How is it that 62" is the best length for 72Mhz receiver? According the this article (which was published somewhere in 2005-2008 I think, but it's still comes up first in Google) the best length for a 72Mhz receiver antenna is 62" (~157.5cm). This puzzles me since in air, the wavelength of a 72Mhz wave is:
$$
\lambda_{72}=\frac{c/n_{air}}{72Mhz}=4.16m
$$
And
$$
\frac{157.5cm}{\lambda_{72}} = 0.38
$$
Which is kinda like a third, so it seem to figure okay, but 50" is about a third as well (same distance), and we see a drop there. Also, 86" is at about half wavelength (~82"), and it doesn't seem to be close to the 62" result.
So, why is it that 62 inch is the right size? Shouldn't half wavelength be a stronger candidate?
Ofcourse you can blame it on the experiment, but the guy describes his environment, and he seems to cancel out most of the "noise".
[This might be a better fit under Electrical Engineering, sorry if so]
 A: You might think that the receiver is tuned to the length of the antenna, it's not. In this case the antenna is not a tuned circuit but rather a signal collector. Receiver has to receive a wide band of frequencies selected by crystals and making a tune circuit could impede some frequencies. Other receivers in the remote control market antennas do not coincide with the frequency but rather what is practical for the user for example a child neads a shorter antenna on the remote control and in the remote control vehicle which could be operating on a frequency of 27 MHz. No one is going to have a remote control with 104 in antenna.  For the 72 MHz receiver in question, there is no ground plane where there are two halves of a circuit. This is only one half which is not tuned, the only other half of the equation is the receiver itself. You can think of it as a microwave dish.  The wire is acting like the dish which is connected to the receiver.  The bigger the dish the more it collects.  It is considered a long wire antenna which acts as both feed line and antenna.  Also called a end fed antenna.  One issue with increasing antenna gain is also increasing antenna directivity which in this case may not be a good thing.  A typical antenna for 72 MHz would be in the 39 inch range or 1 meter.  This would represent a quarter wave radiator which would give you the most uniform signal coverage and less directional than a higher gain directional antenna in this case a 62 inch long wire antenna.
Some RC glider pilots have used long wire antennas trailing off the tip of a wing of a RC glider giving the long wire antenna an L shape changing its directivity compared to a straight long wire antenna being more directional which at higher altitudes may not be an issue if straight.
