Hi Jan, I've been down that path 4 times. Once 20 years ago and more recently for 3 amps under construction. The are: A 4CX1500B with stepper motor driven Plate & Load caps plus Pi, L & Grid roller coils. See: http://tinyurl.com/27qzs for some old photos. A design with 9 stepper motors driving 5 caps & 4 coils -- Don't ask what for! A Transistorized design with 5 gearhead motors driving 4 caps and a bandswitch. A 4CX600JA(x2) with gearhead motor driven Plate & Load caps plus a bandswitch -- The simplest configuation See: http://wc6w.50webs.com/wc6wamps/index.html?fr20.html/ for a.... parts list. In the design process, I considered the relative suitability of relay selected fixed components versus continuously variable parts. Motor driven designs with lumped variable components were selected in each instance based on cost & complexity. Viewing the link you included confirms my research! Here in the states, suitable vacuum caps may be had surplus for $100-$200, add surplus gearhead motors for $10-$20 each. Finally, a couple of gears plus a 10 turn pot and viola! Motor driven tuning. Roller coils were included in all my tube designs excepting the last one where the plate choke problem will be "eliminated". See: http://wc6w.50webs.com/wc6wamps/index.html?fr62.html/ For tune & load sensing, I've included ancient discriminator circuitry similar to that shown at: http://wc6w.50webs.com/wc6wamps/index.html?fr432.html/ Single Sideband Systems & Circuits (any editon) by Sabin & Schonike also details these designs. A PIC microprocessor is used to determine the operating frequency by direct counting. See: http://wc6w.50webs.com/wc6wtest/index.html?fr10.html/ And then to recall "preset" tuning positions from an EEPROM. Final tuning is implemented by allowing the discrimator & load sensors to drive the motors directly in an analog servo loop. The resulting postions are then updated in memory. It sounds almost easy when described in screen ink! :-) 73 & Good morning, Marv WC6W -- jan wrote: Hi, Has anyone tried on building an autotune HF amplifier? Something like the acom 2000 or like this http://kotisivu.mtv3.fi/oh3bu/ampproject.htm ? I´m interested in ideas on making it with a processor. 73 Jan, ON6ZG. * _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps ________________________________________________________________________ Try Juno Platinum for Free! Then, only $9.95/month! Unlimited Internet Access with 1GB of Email Storage. Visit http://www.juno.com/value to sign up today!