An Amateur Radio Base Station

Yaesu FTDX-10 HF SDR Transceiver
 MFJ  998  1.5 KW Tuner
Ameritron AL-811H  800 Watt Linear 4 tube Amp

A big thank you to the [Sitka Ham Amateur Radio Klub KL7SRK] for all the assistance and inspiration for this project.
SHARK Facebook Page

AL5X  4 - 13 - 2023

Hardware and Functional wiring - research with some equipment yet to be received and assembled.
It represent many hours of collecting knowledge in hopes I get this right on the first try.
I cannot be responsible for damages to any ones Equipment or life, know that voltages around a Linear Amplifier can be lethal.
RF at higher power can cause burns as well. Never operate the Linear Amp without the cover on.

Reference Manuals, [See Section - URL's listed below] Please read all manuals for safety warnings, and safe operation.
And lastly have fun, see you on the air 73'.

Photo of Stack

Cabling Layouts

We considered three options for cabling between the Yaesu FTDX-10 and the Ameritron AL-811H linear amplifier.
Plus the one cable that will go between the FTDX-10 Radio and the MFJ 998 Tuner for all three.

1-Using the Yaesu Interface Cable SCU-28 Wiring Option

Cable Pinnout

The Option 1 - SCU-28 cabling method should work with the Ameritron AL 811H as it uses low voltage 12 vdc relay keying control.
It must not be used with other older linear Amps that used HV AC or HV DC to pull up the transmit relay.
Older amps will need to use the Ameritron Amplifier Keying Interfaces ARB-704i2 buffering box. Be sure to get the
model with the i2 on the end, and the cable PNP-10MY for a Yaesu FTDX-10 , or the correct cable for your particular radio.
See Option 2 below.

2-Ameritron Amplifier Keying Interfaces ARB-704i2 Wiring Option

704i2 Keying Interface photos

This option is probably the safest way to interface the FTDX-10 to the Ameritron AL-811H amplifier,
as it fully buffers the Keying line and also brings out the ALC line.
This makes it plug and play for the most part if you can get the correct cable PNP-10MY
for the FTDX-10 Amplifier 10 pin DIN socket.
As this cable has not been available from any of the normal sources,
we chose to make our own in option 1 as shown above until our correct cable arrives.

The cable is due to be available again sometime around June 2023.

3-DXE-YSU-10P-RCA Interface Cable Option

Photo Keyer Cable option 2

DX Engineering also has another cable, with out the ALC line, only the Keying RCA jack that can get you up with this gear,
but the danger of not having ALC power limiting is then present.  DXE-YSU-10P-RCA is a 10 pin DIN to single RCA jack.

The ALC adjustment will ensure the FTDX-10 does not exceed 80 watts output which is the
maximum exciter drive power the Ameritron Amplifier uses at full power out.

All Options also use MFJ 998 Tuner to FTDX-10 Interface Cable MFJ-5114Y

MFJ-5114Y. Pre-wired Rig Interface cable for Yaesu and compatibles.

MFJ-5114Y Photo

8 Pin DIN  on lower left of radio rear Tuner Plug to MFJ 998 RJ 45

The Xmt "key on" RCA line must be run through the MFJ tuner's [Amp enable "In" and "Out"] RCA ports.

This is so the AMP will not key on, when the MFJ tuner is tuning, if you forget to set the amp in the bypass mode.
This is for safety as the tuner cannot tune over 125 watts of power, and the tuner may not tune correctly with the amp in operate mode.

This is yet to be fully tested by me, but the video below shows the correct wiring, and operation.
The tuner uses a fast reed relay to open the circuit when it goes into tune mode.

SCU-28 Method

Tuner Wiring Photo

Sample Video on Youtube

Power Outage Considerations

During an AC power outage, the Amp will be bypassed and shut down. For the Tuner to operate it must be tied into the 12 vdc battery backup system.
The Tuner cannot run off DC power from the FTDX-10 radio jack as it draws 1.4 Amps, it must be run from the DC power socket on the back of the box.
With both the Radio and the Tuner powered off the battery backup system they will continue to work during an AC power outage.

Final Wiring Connections - Plug and Play

Connections Diagram

I do not know if the FTDX-10 radio is smart enough not to operate the "XMT on" on the Linear Amp port,
when it operates the tune function on the Tuner port. This will have to be metered to determine if the
"Keying on" RCA line must be run through the MFJ-998 Tuner Amp Enable in and out jacks.

Reference Manuals

MFJ-998 Product Manual
MFJ-998 Schematic

Ameritron AL-811H Manual and Schematic

Yaesu FTDX-10 Download Pages
Yaesu FTDX-10 Service Manual

Ameritron ARB-704i2 Manual and Schematic

DX Engineering
All component and Radio were ordered from DX Engineering as they ship to Alaska USPS.
Cable connectors and heavy coax lengths with ends, were ordered on Amazon.


This is my first station with a Linear Amp. Often times as we assemble and build, errors are discovered.
I may add notes or make changes to this document during the turn up and operating "learning curve."
To the best of my knowledge it should all work!

Dave L  4 - 13 - 2023

End Document

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