IC-207H works on 9k6, but needs many "tips" to do it workable on 9k6 packet with Symek - TNC2H
- There is not enough to lights the DCD led into TNC2H for decoding, in practice needs much stronger signal to print on the screen of terminal program.
IC-207 has a very low demodulator output on DATA-out of mini-Din, for this reason ICOM has a direct output without any protection-resistor, from TA31136 IC demodulator. If you put a resistor for protection (highly recommended !), the value of it must be 10K or less, not 47K as Symek advises (47K is too high for this RIG).
- Depend on low DATA-out of IC-207, you must increase as high as possible the sensitivity of TNC2H. That it can be by adding the R23 (1K2) into PCB of TNC2H and also by replacing the R14 with a new resistor 10K.
This way increasing the sensitivity of TNC2H to 10mV. (see TNC2H MANUAL page 8)
- The DATA-output of TNC can be drive the IC-207 data-in, through a 10K resistor also (for protection). There is not any problem on this stage, IC-207 accept the data easily, without problems.
If you havn't an oscilloscope to adjust the Vp-p into Data-in Pin of IC-207 for 400mV pp, just "put" the trimmer into TNC2H > to the middle position. Its very close to optimum driving value.
- Keep in mind, for 9600 Bps, IC-207 must be set on this data-speed by INITIAL SET MODE.
- Push the PWR to turn off.
- While pushing "SET", turn power ON to enter INITIAL set mode.
- Push "SET" one or more times till "bPS" appears.
Pushing "MON" reverses the order of selection.
- Rotate the tuning dial for 9600 bps.
- Push "PWR" momentarily to exit of INITIAL mode.
Finally, IC-207 accept a TX-Delay no less of 30, which is a very-large number of TXD for 9k6 Packet operation! Lower TXD-value on TNC2H (with IC-207), in practice generates an unserviceable signal on the air, which is non-decoded from other receivers.
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