R
rbrucecarter
Guest
> Okay, guys. Tell a virtual radio idiot what you mean, in
> English!
> Believe it or not, I AM interested in this setup!
Here is my loop antenna page:
http://www.mindspring.com/~loop_antenna
Its got a lot of information as well as construction projects (some of which work better than others).
Basically - a box loop antenna is a tuned LC resonant circuit. The inductive portion is the loop, and it intercepts the magnetic field broadcast by the station. The larger the dimensions, the more magnetic flux it intercepts - and the more sensitive the antenna. The capacitor resonates with the loop, forming a bandpass filter centered at the tuned frequency. The lower the resistance of the wire, and the higher the isolation in the tuning capacitor, the narrower the bandwidth of the antenna - and to a point that is a good thing because the box loop can enhance reception of distant stations closely spaced with locals. Given too narrow of a bandwidth - audio response can be limited.
A box loop intercepts so much signal that any radio placed in proximity to it will receive gain from it inductively - but many box loop designs include a sense winding in the same plane as the antenna, so inductive coupling between the primary (loop antenna) and secondary (sense winding) can be maximized by transformer action.
In practice, using a loop involves a two step iterative process - tuning the radio close to where the target station will be - hopefully maximize a weak signal if present. Then place the loop in proximity (or connect the sense winding to the external antenna inputs), and tune the loop to the station. If you cannot hear the target station at all until you use the loop - you might have to get close on the radio, peak a nearby station strong enough to be heard, then offset the radio. The out of band response from the loop may be enough to begin to bring in the station, but you might have to go back and forth from radio to antenna to get the station maximized.
There are small loop antennas commercially available from Terk, Select-A-Tenna, and kiwa - a few others - but they are horrendously overpriced for what you get. A pizza box, 120 feet of wire, and a junk tuning capacitor will do just as well. I can even fabricate a tuning capacitor from an old coke can if need be (an old crystal radio trick). So the raw materials are cheap - the results can be astonishing!
> English!
> Believe it or not, I AM interested in this setup!
Here is my loop antenna page:
http://www.mindspring.com/~loop_antenna
Its got a lot of information as well as construction projects (some of which work better than others).
Basically - a box loop antenna is a tuned LC resonant circuit. The inductive portion is the loop, and it intercepts the magnetic field broadcast by the station. The larger the dimensions, the more magnetic flux it intercepts - and the more sensitive the antenna. The capacitor resonates with the loop, forming a bandpass filter centered at the tuned frequency. The lower the resistance of the wire, and the higher the isolation in the tuning capacitor, the narrower the bandwidth of the antenna - and to a point that is a good thing because the box loop can enhance reception of distant stations closely spaced with locals. Given too narrow of a bandwidth - audio response can be limited.
A box loop intercepts so much signal that any radio placed in proximity to it will receive gain from it inductively - but many box loop designs include a sense winding in the same plane as the antenna, so inductive coupling between the primary (loop antenna) and secondary (sense winding) can be maximized by transformer action.
In practice, using a loop involves a two step iterative process - tuning the radio close to where the target station will be - hopefully maximize a weak signal if present. Then place the loop in proximity (or connect the sense winding to the external antenna inputs), and tune the loop to the station. If you cannot hear the target station at all until you use the loop - you might have to get close on the radio, peak a nearby station strong enough to be heard, then offset the radio. The out of band response from the loop may be enough to begin to bring in the station, but you might have to go back and forth from radio to antenna to get the station maximized.
There are small loop antennas commercially available from Terk, Select-A-Tenna, and kiwa - a few others - but they are horrendously overpriced for what you get. A pizza box, 120 feet of wire, and a junk tuning capacitor will do just as well. I can even fabricate a tuning capacitor from an old coke can if need be (an old crystal radio trick). So the raw materials are cheap - the results can be astonishing!
