The K4QCD Dually is two antennas wrapped up into one package. On one side you have an End Fed Half Wave with a 49:1 transformer. Flip it over and on the other side is an End Fed Random Wire antenna with a 9:1 transformer. The dual transformer concept is the best of both worlds. Out in the field you can go either way with the type of antenna you wish to deploy, the only difference is the length of wire that you hook up to it.
The Dually end fed is a compact antenna kit that consists of two separate transformers. On one side is a 49:1 unun wound in a standard 12 turns primary and 2 turns secondary with the crossover in the middle that functions as an end fed half wave antenna without a tuner. On the other side is a 9:1 transformer in a trifilar winding that is the base for a non resonant antenna system. There are binding posts for either the 49:1 side or the 9:1 transformer side and a common binding post for a counterpoise. Two BNC connectors are supplied, one for each transformer. This antenna is intended to be used with only one side at a time.
As this antenna is a kit, you will receive two T140-43 ferrite toroid cores, one for each transformer, and four lengths of 18 gauge enamel coated magnet wire. Three of the wires are used with the 9:1 and one is used with the 49:1. This toroid and winding combination should allow for 100 watts phone and about 35 watts CW or data. Higher power levels may be used temporarily before the core saturates.
The ingenious part of the kit is that everything is built on a double sided printed circuit board. That streamlines the wiring of the transformer, especially for the 9:1 side. After you wind the transformers, You just need to put the wires through the appropriately marked holes and solder them in place.
K4QCD Design https://www.k4qcd.com/
The Dually End Fed Antenna: https://www.etsy.com/listing/1723883178/the-dually-hf-end-fed-antenna-build-kit
BNTECHGO 20 Gauge Silicone wire spool 250 ft: https://amzn.to/3SQOPea
End Fed Antenna Wire length resources:
Non Resonant Antennas:
https://ve3ips.wordpress.com/2021/11/02/the-best-random-wire-antenna-lengthsrandom-wire-lengths-you-should-and-should-not-use-jack-ve3eed-sk/
https://udel.edu/~mm/ham/randomWire/
Resonant Half Wave Antennas:
The formula for a 1/2 wave radiator: 468 / Frequency MHz = Length in Feet
https://calculator.academy/efhw-antenna-calculator/
https://www.sota-antennas.com/efhw.php
Timestamp
00:00:00 K4QCD Dually End Fed Antenna
00:02:15 Dually antenna specs and features
00:03:50 Assembling the Antenna
00:05:21 End Fed Antenna Suggested Wire Lengths
00:07:53 The Dually on the Air
00:12:13 My Thoughts on the Dually End Fed Antenna
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