[time-nuts] Loran and SRS FS700 in the UK

Bob Camp kb8tq at n1k.org
Sat Jul 11 11:22:13 EDT 2015


Hi

One thing to be careful about:

GPS runs at a level that is (depending on the measure) > 10 to > 1000X better than
Loran. Both ultimately trace back to a national standard over very long time periods.
Eventually that is the limit rather than the accuracy of the transmission medium. 

Having a “second opinion” is indeed a really good idea. Loran has the advantage of
being a totally independent system. That makes it a good candidate for checking with. 
You ultimately will come up with a “which one is correct?” sort of question. With only two
inputs, the default answer will be “GPS is right ..”.

Bob


> On Jul 11, 2015, at 1:02 AM, Dr. David Kirkby (Kirkby Microwave Ltd) <drkirkby at kirkbymicrowave.co.uk> wrote:
> 
> On 11 Jul 2015 03:28, "GandalfG8--- via time-nuts" <time-nuts at febo.com>
> wrote:
>> 
>> This is a reply to the topic "Loran-C reception in the UK" with specific
>> emphasis on the Stanford Research FS700.
> 
>> Points to note.....
>> 
>> All three of my units seem to have the Option 01 oscillator fitted,
>> although only one states this on the option label, so perhaps this became
>> standard with later production. I don't know and wouldn't take it for
> granted  but
>> thought it worth a mention. The fitted oscillator in each unit is an
>> identically specified SRS SC10.
>> 
>> Mine are off air right now as I swap about stuff in the timing rack,  and
>> haven't really been run for much more than initial tests, albeit for quite
>> long periods. My general impression so far is that the reported frequency
>> offset  might be a bit optimistic, this is compared with Thunderbolt
> GPSDOs,
>> but I need  to do more work on this.
> 
> Useful to know, but of course it could be the errors are on the
> Thunderbolts! The problem with having multiple GPS units is that they are
> not exactly independent of each other.
> 
>> The latest FS700 firmware I have seen is version 1.20.
>> I can make the 1.20 firmware available if anyone would like a  copy.
> 
> I might take you up on that if I get an FS700.
> 
>> FS700s have become available on Ebay at very good prices since the USA
>> Loran-C chain was closed down, that's why I have three:-), but it needs
> to be
>> noted that these are mainly from "recycling" outfits, what we might once
>> have  referred to as scrap yards in the UK, and usually untested and with
> no
>> warranty.
> 
>> On average mine have cost me about 200GBP each, including shipping and
> tax,
>> but beware of some sellers still asking anything up to 1000USD before
>> shipping  and import tax.
> 
> I have never seen them at anything like the price you see. About the
> cheapest I have seen is $600. I did notice one or two on eBay that are
> rusty, which struck me as odd.
> 
>> That small mains transformer runs really hot, not too surprising perhaps,
>> and I've seen at least one online photo showing two larger transformers
>> mounted  in the space towards the front of the unit. One or two probably
> depends
>> on  what's to hand but I would suggest a very worthwhile change. Mains
>> voltage here  is generally over 245 volts, so a bit on the high side, but
> I do
>> believe that  transformer is underrated.
> 
> Are there multiple secondries? If not getting a replacement should not be
> hard but otherwise it could be tricky.
> 
> I know someone who run his whole house on an autotransformer because his
> mains voltage was too high.
> 
>> Small point, but a nuisance, there's no backlighting on the LCD  display.
>> 
>> Overall impression, an excellent unit with programmable output frequency
>> and built in phasemeter, and I can't wait to get mine back on the air:-)
> 
> If I could get one for £200 imported into the UK I would definitely get
> one. I thought I would need to pay considerably more than that.
> 
> I have seen some in Hong Kong and China. I don't know if the system ever
> worked there,  but if not then
>> Regards
>> 
>> Nigel
>> GM8PZR
> 
> Cheers Nigel.
> 
> Dave G8WRB.
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