using the mx-465p

Using the MX-COM 465P CTCSS Encoder / Decoder Chip

1. Introduction

    The 24 pin MX-465P Tone Chip is a beautiful piece of work.

    Essentially, it will encode and decode the tones 159.8Hz, 183.5Hz, 189.9Hz, 196.6Hz, 199.5Hz, 206.5Hz, 229.1Hz, and 254.1Hz in addition to the 39 standard CTCSS tones, for a total of 47 CTCSS tones and the No Tone situation.

    With on-chip TX and RX speech filters, the MX465 enhances voice/tone multiplexing by attenuating TX and RX speech 36dB at frequencies below 250Hz while passing signals > 300Hz with only 1dB of ripple.

    These filters not only minimize CTCSS talk-off during transmission but also improve Hum and Noise performance while receiving.

2. Use in Radio Conversions

    a) Delta Series Conversions

    Since the Delta's Tone Squelch (CTCSS) board is removed during the conversion to the external M/P, the transmit and receive filters are likewise removed. This is no problem as the MX-465P chip can be used to effectively replace them, if desired. Since the receiver audio is delivered to the Control Head over the Volume / Squelch High lead, the audio may be directed (by means of a switch) through the MX-465P's receive filter and then back to the 'hot' leads of the volume and squelch controls. This not only filters the residual low frequency CTCSS tones from the audio appearing at the speaker, but also provides true tone squelch in that the audio will not be passed through the MX-465P chip if the CTCSS signal it receives does not match the CTCSS frequency latched into it. By using the switch, the Tone Squelch capability and the receive filter can either be enabled or defeated.

    Furthermore, by making two more connections within the Delta to the DB-25 cable, the excellent transmit filter can be used, as well.

    b) Rangr, Phoenix and MVS Conversions

    Since the transmit tone filtering circuitry is not disturbed in these radios during the conversion process, there's no need to use the MX-465P transmit filtering circuitry. Furthermore, the radio's high pass filter that is used to remove the CTCSS audio from the received signal is likewise retained, so there's no problem with the received audio.

    But, if you desire true Tone Squelch capability wherein your radio will be squelched until the desired CTCSS tone is received, then add the simple switch in the control head.

G.E.and the product names Phoenix, Delta, Rangr are trademarks of Ericsson General Electric Mobile Communications.

DISCLAIMER - - If you follow the steps outlined herein, you do so at your own risk. I cannot, nor will not, be responsible for any possible damage to radio equipment, personal property, to yourself or to others caused by modifications that you may make to the radio as a result of your reading this.

The M/P controls TRANSMITTING and receiving on many frequencies, suitable for a wide range of HF, VHF and UHF needs. In the USA, TRANSMIT operation requires a license issued by the FCC for the class of operation intended. Amateur radio licensees must maintain strict control over their equipment, preventing unlicensed operation within or outside of the amateur bands.