A desire to build something useful during the Winter months of 2008 and use up some accumulated components resulted in this linear amplifier project.  It's a 6 band amplifier - 80,40,20,17,15,10 metres.  Due to the reasonably high plate impedance of a single 3-500Z necessitating a large inductance (approx. 38 uH) in the Pi tank circuit, 160 metres was dropped in favour of the 17 metre band.  The inductors in the tank circuit consists of two stacked Amidon T-200 cores and two 'air' cores.  The band switches and input tuning network are from a Kenwood TL-922.  A Collins plate transformer and a full wave bridge rectifier provides a solid 3kV of D.C. for the plate supply.  The rectifiers and filter caps are housed in the compartment directly below the band switch and a TRIAC slow start circuit will be employed to slowly ramp up the A.C. supply at switch-on.  The R.F. portion of the amplifier is pretty much conventional and as per the handbooks.  I'll be using an antenna relay from a Kenwood TL-922 for the antenna switching function.

The meter scales were redrawn and printed on a colour laser printer using some software I acquired on the web.  I have some software to create a front panel lettering template which can then be professionally reproduced by a sign writer to engrave a couple of sub panes.  

Go Back