Efficiency of the 60m Roomcap Antenna
Measured was made of the antenna on the frequency of 5.315 MHz
radiator of size 1m x 1m grid, installed on the car.
There was used a VNA instrument, measured at a SWR 2.62, and found
the bandwidth: 96 KHz (Q = 55.3).
The capacity of the radiator was measured: 59 pF.
Then, instead of the room capacity, a small air capacitor of 59 pF
Here a bandwidth of 12.8 KHz (Q = 414) measured.
With these values follows the Calculation:
Rtot = Xl x Q = 508 x 55.3 = 28'092 Ohm
Rv = Xl x Q = 508 x 414 = 210'312 Ohm
Rs = (Rv x Rtot) / (Rv - Rtot) = 32'422 Ohm
Eta (%) = (Rtot / Rs) x 100 = (28092/32422) x 100 = 87.5 %
The measuring corresponds to the measuring of the 40m Roomcap,
while here a varylink with 7.5 cm diameter is used.
At the 40m Roomcap was used a 5 cm diamater varylink.
The description and derivation of the formulas is found here:
Internet link: analyse-e
The full construction guide is available from me.
Email = felix-abx (at) gmx.ch
Felix Meyer, HB9ABX 9th.January, 2017