This is a 200 Watt PEP step up transformer for end fed full and half wave antennas without radials, designed as a 200 Watt PEP upgrade by PA0EJH for the originaly Par Electronics designed 25 Watt HF endfedz multiband end fed antenna.
The original design has a 27/3 turn ratio ( 1: 81 ) on a small 43 material toroid, but the larger toroid has more wire so the nr of turns had to be reduced for max.efficiency on 10m. The coil now has a 16/2 ratio ( 1: 64 ) For max. performance the 2 turns to ground must be twisted . The 100-150pF capacitor gives a better match on 10m.and both windings start at the ground side of the coil .Don't try to stack toroids for more power for this will increase overall inductance . This makes it impossible to tune the high bands. The best results are obtained with a small toroid.....The 3 band antenna has a length of 10.1m. followed by a coil of about 34 uH ( 90 turns 1mm enamel wire on a 19mm pvc tube ) and a endpiece of 1.85m , offering you a perfect vertical or horizontal antenna for fieldwork at 40 -20 and 10m. There is also a 5 band version with 20.35m wire followed by a 110 - 120uH coil ( about 260 turns 1 mm cul on a 19mm pvc tube ) and a 2.39m. endpiece. This antenna works on 80 - 40 - 20 -15 and 10m.without radials and has a verry low swr combined with a low noise level. Keep in mind that every end fed / vertical needs some kind of counterpoise to push against and in this case that's the coax , so don't forget a line choke near to your transceiver.
|Tranformer with 150pF and 3K3 resistor to ground|
Transformer made by Tony PA3GWO on a smaller FT140-43 toroid for max. 100 Watt pep
High power endfed for 80-40m designed by PA0EJH
Stack 2 FT240-43 toroids and add 3 primary and 21 secondary windings with 1.5mm enamelled wire to form a 500 Watt key down transformer.
Here is the well build transformer optimized for 80-40m. by Gus, VK6WB . You can clearly see the 2 toroids for high power use.