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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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26th Dec 2007, 8:54 pm | #21 |
Hexode
Join Date: Apr 2003
Location: Cotswolds, UK.
Posts: 465
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Re: Frequency Standards
Pete,
You have stated very exactly what the position is. We are in a curious position where officialdom is bringing under its control a large number of bits of kit that have been happily maintained for a long time on a largely amateur basis. The route that we (all the guys who inspect gliders like myself) are taking is that we are submitting descriptions of what we are doing to officialdom and they are being asked to say yes or no. Up to now they are being very reasonable. One of the reasons for the reasonableness is that we haven't had any incidents of getting it wrong in the past and that they have a mandate of not upsetting everyone with over officialdom and cost and highly expensive calibration costs would be one of those. A further wrinkle in the future will be that we will have to fit transponders to the gliders which is not a test job that the average radio person will be kitted out for and we are not sure what the route through this will be. Robin |
26th Dec 2007, 9:52 pm | #22 |
Retired Dormant Member
Join Date: Oct 2004
Location: Bristol, UK.
Posts: 837
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Re: Frequency Standards
I think you need to have and offer to the Men from the Ministry, a defensible position if anything goes wrong. This could be double-checking of everything and expensive calibration of all test equipment, or it could be something less, but which you could stand up in court and defend. The Men from the Ministry would have to explain why they allowed such and such a test regime to exist. Explaining how you tested tranceivers which may have failed and contributed to a crash, with home made equipment, might be a difficult line to argue.
Follow the other line to its conclusion and you have equipment in gliders being maintained to the same standards as trans-Atlantic airliners, glider tranceivers sent off to certified labs every 3 months or whatever and gliding made unaffordable. As far as I know, gliding has never been regarded as a particularly dangerous business, but it only takes one freak accident to cause a complete over reaction. We live in risk averse and compensation sensitive times. Pete. |
27th Dec 2007, 3:55 pm | #23 |
Hexode
Join Date: Apr 2003
Location: Cotswolds, UK.
Posts: 465
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Re: Frequency Standards
IN essence you are right. The men from the ministry have been realising that they have bitten off more than they can easily chew in that every one (from EASA in Europe downwards) has been going mad in that they've realised that doing gliding, and a lot of sport aviation, in the same way that the big boys are done is very very difficult and could easily make the whole thing (not just us but the home build boys in the PFA and a lot of other people) totally uneconomic. As a result a lot of us have been writing up methods for doing things that are being submitted for approval so that we can keep things going in an economic way.
It may be that we have to do things using comercial kit rather than home built but we won't know until we've tried it. The CAA are actually being very reasonable and are not going overboard on any of this. Everybody recognises that the existing standards are written for commercial aviation and are not directly applicable to sport aviation so we are kind of making it up as we are going along Robin |
27th Dec 2007, 9:08 pm | #24 |
Retired Dormant Member
Join Date: Mar 2003
Location: Bishop's Waltham, Hants, UK.
Posts: 939
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Re: Frequency Standards
Robin,
if you contact me via PM, I may be able to help with a couple of contacts, however, if it comes down to it, you will need to refer to the CAA document CAP670, which lays down the legal requirements and standards for aviation radio ground stations (and is guarenteed to cure insomnia), I believe that aircraft stations are covered in the Air Navigation Order, and derived from ICAO Annex 10 & 11. I suspect that the work you and your colleagues are doing will lead to an ammendment to some of that documentation. Jim. PS CAA CAP670 is available online |
28th Dec 2007, 12:28 am | #25 |
Octode
Join Date: Mar 2006
Location: Watford, Hertfordshire, UK.
Posts: 1,270
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Re: Frequency Standards
When I worked in a cal lab we would send our standards receiver to a NAMAS calibration facility for accreditation. This was deemed acceptable by which to check all crystal sources in the sweepers, spectrum analyzers and counters our company used. As long as your standard is traceable to a NAMAS calibration house you should be ok.
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Whether the Top Cap is Grid or Anode - touching it will give you a buzz either way! |
28th Dec 2007, 6:48 pm | #26 |
Retired Dormant Member
Join Date: Nov 2007
Location: Maidstone
Posts: 5
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Re: Frequency Standards
NAMAS has now changed to UKAS (United Kingdom Accreditation Service) but is still based at NPL Teddington. All equipment used for 'legal' measurements should be calibrated in such a way as to be traceable to UKAS at a frequency stated in the relevant British or ISO Standard.
HTH Fred BVWS and Radiofil (France) member |
29th Dec 2007, 12:20 pm | #27 | |
Octode
Join Date: Sep 2004
Location: St. Albans, Hertfordshire, UK.
Posts: 1,477
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Re: Frequency Standards
Quote:
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Regards, Richard, BVWS member |
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30th Dec 2007, 2:12 am | #28 |
Hexode
Join Date: Apr 2003
Location: Cotswolds, UK.
Posts: 465
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Re: Frequency Standards
That's effectively what I want to do. It won't receive 198 kHz directly (only goes down to 400 kHz) but it will take an external 10 MHz.
So, build externally driven 10 MHz and then tie comms tester to it Robin |
30th Dec 2007, 10:44 am | #29 |
Octode
Join Date: Sep 2004
Location: St. Albans, Hertfordshire, UK.
Posts: 1,477
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Re: Frequency Standards
Going a bit OT now, but another possibility - Find a reciever that can pick up one of the WWV transmissions on 5/10/15Mhz http://tf.nist.gov/stations/wwv.html
Then loosely couple the output of your comms tester sig. gen. tuned to the same RF as the reciever and adjust the reference oscillator for zero beat. That ought to work in theory.
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Regards, Richard, BVWS member |
30th Dec 2007, 5:35 pm | #30 |
Retired Dormant Member
Join Date: Mar 2006
Location: Sheffield, South Yorkshire, UK.
Posts: 1,587
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Re: Frequency Standards
Hi Robin,
Whatever you build (externally driven 10 Mhz) , for your own piece of mind or even legal position it will have to be UKAS traceable.Their service is not to just check calibration from a measurement point of view but to also specify the method of testing and all of the theory to support required cal intervals and measurement errors. It is they that then take full technical and legal responsibility for the calibration. How do the Germans cope with the legality, my understanding of their law is that they are far more restrictive and demanding. Mike |
30th Dec 2007, 6:47 pm | #31 |
Octode
Join Date: Mar 2006
Location: Bracknell, Berkshire,UK.
Posts: 1,169
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Re: Frequency Standards
WWV will work OK if you are in the USA. At this time of the sunspot cycle you will be lucky to even detect it over in the UK, never mind do any serious measurements from it. Since Rugby stopped transmitting MSF there has been a distinct lack of useful frequency standards in Europe - the only one I know of is the Moscow one on 9996kHz, but can't even hear that at the moment.
Dave |
5th Jan 2008, 5:08 pm | #32 |
Hexode
Join Date: Apr 2003
Location: Cotswolds, UK.
Posts: 465
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Re: Frequency Standards
Well MSF is still available from the new site. Also if you look at the NPL site their declared frequency standards are droitwich, MSF and GPS satellite based. They don't underwrite the other 198 kHz transmitters as they don't monitor them.
Robin |
5th Jan 2008, 6:42 pm | #33 |
Octode
Join Date: Mar 2006
Location: Bracknell, Berkshire,UK.
Posts: 1,169
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Re: Frequency Standards
Guess you are talking about MSF on 60kHz - now from Anthorn. MSF used to also transmit on HF at 5MHz, 10MHz, 15MHz etc and was quite handy for checking frequencies of receivers. Now there is nothing in Europe on those frequencies and reception of WWV from the USA is pretty patchy until the sunspots return.
Dave |