DIY DF device

Interesting idea.

I'd like to have one of these in the aircraft. That way if I'm listening in
on approach, I'd have an idea of the relative bearing to another aircraft
that is transmitting. For example, another aircraft reporting over the same
fix - it would be nice to know which direction to look. A circular 8 LED
display would be fine.

Anybody know how to do this?

Bill Daniels

"Mattsson" wrote in message
...
So, this may be an utterly stupid idea, but...

I know I can get bearings from an airport, or more specifically the tower,
by using my com and talking to them when flying and within range. Also,
radio amateurs have these "fox hunts" where they hide a small tx and then
hunt it down.

Now, I have a scanner that covers the civil airbands on AM and I already
have built a few homemade base antennas for it, following some nice
designs
made by others. This allows me to listen to nearby airfield traffic
pattern
communication.

Now, it would be a lot of fun to be able to use my scanner with a suitable
antenna array, to get bearings to an airplane talking to for instance
tower.
I know I know, you report positions most of the time, but sometimes the
small planes give pireps on local weather conditions and the like,
sometimes
they just give position reports and so on, not being that accurate on
their
position. At other times, spending time at relative´s summer cottages,
having the scanner with me, it would be great to quickly get info on where
to scan the sky for nearby airplanes on the air, then get the binoculars.
And as the chit chat on the airwaves usually is very brief, there is no
time
to start pointing that yagi or whatever to get some idea of where the
plane
is. You would need some kind of automatic direction finding, something
that
would give a direction for you in a second or two.

Is there anything like this for a DIY project? I googled a bit and found a
lot on automatic FM DF projects, but not for AM. It´s understandable that
most people are interested in searching FM transmissions, especially those
interested in finding noise sources and the like, but I´m just interested
in
spotting and plotting those planes up there! =)

Any thoughts and suggestions appreciated, Ken

On Mon, 12 Apr 2004 18:27:05 GMT, "Bill Daniels"
wrote:

I'd like to have one of these in the aircraft. That way if I'm listening in
on approach, I'd have an idea of the relative bearing to another aircraft
that is transmitting. For example, another aircraft reporting over the same
fix - it would be nice to know which direction to look. A circular 8 LED
display would be fine.

Ummm. Personally, I think it's better to keep one's attention OUTSIDE the
cockpit at a time like this. It takes a finite amount of time to remove
your attention from the exterior, focus on a panel-mounted dial. By the
time you've realized the guy is reporting the same location and look at
your readout, he's probably let loose of the mike button and the LED is
dark.

Sure, you could set up some sort of latching system, but on busy days, as
soon as one guy quits transmitting someone else punches the button.
Inaccurate data is far worse than no data at all. If you're close and
maneuvering, the relative positions are probably changing rapidly, anyway.

Ron Wanttaja

"Ron Wanttaja" wrote in message
...
On Mon, 12 Apr 2004 18:27:05 GMT, "Bill Daniels"
wrote:

I'd like to have one of these in the aircraft. That way if I'm listening
in
on approach, I'd have an idea of the relative bearing to another aircraft
that is transmitting. For example, another aircraft reporting over the
same
fix - it would be nice to know which direction to look. A circular 8 LED
display would be fine.

Ummm. Personally, I think it's better to keep one's attention OUTSIDE the
cockpit at a time like this. It takes a finite amount of time to remove
your attention from the exterior, focus on a panel-mounted dial. By the
time you've realized the guy is reporting the same location and look at
your readout, he's probably let loose of the mike button and the LED is
dark.

Sure, you could set up some sort of latching system, but on busy days, as
soon as one guy quits transmitting someone else punches the button.
Inaccurate data is far worse than no data at all. If you're close and
maneuvering, the relative positions are probably changing rapidly, anyway.

Ron Wanttaja

I'd still like to have the DF on the comm radio. When somebody is talking,
I'd like to know what direction they are coming from. So, maybe instead of
LED's we need a 3D aural display so the voice seems to come from the
direction of the transmitter.

Bill Daniels

I guess one of these newfangled TCAS systems that monitor for nearby
transponder squalks are out of the question since you would have to take
your eyes out of the skies to look at the little led's!

Hey go to the listed web page and look at the display. It only takes a quick
glance at the display to get an idea where its coming from. If you've let
another plane get so close to you that you can't glance at the display to
see where neigboring traffic is then you weren't flying your plane. Sure
there will be times when you miss one transmission and view a second but
they will be few and your still looking all around for traffic anyway. Your
main advantage is most of the time you will start your scan where the
display indictes it originating from and if you don't see it contiunue on
from there.

Last I looked the last word in this newsgroup was "homebuilt" to me that
screams "EXPERIMENT", go for it try a new project and enjoy the process and
journey!
As far as antennas you need 4 each 1/4 wave antenna's which is no biggy
unless your driving around in one of these 200+ mph monsters and are
concerned about drag. One idea for antennas since this is a receive only
concern is to use an electically shortened antenna say take a piece of pc
board and etch an inductor/antenna on it and cover it with a layer of
foam/fiberglass suitable shaped aerodynamically, should be able to get away
with only a 4-6 inch antenna especially since you really don't want a long
range system anyway.
Good luck and go play with it


John






Bill Daniels wrote:


"Ron Wanttaja" wrote in message
...
On Mon, 12 Apr 2004 18:27:05 GMT, "Bill Daniels"
wrote:

I'd like to have one of these in the aircraft. That way if I'm
listening
in
on approach, I'd have an idea of the relative bearing to another
aircraft
that is transmitting. For example, another aircraft reporting over the
same
fix - it would be nice to know which direction to look. A circular 8
LED display would be fine.

Ummm. Personally, I think it's better to keep one's attention OUTSIDE
the
cockpit at a time like this. It takes a finite amount of time to remove
your attention from the exterior, focus on a panel-mounted dial. By the
time you've realized the guy is reporting the same location and look at
your readout, he's probably let loose of the mike button and the LED is
dark.

Sure, you could set up some sort of latching system, but on busy days, as
soon as one guy quits transmitting someone else punches the button.
Inaccurate data is far worse than no data at all. If you're close and
maneuvering, the relative positions are probably changing rapidly,
anyway.

Ron Wanttaja

I'd still like to have the DF on the comm radio. When somebody is
talking,
I'd like to know what direction they are coming from. So, maybe instead
of LED's we need a 3D aural display so the voice seems to come from the
direction of the transmitter.

Bill Daniels

On Tue, 13 Apr 2004 09:47:20 +0000, John wrote:

I guess one of these newfangled TCAS systems that monitor for nearby
transponder squalks are out of the question since you would have to take
your eyes out of the skies to look at the little led's!

Don't know much about TCAS, but I believe the system has an voice warning
that actually tells you how to maneuver. In any case, most aircraft
current with TCAS have two pilots. TCAS also is tracking transponder
squawks, not radio calls made at 1 minute intervals.

Hey go to the listed web page and look at the display. It only takes a quick
glance at the display to get an idea where its coming from. If you've let
another plane get so close to you that you can't glance at the display to
see where neigboring traffic is then you weren't flying your plane.

But isn't that what the system is for...helping you spot traffic that's
close to you? If I'm two miles from the airport and someone transmits from
the pattern, there's already a relatively narrow arc they can be in.

Here's an experiment for you: Next time you're in a busy traffic pattern,
glance down at, say, the oil temperature gauge, note what the reading is,
then go back to your visual traffic scan. *Every* time there's a
transmission on the radio. Then decide whether looking at a panel-mounted
instrument is a good idea.

My home drome is a very busy uncontrolled airport with a single 3,000-foot
runway. I've been in the pattern with ten other aircraft....don't know how
busy the radio was then, 'cause that was in my NORDO days. But my guts get
a little loose at the prospect of one of those ten other people fiddling
with a gauge on his panel when he should have his eyes open for traffic.

Last I looked the last word in this newsgroup was "homebuilt" to me that
screams "EXPERIMENT", go for it try a new project and enjoy the process and
journey!

And if the LEDs aren't bright enough in the sunlight, go ahead and paint
the windows black. After all, it's just an "experiment."

Actually, I'm not too worried in this case. I think Ken has an interesting
project on his hands, but will find that it probably isn't all that useful
once it's in his airplane. I doubt we'll be faced with a flood of these
things. And he doesn't fly around here. :-)

Ron Wanttaja

Yes there's a time and place for everything and experimenting with 10
aircraft in the pattern is not one of them. But It is an interesting
prospect and educational and fun thing to try out. Isn't that what most of
us are into homebuilts for. Of course I've been working on my plane for 10
years now and am 5% complete! ;-)

Properly placed the display would not need to distract your attention much.
Also there are no operating controls to fiddle with if your are only
operating from your local airport. The only real control is the frequency
dial and once set it is a hands off deal!

I probably wouldn't put one in my plane but hey He asked and I gave a link
to one of many such units out there let him decide if he's interested and
would like to experiment.

John

I probably wouldn't put one in my plane but hey He asked and I gave a link
to one of many such units out there let him decide if he's interested and
would like to experiment.

John

John and Ron,

Thanks for the link and the wishes for an interesting project!

And by the way, I´m not going to put this gizmo in a plane, I just NEED to
build one...that´s what it´s mainly about. I get this "fantastic" idea, that
I need to do something about. =))

As I said, it would be nice to have such a DF unit to be used with the
scanner, so I could get some help with knowing in which direction to scan
for GA aircraft passing by, somewhere near where I happen to be, that being
at home with my VERY NICE :-) plumber´s delights (thanks Jim and the other
guys) or at the summer cottage or wherever, when gettin the time to stare at
the sky.

I´ll have a look at the link now! And feel free to bomb me with more DIY
project links like this, I didn´t find that many myself!

Cheers, Ken

P.S. You may relax, I´d probably run out of avgas and would have to ditch
before I´d get to your usual flying sites! Since I don´t like the idea of
swimming the last bit over the Atlantic, I think I´ll pass on this one!
=))))

What we need is for some bright soul to develop a radio we can all buy
for a coupla hundred bucks that will transmit at some quiet freq every
second. Then a nice little LED in the cabin, linked to the DF, would be
lit whenever traffic is near. We have FM radios in the steel mill that
automatically transmit a morse code ident (per FCC regs) every 30 minutes.

Ron Wanttaja wrote:


Don't know much about TCAS, but I believe the system has a voice warning
that actually tells you how to maneuver. In any case, most aircraft
current with TCAS have two pilots. TCAS also is tracking transponder
squawks, not radio calls made at 1 minute intervals.