This is a updated collection of easy to build projects for radio amateurs and swl's.
Have fun.
73 John

Thursday, April 19, 2012

Multiband end fed antennas 3.5 - 30mHz


The picture shows 1 turn to much in the secondary winding (red)

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

Update 2014-03-21
I live in a apartment on the first floor so you can imagine my antenna problems....
My balcony however is 10m. long ,so i mounted a horizontal endfed antenna without the coil, for 20-10m on the wooden windowframe . Because of the capacity of the wood and the paint overall length was reduced to aprox. 9m.. but provided a near 1:1 swr on 20 and 10m.
First contact on 10m. was with 5B4AHL (5-9) on cyprus folowed by 9K2QA (5-9) in Kuwait  and 4S7VG (5-8) in SRI Lanka despite of a huge pile-up. This antenna is going to stay HI.
Disclaimer:I'm not responsable for any damage due to reproduction of my projects.

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