There was also a design for a six meter amp in one of the fairly recent ARRL
handbook that used a compressable coil. The amp was tuned by turning a threaded
rod which in turn would compress or expand the the coil using the Cout of the
tube.
Frank
W2FCA
"Michael J. Tubby B.Sc. \(Hons\) G8TIC" <mike.tubby@thorcom.co.uk> wrote:
>> The most significant problem is that the large input and output
>> capacitances are hard to deal with at 6M. ?At least that is my
>> conclusion. A while ago, on this reflector, someone was dealing
>> with a similar problem (although not with the 8171), and suggested
>> using the W6PO circuit, scaled to 6M.
>>
>> Thanks, Barrie, W7ALW
>>
>You might find a better approach would be to use the L/L-C tank circuit >with
>a rotating shorted-turn loop to vary the L - my 3-500 6m amp (copy
>of the 1971 QST design) uses this technique to great effect. I got the
>tank circuit to work first time by putting a 3K3 resistor across the
>tube and sweeping the output socket and adusting (bending) the coil
>around until it covered 48-52MHz when rotating the shorted-turn loop.
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