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

GandalfG8 at aol.com GandalfG8 at aol.com
Fri Jul 10 17:39:57 EDT 2015


This is a reply to the topic "Loran-C reception in the UK" with specific  
emphasis on the Stanford Research FS700.
Apologies for starting a fresh topic but I'm still not able to take emails  
from the list due to incompatibility problems with AOL and I don't see how 
to  reply to an existing subject directly from the archive, if anyone knows 
how  to do this please let me know.
 
There is an excellent reference to eLoran in the UK, including downloadable 
 publications, starting here......
http://www.gla-rrnav.org/radionavigation/eloran/index.html
 
As far as I can tell, the Lessay chain, which includes the UK station at  
Anthorn, is currently transmitting eLoran, with the extra data  channel, 
rather than Loran-C but this is totally backwards compatible and  the FS700 runs 
fine here, as does the Austron 2100 series.
This is why it's difficult to find specific GRIs quoted for eLoran as  
opposed to Loran-C, it's effectively the same network, using the same  
transmitters and GRIs.
 
It seems that enhanced accuracy for navigational purposes in harbour  
approaches etc is provided by Differential Loran Reference Stations,  similar to 
differential GPS, with the correction data being transmitted on the  eLoran 
data channel, more here......
http://www.trinityhouse.co.uk/news_info/press_releases/2013/uk_switches_gps_
backup_english_channel.html
 
Again this will not affect operation of the FS700.
 
I've run three FS700s in the UK, about 150 Km north west of Anthorn,  but 
when Anthorn is down for maintenance I can also run quite happily from the  
master station at Lessay in France.
 
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.
 
The latest FS700 firmware I have seen is version 1.20.
The station identification data is stored in the firmware and  this looks 
to be the only version with included data for the Lessay chain,  although 
Anthorn identifies as Loop Head in Ireland, a proposed station that  never went 
into service with Anthorn taking its slot.
Attempts to edit the firmware to change the identification text resulted in 
 boot failures with a faulty Eprom warning, presumably due to a checksum  
failure. I haven't pursued this.
I can make the 1.20 firmware available if anyone would like a  copy.
 
There is a full FS700 manual available on the KO4BB manual site, complete  
with schematics.
The schematics may not fully match the text though as a scanned set of  
schematics have been added to the last version of the online manual  without 
schematics that was available from SRS.
 
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.
Packaging quality from these sources is definitely variable and only  one 
of mine arrived undamaged.
A particular weak spot is the cutout for the small mains transformer on the 
 rear panel, one ding on the transformer can cause some severe panel 
distortion  in that area, with possibly a strip down and some panel beating being  
required. Another weak spot is the flip up cover over the mains switch.
Luck of the draw really, some outfits are better at packaging than others,  
but don't take this for granted and be prepared for some making good.
 
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.
 
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:-)
 
Regards
 
Nigel
GM8PZR
 
 


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