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@g0ruz.com>
To: <amps@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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