Thursday, April 29, 2021

An unusual engineering simulation

Altair Engineering, a company that markets Engineering and Design software sends out a monthly news letter.

My email address ended up on one of their lists.

This is an extract from one of mailings:

Does holding a wireless car key-fob to your head extend the range?

The chip. The loop around the perimeter is the antenna for the 315 MHz signal

Gain chart, plan view. Chip floating in space.

Gain chart, side view

Then a human body was added to the simulation.

It was interesting that a fat, healthy side-lobe forms off the human's "weak side". I never would have anticipated that. The weakest signal is behind

The optimum positioning for the fob was to place it on TOP of your head.

The signal is 10dB (ten times) stronger in the 1 O'clock position (if held in the right hand) than the free-standing chip. Perhaps more important, the gain is nearly circular so there are no dead-zones like when held in front of you. The weakest signal direction of the "on top of head" is still ten times greater than the weakest direction for "fob held in forward position"

If signal decreases by distance^2, then 10dB should triple the distance the signal can travel and still actuate the circuit in the vehicle.

This work was not replicated for people who cranial cavity is filled with a vacuum or air.


  1. I wonder if it will help unlock my failing memory.---ken

  2. TV Program for kids demonstrated this , more or less. "DIY Sci" They do science experiments for kids. In one episode the main character needed to unlock his car which looked to be about 50 yards away so his assistant could get inside. He put the remote on his head and hit the button and it worked. He stated it was mainly the radio waves being amplified by the water ( fluids) inside your skull. Clearly it worked.

  3. Must be nice having a truck with electric locks. On the other hand nobody wants to get near my beater 1986 nissan truck, so why lock it?

  4. Did they do any testing on the effective range impact of wearing a tin foil hat ? (I'm not up on tin foil hat design, but maybe there's a shape that increases the remote's range substantially; are parabolic Stetsons in our future?)

  5. I am SO sorry but I just can't resist. It sounds like that Engineering firm has the lobes for business

  6. Interesting that somebody finally 'proved' what we already knew...