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Author Topic: FT-897 acc  (Read 334 times)
G3BBD
Member

Posts: 1




Ignore
« on: December 15, 2007, 07:28:56 AM »

I would like to
control the power
output of the FT897
when using the acc
jack to give a steady
cw signal but with
reduced power.
 On the acc jack the
center pin is marked
'ALC' and isintended
to couple to a linear
such as the Yaesu
VL-1000 to provide
control of the driver
power. The voltage
is specified as 0 to
negative10 volts.  
TP4030 on the front
panel board of the
FT897 is
connected to this
lead but there is no
indication in the
service manual of
the level.
It would seem
possible to place a
negative voltage on
the ALC line when
the ACC line is used
to switch the rig to
transmit. This could
be a preset voltage
from a small 9v cell
adjusted to give the
lower output
required.  Has this
been done - it
seems as though
the 'Tuneright' plug
in module uses this
system with a time
delay. Any help
would be
appreciated.
John G3BBD /
N3YZR
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K9ZF
Member

Posts: 76


WWW

Ignore
« Reply #1 on: December 15, 2007, 02:07:57 PM »

Seems reasonable.

Down East Microwave makes an interface for doing this.  It is intended to couple rigs to transverters, but you can "tune" it to whatever power output you like.  Look for the "Transverter Interface Box" or TIB.  I think the web site is

http://www.downeastmicrowave.com

Good luck,

73
Dan
--
K9ZF /R no budget Rover ***QRP-l #1269
Check out the Rover Resource Page at: <http://www.qsl.net/n9rla>
List Administrator for: InHam+grid-loc+ham-books
Ask me how to join the Indiana Ham Mailing list!

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--
K9ZF
Amateur Radio Emergency Service, Clark County Indiana. EM78el
The once and future K9ZF /R no budget Rover
 ***QRP-l #1269
Check out the Rover Resource Page at:
<http://www.qsl.net/n9rla>
List Administrator for: InHam+grid-loc+ham-books
Ask me how to join the Indiana Ham Maili
G4AON
Member

Posts: 518




Ignore
« Reply #2 on: December 16, 2007, 09:18:56 AM »

John

I used "ALC" Voltage to control an FT857D, it was suffering from high power spikes on initial transmit. The circuit is easy enough to experiment with, see:

http://www.astromag.co.uk/ft857d/

73 Dave
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PE1HZG
Member

Posts: 56




Ignore
« Reply #3 on: December 18, 2007, 12:52:13 AM »

You don't need to muck about with external ALC voltages at all. In fact, I recommend against it, because if the plug isn't in in full, these foreign voltages will directly go to the CPU and may cause damage, and you'll need an external battary, yeach.

The ACC plug is a stereo plug. The other pin of the plug is called 'TXREQ' and does produce a steady carrier when connected to ground, exactly what you need to tune.

I designed a small mod which tricks the FT897 into thinking it runs on battaries when TXREQ is grounded, and it automagically reduces it's output power to 20W max, irrspective of the actual power set.
When you release TXreq, original power level is restored, hence tuning is automatically done on lower power just as you want.

You can find a detailed description of the mod in the 'files' section of the Yahoogroups FT897 group, just look for my callsign.

I believe this is a much cleaner solution than what you're trying to do?

73,

Geert Jan PE1HZG
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