[time-nuts] 60 KHz Receiver

[Bob Camp]

Hi

The one thing that an alternator system had available was *power*. They are fairly efficient and you put lots of horsepower into them. Numbers in the 100's of KW come to mind....

What we're talking about here is more or less a page from the history of radio in the early 1900's. People that were used to the requirements of a VLF system simply didn't believe that a few watts would get very far at "short wave". It took a bunch of crazies to prove them wrong ...

Bob


On Oct 6, 2010, at 8:30 PM, Magnus Danielson 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
> 
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