[time-nuts] Firmware and antenna for Stanford Research FS700 Loran C frequency standard

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 16 July 2015 at 08:05, Ole Stender Nielsen <olstni at mail.tele.dk> wrote:

> I use a home-made untuned loop antenna with 4 windings of 2.5 mm2
> insulated wire on a 80 x 80 cm wooden frame, and with a grounded base
> pre-amplifier mounted on the antenna frame. A schematic is enclosed for you
> to copy.
> The pre-amplifier is powered through the cable, and loads the FS700 input
> as required.
> I live about 290 km from the island of Sylt, and get nice noise margin
> figures from the FS700, normally about 40 dB, often up to 46 dB.
>

A couple of questions

1) Do you have any suggestions for a replacement for the LM394CN, which is
obsolete and unobtainable from any reputable source? There are plenty on
eBay for a few $'s from China, but the probability of them being fakes is
greater than 0.99. The MAT12 seems to be one possible candidate for a
replacement and while not cheap, is available from reputable sources like
Farnell.

2) What is the "Ca. 3 Ohm" to the left of your circuit? Is that what you
estimate the input impedance is? I've got 95 m of 2.5 mm^2 wire. The
resistance of that is about 7.41 mOhm/m so my 95 m would have a DC
resistance of around  7 Ohms if I used it all.

I have built the loop 1.0 x 1.2 m. Hopefully that will be ok to receive at
least one or both of

* Lessay, France, power = 250 kW, distance = 321 km, bearing = 211 degrees.
* Anthorn, England, power =- 250 kW, distance = 419 km, bearing 331 degrees.

I now need to work out how many turns to put on it.

Dave