<html><body><div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:12pt"><div>While doing a google search concerning the Heathkit SB-240, I came across a couple of blogs where some users think this amplifier was simply an SB-220 with a face-lift. Well, I was employed as a manual writer when the SB-240 was being engineered and know all about it. I even have one. Although the power supply and tank circuits between the SB-240 and SB-220 are very similar, there are several differences. One obvious was that is was styled to match the SB-104 line, which was our top-of -the-line amateur HF equipment at the time. The HL-2200 and SB-1000 amplifiers were not even a thought at the time.</div><div> </div><div>First, the SB-240 has zero idling current, the SB-220 does not.</div><div> </div><div>The SB-240 has an additional circuit board (approx. 6" by 6") that is mounted between the front panel
and the filter stack, and a small circuit board underneath. These additional circuit boards provided the circuitry for the following features:</div><div> </div><div>1. Pushbuttons that allowed you to select Forward Power, Reflected Power, and PEP.</div><div> </div><div>2. SWR and overload indicators and protection. If a high SWR or overload condition was detected, the amplifier would automatically switch to standby.</div><div> </div><div>3. A pushbutton so you could manually switch the amplifier to standby.</div><div> </div><div>Although the amplifier was completely designed and went through the normal two proofbuild cycles, it never made it to shipment for the following reasons:</div><div> </div><div>1. The SB-8000/SB-9000 transceiver was being designed and the SB-240 would not match the styling of this new transceiver.</div><div> </div><div>2. The amplifier included 10 meters during the time when the 10-meter ban was
eminent.</div><div> </div><div>3. An adjustment needed to be made through a hole in the underside of the cabinet. If a regular screwdriver was used to make this adjustment, the user could come into contact with full RF power. The company didn't want to take this chance.</div><div> </div><div>I used my proofbuild unit to make most of the 354 DXCC contacts that put me on the ARRL Honor Roll.</div><div> </div><div>Now, does anyone want to know about my SB-2001 amplifier?</div><div> </div><div>Randy, K8TMK</div><div> </div><div> </div><div> </div></div></body></html>