[1000mp] RTTY and the FT1000MP

[Pitman, Zoltan, VF-NL]

exactly. 

I wrote about this here last summer: 

http://mailman.qth.net/pipermail/1000mp/2005-August/018463.html

there are optocouplers with FET-output who can easily do sink below 40 ohm on D-S. 

73, 

Zoli HA1AG


> -----Original Message-----
> From: 1000mp-bounces at mailman.qth.net 
> [mailto:1000mp-bounces at mailman.qth.net] On Behalf Of Kok Chen
> Sent: Saturday, March 18, 2006 22:36 PM
> To: All about Yaesu 1000mp
> Cc: George Johnson
> Subject: Re: [1000mp] RTTY and the FT1000MP
> 
> 
> 
> On Mar 18, 2006, at 11:51 AM, Ted Boerkamp wrote:
> 
> > I have used the opto-coupler circuits shown on a few 
> websites for this 
> > purpose and I am tying into the RTTY jack on the back of the 1000MP 
> > (original model). When I click on TX in MMTTY, a LED lights on the 
> > input side of the opto IC, but the 1000MP is not keyed. So 
> I know that 
> > the signal is getting to the opto-coupler but the output 
> doesn't seem 
> > to be right to key up the radio.
> 
> The problem with the FT-990, FT100D and FT-1000MP series 
> transceivers  
> is that Yaesu had opted for a diode wired-OR circuit to isolate the  
> various PTT inputs rather than providing a transistor switch 
> for each  
> PTT input.
> 
> Because of that, you need to key the PTT with a very low impedance  
> switch.  The FSK input does not suffer the same malady.
> 
> Back in July 2004, George W1ZT did a careful study of it (I-R plots  
> and all) and the gist of it is that you need an "on" state of better  
> than 0.63 volts at 15.4 mA (or a resistor of about 40 ohms) to  
> reliably turn the PTT of a Yaesu FT990/1000D/1000MP on.
> 
> Among devices that do NOT work reliably are: 4N33, 4N29A and a  
> Silicon diode towards ground.
> 
> Any transistor with a guaranteed Vce(sat) of less that 0.6 volts and  
> capable of sinking 15.4 mA would work reliably.
> 
> I have George's pdf document and if someone wants to post that at a  
> web site, please write to w1zt at arrl.net and if George does 
> not have a  
> copy handy but agrees to let it be published, I can supply 
> the document.
> 
> 73
> Chen, W7AY
> 
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