[1000mp] RASCAL and 1000MP

[Bill Evans]

Todd

About a year ago I bought the Rascal and connected it to My 1000MP.  I  
had problems keying the rig through  the PTT.  The problem is that some 
1000MP's have a 1K pull up resistor to 13-14V.  The standard Rascal can 
not sink this much current.  Below is an exchange of e-mail with Buck, 
K4abt, on the problem.  You did not say if the PTT was your problem, but 
the measured data in my e-mail may help.   K4ABT  made the upgrade 
quickly and I have enjoyed many contacts on PSK31 since.  

Bill



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My note to K4ABT:

"I recently purchased the Rascal R 1000D to be used with my Yeasu 1000MP.

The PTT does not work.  Here's the data.  The Rascal LED
lights when the transmit button is pushed on the DigiPan screen.  
The Output impedance of the Rascal drops from "open circuit" to less
the one ohm with no connection to the transceiver.  With the
Rascal connected to the transceiver, the voltage on the output drops from
about 14V ( which is the normal open circuit voltage on the FT 1000MP
PTT lead) to about 10V.  It appears that the Rascal cannot handle
the current form the FT 1000MP. ( The short-circuit current from the PTT
is about 15ma.)  What do you think? Was the unit designed to
sink this current?  Have other users had this problem?"
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Reply from K4ABT

YES, about 3% of the MP users report a problem with the PTT... seems all
MP's are not created equal.

If you will return it, I will build a FET keying circuit into it that will
sink it to .1 ohm, and handle the 1kmp.

I talked to a tech at Yaesu Monday....

It appears that all the late model 1Kmp are TTL at the PTT jack.  So, I must
use another design to handle the change.
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