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Re: [Amps] AL1200 on AM - max carrier?

To: "" <>
Subject: Re: [Amps] AL1200 on AM - max carrier?
From: Kimberly Elmore <>
Reply-to: Kimberly Elmore <>
Date: Thu, 30 Oct 2014 07:04:22 -0700
List-post: <">>
Any amp will be inefficient when used as a linear amplifier for AM because as 
drive is reduced, efficiency is reduced. They will all generate a lot of heat 
in this application. However, the AL-1200 should hold up well to the 
lock-and-talk culture. In AM, PEP is 4X the carrier, Overall, you want the 
carrier to be at 1/4 of the amp's rated PEP output. 

Assuming the driver  generates 100 W output, tune the amp for max or 1500 W 
output (whichever comes first) with the amp in SSB mode. You want SSB mode 
because you want the best linearity. Whether or not you use SSB or CW makes 
little difference in the efficiency for your application but makes a big 
difference in linearity. 

Usually, when the driving rig is in AM mode, the carrier is reduced to 1/4 of 
the max PEP SSB output. In such cases, you should see no more than 375 W 
carrier power (375 x 4 = 1500).

If you are trying to drive it with an older plate-modulated tube rig, you ill 
have to be careful if you reduce the power output because the modulation 
transformer is designed with a particular output impedance in mind. If you 
reduce the drive to the PA, the impedance changes and you will have to set the 
proper audio level using a scope or modulation monitor.Start with audio gain at 
zero, bringing it up slowly. Otherwise, you risk arcing in and destruction of 
the modulation transformer. 

Kim N5OP

On Thursday, October 30, 2014 8:05 AM, Gary Smith <> wrote:

One thing for sure, run it at the CW 
setting, use the lower KV setting and you 
will run far cooler for a given KW out.


> I want to run my AL-1200 on AM for a short stint (2 hours operating 
> time, 50% overall duty cycle). I have tested it at about 225 watts 
> carrier output, and with moderately high duty cycle transmissions (known 
> in the AM crowd as 'Old Buzzarding'), it gets quite hot.
> What is the max recommended AM carrier power for long-winded transmissions?
> Also, I'm assuming it should be tuned up for proper operation at double 
> the carrier power.
>   I searched the list finding no real answers.
> Thanks,
> Tony, K1KP

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