[Yaesu] FT-897D jumpers for keying/isolation relay

[mikea]

On Sat, Jul 07, 2007 at 12:02:19PM -0500, Mike Miller wrote:
> Hi Mike,
> 
> See page 10 of the manual. The CAT/Linear Jack has a TX Gnd pin 
> that is an open collector circuit rated at 50VDC and 400mA max. 
> I have the FT-857 and have never used this output. I'm not sure 
> about the timing of the circuit i.e. will it pull your coax 
> relay before RF appears at the coax connector? 
> 
> You might want to key the 897 off a contact on the coax relay to 
> make sure it has switched before there is RF on the line.

Thanks for that idea. 

The CAT jack already is in use, but it turns out that on an 897D
there is a jumper (J217, I think) to change the behavior of the ACC
jack. With the jumper in 1-2 (the factory position), grounding the
ring contact keys the TX. If the jumper is across 2-3, then the ring
contact label changes from TX-REQ to TX-GND, and there's a transistor
driven to conduction between TX-GND and ground, making an effective
contact closure.

There's more about it on the Yahoo FT-897 group, under the general 
heading of keying an amplifier from an 897D. 

I am a bit concerned about the actual timing sequence, and about RF on
the line before the relay pulls in. I'll be testing this evening. It
may be that I need to buy a new coax relay with aux contacts. *sigh*
I also need to get a diode across the coil to snub the inductive kick
from all the energy stored in the field. 18VDC at 70 mA turns out to
produce a pretty good tingle acrss a finger tip when I open the coil 
circuit, and I don't want to expose that transistor to the EMF in 
either direction.

73, de

-- 
Mike Andrews, W5EGO
mikea at mikea.ath.cx
Tired old sysadmin