Total posts : 45366
What I have claimed differs from the cited references only for vertical monopoles over ground used in the receiving mode where the elevation angle of the incident radiation is zero degrees, in which case I assert that the receiving gain is lower than the transmitting gain by 6 dB. I think I can prove my assertion by using the development of the effective aperture in Kraus.
I do not claim any credit for what I said. I am only retelling what others have said.
The demo copy of EZNEC I use does not permit analyzing an antenna in the receiving mode. I would therefore greatly appreciate finding out what result NEC gives for the following receiving antenna situation:
Plane waves are applied to a vertical quarter-wave monopole above ground, with the electric field parallel to the monopole. Said plane waves travel in a horizontal direction along the surface of the ground plane. The height and width of the plane waves are very large compared to the height of the antenna. The field strength is 10 mV/m, and the frequency is 1.7 MHz.
I would like to either find out the induced open-circuit voltage between the base of the antenna and the ground plane, or the power applied to a 36.5 ohm load resistor between the base of the antenna and ground. Either of these results would tell me if NEC agrees with my concepts or not.
Corrected on 4/10/08:
Since posting, I found out that it is difficult to use simulated plane waves in the NEC program if a ground plane is used. The ground plane interferes with the plane waves, and it is difficult to get the desired field strength.
So, I am proposing another method for finding out if the the gain of a quarter-wave monopole is the same as the transmitter gain when receiving groundwaves, or if it is 6 dB lower.
I propose simulating two quarter-wave monopoles over a ground plane; one a receiving antenna and one a transmitting antenna. The two antennas are separated by a long enough distance so that the receiving antenna is in the far field of the transmitting antenna. 1 km is a good separation to use. 1.019 watts of radiated power provides a field strength of 10 mV/m at 1 km. 6.1 V applied to NEC transmitter antenna terminals gives 1.019 W of radiated power.
From the information about effective height in Kraus, which gives the relationship between the field strength applied to an antenna, and the induced open-circuit voltage at the antenna terminals, at 1.7 MHz, 10 mV/m incident on a quarter-wave monopole induces .565 V (open circuit) if the receiving gain is the same as the transmitting gain, and .282 V (open circuit) if the receiving gain is 6 dB less than the transmitting gain. With NEC, it is easier to find short-circuit current than open-circuit voltage. The corresponding values of short-circuit current are 15.48 mA and 7.74 mA. In the simulation, the receiving antenna can be connected directly to ground, and the induced short-circuit current can be read from the segment of the receiving antenna connected to ground.
What I have described can even be done with the demo EZNEC program that I use. I am going to do the simulation. It would be very good if Rich would also do the simulation on his NEC-2 program so that the results can be compared.