ST500 TRANSMITTER OPERATING INSTRUCTIONS 1892 1210 These operating instructions are intended to provide the user with sufficient information to install and operate the unit correctly. The Wood & Douglas ST500 UHF transmitter is intended to fulfil numerous OEM applications by virtue of its highly flexible synthesized design approach, miniature size and cost-effective performance.
DIMENSIONS AND FIXING The unit is intended for PCB mounting within the customer’s equipment. Figure 1 - ST unit dimensions and connectors 2 1892 1210 - ST500 Transmitter Operating Instructions - v2.
CONNECTION Connection to the unit is via PL1, PL2 and PL3 which plug directly into the user's own equipment. The location of these connectors is shown in Figure 1 and detailed in the following tables. (The unit is fitted with a 10 pin connector when parallel frequency select facility is provided). PIN NAME 1 0V 2 TXE 3 FUNCTION REMARKS 0 volts common ground transmit enable o/c = transmitter disabled LOW <+0.5V = transmitter enabled 1K nom.
OPERATING FREQUENCIES Each radio is made to order to cover a band (the switching bandwidth) of 5MHz within the range 400 - 540MHz. Each radio is also manufactured to work within a particular channel width of 12.5kHz, 20kHz or 25kHz. Within the switching bandwidth, the unit can operate on any frequency provided it is a multiple of the channel width, and up to 128 frequencies can be stored as numbered channels.
Figure 2 - Programming screen The screen shows the default settings which are displayed whenever the software is run. Greyed items are display-only, and cannot be programmed by the user. The two tables at the left-hand side are used to set and display channel frequencies. The top right-hand panel sets and displays general unit parameters, and the lower right-hand panel is used to issue commands to the unit.
DESCRIPTION OF USER INTERFACE Top Level Menu Bar (Outer Window) File Load Setting From Load a pre-stored set of data from a standard File Open dialog. Save Setting To Save the current set of data. A default name is given which you can change, and you can navigate to the directory of your choice. Print Print the current set of data; only available when Report File window is open. The currently selected Windows default printer will be used. Exit Exit the program. Duplicates the Exit button.
Comparison Freq. (Fc) Fixed by the hardware. Channel spacing can be set to an integer multiple of this value by setting Table Step Size accordingly. For example, a Table Step Size of 2 sets Fc to 25kHz if Osc Freq is 12.5kHz. Intermediate Frequency Displays High Side/Low Side and the Intermediate Frequency, which is fixed by the hardware and cannot be changed. PIC Code Only displayed when the Readback function has been used to download the contents of the unit EEPROM.
drop-down list displayed when selecting channel frequencies. Receiver Offset The SX500 normally operates with identical transmit and receive frequencies. This parameter allows a positive or negative offset to be added to the receive frequency. Note that this does not change the RX switching bandwidth, and that the actual receive frequencies programmed into channels must still fall within it. Max.
PROGRAMMING THE UNIT Three steps are necessary: v v v Upload values from the unit Edit the values Download values to the unit Uploading Current Unit Settings First, you must read into the computer what is in the unit’s memory at present. To do this, issue the Read From Unit command by double-clicking over it. The data replaces the defaults on the screen. v The program insists that you do this before allowing you to reprogram the unit to make it less likely that inappropriate values be entered.
Programming Sequential (Table or Block) Channels (24-255) Channels 24-255, whose frequencies are set sequentially by providing a starting frequency and a spacing, are displayed and set in the lower left panel of the window. To set their frequencies, which can only be done as a single block: 1. 2. 3. 4.
Parallel channel mode select must be the last action before disconnecting the unit: any further serial communication will reset it to serial mode. Completing Programming This completes programming and the unit may be disconnected. It is not necessary to switch off power or stop the program first. Programming Further Units Further units may be programmed by disconnecting one unit and connecting the next, which may be done without switching the power off.
CHANNEL SELECTION DURING OPERATION There are three ways to select a channel during operation: v v v In hardware, using three logic lines to select channels 0-7 Using the SXn00.exe software and a serial connection from a PC to the unit By sending a short serial data message to the unit from your own equipment. Parallel Channel Selection v The unit must have been left in parallel mode when it was programmed.
Serial Channel Selection (own equipment) If you want to select a channel using serial mode from your own equipment rather than using the supplied software, then you must use this protocol: 1200 baud, RS232 levels, 1 start bit - 8 bit data - no parity - 1 stop bit and send the following data sequence to the RS232 input, allowing at least 5ms between the characters in the data stream: x40 (decimal 64) synchronising code Channel number in hex (decimal 0 to 255) x95 (decimal 149) confirmation byte Any channel b
RANGE INFORMATION The following table gives an indication of the typical ranges to be expected between a transmitter and receiver that have simple end-fed dipole antennas.
TECHNICAL SPECIFICATION Frequency range : Switching bandwidth Frequency stability Number of RF channels : : : RF channel selection: : RF output power into 50O : : : : Adjacent channel power TX switching time Modulation input analogue : digital : Frequency response : Deviation 25kHz channel spacing : 20kHz channel spacing : 12.5kHz channel spacing : Channel switching delay : Channel spacing : Modulation type : Spurious emissions (conducted & radiated) : Supply voltage : Supply current at 7.
APPENDIX: TTL TO RS232 ADAPTOR Many PCs do not require true RS232, and will work with the simple adaptor of Figure 3. The transistor used must have a gain of at least 30. Figure 3 - Simple programming adaptor Figure 4 shows the circuit of an adaptor providing true RS232 for readback when programming a unit. Figure 4 - Programming adaptor (True RS232) 16 1892 1210 - ST500 Transmitter Operating Instructions - v2.
A suitable inverting TTL to RS232 buffer circuit using the industry-standard MAX232 part is shown in Figure 5. Figure 5 - Suggested RS232 buffer circuit The MAX232 is obtainable from many component suppliers, e.g. RS Components stock no. 655-290. Wood & Douglas Ltd, Lattice House Baughurst, Tadley, Hants, RG26 5LP Tel:+44 (0)118 981 1444 Fax: +44 (0)118 981 1567 email: sales@woodanddouglas.co.uk website: www.woodanddouglas.co.uk 1892 1210 - ST500 Transmitter Operating Instructions - v2.
