Can antenna factor(AF) be used to generate a known E-field on a transmit antenna?

Dear All,

I am trying to calculate the E-field (in dBuV/m) generated by an antenna, given the input signal on the antenna's terminals and the antenna AF supplied by the manufacturer, all at a specific frequency.

Example: Signal generator feeds the antenna with Vt=100dBuV at 40MHz (ignore cable losses for simplicity). The AF at 40MHz is 12dB/m.
So, the E-field generated by the antenna is: E = AF + Vt = 12dB/m + 100dBuV = 112 dBuV/m. Right?

I have been using AF to assess the E-field incident on the antenna, and I am wondering whether the AF can also be used to estimate the E-field generated from a transmit antenna.

Thanks.

Kostas

Field strength generated at the antenna place isn't a useful field quantity. You would determine the field strength at a specified distance. In so far, the suggested calculation makes no sense.

It's however possible to derive transmitter antenna performance from receiver parameters. Antenna gain applies to receiver and transmitter operation.

FvM said:

Field strength generated at the antenna place isn't a useful field quantity. You would determine the field strength at a specified distance. In so far, the suggested calculation makes no sense.

It's however possible to derive transmitter antenna performance from receiver parameters. Antenna gain applies to receiver and transmitter operation.

Click to expand...

Thanks for the answer. Actually, you are right: I forgot to consider the fact that AF has to be determined at a specific distance as well, 10m in my case.

The reason I want to do E-field estimation 10m away from the antenna and along its main axis, is to verify the site attenuation. I use a receive antenna and a RF meter on the receive end (again: 10m from the transmit antenna)
to verify that the measurement agrees with theory. The RF meter incorporates the value the AF of the receive antenna, so I get immediate values in dBuV/m. So, in my case, theoretical knowledge of E-field intensity on the receive end and on a predetermined distance from the transmit antenna is useful.

The other alternative is to carry out theoretical calculations using the classic Friis formula, in which case all I need to know are the transmit power, gain of each antenna, path loss on specific frequency and distance. In this case I need to configure the RF meter to read in dBuV and consider the gain of the receive antenna instead of the AF. But, for my theoretical calculations, I wanted to use the AFs as a first approach.

Also, after posting my question here, I found this useful link about AFs: www.ets-lindgren.com/pdf/antparameters.pdf
It is clearly indicated that, for a given antenna, the transmit AF is not identical to the receive AF. So, my generated E-field calculations were wrong in first place, anyway, because I used the receive AF on the transmit antenna (as the transmit AF is not provided by the manufacturer) and I need to recalculate the transmit side.