Results (with new matching system) pa0nhc 20200607 / 20201029 / 20210817
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20210817 : My 145MHz
loop antenna free field measurement experiment, and a directivity
calculation, showed that the G0CWT video demonstration about the directivity of
such antennas is faulty. His faulty results are generated
due to UNbalanced feed, lack of coax common mode suppression, and
reflections from surroundings.
A horizontal polarized 1/4 lambda circumference delta loop in a free location has nearly no directivity, but is nearly omni directional.
The results of balanced feed :
- On 80m, the frequency of maximal magnetic field strength, and VSWR 1 : 1.0 now coincides exactly.
Just tune to VSWR = 1.0, and you are sure to be tuned for maximal transmitted field strength too.
- The loop is now :
- Better balanced,
- No common mode problems,
- Very insensitive for non-resonating metal objects in the near field (See my location photo).
- Signal reports received are definitively stronger.
- Selectivity is far better.
- No TVI / BCI in consumer equipment, at a distance of about 3m below the loop.
loop Q (formula
Antenna bandwidth and selectivity (3700 kHz).
Cross band selectivity :
: my coax feeder is about 19m long. Measurements
were not done at the antenna, but at the beginning of the feeder.
tuning range for VSWR < 1.5
Loop is tunable to resonance between 3.0 MHz and 9.95 MHz.