I've been an active ham since I got my ticket in April 1977. I put a lot of effort into the antenna system from day one. I am a firm believer in using resonant antennas.
I enjoy working DX. Most of the time, from the primary station I run 100 watts. With my antenna system I find I have great results at that power level. If needed I will run the below pictured home brew amplifier.
Lately I’ve been operating more QRP portable then I have from the primary station. I find operating QRP to be fun and challenging. I’ve worked a lot of DX running only 5 watts with resonant wire antennas while sitting at a picnic table at my favorite park.
Home Brew Amp:
Pictured is my home brew amplifier that uses a single 3CX1000A7 tube in grounded grid. This tube is no longer made but is one of the smallest tubes that can be rebuilt. My low voltage power supply runs 2800 volts key down. At 100 watts of drive power the amp will easily produce 1500 watts out. My higher voltage power supply runs about 3200 volts key down and the amp will easily supply 1500 watts out with much less drive power. I tried to keep the Q of the Pi-L tank system around 12. The amp will cover 10 to 160 meters and has tuned inputs. It will cover the WARC bands by putting the tuned input swith in the bypass position and using the tuner in the radio to couple the amp. The plate dissipation of the tube is rated at 1000 watts. With extra cooling the plate dissipation can be as high as 1500 watts, as per Eimac specs.
The 3CX1000A7 is an old but interesting tube. It’s kind of a cross between an 8877 and a 3-1000Z tube. It was developed before the 8877. It looks something like an 8877 but uses a thoriated tungsten filament like the 3-1000Z uses. It is a directly heated cathode, like the 3-1000Z so the tube is instant on, no waiting for the filament to heat up like the 8877.
If cooled properly the tube can easily deliver over 2000 watts in grounded grid class AB2. I run my amp around 1200 to 1300 watts out. You’ll never see the difference between 1200 watts and 1500 watts, so why bother? At that power level the tube will last longer and everything runs cooler.
10 to 160 meter 3CX1000A7 Home Brew GG Amplifier
(1500 watts output power, all modes)
The power supply uses a 2.82 KVA hermetically sealed transformer configured in a full wave bridge and is capacitive input with 26 mf of capacitance. I use a step start with a time delay of 1.5 seconds. No load voltage is 3200 volts and full load voltage is 2800 volts. If driven with 120 watts the amplifier can easily produce 1500 watts output power, more into a dummy load. YES.....I do in fact have a 2500 watt dry dummy load !
Primary Station Radio:
My Kenwood TS 950 SDX.
There are two sets of paddles in the picture. To the left is the Bencher BY-2 paddles and to the right is the MFJ 490 Memory Keyer and Bencher Paddle combo. The TS 950 SDX has a great built in keyer but there are times I like using the memory keyer built into the MFJ 490. When I set up portable I either use the Begali Magnetic Traveler Light paddles or the MFJ 490. Over the many years I’ve been a ham I’ve tried numerous types of CW paddles. I found the Bencher Paddles to be a great design. I just picked up the Begali Paddles and really like them.