Getting into HF is easy and challenging simultaneously for modern homebrewers ! The difficulty lies with the fact that almost all modern ham HF QSOs occur in SSB and homebrewing SSB rigs is a bit tricky . However it is easy to get a large amount of resource from internet regarding the various transceiver circuits , test gigs etc . 40m (7MHz) is a ham band that is still very active . However all my attempts to make a rig for this band failed due to VFO problems. Browsing the web one of the circuits that grabbed my attention is an old one - Doubler VFO by VU2ITI - OM Mani .( See here www.qsl.net/vu2msy/homebrew/Ceramic_Resonator_VFO_VU2ITI.pdf ) It a great circuit and the concept is beautiful . Make a ~3.5MHz sine wave , use a multiplier (a nonlinear circuit) , get a 7Mhz output ( and perhaps some undesired harmonics Thanks to OM Joseph Fourier , HI !) . This sounded beautiful as 3.58MHz ceramic resonators are available in plenty in my hometown ( Payy...