[Antennas] Link vs Pi

[Adam Farson]

Hi Ron,

Agreed. A push-pull tube PA with a symmetrical, link-coupled anode tank
circuit will most likely be compliant.  The low-pass characteristics of a
properly-designed pi-network are such that a pi-output tank in a
single-ended PA will also be compliant. Both types of tank circuit are
designed for a working Q of about 12.

The coupling transformers used in solid-state RF power amplifiers have a
working Q of unity or less, so the filtering action of a tuned tank circuit
is absent. This imposes more stringent requirements on the LPF bank
following the PA.

Cheers for now, 73,
Adam VA7OJ/AB4OJ


-----Original Message-----
From: antennas-bounces at mailman.qth.net
[mailto:antennas-bounces at mailman.qth.net] On Behalf Of Ron Youvan
Sent: 16 January 2006 16:24
To: a
Subject: Re: [Antennas] Link vs Pi

> It is interesting how solid-state transmitter technology has brought 
> the wheel almost full circle. All solid-state linear HF PA's are 
> push-pull, and transformer-coupled, with a bank of LPF's following the 
> output-transformer secondary.

   Remember push pull cancels out the second harmonic making it easier for
the output filters to meet the spurious requirements of our rules &
regulations.
-- 
    Ron  KA4INM



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