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

[NeverBlue]

108.00 is a VOR test frequency.

Almost every test set uses 108.00 as a preset test channel. And yes...transmit freely at any airport without repercussions.

There are no terminal VORs or VORTACs or any other VOR ground station that operate at that frequency.

If a pilot is using VOR test frequency to navigate with?.......well.......

Industry Canada has an acceptable transmit power limit in that band without a license requirement.

I doubt very much that Photofly's set-up will cause any problem to anyone...even if someone else is using 108.00 to test their aircraft with.


...there...is that "Neverblueing" it up enough for you Photofly?

...just terrible of me....

Poetry...

[CID]

Believe it or not, 108.00 is not reserved for test and there are a few VORS in the world that use it. There is also no guarantee that someone will always use this setup in a metal hangar.

Ingenuity? Any electronics tech can figure out a multitude of ways to broadcast a VOR test signal but why reinvent the wheel or choose what is arguably the worst way to do it and with risk to damaging your computer?

Square waves are composed of a fundamental frequency with an infinite number of odd harmonics in decreasing amplitudes. Operating this gizmo is wreckless at best. Thinking it's a valid test is inadvisable.

[photofly]

Believe it or not, 108.00 is not reserved for test and there are a few VORS in the world that use it. There is also no guarantee that someone will always use this setup in a metal hangar.

I have a suspicion you won't find a real VOR using 108.0 anywhere in North America. I know there isn't one within 500 miles of here.

There's no guarantee that someone won't use the raspberry Pi circuit board as a knife to slit open your abdomen and make you swallow your own bowels either. Sometimes we just have to trust people not to do the wrong thing.

Ingenuity? Any electronics tech can figure out a multitude of ways to broadcast a VOR test signal but why reinvent the wheel or choose what is arguably the worst way to do it and with risk to damaging your computer?

Go ahead, argue this is the worst way to do it. It's about one thousand dollars cheaper than any other wheel I've seen, and I get a kick out of wheels I've designed and built myself vs. ones I bought from someone else. I'll fight for your continued right to feel "anything I bought is better than anything I made myself", though.

Square waves are composed of a fundamental frequency with an infinite number of odd harmonics in decreasing amplitudes. Operating this gizmo is wreckless at best. Thinking it's a valid test is inadvisable.

I'm confident it's entirely wreckless, although you meant reckless. I'll do some tests to look for the third and fifth harmonics. Does anyone know who uses 324MHz? I note that 540MHz is in between UHF tv channels 25 and 26. Maybe my checking my VOR receiver is causing fuzz on reruns of I love Lucy in the Orange hangar next door - I'll ask.

[CID]

Reckless. Yup you got me there. Had a momentary lapse in spelling. You are right. It's reckless to do this.

And yes, likely none in North America that's why I said "the world" and since the Internet is global.....well you probably get the point.

[CID]

Go ahead, argue this is the worst way to do it. It's about one thousand dollars cheaper than any other wheel I've seen, and I get a kick out of wheels I've designed and built myself vs. ones I bought from someone else. I'll fight for your continued right to feel "anything I bought is better than anything I made myself", though.

So....you can't build a simple oscillator and AM modulate it for under a thousand? Maybe I gave you too much credit.

[NeverBlue]

Please...show me a VOR ground station on 108.00 Mhz!...don't just say it.

Every VOR test set I've ever seen has it as it's test frequency....RADIATED!...in free air...

[NeverBlue]

....and somebody please explain these "square waves".....

[photofly]

Go ahead, argue this is the worst way to do it. It's about one thousand dollars cheaper than any other wheel I've seen, and I get a kick out of wheels I've designed and built myself vs. ones I bought from someone else. I'll fight for your continued right to feel "anything I bought is better than anything I made myself", though.

So....you can't build a simple oscillator and AM modulate it for under a thousand? Maybe I gave you too much credit.

When did I say that? But this uses a single $5 off the shelf part, a length of wire, and a phone. It requires no test gear to tune an oscillator or adjust the depth of modulation.

Here's your challenge then: You find another way to do it that other people who are interested can try for themselves without lifting a soldering iron. don't forget you need to be able instantly to change the frequency to 329.15MHz to test your glideslope receiver, too.

Come back when you finally have something intelligent to say; I can wait as long as it takes.

[all_ramped_up]

Ingenuity? Any electronics tech can figure out a multitude of ways to broadcast a VOR test signal but why reinvent the wheel or choose what is arguably the worst way to do it and with risk to damaging your computer?

Square waves are composed of a fundamental frequency with an infinite number of odd harmonics in decreasing amplitudes. Operating this gizmo is wreckless at best. Thinking it's a valid test is inadvisable.

It's not hard to solder up a simple bandpass filter if one was motivated enough.

Two caps and a resistor... that's what? $5 and 15 mins of effort? The filter would also take a little off the radiated power even if slightly.

[NeverBlue]

...it's not reckless

http://www.ic.gc.ca/eic/site/smt-gst.ns ... 10208.html

[CID]

But this uses a single $5 off the shelf part, a length of wire, and a phone.

So...your phone is free? Please let me know where I can get a free phone. Also let me know where to get a free replacement when it breaks from using the way you suggest here.

As for 108.00, it looks like my information is outdated. There weren't many but the last ones (I think the last one was in Germany) changed when Europe adopted VHF FM Immunity. 108.00 was just too close to some commercial FM radio stations. There are still however some airports that use 108.10 for LOC/ILS. You can check them out here:

http://www.icao.int/apac/documents/edoc ... list02.pdf

photofly, airplanes are not highschool science fair experiments. I'm not going to invent or suggest a shitty way to do anything to an airplane because it's cheap. That's not to say that I think the most expensive way is always the best way but this idea is half baked. That's my opinion. Go ahead and use this to your heart's content but at least people won't just blindly do this. Maybe my opinion will have them think twice.

Now let's go on to how to test a DME with paper clip and free DME test set set.....

[CID]

When did I say that?

Go ahead, argue this is the worst way to do it. It's about one thousand dollars cheaper than any other wheel I've seen

[Posthumane]

Photofly - I, for one, am interested in a little more detail about how you synthesize the wav files. Might try this with my Pi, though with a couple modifications. Btw, do you have any way to measure the transmitted power?

SDR sure has made it easier to play around with RF these days. Bitch as some people might, there are many great things about living in our times.

[photofly]

When did I say that?

Go ahead, argue this is the worst way to do it. It's about one thousand dollars cheaper than any other wheel I've seen

Your English comprehension sucks. That doesn't mean something can't be built for less than $1000; it means that the off the shelf ready built options are limited. Regardless of your idiocy, using a $5 single board computer as a crystal controlled synthesized RF source is a cool hack.

I'm still waiting for an intelligent contribution on this topic from you.

[photofly]

Photofly - I, for one, am interested in a little more detail about how you synthesize the wav files. Might try this with my Pi, though with a couple modifications. Btw, do you have any way to measure the transmitted power?

SDR sure has made it easier to play around with RF these days. Bitch as some people might, there are many great things about living in our times.

I'll post the code tonight. I don't have any way to measure the ERP unfortunately.

[CID]

I'm still waiting for an intelligent contribution on this topic from you.

photofly, that's exactly what I was thinking about you and your posts. I'll leave you to discuss your "hack". Arguably one of the most awkward uses of a Raspberry Pi I've seen so far. But...whatever.

[photofly]

For Posthumane, here's the code that churns out the baseband signal.

It's based on the code from this webpage: http://soledadpenades.com/2009/10/29/fa ... ve-module/

The wikipedia page on VOR was mostly unhelpful, because it makes something very simple sound very complicated. This reference was much more use: http://www.nist.gov/calibrations/upload/tn1069.pdf

Let me know what you try and how it goes.

produce_VOTwav.py 2.zip

(848 Bytes) Downloaded 55 times

[iflyforpie]

Thanks for the info, photofly. Don't let the pedants discourage you.

[photofly]

There are about a million and one ways to improve this; I'm as usual vastly amused by the particular nits people choose to pick. Hoping Posthumane finds something interesting to do.

[NeverBlue]

If it's designed to give a 0 degree radial From indication...or whatever...and that's what it does, then why isn't it a valid test?

What's the difference from using 114.80 Mhz VOT? ...you're not calibrating anything. It's just a check.