Using the LDG AT-1000ProII with Yaesu FT-991:
Using the LDG AT-1000ProII with Yaesu FT-991:
By KN5G:
31-December, 2015
After scratching my head for a few days and looking through the FT-991’s manual and the LDG AT1000ProII’s manual, and perusing everything I could find on the Internet, I finally figured out how to use
the LDG AT1000ProII with the Yaesu FT-991. I wanted to be able to press the TUNE button on the face of
the AT1000ProII for a couple of seconds and have it initiate a tuning session like I was used to doing with
my FT-857. With the FT-857, pressing the Tune button on the AT1000ProII for a couple of seconds would
cause it to close an internal contact, which the FT-857 would sense at its ACC Jack, and switch to
transmit mode while the tuner completed a tuning cycle.
The FT-991 does not have an ACC, “Accessory Jack” like the FT-857, but it does have a jack named
REM/ALC on the back skirt. (See page 17 in the FT-991 manual). Fortunately, this jack accepts an
External ALC signal and an External TX REQ signal, (Normally
used by a linear amplifier with an internal tuner built into the
amplifier, I suspect).
Basically the same two conductor cable, (LDG calls it an
“Optional Y-ACC Cable”), used for the Yaesu FT-857 and FT987 will work with the FT-991. But there is a catch!
Optional Y-ACC cable has a red plug on the radio end of the cable and a black plug on the tuner end of the cable.
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Using the LDG AT-1000ProII with Yaesu FT-991:
By KN5G:
The “catch” is that while it only seems logical to set the FT-991’s menu location 143 - Tuner Select, to
“EXTERNAL” that did not work, (or at least it did not work with my FT-991), which is running the Main
Firmware version V02-08. With a VOM connected across TX REQ and Ground, there was no signal
voltage read until the menu location 143 was set to LAMP, (Linear Amp).
With LAMP selected in menu location 143, a voltage of approximately 3.5 VDC was read on the volt
meter across the TX REQ line and Ground. When the TX REQ line was touched to ground, the FT-991
switched to transmit.
Two depictions of the control cable
between the LDG tuner and the FT-991.
Using this arrangement the AT-1000ProII can be placed in the Tune Mode by pressing the Tune Button
on the face of the tuner and holding it for more than two seconds. When the tuner closes its internal
relay, the FT-991 senses the TX REQ from the tuner and goes into transmit mode. The FT-991 does not
indicate what mode it is transmitting in on the TFT display. With LSB selected before a tuning cycle, the
LSB indication never changes, but the radio does transmit and the tuner cycles its relays. You can see the
SWR reading on the radio’s meter, if SWR is selected. You will also see the SWR indicated on the LED’s
on the face of the tuner as it cycles through the various combinations to find a match.
If you want to use the ALC signal from your amp, to the FT-991, you will have to build up a “Y” cable,
with one end plugged into the FT-991, the second end plugged into the Radio plug on the tuner and the
third plugging into the ALC output port on your amp.
Below is the arrangement I am using at my QTH.
73, KN5G
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