[ICOM] Why are we so SWR-phobic

[Adam Farson]

Hi John,

The following should address your concerns about SWR:

Excerpt from "HF Radio Systems and Circuits", Sabin et al., ch. 12,
pp.483-484 (the "Collins reference book"), in which linearity criteria for
solid-state RF power amplifiers are discussed. Note the statement on load
VSWR.

A well-regulated collector/drain dc supply is essential to obtaining good
linearity. It allows optimizing the collector-to-collector (or drain) load
resistance for good efficiency and controlled current swing without going
into saturation. The collector-to-collector (or drain) load impedance must
be maintained as close to resistive as possible. This in turn requires
optimizing the output wideband transformer(s), combiner (if used), and
lowpass filter passband VSWRs to as low values as possible.

The base-/gate-bias regulator must be absolutely stable and free from RF or
envelope modulation. The bias regulator for a BJT amplifier must be capable
of supplying the peak current required from the lowest-gain devices
anticipated in production and at the highest RF power level. Careful
attention to the bias supply performance is necessary for the best linearity
that the devices are capable of.

Cheers for now, 73,
Adam VA7OJ/AB4OJ

P.s. The autotuners in my transceiver and amplifier take care of the problem
very nicely for me.



Scanned for viruses by Blue Coat
http://www.WinProxy.com/