CTCSS encoder / decoder
For Two-Way Radio Applications
Model CT-30 Click here for schematic, parts list, construction, installation and set-up instructions.
Ordering instructions on bottom of page.
This board can be added to any radio or repeater that has a suitable discriminator connection.
It is built with mostly through-hole components to allow repair or modification by the common technician.
It is used to create a quality CTCSS logic to be interfaced with a standard repeater controller or radio interface with AllStar, IRLP, or similar application.
This board can encode or decode BUT it cannot do both at the same time.
Kit - $30.00 each.
Kit with soldered surface mount MX465 chip - $35.00 each.
Assembled and Tested - $50.00 each.
US shipping and handling $7.50 in small quantity.
PayPal accepted - order below.
Actual Size CT-30 photo.
(Click image to enlarge)
The CT-30 is a CML CTCSS decoder/encoder on a single printed circuit board. A MX-465 (FX-465) CTCSS chip is used for "PL" detection. This chip is not duplex - meaning it will not generate (encode) and decode a tone simultaneously. Since the main purpose of this board is to allow easy connection of detected logic to a repeater controller, AllStar or other radio interface, the CTCSS encode would be done elsewhere in hardware or software. The MX/FX-465 is the only surface mount component. The kit can be purchased with this surface mount chip soldered onto the board for those not familiar or comfortable with SMT soldering techniques.
There is one LED for status. It is red and indicates a valid CTCSS (PL) tone detection. The tone frequency is set by DIP switches. All of the functionality of the FX-465 is brought out to pins on the connector (DB-25F). They include the logic line to tell the chip to encode or decode, as well as all of the audio filters and muting that is available for the transmitter and receiver - in case someone wants to utilize them. There are six 'spare' traces on the circuit board allowing you to have access to six different pins on the DB-25F that you may jumper to anywhere on the board you like. This includes the six frequency select logic lines (connected to holes 1 thru 6) so you can change the tone frequency remotely!
About the inputs and outputs.
There are only three necessary connections for input; buffered discriminator audio, power, and ground.
The logic outputs are not totem pole, however, separate active high and active low logic outputs are available. There are open collector outputs available from 2 holes marked A - B that are included on the circuit board. These outputs can be used for operations that are beyond the original scope of this board.
The 6 spare hole traces that terminate to individual pins on the DB25 can be used to wire up remote control of the tone frequency, or other things I may not have thought of.
Why do we need this board?
Not all radios have easy access to quality PL logic signals. Some repeater hardware may not include CTCSS detection or may require reprogramming just to change the PL tone frequency. The Com-Spec TS products are great, but the audio filter in them leaves a lot to be desired. The filtering properties of the CT-30 are superior in response, group delay, and filtering depth. Remotely changing the tone frequency of a TS product can be challenging because of board size and type, while we make it easy to connect to the tone frequency switches.
|Recommended Power Source: +7 to +16 VDC, must be constant, not switched. Maximum is 24 VDC.|
|Onboard regulation +5V for the FX465 and logic.|
|CTCSS tone is set by DIP switches, or remote programming via holes 1 - 6.|
|Low current draw, about 7 mA standby and 20 mA with the LED lit, depending on logic sourced and its input impedance. (Measured at 13.8 VDC input)|
|All logic is sourced from 5 VDC. Pull-up and pull-down resistors are included.|
|Small size - can fit inside many radios.|
|Add a quality CTCSS decoder to that radio whose logic signals are hard to get to.|
|Simple to hook up and set up. Requires a few hundred mV RMS of audio.|
|90 day Limited Warranty. Repair available for units out of, or not covered under, warranty (my determination).|
|Mounts with double-sided foam tape or stand-offs (not included).|
|Hookup is made with a mating DB25 male connector (not included).|
|Comes with thru-hole resistors and capacitors, but isn't recommended for the first time
builder due to surface mount IC.
The kit can be supplied with the surface mount 24 pin IC already soldered onto the board. Select option below - $5.00 charge for this service.
Click here for schematic, parts list, construction, installation and set-up instructions.
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Product of Masters Communications, all rights reserved.
Specifications may change without notice.
Images are property of Kevin Custer - W3KKC
Board layout by Chuck Kelsey - WB2EDV
PL is a Motorola Trademark, and is synonymous with the term CTCSS.
HTML December 7, 2015, W3KKC All Rights Reserved!