Heathkit SB240 2kw amplifier. What! You say you never heard of a Heathkit SB240 amp. Well you and most of the ham radio operators around the world never heard of this amp, and there is a story behind it. This is a very, very, very, rare piece of Heathkit history.
Photo by KC8IV
First let us tell you about the amplifier and some of it’s very unique features, that placed this amplifier well ahead it’s time. This amplifier was built around the very successful SB220. It uses the very same 3-500Z tubes. It was housed in the cabinet style of the SB104 series and here are some of the very unique features about this amp. Plug in transformer, SSB/CW switchable power supply so you can run 1kw CW/SSB or 2kw SSB. Temperature controlled two stage fan. Built in over drive grid current lock out protection. Built in SWR protection at 5:1 swr. Zero signal plate current. Normal and over drive LED’s. Multi-metering of forward PEP, reflected power, plate current, grid current, hi voltage. Less than 100 watts to drive. Operates on 80,40,20,15,and 10 mtrs. It is currently wired for 220vac but can be rewired for 125vac if you wish. This amplifier is like an SB220 on steroids.
Photo by KC8IV
Since Heathkit no longer exists, KC8IV have decide that he now can sell this amplifier. He have had this amplifier in storage since 1976 and it is beautiful. It does have one scratch top right rear and one very small paint chip left front top corner. During beta testing to disguise the amplifier the front trim strip said HOHMBREW Electronics model SIGNAL 2400EX and was painted a two tone tan and brown color.
Here is why you never heard of a Heathkit SB240. When this amplifier was developed, it was sent from final engineering through the normal Heathkit manual proof build cycle, to establish not only the engineering and build ability as a kit, but it also was an opportunity to build using production parts. This however was a limited proof build of only 10 units. So there was ONLY TEN of these amplifiers ever built. To my knowledge there are only three still in existence. As far as engineering and manual department was concerned, this amplifier was ready for final production. Here is the reason this amplifier never make it to market. About the time this amplifier was ready to go was about the time the FCC was taking a stance that they were going to ban the manufacturing of amateur radio amplifiers with 10 mts on them. The decision hadn’t been made for sure yet, but the amateur radio product manager in charge at the time, decided he didn’t want to pick a fight with the FCC over the issue. So he decided to put the product on the shelf and that’s where the design stayed. How do he know this is true. Because he worked at Heathkit for 25 years and I was one of the 10 builders. Some of us were lucky enough to retain our proof build units.
Photo by KC8IV
So KC8IV have the ONE OF THREE that still exists, full kit building manual, operating instructions and schematic.
To ship the amplifier he will pull the transformer and tubes and ship in separate boxes unless you want too pick it up.
Asking $2800.00 OB reasonable O, plus packing and shipping cost. You can figure around 60#’s for shipping. Please also be aware that since this amplifier is over 36 years old, I am selling it, as is but you can see in the pictures that the high voltage is around 3100 vdc.
He will accept USPS postal money order, cash or your bank check. Shipping after check clears.
If interested please contact KC8IV@arrl.net
Read also April 2013 QST (pages 96-97)
OM POWER high power HF combiner OM10C
The high power combiner OM10C is designed for all short wave amateur bands from 1.8 to 29.7 MHz and maximum 10kW PEP output power.
Specification of OM10C:
OM POWER HF automatic linear amplifier OM3501A he automatic linear amplifier OM3501A is designed for all short wave amateur bands from 1.8 to 29 MHz (including WARC – bands) and all modes. It is equipped with a one piece of ceramic tetrode GU78B.