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arkmark
1st Jul 2005, 05:39
Hi All,


I need a hand with obtaining some VLF Omega receivers. They were installed everywhere in the 90's in top end aircraft, but are now redundant. I'm looking for one or two as I need the clocks out of em.

tinpis
1st Jul 2005, 05:43
1981 was a few Nomads with GNS.
Luckily for everyone both the system and the Nomads were committed to the shiteheap.

B772
1st Jul 2005, 05:50
Some of the AN jet fleet in the mid 80's were fitted with Omega receivers so there could be a few still 'floating around'.

BTW Is the Omega transmitter station in Gippsland and North West Cape still in service.

Sunfish
1st Jul 2005, 06:03
The Omega transmitter in Gippsland is in the Port Albert Museum. It was all shut down years ago.

I'de be very surprised if the atomic clocks in the Omega receivers would be nearly as accurate as the GMT signal out of a modern $200 hand held GPS.

arkmark
1st Jul 2005, 06:32
I'm betting that they are more accurate than that - especially two averaged against each other.

We want to use them as part of a NTP server for our community wireless network at www.mervin.net.au/wireless.

I installed an Omega receiver many years ago to a large helicopter - big job!!! it was a few of big boxes too !!

V1OOPS
1st Jul 2005, 07:06
I think it was better suited to the subs it was designed for - we were usually about 4 miles ahead of the Omega read-out on most flights until we slowed joining the circuit. By park brake 'on' it was just coming up the taxiway ;)

Still, better than a couple of wandering ADFs.

404 Titan
1st Jul 2005, 07:08
Sunfish

Why do you think the clock in your GPS unit is so accurate? Itís not because of its own internal clock. It is because every time you turn it on and use it, its internal clock is updated by the atomic clocks in the satellites.

Sunfish
1st Jul 2005, 07:24
Thank you 404t, I didn't know that.

I just follow in the general direction that the arrow thingy on my Etrex is pointing - which can be a problem if I'm not holding it absolutely flat, because then I climb or descend a bit:E

Seriously though, last week a mate was delivering a vessel to Adelaide and the GPS went "strange" for about half an hour. Way off course. Haven't checked RAIm ephermises etc., but the only thing he could put it down to was a dud satellite.

Going Boeing
1st Jul 2005, 07:48
The RAAF's Caribou aircraft had VLF Omega systems (taken out of the P3B Orions when they were traded in) so it may be worth an enquiry with the Department of Defence.

DirectAnywhere
1st Jul 2005, 09:44
Seem to remember each GPS satellite has four atomic clocks - two caesium and two something else.

Be nice if you could piggyback on the time signal from that - although you'd have to correct it for signal delay, relativistic effects and a whole heap of other stuff.

Where are you going to get your time signal from to input into the clocks initially or doesn't it matter provided they're both on the same time - any time?

Sounds interesting. I can't help you but....

bushy
1st Jul 2005, 09:45
And the RFDS central section Chieftains also had Omega.It was better than DR, and the only navaid we had most of the time. It went into DR mode whenevr you flew through rain.

footloose
1st Jul 2005, 11:36
and RFDS W A Section used them in their Conquest II's up til mid 90's.
Good Luck

OzExpat
1st Jul 2005, 14:12
Yes, Omega was pretty accurate - right up until the time you were forced to fly through cloud above the FZL... :eek: Sorry that I can't help about the clock issue, but I'm really glad that I haven't had to use them for nav since GNSS came along!

mattyj
1st Jul 2005, 21:19
Try calling this number..064-0-9-296 2526
Dwen Airmotive in New Zealand..they have piles of junk in containers at Ardmore..mostly Airforce Surplus..if they don't have it, the old hoarders might be able to point you in the right direction..

..Oh and don't be shocked if they try to charge a bomb..just haggle

OZBUSDRIVER
1st Jul 2005, 23:03
Why don't you use the time signal off the GNNS? Got a brother in radio who is puzzled why you need such accuracy

The Brent
2nd Jul 2005, 07:34
Aarkmark,

Have sent you a private message.

I may have one for you.

Cheers

arkmark
2nd Jul 2005, 11:48
It is true that we could use GPS (I don't call it GNSS because I think this is a BAD BAD BAD name for it as it is too close to GNS which was VLF Omega).

There are three rasons that we don't want to just use GPS time.

1. Our wireless is designed to be self sufficient. Perfect time up the network referenced from within the network is an ideal.

2. As a result of making this rather cool reference, we can make our world class stand alone time server available to others on the internet for no other reason than the fact that we can.

3. Locally there is a guy on the network who has a fettish for the concept of time, who want's to do some experiments with relativity AS A HOBBYYYYYYYYYYY. Ceasium time bases are not all that common, and hence the link with me as an avionics LAME I worked with GNS and recall that they had them, and as such might be able to put my hands on some if I ask the aviation community.

Sound like a strange hobby - so is the whole community wireless network - but then again so is stamp collecting and renovating old V8's :)

Weapons_Hot
6th Jul 2005, 10:04
404 Titan
The time reference on a GPS receiver is only as accurate as the time reference data uplinked to the particular "star" by the Master Control station at AFB Schriever, CO.
I would prefer one of the clocks from one of the "stars", which as a stand-alone (and left alone) is accurate ;)

reynoldsno1
6th Jul 2005, 22:36
Why do you think the clock in your GPS unit is so accurate? Itís not because of its own internal clock. It is because every time you turn it on and use it, its internal clock is updated by the atomic clocks in the satellites.
Not quite. To achieve a 3D navigation solution from GPS, you should only need to receive signals from 3 satellites. However, you are not directly reading the range of the satellites to achieve this, but using a time based solution (sometimes called pseudo-range). Since the receiver and satellite clocks are not synchronized, a fourth satellite is used to eliminate the time error i.e. the receiver software resolves four simultaneous equations with four unknowns...

pullock
7th Jul 2005, 06:56
Actually, Weapons hot is correct.

The time piece in the GPS it's self is no more than a Quartz clock, and it is updated at power up and other intervals from the GPS satellite time bases - this is how they keep the cost of GPS receivers so low.