[1000mp] RASCAL and 1000MP

[Gorsline]

I had a similar problem with a homebrew PSK interface using serial port PTT
keying using one of the many circuits with an optisolator.  It would only pull
the PTT line down from 13.2V to about 2.5V - not enough for PTT "closure."  So
added a resistor across the PTT line to ground (~50ohms range - YMMV - started
with higher values, tried successively lower values until found one that worked
and didn't seem to bother normal VOX/QSK).  The resistor value still keeps the
voltage above what the PTT pull-in needs ( ~0.6V)  and then when the opti
switches, the PTT "closes" just fine.  I had to think long and hard about
current draw on the rig, etc., until it occurred that the PTT is a short, so the
current limiting has to already be in the rig.  You could solder it across the
PTT jack if needed.
Hardly an elegant solution, but it works and got me on PSK.
73,  George  VE3YV / K8HI

PS - not being a electronics techie - old IT type - if anybody who is feels this
is potentially harmful, please let me know!  With the current turnaround times
at Yaesu repair for parts to my local dealer, this baby is being treated with
respect!

Bill Evans wrote:

> 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
>
> ***********************************************************
> 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?"
> ***********************************************************
> 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.
> ************************************************************
>
> _______________________________________________
> List Moderator: Richard Lubash N1VXW
> 1000mp mailing list
> 1000mp@mailman.qth.net
> To Change Options or Unsubscribe:
> http://mailman.qth.net/mailman/listinfo/1000mp