On Fri, 24 May 2002, Geo wrote:

>On 24 May 2002, at 12:47, Lawrence Lile wrote:
>
>> 1.  Produce 60KHZ 5V signal
>> 2. Superimpose a WWV compatible time code on it
>> 3. put the whole thing into a very well shielded enclosure
>> 4. Attenuate it with a variable resistor array by 1E-6 or so inside another
>> good enclosure
>> 5. inject said signal into another well shielded enclosure using an antennae
>> that has a ghost of a chance of transmitting it
>>
>>
>> Now, a half-wave antenna at 60KHZ is only 7800 feet long, which will be a
>> little impractical to do in the lab.  Hmmmm...  Doesn't look so simple.
>
>Assuming that your 'device' cannot have a direct connection to its
>aerial? Also assuming that it does not use a long wire for reception -
>perhaps a ferrite rod?
>If this is true then the screened room is still required to keep out the
>/real/ 60 kHz transmission but your signal can be coupled locally
>into the reciever by driving a similar coil on ferrite rod. This restricts
>the radiated signal and allows accurate positioning of the two
>antenae to keep the measurements similar. In the early transistor
>radio days (1959ish) absolute sensitivity was measured by placing
>the receiver at the centre of a "standard" large coil (about 1 metre
>square) wound in aluminium channel.

Relatively bright idea:

Ferrite antennas are highly directional. So you can null the real xmitter.
Make a (vertical) loop at 90deg. to the real xmitter and have all the
alignment done with that and a signal generator.

Peter

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