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Re: [Amps] Alpha 8410 using 4CX1500B - why?

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Subject: Re: [Amps] Alpha 8410 using 4CX1500B - why?
From: "Leigh Turner" <>
Date: Thu, 30 Oct 2014 10:51:07 +1030
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Indeed Peter.

And high plate bias current and associated low efficiency is part and parcel
of achieving high linearity and low intermod from AB1 tetrodes.

Low plate idle current and low IMD are mutually exclusive objectives. There
are no free lunches here :-(

At least in an SSB linear amplifier one can significantly offset the impact
of high idle current with a competently implemented EBS system. When EBS is
done properly there are no audible or spectral artefacts stemming from the
tri-state transitional bias switching.

An alternate possibility along the lines of what Manfred was advocating may
also prove useful. I quite like simple analog linearization systems that
extract improved intermodulation distortion characteristics from the
imperfect PA using a pair of log-amps for detectors, one on the input and
one on output of the RF power amp (via a signal sniffing directional
coupler) feeding a comparator then the error signal drives a VCA on the
tube's bias feed. I much prefer this hardware based approach over doing the
PA linearization in the current fad using SDR pre-distortion correcting



-----Original Message-----
From: Amps [] On Behalf Of Peter Voelpel
Sent: Thursday, 30 October 2014 10:20 AM
Subject: Re: [Amps] Alpha 8410 using 4CX1500B - why?

Funny, most TV transmitters in Europe with combined sound and vision
amplification have been with tetrodes in their final because of their high

I never saw a commercial communication HF amplifier made in Europe with
triodes and all were designed for ISB. 


-----Original Message-----

From: Amps [] On Behalf Of Carl

Welcome to tetrodes Manfred. Very few are designed for very low IMD 

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