[Amps] ALC control with Yaesu FT- 897D and Ameritron ALS-600

[Jim Garland]

Hi Dick,
I believe you're making the hookup of your FT-897D to your ALS-600 seem
harder than necessary. First, you don't need the Ameritron interface module
at all. A modern solid state amp will already be compatible with your
FT-897D amplifier keying circuits.  Relay interface devices are useful for
older amplifiers whose relays require more voltage or current than newer
transceivers can supply, but that certainly won't be the case with a modern
solid state amp.

Second, if you want to use ALC to control your Yaesu, then just run a single
shielded cable from the ALC accessory jack on your transceiver to the ALC
output on your ALS-600. I've not used either piece of equipment, so can't
advise you specifically which cable to use. However, most folks these days
advise against using ALC at all with an amplifier, because ALC introduces
some distortion to the transmitted signal. Some modern transceivers, such as
the Elecraft K3, don't even have an ALC input jack. An ALC was helpful in
the days of vacuum tube transceivers which didn't have an adjustable power
output control. For modern transceivers, the recommendation is simply to
turn down the power output to avoid overdriving the amplifier.

Thus, if this were my equipment, I'd just hook the output  of my transceiver
to the ALS-600, plug in a single relay control cable, and get on the air. If
others disagree with me, I'm sure they will weigh in with their own
opinions. Good luck, and enjoy your nice new station.

73,
Jim W8ZR


> Recently I purchased the following equipment with the idea of having a
"Yaesu" FT-897D
> serve as an exciter for an "MFJ ALS-600 solid-state amplifier.  The MFJ
amplifier comes
> complete with the appropriate power supply.  An optional piece of
equipment that can be
> purchased and used with the ALS- 600 amplifier is the "Ameritron",
ARB-704, solid-state
> interface module.  The ARB-704 module connects between the radio and the
amplifier and
> serves as protection for the radio from the harmful effects possible from
the amplifier and
> the T/R relay.
> 
> "Plug and Play" cables specifically constructed for a wide variety of
radios can be
> purchased with the ARB-704 interface to connect the interface with the
radio and amplifier.
> The plug-and-play cables fit the wide variety of jacks provided on
different brands and
> models of radios that can serve as connections for control functions.
> 
> Throughout MFJ's discussions in the operation manual on station set up,
interfacing, and
> operation of the amplifier in a multitude of transmission modes another
cable is mentioned
> in addition to the "plug-and-play" cables.  The  second type of cable
furnished in the cable
> package is a collection of three "ALC" cables.  The ALC cable is a
shielded audio type of
> cable having RCA plugs on both ends.
> 

> In my radio configuration I have a "Yaesu" FT- 897D transceiver;
"Ameritron"  ALS-600
> solid-state amplifier; Ameritron ARB-704 solid-state relay interface -
with MFJ plug-and-
> play cable constructed specifically for the FT- 897D transceiver.
> 

> Each of the above three devices have a ALC jack on their rear panel.
> 
> The Yaesu FT- 897D transceiver uses an "acc" jack to provide an ALC
connection.  The
> schematic of the accessory jack shows that a 3.5 mm, 3-pin plug is used
with the"acc" jack.
> The sole function of the accessory jack and its 3-pin plug is to provide a
means for
> receiving ALC control signals from the amplifier.   The jack accepts
"external ALC
> voltage" from the linear amplifier on the tip connection of the plug,  the
"Transmit Request"
> command is on the ring connection.  The main shaft is a ground return.
> 
> I purchased the accessory "plug and play" cable that is manufactured to
connect my specific
> transceiver to the rest of the system.  The part number for the
plug-and-play cable package
> is  "PNP-8M".  The "PNP-8M" cable has a  8-pin mini-DIN plug to connect
the
> transceiver's CAT/LINER jack on one end and a 5-pin connector that fits
the "multiport"
> jack on the interface module.
> 
> This accessory cable package is supposed to contain all the cables needed
to make the FT-
> 897D work with the ALS-600 amplifier.  Nothing is said in the instructions
concerning the
> use of the "accessory jack" on the rear panel of the FT-897D transceiver.
Because the cable
> nomenclature can become complicated I have summarized the contents of the
accessory
> cable package:
> 
>           A. One "plug-and-play" cable manufactured specifically for the
FT- 897D transceiver
>           B. Three audio style cables with RCA plugs on each end.

> I called Ameritron technical support and ask if I needed to fabricate a
special cable with an
> RCA plug on one end and a 3.5 mm, three-pin plug on the other end to
connect the radio to
> the interface module.  The answer that I received was no.
> 
> The set up as I have described it does not have a connection to an ALC
jack on any of the
> three piece of equipment: the radio, the interface device, or the
amplifier.  The ALC signal
> cannot be correctly calibrated.  The ALC limiting control on the rear of
the amplifier does
> not correctly limit an ALC signal.  ALC voltage is passed even when the
ALC limiting
> control is in its lowest position.   The ALC can only be affected using
the "ALC  SET"
> control on the front of the amplifier.  This probably removes one of the
safety devices on
> the amplifier or radio as well as allowing excessive compression.
>
> I would appreciate advice from anyone having a similar set up or knowledge
of the station
> configuration I mentioned.
> Dick Zseltvay, kc4cop
> I have thought about using one of the audio cables and plugging one of the
RCA plugs into
> the ALC jack on the interface module and the other end into the ALC  jack
on the amplifier.
> I will wait and see if I get any response to my post before trying this.
> 
> 
>