The coil allowed an ok match, but an antenna that is a tiny fraction of a wavelength is going to be inefficient from ohmic loss in the antenna. You could use a superconductor, but that brings another set of problems (matching networks that also have low loss and can adapt to the changing impedance of the antenna)
On Oct 6, 2010, at 5:30 PM, Magnus Danielson <mag...@rubidium.dyndns.org> wrote: > On 10/05/2010 11:52 PM, Bob Camp wrote: >> Hi >> >> Ok, the next layer to this onion is the antenna. At 100KC your antenna is >> 35X smaller than it is on 80 meters foot for foot. In other words, your 100' >> tall vertical on 80 equates to a<3 foot tall antenna at 100 KC. QRP on 80 >> with a 3' transmit antenna anybody? Been there done that, not much range at >> all. At VLF forget about transmitting with a horizontal antenna unless you >> are airborne. >> >> It's not just the antenna, the ground counts as well. If you are by the >> seashore that may not be a big deal. If you are inland, prepare to lay many >> very long radials. >> >> ---------- >> >> After that you hit signal to noise. The receivers worked as well as they did >> because they had an enormous signal to work with. There's an amazing amount >> of crud running around down below 200 KHz these days. Even for timing you >> need a lot of signal to get good results. >> >> Bob >> KB8TQ >> >> Ham for way more than 30 years.... > > Well, in the OLD days, Alexanderson extended the antenna using a coil. That's > how the 127 m high antenna towers of Grimeton transmits the 16,7 kHz of 18 km > wavelength signal across the atlantic. The modulation was CW in 80-speed, but > anyway. That transmitter has several interesting features in it for its > time... like feed-forward frequency stabilisation. > > Cheers, > Magnus > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
