Build your own VOT for $5 - no, no joke

[photofly]

It's a fair amount of work:
http://www.aholme.co.uk/GPS/Main.htm

It would be considerably easier to build your own VOR receiver.

[NeverBlue]

What the?

A receiver is a receiver...they're pretty much all the same.

The decoding and processing of the signal is what can be complicated...but not in a simple GPS receiver!

It just receives a signal and calculates your position pretty much the same way LORAN did...through timing...

Yes the signals are different...but GPS is just a reciever...a decoder...not an encoder

All that mapping stuff is not part of the receiver at all.

What photofly is doing is generating a signal...way more complex to do.


And in no way shape or form is he using his airplane as a "scientific experiment"...he's not altering his airplane at all.

108.00 Mhz : ICAO, Honeywell, Rockwell, Garmin, Becker, IFR, TKM, HP, VOR test frequency
108.10 Mhz : ICAO, Honeywell, Rockwell, Garmin, Becker, IFR, TKM, HP, ILS test frequency
118.000 Mhz: ICAO, Honeywell, , Rockwell, Garmin, Becker, IFR, TKM, HP, Comm test frequency

It's no reckless experiment...it's "Standard Practice"

[NeverBlue]

http://www.elecfreaks.com/store/fastrax ... p-236.html

There I just built one...by clicking a mouse...

[NeverBlue]

You said a GPS isn't complex because it comes in every smartphone. So you're saying GPS and/or smartphones aren't complex.

What? You should re-read what you wrote.

You have a convoluted way of drawing conclusions.

[Posthumane]

http://www.elecfreaks.com/store/fastrax ... p-236.html

There I just built one...by clicking a mouse...

Right. And I built an airplane by going on barnstormers.com and calling some people. I also built a house by calling up a realtor. Wait, maybe "built" isn't the right word... Bought? Well, they both start with the same letter so they must mean the same thing.

The RF front end in a GPS receiver may not be anything spectacular, but processing the signals to determine a position definitely is. The principle is similar to loran, but the mechanics of it are quite a bit different.

Just transmitting a signal isn't all that complicated either - it can be done with a spark gap and an LC circuit made with some metal plates and a coil of wire.And receiving and demodulating an AM signal can be done with an LC circuit and a non-linear junction (such as a diode, or in a pinch an old razor blade and pencil).

[photofly]

I was looking at the webpage of the guy that built his own GPS. The use of Gold codes means a 1-bit A to D converter can reliably pick out signals from individual satellites (all on the same frequency) that are all 20dB below the noise floor. Might not mean much to some, but as a system design, that's quite stunning.

[NeverBlue]

GPS signal contents are not complex at all.

Civil aircraft GPS receivers do not use the information contained in the signal as it was originally designed to be used.

They only use it to recognise the signal. It is all done by timing...that's it...nothing else.

Advacements in technology makes things easier to deal with...not more difficult.

It is much easier to send information digitally than with analogue technology...easier to encode and decode.

Why do you think mankind is slowly abandoning analogue technology?...because it's less complex?

Ok.....

[Posthumane]

You have a funny definition of complex NB. I suppose on the face of it any RF signal, either digital or analog, is "simple" in that it's just a time varying electromagnetic field. The way those signals are modulated and demodulated is what makes them interesting. Any RF engineer would consider modulating a VHF signal twice (once AM and once FM) a relatively straighforward process, but generating even the "simple" C/A code used to modulate the L1 GPS signal takes a bit more head scratching*. The L1 signal is also double modulated with both the C/A code and the encrypted P code.

Also, analog technology is very much alive and kicking. Digital transmissions allow you to do much more complex things than you could with analog though, such as having a lot of different transmitters operating simultaneously on the same frequency through things like CDMA.


*Btw, the C/A code is used exactly as it's intended on civil GPS receivers. Saying "it's just timing" is a lot like managers saying "it's just engineering" when asked about solving a problem. I suppose everything is simple when someone else is doing it. When you manage to design something (anything, really), then you'll have some basis on which to call it simple.

[Aviatard]

It comes in every smart phone now...complex????

I don't know what you're reading...

but I NEVER SAID THAT AT ALL!

what is the matter with you?

You have a convoluted way of drawing conclusions.

You have a convoluted way of expressing yourself. What exactly did the complex???? mean? I interpreted it in exactly the same way: you were saying cell phones aren't complex. If that wasn't your intent, then what was the purpose of the 4 question marks?

[NeverBlue]

What about P code?

GPS receivers and Smartphones are 2 entirely different things.

I no very little about smartphones.

Complex?....they're computers...you decide

I never ever said smartphones weren't complex.

Please show me where I said that...

[Aviatard]

I never ever said smartphones weren't complex.

Please show me where I said that...

It comes in every smart phone now...complex????

Right there ^

And if that doesn't mean you think smart phones aren't complex, then what does it mean?

[CID]

And in no way shape or form is he using his airplane as a "scientific experiment"...he's not altering his airplane at all.

If you consider it a maintenance action, he's "testing" a system with a device that can't be traced to any standard. If it's an operational check, how exactly can he verify the VOR is within the acceptable error for instrument flight?

It's no more than a science fair experiment or a cheap magic trick if you can't take any meaningful credit for the test.

[NeverBlue]

There is No Standard for this type of radiated test.

That's why they're called "Go-No Go"

There is no test required for your VOR receiver.

It's completely up to the PIC to decide whether it's working or not. How would he do that?...by using a VORTAC, VOR station, VOT, and/or a generated VOR test signal...just like the Manufactures Operating Instructions for the Nav receiver says...

There is no standard for the ERP of the signal.

There is no requirement to have your VOR annually checked or calibrated like there is for mechanical TACH!

[photofly]

a device that can't be traced to any standard.

Of course it can be traced. I can put a 'scope on it and compare all the parameters to the VOR standard. I can even have my 'scope calibrated first, if that makes you feel warm inside.

It's no more than a science fair experiment or a cheap magic trick if you can't take any meaningful credit for the test.

I can take meaningful credit for the test. I actually put in my journey log today "VOR alignment verified within tolerance using VOT signal." Then I signed it. In ink. With my name. Goodness me, that must rip you up inside.

[NeverBlue]

Ok now that's completely wrong.

You can not "align" your VOR in the aircraft with a VOT signal.

You in no way did that...
You did nothing that required a log book entry....why did you?

Now you would have to prove that your Test Set is calibrated to a known standard...which you can't because there is none....you can't prove it's in tolerance because you have not calibrated your test signal.


Your entry is false...why would you do that?

[photofly]

I didn't say I aligned it. I said I verified the alignment.

Even PPLs are required to know - and are examined by TC on - the go/no-go tolerances of all their flight instruments, and of a VOR receiver should they have one. If an instrument fails such a check by the pilot it's not considered useable.

A VOR is considered useable for navigation if the pilot carries out one of the four tests you mentioned. Nothing wrong with making a note in the journey log that the pilot carried out one of those tests and found the equipment passed.

In the US, it's actually required for a pilot to carry out just such a test and record the results within the previous 30 days of an IFR flight using a VOR receiver.

AMEs do not own a monopoly on testing equipment and deciding if it's fit for use. Nor on recording the results of such a test in the technical records.

As far as what is "required" - I log lots of things that aren't required. I log every time I update the GPS database. I log every time I add a quart of oil. I've even been known to log how the weather was and if my passenger was cute. If my passenger was my wife, then yes, she was!

[CID]

Goodness me, that must rip you up inside.

Nope. You breaking the law doesn't bother me in the least as long as I'm not anywhere near your airplane.

The very first paragraph in CAR standard 571 is:

Persons who perform maintenance or elementary work are required to follow the manufacturer’s recommendations, or equivalent practices. Where the recommendations of the aircraft manufacturer are incompatible with those of the engine, propeller, or appliance manufacturer, the recommendations of the aircraft manufacturer shall be used. Where the manufacturer has not made specific recommendations, standard industry practices are to be used. These practices include, but are not limited to, methods published by Transport Canada, a foreign Civil Aviation Authority, the manufacturer of a similar product, or other practices that may not be published provided they are generally accepted by the Canadian aviation industry. Similar requirements apply to the selection of parts, materials, tools and test apparatus.

So how does your gizmo and your actions fit in to that? By the way, you didn't break any laws until you entered it into your logbook.

Neverblue, no matter what you write, it's always wrong. But at least you're consistent.

[photofly]

Checking a VOR receiver by using a VOT is neither maintenance nor elementary work, so nothing you wrote has the slightest relevance.

[CID]

Checking a VOR receiver by using a VOT is neither maintenance nor elementary work, so nothing you wrote has the slightest relevance.

So a maintainer can't sign off a VOR as tested serviceable by using a VOT station on the field? And your statement has a sliver of truth. Just doing a test isn't maintenance. It isn't "anything". Writing it down and taking credit for the test....that's a different story.

If you had a snag on that airplane regarding a VOR and you did the test with your POS and made a logbook entry to that effect to clear the snag....I think TC would have a problem with that.

[NeverBlue]

Ahhh...I read your entry wrong...my bad.

Who said anything about a monopoly on test equipment??

...this is Canada right? TC rules not FAA...