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Author Topic: Connecting a Yaesu FT-897D to a Heath SB-200 amplifier  (Read 6737 times)
EA8NQ
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« on: May 28, 2014, 11:27:21 AM »

Hello all...  I want to use a Yaesu FT-897D with a Heathkit SB-200 amplifier.  I bought and installed the "soft-keying" SK-201 module from Harbach inside the amplifier, so the FT-897D can switch the amplifier.  But I don't know if the ALC voltage from the amplifier can be applied directly to the transmitter.  The amplifier's manual states something about a 10 volt threshold (nothing about how many volts come from the ALC jack), and the transmitter's manual says it can handle 0 to -4 volts.  Has anybody tested this?  Is there an interface to use?  Is really there any need to connect the ALC from the amplifier to the transmitter?  Thanks a lot to everyone...

73 de Isidro, EA8NQ
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KM4AH
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« Reply #1 on: May 28, 2014, 01:00:25 PM »

I don't see any point in connecting the ALC if you set the transmit power of the rig to the drive level you need for your amp.
« Last Edit: May 28, 2014, 01:02:46 PM by KM4AH » Logged
VK5DO
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« Reply #2 on: May 28, 2014, 01:33:37 PM »

Ignore the ALC.  Don't even use it.
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W7VO
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« Reply #3 on: May 29, 2014, 01:48:33 PM »

Agreed..... No ALC needed.

 Smiley
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EA8NQ
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« Reply #4 on: June 02, 2014, 10:04:04 AM »

Thanks a lot to everyone for the answers.  Yes, may be the ALC is not so necessary if I drive the amplifier with the proper level.

Best 73!

Isidro, EA8NQ
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WA7PRC
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« Reply #5 on: June 02, 2014, 07:42:33 PM »

Yes, may be the ALC is not so necessary if I drive the amplifier with the proper level.
...as determined by your monitor oscilloscope.

If I still used my olde Heathkit SB102, I'd consider connecting ALC from my SB220. However, I learned that ALC won't prevent amplifier underloading (and considerable flat-topping & splatter).

Today, I use my SB220 with my Kenwood TS850 w/o ALC.  I monitor the RF waveform, and utilize audio peak limiting/compression (Symetrix 528E) prior to the rig's microphone jack. Once setup, the audio processing prevents overdriving the amplifier. I see MFJ offers a similar unit, the MFJ-655B. Its downward expander does a good job of reducing background noise when you pause, and the parametric equalizer can be used to shape frequency response.

vy 73,
Bryan WA7PRC
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