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Small HF Antennas NNN0OAA

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Presentation on theme: "Small HF Antennas NNN0OAA"— Presentation transcript:

1 Small HF Antennas NNN0OAA
Magnetic Loops Crossed-Field (CFA) E-H (“STAR”)

2 Magnetic Loops Not magic Keep losses low Capacitor challenges Low loss
High voltage High capacitance value Remotely variable

3 Capacitor Solution #1 “Dielectric loaded” variable capacitor
Jef Verborgt, SWL

4 Capacitor Solution #2 From ARRL Antenna Book Richard Plasencia, W0RPV
Aluminum plates separated by .063” glass 4-1/2” x 4-1/2” and .063” glass (K = 8, 300 V/mil) 16 to ,000 volts 300 V/mil x 63 mils = 18,900 V .224 x 8 x (4.5” x 4.5”)/.063” = 576 pF

5 Capacitor Solution #3 Glass dielectric (K=8) Art Heft, W2BRI
Electric screwdriver Nylon threaded rod drive

6 Capacitor Solution #3a Glass dielectric (K=8) Art Heft, W2BRI
Electric screwdriver Nylon threaded rod drive

7 Capacitor Solution #4 Integrated Capacitor
Bernie Wright

8 Crossed Field Antenna E-H Origin?

9 Crossed-Field Antenna Maurice Hately, GM3HAT and Fathi Kabbary

10 Does the CFA work? Egypt Australia Amateurs VK2EDB on 20 Meters
San Remo (Italy) AM broadcast, 6 meters tall Supressed unwanted sky wave A viable alternative (for AM broadcast) to the driven mast antenna

11 E-H Antennas Ted Hart, W5QJR
“For more than 120 years all antennas have been Hertz antennas, except the Crossed Field Antenna. In the future all antennas will be EH Antennas.”

12 E-H Antenna STAR configuration

13 E-H Antenna STAR configuration

14 E-H Antenna STAR configuration

15 E-H Antenna STAR configuration
Choke: See

16 How does it work? Synthesizes EM wave … or …
Common mode current on coax 5%? 11%? or more? See: Lloyd Butler VK5BR

17 Evaluations Ted Hart, regarding AM broadcast version
Few dB > than ¼ wave vertical with 120 radials, near field Steve Katz, WB2WIK/6 On air: -20 dB vs. roof-top vertical On air: -20 to –35 dB vs. beam Anechoic chamber: -20 to –22 dB vs. ½ wave dipole Adam MacDonald, N1GX (and WA1ZEB), 3/2003 Compass Rose (near Edwards AFB) -28 dB (zero length coax) Significant radiation from coax Desert site, south of California City, CA H R Henly, G3IHR The 20m and 40m versions were tested. The antennas both faired well compared to a 12AVQ and a G5RV when operated under similar conditions, i.e. at a similar height and position with relation to surrounding objects

18 E-H at NNN0OAA? So far … maybe –20 dB
Compared to semi-indoor inverted-L 70' indoor horizontal segment at 18 feet distorted external vertical feed 20 feet long 8’ ground rod, 80’ and 95’ radial SGC230 autotuner EH on deck railing at 10 feet EH in basement 22” off floor EH in basement on floor Two-way contacts were made

19 Suggestions Magnetic Loop CFA E-H Throw a wire out the window
Build it … correctly! CFA Wait … watch the debate, litigation, etc. E-H Build one for FUN and follow the “soap opera” at SWR meter (a must), FS meter, SWR analyzer Throw a wire out the window

20 URLs N1GX (E-H) “Compass” N1GX (E-H) “Desert” KB1EGI (E-H) “Pspice”
N1GX (E-H) “Desert” KB1EGI (E-H) “Pspice” Bernie Wright (Magnetic Loops)

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