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

[Dr. David Kirkby (Kirkby Microwave Ltd)]

ZOn 15 Jul 2015 22:18, "Poul-Henning Kamp" <phk at phk.freebsd.dk> wrote:
>
> --------
>  David Kirkby - Kirkby
>  Microwave Ltd " writes:
>
> >What's the best sort of antenna for these?
>
> I use a $20 loop antenna I have rigged up myself, it lives in my attic:
>
>         http://phk.freebsd.dk/loran-c/Antenna/

Hi,
Thank you for that. But it is a bit short of information.  I appreciate
your use of "the nearest bent nail" principles, but roughly how many turns
were there on the coil? Do you have a circuit for the amplifier? The AD797
data sheet you link to is broken, but the error message is quite funny. I
found the data sheet on the AD797 and see it is a very low noise op-amp.

I must admit to knowing next to nothing about antennas at the Loran 100 kHz
(+/- a lot) frequency. How does one go about testing the antennas? I'm
about to place an order for an FS700, but will not have an antenna when it
arrives. I have a short period of right of return, and I'd like to get
something in place so I can quickly test this.

I have an HP 4284A precision LCR meter which works at more than 8000
discrete frequencies between 20 Hz & 1 MHz. Those frequencies include 60,
80, 100, 120 and 150 kHz.  That's the only thing I have got that measures
impedance as low as 100 kHz.

There's a description of the active antenna for the FS700 in the manual,
but with no circuit diagram, it is a bit tricky to understand. I assume
that the FS700 has some sort of bias-T to pass DC up the cable to power the
amplifier - is that so? If so, do you know the voltage?

No doubt all these things will be revealed when I get the FS700, but I'd
like to be ready to test it when it arrives.