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

[Dick]

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.