Hans,
I'm sure it would work fine, but switched pi-nets seem much more practical for
an 8 or 9-band amplifier.
73,
Vic, K2VCO
Fresno CA
Hans Goldschmidt wrote:
>
> No need for ARCO trimmers, bifilar filament chokes and pi input filters in
> grounded grid linears:
>
> Use instead a coil made of copper tube beetween cathode and ground which
> feeds one filament connection. The cold end of the coil is rf grounded by a
> condenser-the coil is tuned by a variable condenser across the coil ( 13 uuF
> per meter wavelength ) - excitation fed to the coil via a tap connection.The
> other filament connection is fed with a wire inside the coil grounded by
> another condenser at the cold end as shown in the RADIO HANDBOOK twentieth
> edition. ( a six meter 3-400Z linear on page 22.12.). The circuit was also
> shown in several EIMAC newsletters for example AS6 on grounded grid linears
> as well as in AS5 describing a 3-400Z linear. Another newsletter on 3-400Z
> and 3-1000Zs had the circuit. As far as I remember the same circuitry was
> used in an QST 3-1000Z amplifier years ago.
>
> The circuit covers easily many of the higher amateur bands without any
> switches but may be rather bulky on the lower freqencies as you must there
> use broadcast type variable condensers or switchable parallell fixed
> condensers. I am not sure you could use the same input tap on all bands.
>
> Has anybody ever tried the circuit? / de Hans SM5KI
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