[Elecraft] OT:switching transistors

[Steven Pituch]

Hi all,
I know this is not directly related to Elecraft, but I think it is an
acceptable OT topic per the admins, and I think I remember Wayne even
talking about this subject long ago, so here goes.

I have a radio (FT8100) that I want to use with a TNC-X PIC modem.  However,
the tnc will not put the FT8100 into transmit.  The tnc uses a simple
2n2222a switch with a 10K resistor in series with the PIC output and the
base of the 2n2222a.

1) If I disconnect the radio cable from the tnc and ground the PKS (ground
to transmit) wire, the FT8100 goes into transmit.

2) If I connect the same cable to a new Icom IC-208H, the TNC-X works fine
and keys the radio.

John Hansen the designer of the TNC-X says that there are many hams using
the FT8100 with the TNC-X and there are no currently known problems with
using the TNC-X and FT-8100.

I am thinking that the 2n2222a might be a little weak or have too much on
resistance.  I will be checking the 2n2222a with my analyzer.

I think I remember Wayne, N6KR, saying how great the 2n7000 was over a
bipolar transistor for use as a switch.  Can anyone recommend a circuit
change using a 2n7000 or perhaps some other simple mod to the tnc other than
using a reed relay to let the FT8100 do its thing?  I relize that I should
probably go into the FT8100, but I am not looking forward to that.


Thanks,
Steve Pituch, W2MY
Corpus Christi

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