[time-nuts] 60 KHz Receiver
jimlux at earthlink.net
Thu Oct 7 01:01:21 UTC 2010
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 <magnus at rubidium.dyndns.org> wrote:
> On 10/05/2010 11:52 PM, Bob Camp wrote:
>> 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.
>> 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.
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
More information about the time-nuts