Which receiving antenna yields the highest voltage ?

Hi.
Which should be the length of a long (or not that long) receiving antenna, not terminated, single wire, unbalanced, that will provide the most voltage signal for a receiver ?
(Either in wavelengths multiples or submultiples, or centimeters)

The frequency to be received is 520 MHz (~57cm band) , the tuner impedance more than 2000Ω

- And why ?

This is not about yagis, dipoles, standing waves, gain, directionality... just about the optimal theorical length of a properly oriented single wire antenna.

My antenna book shows mostly sensitivity lobes, impedances... but cannot discern reception voltages.

Your restrictions don't make a lot of sense to me, so here are some comments. In order for an antenna to make suitable connection to the 2000 ohm input of your tuner, the antenna terminals must connect directly to your tuner terminals, with no transmission line in between. Also, since you insist on using a single wire, we must know what counterpoise is to be provided by the tuner, or by the environment to work with this single wire. I don't think it is possible to couple a receiver that is very small (relative to a wavelength) to the end of a wire effectively without knowing what to do with the "other" terminal of the receiver, the terminal that provides the voltage reference. This applies in free space. Near the ground it is a different matter. So, where is the receiver?

If the receiver does indeed have a voltage reference, by virtue of being grounded for example, then the answer is that your antenna should be one half wavelength or any integer multiple of one half wavelength. The voltage distribution on a half wavelength wire antenna has a current maxima in the center, along with a voltage minima at the same point. At the ends, the opposite occurs, you have a current minima and voltage maxima. If your receiver has infinite input impedance then this works out fine. However, 2000 ohms is not infinite, so a small adjustment in length is needed to find the 2000 ohm point on the wire rather than the maxima. This change in length can be slightly shorter or slightly longer than half wavelength, and it won't be very much.

maximum voltage at the "feed point" results from a 1/2 wavelength (and odd multiples of 1/2 wave, such as 3/2 wave, 5/2 wave) end fed element. maximum current would result from a 1/4 wavelength element

that applies for transmitting OR receiving.

Normally you would use a 1/4 or 1/2 wave whip over a ground plane, which has an output impedance of 36.8Ω, and use an RF transformer to convert that to your 2000Ω amplifier impedance for maximum voltage.

Thanks, gentlemen. Good help. Half wave will be then.

To clarify, the tuner metallic cabinet is decently large to act as the 'second' reference ground terminal for the counterpoise.
The tuner sees the outside world by a coaxial connector on its cabinet chassis where a single non-shielded wire will act as antenna.

Feeding a 1/2λ wire from the end is problematic. At resonance, the feedpoint impedance is infinite, the voltage is infinite, and the current is zero, which you cannot achieve in practice. If you make the antenna a little longer, say 5/8λ, then feeding it becomes a little easier.

It is all about power transfer from an antenna to the receiver input terminals, not about voltage at the receiver terminals. Most VHF/UHF receivers have an input impedance of 50Ω, so your best bet is to start with an antenna that has 50Ω impedance naturally, use 50Ω coax, and dispense with a lossy tuner...

My antenna book shows mostly sensitivity lobes, impedances... but cannot discern reception voltages.

Click to expand...

Well, the voltage will depend on the field strength of the signal.
Your antenna book should tell you the gain of any particular antenna with reference to a dipole on an isotropic radiator.
From that you should be able to calculate the voltage.

Oh, but I am forgetting, antenna gain is usually expessed in dB.

Abolish the deciBel !

Click to expand...

So I guess you are just a bit stuffed in that department!

JimB

If your lloking for max signal then an atu would be a good idea