[Amps] Duty cycle for processed SSB in contest conditions?

[Carl]

Youre to be commended for this as most of the SS amps I hear on VHF/UHF 
sound worse than on CB plus the low noise floor makes it even more 
destructive to others on the band.

About a 25% duty cycle is considered the base line without processing and 
50% is already overdoing it. About a -30db IMD3 is considered the minimum 
considering even ceramic tetrodes can do that or better and some triodes get 
to around -45 dB.

Of even more importance is what are the other IMD's out to say 5-10 KHz or 
so. Some SS stays pretty flat for a long way out.

Also consider the exciter which in many cases has horrendous phase noise 
plus high IMD out of the box without even processing.

Carl
KM1H




----- Original Message ----- 
From: "Conrad Farlow" <conrad at g0ruz.com>
To: <amps at contesting.com>
Sent: Saturday, February 22, 2014 12:25 PM
Subject: [Amps] Duty cycle for processed SSB in contest conditions?


> Can anyone suggest what the duty cycle for sensibly processed SSB would be 
> during contest conditions? When an LD-MOS PA is backed off to achieve good 
> linearity then the efficiency reduces from 80% at P3dB for CW or 100% duty 
> cycle data modes down to around 65% for IMD3 of better than -30dBc. The 
> thermal impact of this is quite severe and I am trying to calculate what 
> is acceptable for SSB during a typical contest. Personally I am looking at 
> 6m and above but it holds true for HF amplifiers as well.
>
> I know that it is difficult to say what the ratio of TX/RX time is but 
> lets be pessimistic.
> -- 
>
> __________________________________________________
>
> 73
>
> Conrad G0RUZ IO93FR
>
>
> North Wakefield Radio Club
>
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