Thanks to SGC for contributions to the application note.
December 06, 2003
| PTC-II 8 pin Euro-style Din connector. "HF Transceiver Audio" (listed colors are for the pigtail that comes with the SCS PTC-II) | J-301 Aux. Audio input/output and PTT terminal strip on back of radio. |
| Pin 1, violet, TX Audio Output >>> | >>> Audio Input, Pin 1 |
| Pin 2, white, ground | Ground, Pin 2 |
| Pin 3, yellow, "Push To Talk" PTT >>> | >>> PTT, Pin 4 |
| Pin 4, green, Rx Audio Input <<< | <<< Audio Output, Pin 3 |
Check the manual for the PTC-II for the pin locations on the connector! They do not necessarily agree with the pin numbers of the connector that you might buy, depending on that connector's ancestry.
Unless you are using remote control (see below), set up the settings in the AirMail software as described in the SailMail Primer section, "Getting Connected". It will be easiest to use USB (J3E) mode and set up the frequencies as the carrier frequencies (i.e. center frequencies - 1.5 kHz.), and set up for 1500Hz tones on your modem.
The SG-2000 radio can have its frequency remotely set by AirMail, using either an additional serial port on your laptop or by using the RS232 level (V24) output from a SCS PTC-IIpro. For details on how to set up to do this, see the help files that are contained in the AirMail software.
The SGC SG-2000 is not rated for continuous operation at its peak power capability of 150 watts output. If you retrofit your radio with a fan kit (SGC part # 51-81, about $350) then the radio is capable of about 100 watts continuous output. Without a fan kit, SGC recommends a power output setting of about 50-75 watts.
Watch the "TEMP" indication on the radio's front panel. SGC describes that when the "TEMP" indicator flashes, the fan would normally turn on (if so equipped). When the "TEMP" indicator flashes quickly, the radio is running hot but ok. If the "TEMP" indicator stays on steadily, the radio has overheated and has reduced power output to recover. You should avoid repeatedly putting the radio into this condition.
If you do not have the #51-81 fan kit, SGC recommends that you set up the drive level to the radio so that the radio draws about 10-12 amps from your boat's 12 vdc supply. SGC further recommends that you monitor the radio's "TEMP" indicator. If the radio ever goes into its low-power mode due to an over-temperature condition (indicated by a steady "TEMP" indicator) then you should reduce the drive level still further to prevent a re-occurrence.
If you do add the #51-81 fan kit, then SGC recommends that you set up the drive level to the radio so that the radio draws about 18-20 amps from your boat's 12 vdc supply, but still monitor the "TEMP" indicator and reduce the drive level if necessary.
See the Application Note on Setting Drive Levels, for details on how to set your drive levels.
The SG-2000 emits RF through its 12 vdc power line input. One fix for this is to purchase from Digi-Key (800)344-4539, www.digikey.com , their item #CCM1335-ND "Line Filter 2 Stage Term 20A" for $56.28 Mount it close to the radio, in the 12 vdc power line leading to the radio.
(For engineers: The above filter has two stages of differential and common mode filtering and provides about 60 dB attenuation to both common and differential mode RF, from 2 through 20 MHz. You might note that this particular powerline filter is rated for 120 vac, but it works great at 12 vdc as well. AC rated filters can be operated up to the same numerical DC current level. Reliability will be slightly improved: inductor core hysteresis loss will be lower, and there will be an absence of capacitor reactive current. Internal filter component temperatures will be correspondingly lower.)
This has been a sure fix for troublesome installations of SG-2000's in which RF from the radio was getting into the laptop, the HF modem, and everywhere else. It also might help reduce conducted RFI from getting into the radio from your inverter etc. It won't help with radiated RFI.
Current models of the SG-2000 have a very sensitive audio input connection, requiring low drive levels and also making the input very sensitive to RF feedback. There is also no RF filtering on the audio-in connection. It is helpful to add a (shunt to ground) resistor to the SG-2000's audio input, to reduce the input impedance and hence the sensitivity to RF feedback. (This also requires a higher audio drive level). A suitable value is 220 ohms between terminals 1 and 2 of J301. Also consider adding a 0.001 uF capacitor in parallel, to further reduce the impedance at RF frequencies and filter some of the RF.
Please email any suggested changes or corrections to this app-note to sysop@sailmail.com