[1000mp] RTTY and the FT1000MP

[Kok Chen]

On Mar 18, 2006, at 1:35 PM, Kok Chen wrote:

> Back in July 2004, George W1ZT did a careful study of it (I-R plots  
> and all) ...

Sorry, I mean "I-V" plots.

There is something else that I have used which works if your  
transistor's on state is capable of going lower than 0.62 volts but  
it does not have enough sink current:

We know that anything above 41 ohms will not trigger PTT.  Go into  
your junk box and pull all the 47 ohm resistor that you can find.   
Ohm meter the bunch and pick one that is no lower than 47 ohms.

Connect this between the PTT line and ground to bias the "on" current  
(the PTT line will then sit at around 0.72 volt with 15.2mA going  
through the resistor).

Make sure you remove this resistor when you want to use the same PTT  
device on a different rig or you might find that the other rig will  
never turn off :-).

73
Chen, W7AY