also be used to help determine if the batteries are in good condition.

In order to check the battery condition, the TUNE button is pressed for approx 3-5 seconds, and then released. Immediately after releasing the button, the battery condition can be determined by checking the meter and making sure that the meter indicates in the GREEN area of the meter face.


5) Battery Level / Transmitter Output Meter

The front panel meter serves two functions, depending on whether the radio is being used in Receive or Transmit mode.

When the radio is in Receive operation, the meter indicates the relative condition of the batteries. As long as the meter needle indicates in the far GREEN area of the meter face, the batteries are in useable condition. Please see "TUNE" button description for further information on battery testing.

When the radio is in Transmit mode (either by pressing the TUNE button, or by speaking into the microphone while pressing the Push to Talk Switch on the microphone) the meter will indicate that the transmitter is applying power to antenna. The meter moving into the GREEN area on voice peaks shows normal operation. In other words, the meter moves at the same rate as the radio operator is speaking.


General Radio Operation and Setup Procedures


Using the Microphone

The microphone should be held close to the mouth, directly in front or slightly to the side of the operator's mouth. Holding the microphone further away will increase the level of background noise and may not allow the radio to deliver full output power to the antenna. Press the microphone "Push to Talk" switch, and speak slowly and clearly, in a firm voice. Keep an eye on the front panel meter to make sure that power is being delivered to the antenna. As mentioned earlier, the meter should indicate in the GREEN range, following the peaks of the operator's voice.

Proper Care of Batteries

Without a doubt, one of the two most important factors in radio operation is the battery condition (the other is the antenna). Of course, fresh batteries are always a requirement when the radio is being depended upon for reliable communications. In very cold operation (below about -10C) the batteries should be protected from freezing, which can render them useless. All batteries lose a SUBSTANTIAL amount of their power delivery potential when they are cold.

So, try to keep the batteries (and the radio!) from freezing solid. This is sometimes as easy as rolling the radio in a blanket or sleeping bag during travel. This tends to hold the heat in the radio for many hours. Some users keep their batteries in their parka when the temperature drops, and install them when required. This should only be necessary when the temperature drops below -20C, or so.

Also, keep the radio in the pack-sack whenever possible. It keeps the radio from damage, and tends to trap the heat in the radio. The pack-sack can also sit on a tabletop and provide a holder for the radio. See Figure 3, located below.

Figure 3 - PCX-250 ready for use in Pack-Sack


Antennas for HF Radio

The most common type of antenna used with portable HF radios is the wire dipole antenna. There are few other antennas that can match it for it's simplicity, ruggedness, and it's ability to radiate an effective signal.

The dipole antenna consists of two wires, a center insulator, and a lead-in wire called coaxial cable or coax (pronounced "koe-ax"). The coaxial cable is the part of the antenna that is connected to the radio. It is used to connect the radio to the actual antenna.

The length of the wire part of the antenna (which can be over 100 feet long) is important. The antenna will radiate most effectively if the length corresponds to the channel frequency. ParaComm manufactures a wire antenna (the TDA-250) that is marked in frequency (i.e. 4.5 MHz, 5.0 MHz) so that it can be rolled out to the appropriate length.

It should be mentioned that the radio would work with an antenna that is not the right length for the frequency used, (and some times it is not practical to change the antenna length while in the field) but it will not radiate as well as one that is correctly adjusted. This can make a difference if the signals are weak or noisy.


Antenna Wire Height above Ground

Keep the antenna wires as high above ground as is practical. If at all possible, try to keep at least the center of the antenna above the ground. It's usually fine if the ends of the wires are brought down to the ground at an angle, with the center elevated above the ground as much as possible. This configuration is called an "Inverted Vee" antenna.

Placing the antenna at a height of 6 -10 feet (2-3 meters) above ground can make a huge difference in the quality of received and transmitted signals, when compared to signal levels that are received when the antenna is laid directly on the ground. In some cases, however, where supports are not available, laying the antenna on the ground is the only option.

Just remember: The earth does a very good job of soaking up transmitted signals, (especially when the ground is wet!) and so set up the antenna with this in mind. In general, the higher the antenna is, the better, but little improvement is seen above 25 feet (8 meters) in height.

The antenna should also be set up so that the wires face the direction that you wish to transmit towards (the ends of the antenna would be perpendicular to this direction), however this is not a particularly critical requirement. Just remember, the antenna does NOT radiate well off of the ends of the antenna. See Figure 4.

Figure 4 - Sketch of Dipole Antenna showing Radiation Pattern


Connecting the Antenna to the Radio

The antenna should be connected to the radio so that the antenna connector allows the coaxial cable to be routed away from the faceplate of the radio. Important Note: There is a CORRECT way to attach the antenna connector. If the antenna is not connected to the radio this way, the radio may not work well. See figure 5, below.

Figure 5- Proper Antenna Connector Attachment


Radio Operation Summary:

1) The PCX-250 is designed to be very similar to the SBX-11 in operation and in operator controls.

2) The radio is designed to provide years of trouble-free operation if handled with some care. Remember that your life may depend on it one day, so treat it accordingly. Rough handling can cause the radio to go out of tune, or cause an outright failure.

3) The batteries are sometimes the "weak link" that can prevent you from getting a transmission through. Keep them in good shape, replace them often and protect them from extreme cold. When very cold, warming them before use is always a good idea. Remember that the FLAT side of the battery always goes against the SPRINGS in the battery holder!

4) Keep your antenna in good repair, and always elevate the antenna above the ground as much as possible. Test the antenna connection by pressing the TUNE button and make sure the meter indicator moves into the green area. Make sure that the antenna connector is installed properly on the radio.

5) Keep the microphone close to your mouth, and speak in a clear, firm voice. Try to keep unwanted background noise to low levels when operating the radio.


End of Radio Users Guide

Copyright ParaComm Technologies Inc.
# 1 – 3310 Appaloosa Road
Kelowna, BC Canada
V4V 1G1
Phone: (250) 491-9343
Fax: (425)-952-7674