I had not been paying attention to the thread but it has evolved into an area I had a question about. Typical LORAN C systems are the vlf preamp and whip. You never see anything about larger antennas such as might be used from the US to receive Europe stations.
For WWVB 60 KHz I built a large loop 10' X 10' and 800' of wire tuned with preamp. The gain was dramatic to say the least. So I have been interested in building a large loop for LORAN C. But never really found any detail. From this thread it may be actually useful. I would build the same size loop but not make it sharply tuned because of the large signal bandwidth +- 10Khz. With the whip on winter nights I do get occasional lock of the European signals. Granted this will be an over the summer project. Regards Paul WB8TSL On Fri, Jul 17, 2015 at 8:31 AM, Dr. David Kirkby (Kirkby Microwave Ltd) < [email protected]> wrote: > On 16 July 2015 at 23:23, Bob Camp <[email protected]> wrote: > > > Hi > > > > Quick and simple: > > > > 1) Signal power is proportional to the area of the loop. Bigger is > better. > > 2) Inductance is proportional to the turns squared. Turns do not directly > > affect signal to noise. > > 3) Inductance may be resonated with a capacitor. This gives a bandpass > > function. > > 4) The coil shapes are very common. The many inductance calculators on > the > > web will give you an inductance estimate. > > 5) If the inductance is resonated, the system Q (and thus bandwidth) is a > > function of the coil losses and the amplifier’s input impedance. > > 6) More turns gives a power match into a higher impedance ( more > voltage). > > 7) *Practical* matching of the amplifier to the antenna will give you an > > reasonable target number of turns. > > > > Bob > > > > It's interesting that > > http://www.vlf.it/feletti2/idealloop.html > > says that sensitivity is set by the mass of copper used. To quote > > "A single turn square loop, 1m side, made with 1kg copper has the same > sensitivity of a 1000 turns square loop made with 1kg copper and same > dimensions. In this context, the sensitivity limit is represented only by > loop thermal noise: > > noise floor (nV/sqrt(Hz)) = 4 sqrt(R in kOhm)" > > It is not immediately obvious where that equation comes from, but > re-arranging the equation for thermal noise power > > P=k T B > > (P in watts, k= Boltzmann contant, B is bandwidth in Hz) > > and assuming a temperature T of 300 Kelvin, k = 1.38 x 10^-23 J/K, one > finds the constant is 4.06, so the 4 in that equation is fairly accurate at > 300 Kelvin. > > I'd much rather wind a loop with a few turns than a few hundred turns! But > obviously the voltage rises with the number of turns, so requires less > gain. > > Dave > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
