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

Magnus Danielson magnus at rubidium.dyndns.org
Fri Jul 17 04:03:00 EDT 2015


Hi Ole,

Many thanks, 2.21 Ohm sounds more reasonable than 2 ZettaOhm (or 2 ZO), 
which is what 2E21 would translate into if it where 2*10^21, so I wanted 
to make sure there wasn't a typo. :)

Then I know that my values may vary for that part of the design.

Cheers,
Magnus

On 07/16/2015 09:21 PM, Ole Stender Nielsen wrote:
> Hi Magnus,
>
> The 2E21 is a 2.21 Ohms resistor.
> The RC network was found useful to ensure loading at higher frequencies.
> Best regards
> Ole
>
> Den 16-07-2015 kl. 18:27 skrev Magnus Danielson:
>> Ole,
>>
>> What is the value of the "2E21" resistor?
>> Looks like a typo. 2k?
>>
>> Feel inspired to rig up something for my FS700.
>>
>> Will wooden frame my TP-cable wired to form a 8 turns times the
>> cable-turns.
>>
>> Cheers,
>> Magnus
>>
>> On 07/16/2015 09:05 AM, Ole Stender Nielsen 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.
>>>
>>> For larger distances to the transmitter site, you may need to insert
>>> additional amplification between the grounded base pre-amplifier and the
>>> FS700, and that requires that you provide power to the pre-amplifier
>>> through a bias Tee, and that you load the FS700 input to keep it happy.
>>> A while after I installed the antenna in the attic, I added additional
>>> amplification, not due to a low signal level, but because I wanted to
>>> use the loop antenna for other longwave services too, and that required
>>> that I had to split out the signal.
>>>
>>> Best regards
>>> Ole
>>>
>>> Den 15-07-2015 kl. 18:02 skrev Dr. David Kirkby - Kirkby Microwave Ltd :
>>>> Does anyone know of the latest firmware for the Stanford Research
>>>> FS700 Loran-C frequency standard? I know someone who has one with
>>>> firmware 1.20, but I don't know if there's any later firmware. I
>>>> recall asking Stanford Research about firmware for the SR620 but got
>>>> no response, so I don't know if I will have any better luck with the
>>>> FS700.
>>>>
>>>> What's the best sort of antenna for these? I know Stanford sell one,
>>>> and by the cost of new professional equipment, the $250 is not
>>>> abnormally high, but I'd rather look at building something if I
>>>> purchase one of these standards. I did think of using a half-wave
>>>> dipole, but my garden is just a wee bit  too small.:-)
>>>>
>>>> Dave
>>>>
>>>>
>>>>
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>>>
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