A max. performance 40m - (60m) - 80m transmitting loop antenna.
Please watch my video presentation first : TXloop English
201810 : Installing the new match box at the top (current maximum) of the 10m circumference loop.
The tuningC is at the bottom.
This is (according to my experiences) the best feeding system at the ONLY good feeding point.
Resulting in a purely H-field radiating, BALANCED antenna and immediately good VSWR.
Wide band matching.
PCB available => PCB galery
New versiion. More space for the series tuning capacitors. Their bottom tracks are interconnected with their top tracks.
Different kinds of capacitors will fit : high current SMD, Mica, film.
The transformer is wound on one 61mm #61 core, maximal power is 400W at 3.5 MHz
The maximal antenna current at 3.5 MHz is then 25A.
Red = blanc copper wire.
Orange = one insulated copper wire.
New improved matching system.
More detailed descriptions :
- Small, only 2.5m square
- Omni-directional NVIS radiator for 40 - 60 - 80m.
- No radials nor grounding.
- Installed at low height (loop center at 2.5m up), it radiates predominantly vertical (NVIS), optimal for regional traffic.
- If installed at 7m height => also useable for DX (see calculated radiation patterns below)
- For leakage inductance compensated transformer coupling => Immediately perfect wide band match on three bands.
- No ATU needed. JUST tune the loop for min. VSWR => ready for transmitting with perfect match.
- Closed, balanced system.
pure magnetic radiation
While receiving : Insensitive for E-filed man-made-noises
While transmitting : Minimal chances for BCI/TVI
- This low-Q, wide band, max. performance 10m circumference loop is developed after reading valuable experiences of G0CWT.
- NO tuner is needed at 80m and 40m. Perfectly and wideband matched at 40m and 80m.
- The transformer matching circuit is vastly improved by me, pa0nhc. Using a remotely switched ring core transformer.
- The matching circuit at the top of the loop is tested with 10 minutes 100W continues carrier and used without problems at 300W SSB.
- Due to transformer leakage induction compensation, =>> when tuned to lowest VSWR, you are tuned for maximal radiation. <==
- This loop has its maximum efficiency (-0.5dB) at 40m, and only a little less at 80m.
- It has omni (non-directional) radiation characteristics.
- Installed at low height it is an NVIS (Near Vertical Indent Sky wave) antenna, optimal for regional QSOs (up to 300 km).
- Installed at 7-10m height above surroundings, it has DX possibilities at 40m and 80m.
In a large
ABS installation box at the bottom of the loop are the air
tuning capacitor, a little 12V DC tuning motor, and a simple to construct 1 : 13.500
mechanical reduction system.
A smaller ABS box at the top of the loop contains the transformer impedance matching system.
Both boxes are guarded against condensation by internal 5W heathers.
patterns of my 10m circumference loop.
Calculated with "MMANA-GAL_basic" for specified loop center heights.
"Antenna height" is the height of the CENTER of the loop above "Ground" (the roof).
The loop bottom and tuning capacitor are 1.25m closer to the ground.
At low height NVIS properties on 80m band. NVIS and DX properties on 40m band when at elevated height.