I am trying to build one of those "booster" loops similar to
the ones that people use to position near an A.M. radio to
improve reception, BUT I'm wanting mine to work at 433 MHz!
Can any of you folks point me to some library or internet
resources that would describe optimum loop geometry and size?
Also, where to find the tuning capacitor that matches?

TIA

On Feb 19, 7:46 am, "kelvin_cool_ohm"
wrote:
I am trying to build one of those "booster" loops similar to
the ones that people use to position near an A.M. radio to
improve reception, BUT I'm wanting mine to work at 433 MHz!
Can any of you folks point me to some library or internet
resources that would describe optimum loop geometry and size?
Also, where to find the tuning capacitor that matches?

TIA


Loop antennas of the sort used for 2MHz and below are of a different
nature than a loop that would be used for 433MHz, generally. That is,
low frequency receiving loops are generally a small fraction of a
wavelength across (like commonly less than 1/100th), but at 433MHz, a
loop that would be worthwhile is generally going to be a large
fraction of the 27-inch wavelength of that frequency. The behaviour
of the loop will be different than the AM broadcast ones. I suspect
you will do better with a different external antenna. What sort of
receiver will you use it with? Does that receiver have a connector
for an external antenna? Could you put the antenna higher up in the
air, and run an antenna lead to the receiver? Exactly what are you
trying to accomplish? If the only thing you are trying to do is make
an accessory that looks cool, the dimensions don't matter, but if your
goal is to receive some specific signals you're now having trouble
with, let us know a bit more about that problem and we can perhaps
offer some suggestions.

Cheers,
Tom

"K7ITM" wrote in news:1171902287.663998.89440
@j27g2000cwj.googlegroups.com:

snip

Loop antennas of the sort used for 2MHz and below are of a different
nature than a loop that would be used for 433MHz, generally. That is,
low frequency receiving loops are generally a small fraction of a
wavelength across (like commonly less than 1/100th), but at 433MHz, a
loop that would be worthwhile is generally going to be a large
fraction of the 27-inch wavelength of that frequency. The behaviour
of the loop will be different than the AM broadcast ones. I suspect
you will do better with a different external antenna. What sort of
receiver will you use it with? Does that receiver have a connector
for an external antenna? Could you put the antenna higher up in the
air, and run an antenna lead to the receiver? Exactly what are you
trying to accomplish? If the only thing you are trying to do is make
an accessory that looks cool, the dimensions don't matter, but if your
goal is to receive some specific signals you're now having trouble
with, let us know a bit more about that problem and we can perhaps
offer some suggestions.

Cheers,
Tom


Thank you for replying.

This project was originally intended to help my dad who had mobility
problems, and though it is no longer needed for that purpose, I wanted
to carry it through to completion out of curiosity.

The application is for use with one of those remote-reading barbecue
thermometers which is at the end of its 100 foot range and where the
receiver is located inside a condominium which has metal-framed windows
and metal doors. The receiver will work 10 feet closer to the cooking
area (and ten feet further from the structure) but since it is then
outside, it loses its remote-reading usefulness.

I was hoping to find an unamplified way to make the signal slightly
stronger just inside a window. The only method I have of determining
sufficient signal strength is to push the "synchronize" button on the
transmitter and see if the receiver display changes from "-----" to an
actual temperature reading. I had hoped that a small loop in the center
of a window pane would allow me to set the receiver on a box inside the
window.

These units have no external antenna conections, but looks is of no
importance as far as coil design goes. If someone can suggest a way to
use a "pickup" coil closer to the cooking area cabled to a "relay" coil
on the outside of a window, that would even be acceptable.

If someone can suggest a weak local oscillator circuit (preferrably
crystal controlled) that I can use to beat against the 433MHz transmitter
frequency in a standard broadcast receiver front end so that signal
strength measurement could be taken, I would also be interested in that.

Thanks in advance for any suggestions.

Rick