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[Yaesu] Automatic band change for Quadra and FL-7000 amplifiers

To: <yaesu@contesting.com>
Subject: [Yaesu] Automatic band change for Quadra and FL-7000 amplifiers
From: jeflanders@comcast.net (Jerry Flanders)
Date: Fri Feb 7 11:42:27 2003
My Quadra amplifier now comes on whenever I turn on my ICOM IC-756PRO, 
follows it from band to band from 160 meters to 6 meters (all WARC bands 
included), and selects the appropriate antenna port and ATU presets just as 
if it was connected to a Yaesu transceiver.

This can also be done with most other modern transceivers.

See  http://www.qsl.net/ab4oj/quadra/w4uk.html for full details and cable 
wiring instructions.

No mods to the transceiver or the amp are required.

FL-7000 users can apply the same information, but actual wiring 
instructions are only provided for the Quadra. (FL-7000 uses a different 


Yaesu's method of band changing uses a TTL level 4-bit code. When the code 
is generated inside compatible Yaesu transceivers and fed to the amp by the 
Yaesu "band data" cable, the amplifier follows the transceiver from band to 
band and also enables antenna tuner presets . Any method of generating a 
similar code will cause the amp to switch just as if the transceiver were a 

Ham logging program developers followed the Yaesu code to implement what 
they typically call "antenna relay" switching on a LPT port. Most current 
logging programs provide antenna relay signals, so those logging programs 
emulate the band-data signals of a genuine Yaesu-compatible transceiver. 
The LPT port provides TTL level signals, the Yaesu amp uses them directly - 
only a cable is required to connect the LPT to the amp. I used my Yaesu 
band-data cable by adding a $3 plug from radio Shack.

Jerry Flanders, W4UK

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