I have a linear array of 8 dipoles, all separated by the same distance,
if 10 mW of total power (for the sum of elements)
would be used, and we can assume the receiver has 0dB gain and a signal of 1 microvolt would be needed for reception?
How can I calculate the range. I know I can can calculate the the path loss from the gain and transmitted power. but how would I convert the 1 microvolt to power, since no impedance is given?
The frequency is 2400 MHz
Shiwam,
I have to assume that you are using the dipoles for a synthetic aperture antenna array and they are properly spaced and are properly connected with the correct phasing.
The theoretical maximum gain of a dipole antenna is 2.18 dBi (dB compared to an isotropic radiator). When you double the number of dipoles, you theoretically increase the gain by 3 dB but, in reality, you get somewhat less. With 8 dipoles, you will get a maximum theoretical gain of 11.18 dBi.
Almost universally, a radiation resistance of 50 ohms is used in these calculations. The available power is the 1 microvolt across 50 ohms.
Good luck
Steve
This company makes a TV UHF antenna, four stacked dipoles, with reflectors, that it claims has a gain of 15.8 dB. Eight dipoles, in a similar configuration, might give you a couple or 3 dB better. But 15.8dB sounds plenty optimistic.
https://www.antennasdirect.com/store/DB4-Pro-Signature-Series-DB4-PRO-TV-Antenna.html
I haven't verified the figure, but I do use two of them, mounted indoors at ground level, inside a fireplace, and reception is quite good. I'll assume that antenna is used as a transmit antenna.
As Steve says, other than for TV, antenna impedance is almost always 50 ohms. In your case, you should use 50 ohms as the likeliest value, to convert voltage to power. (For TV coax antenna leads, the universal standard seems to be 75 ohms.)
Reception depends on many factors. Certainly, transmit effective radiated power is one of them. Usually all of these calculations are done in dBm (dB related to 1 mW) and dB.
So, if I understand what you are describing, a total transmitter power output of 10 mW is sent to this array of dipoles. 10 mW = 10 dBm.
That 10 dBm signal is sent to an antenna array that we'll assume has a gain of 15.8 dB, so the signal (main lobe) has an effective power (ERP) of 25.8 dBm.
Now you experience propagation path loss. There are many models that provide this. The most benign is free space propagation, which assumes no terrain effects and no antenna height above ground dependency. For the sake of simplicity, which will probably turn out to have overly optimistic results, let's assume free space propagation.
And then there is the receive antenna gain and the tuner sensitivity.
Working backwards. A good tuner sensitivity figure is -85 dBm, for minimum required receive signal strength at the antenna lead to the receiver. (I think your suggestion of 1 uV required, or -107 dBm assuming 50 ohm receive antenna, is probably optimistic, unless perhaps for very narrow band or very expensive receivers.) And you say to assume no receive antenna gain.
So let's go with -85 dBm of receive power required, and unity gain receive antenna.
The maximum propagation loss plus lead and connector loss you can tolerate, and still get reception, is 25.8 - (-85) = 110.8 dB of total signal loss. Assume your lead loss to be 5 dB (actually this is optimistic too). Your maximum propagation loss becomes 105.8 dB.
Now you can find the maximum range. With the numbers above, and using the free space propagation model, your max range is 1.94 km or 1.2 mi, at 2400 MHz. And I didn't subtract any margin, so this is all optimistic.
Free space propagation is explained here:
https://en.wikipedia.org/wiki/Free-space_path_loss
You can find other models too.
dear Albert Manfredi ,
Why do you assume 15.8 dB if the gain is maximum 11.18 dBi?
You really need to pose your question properly. With the information given here no answer can be given. All the answers given so far have to rely on the respondents making assumptions. I suggest you speak to Prof Frank Leferink at your university. He will be able to help you with these problems.
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