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Thanks - RE: FT-817/100 Transmit Inhibit Function?



Thanks to everyone who responded to my question.  I took some additional
time this weekend to experiment with the FT-817 and found the following,
which was validated by several responses from the list.

The ACC jack senses when the appropriate 8 pin mini-DIN plug is inserted and
disables the transmit function.  The radio still looks like it's
transmitting (red TX light and display changes), except the PO meter doesn't
show any output and no significant power is transmitted.  The TX INH pin is
weakly pulled high to 5 VDC internally in the rig.  If this pin is pulled to
ground, the transmit is once again enabled.  A couple responses talked of
directly pulling this pin high, but that appears unnecessary.

A couple of respondants noted that the FT-100 can dial the power down to
very low levels and implied that the same could be done with the FT-817.
For those unfamiliar with the '817, it has only discrete power settings, the
lowest of which is 1/2 Watt.  While the FT-817 does have a hidden menu that
can be used to adjust the power output of the various band/power setting
combinations, it could not set the power low enough to prevent damage to
receive systems.  Using hidden menu setting #43, "VHF Low power", I could
adjust the 2 M power from about .3-.7 Watts using an HP-431 power meter.
This contradicts other posts in the past which claimed 1 mW was possible
with this setting. 

Thanks for everyone's help.

John Oppen, KJ6HZ

-----Original Message-----
From: Oppen, John D 
Sent: Friday, July 11, 2003 2:26 PM
To: ; 'amsat-bb@amsat.org'
Subject: [Sbms]FT-817/100 Transmit Inhibit Function?


Has anyone used the transmit inhibit function on the Yaesu FT-817 or FT-100?
The manual shows a pin on the rear panel accessory jack (8 pin mini-DIN)
which is supposed to inhibit the transmitter.  Grounding this pin does not
appear have any affect on my FT-817.  If anyone knows how to activate this
function, I would appreciate hearing about it off the list.  I want to make
a circuit that prevents damage to a receive converter in case I
inadvertently use the PTT with the down converter in line.
Thanks,
John, KJ6HZ
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