[TenTec] AM with the centurion amp

ac5e at comcast.net ac5e at comcast.net
Sun Nov 23 04:05:29 EST 2003


Adam's comments about the Centurion on AM are correct - but two more items deserve mention. 

The first is that 375 Watts of resting carrier is the legal limit under FCC rules. As Adam says, that's completely equivalent to 1500 Watts PEP SSB. 

The second is that overmodulation not only causes flat topping on positive peaks, it causes "flat bottoming" on negative peaks as well. You should be able to see a complete sine wave with no distortion on both positive and negative peaks. That is, your scope pattern with sine wave modulation should be a series of smooth sine waves with NO straight lines anywhere. 

If you get a flat top, or get that straight line between individual pulses, please back off on the audio gain. 90 percent modulation sounds great. 101 percent modulation sounds awful. 

73  Pete Allen  AC5E
> Hi John,
> 
> Any linear amplifier will work in AM mode. You will need to de-rate the
> amplifier by 6dB or 75%; if it is designed for 1.5kW PEP SSB or CW output,
> you will need to set the drive for no more than 375W resting carrier output.
> 
> You should check the output envelope with an oscilloscope or monitor scope
> to ensure that there is no flat-topping on voice peaks. The best way to
> perform this test is to apply a 1kHz pure sine wave to the mic input, adjust
> the Mic Gain until you just begin to see flat-topping, and back off the
> drive. At this point, the average power output (as measured on a Bird or
> equivalent power meter) should be 1.5 times the resting carrier output. The
> peak amplitude of the envelope at 100% modulation is twice the
> resting-carrier amplitude.
> 
> 375W resting-carrier is equivalent to 1.5kW PEP or 562.5W average at 100%
> modulation.
> 
> Hope this is helpful.
> 
> Cheers for now, 73,
> Adam VA7OJ/AB4OJ
> 
> 
> -----Original Message-----
> From: tentec-bounces at contesting.com

> [mailto:tentec-bounces at contesting.com]On Behalf Of John
> Sent: Saturday, November 22, 2003 18:55
> To: tentec at contesting.com
> Subject: [TenTec] AM with the centurion ampo
> 
> 
> Hello all can any one tell me if the centurion can work on AM  ?  thanks
> John
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