Efficiency of the 60m Roomcap Antenna  
Measured was made of the antenna on the frequency of 5.315 MHz with a
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 used.
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 % Efficiency

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    http://hb9abx.no-ip.biz/analyse-e.htm    

The full construction guide is available from me.

Email = felix-abx (at) gmx.ch
Felix Meyer, HB9ABX   9th.January, 2017