07-11-2015, 06:14 PM
From what I've read the only way to improve on a bog standard xtal set is to make a better one....Get as long a wire up as high as you can to intercept those volts per meter, most of us are restricted by garden size which will usually mean that the antenna will most probably be capacitive for the broadcast band frequencies, the capacitance should be cancelled out and the resultant impedance matched to the tuned circuit as best as possible, the output from the tuned circuit needs to be matched to the detector, the detector's output needs to be matched to the headphones/speaker or whatever.
Power and selectivity is everything, each mismatch means a loss of available power and also a reduction of Q in the tuned circuit, for maximum Q construction wise the consensus from what I have read is to use coils wound with fine Litz wire if the set is intended to receive broadcast band transmissions, other factors, such as relative dimensions of the coil, form material, proximity etc can also influence Q.
Designed and built correctly the xtal set is capable of DX with quite good selectivity, I've read of bandwidths around 10 khz being possible.
Rightly or wrongly, that's my take on it.
Lawrence.
Power and selectivity is everything, each mismatch means a loss of available power and also a reduction of Q in the tuned circuit, for maximum Q construction wise the consensus from what I have read is to use coils wound with fine Litz wire if the set is intended to receive broadcast band transmissions, other factors, such as relative dimensions of the coil, form material, proximity etc can also influence Q.
Designed and built correctly the xtal set is capable of DX with quite good selectivity, I've read of bandwidths around 10 khz being possible.
Rightly or wrongly, that's my take on it.
Lawrence.
