Notes on 75 Meter Europe Wire Beam

14 September 2003 - PJ2DX

1. Initial reading was 3.500 1.2:1.0 42 ohms

2. Collapsed reflector and director out of shape - no change in resonant freq or impedance or SWR.

3. Short out ladder stub at bottom center of loop: 3.499 1.1:1.0 40 ohms. Essentially no change as predicted by ON4UN article because this is a voltage max -- lumped impedance will only affect the antenna where there is current flow, near the corners. (Basic electronics.)

4. Fussed for over two hours with shortening the driven element. Finally ended up completely removing the ladder Jim and I made and then added 12 feet of length to the loop. Ended up with 1.2:1.0 at 3.880, 42 ohms.

* Lesson: When the DE is within three feet of the ground, or lower, the resonant frequency drops dramatically. Raising it higher than about 3 feet has negligible effect.
* Lesson: Dropping or raising the reflector in to position has little effect -- only the slightest meter reading changes.
* Lesson: Adding one foot of wire, hanging vertically toward the ground at the center of the bottom of the DE lowers the resonant frequency 20 kHz.
* Lesson: All readings were taken in the field with about 20 feet of coax from the feedpoint to the meter. Convenient, and removes any bogus effects in the intervening coax, switches, and possibly filters.

5. Reflector, as measured at 1 foot away from corner on bottom side, resonates at 3.500. Desired frequency is 3.591, which is 5% below 3880. 

6. With the ladder line removed, netting a simple loop, reflector is at 3.996, with 2.0:1.0 SWR (because it is not measured at the same point as the coax feedline). I put the ladder line back in the reflector and it is now at 3.570. This is close enough to the 5% lower target. the freq went up from the first measurement because I had to cut out a bit of length.

7. Director readings at the NW corner seem bogus -- it doesn't really dip anywhere.

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8. Restored the ladder to the reflector and got resonance at about 3.490, but not a pronounced dip -- need to measure this at the feedpoint on the next effort. For now, it is good enough to reflect.

9. Added approximately 20 feet of single conductor wire at the center of the bottom of the driven element, with a SPST ceramic knife switch. This capacitive loading, per ON4UN, works PERFECTLY and provides a good CW dip at about 3.510. this technique will also be very effective for tuning the parasitic elements, once their actual resonant frequencies have been determined with confidence. 

10. Next steps: Put in post at wall for reflector, and same for DE and director, making them permanent and slightly higher. Then, remove the ladder from the reflector and make it a single wire, making it resonant at the desired SSB freq. Do the same at the director. Then add knife switches to lengthen those wires to achieve the desired CW frequencies.

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In on-air tests, Europeans reported one S unit (about 6 dB) better with the loop, and in the US we were getting 20 - 30 over 9 reports all the way to the West coast at about 0245Z. I could also hear LU very well with the loops.

27 March 2019

KB7Q replaced two knife switches, strung up the capacitor wires, and tested, all looks good.

27 October 2023

Found broken wire coming out of center insulator. Threw out the fixture and replaced with a direct pigtail connection.

11 November 2023

Above repair did not work. I had to fabricate a new coax pigtail, replace two bad barrels outside, and replace the 25 foot piece of coax from the hardline up to the pigtail. Looks like a lightning surge probably took all of these out, although it was not hard, burned parts, but rather SWR of 4:1 or so introduced by the bad parts. Tests good at high power November 12.