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APRS Antenna Question

T

tacaruth

Well Known Member
I am interested in building a tracker and have a question about the transmit antenna. Would this antenna look similar to an elt antenna? I would like to install my tracker in a removable location in the baggage compartment of my RV-7A. The antenna sold by byonics is roughly 18" inch long whip. Is this the best antenna for a portable unit? My thought is to have it removable/portable so I can take it with me when I go backpacking, hiking, etc. I realize that a rubber-duckie antenna is not very good but would it be workable? The rest of the stuff is very portable. According to byonics, a 9V alkaline battery would run the system for about 9 hours. When in the plane, I would have a socket to plug into for airplane power.

Thanks,
Tom RV-7A N175TJ Flying
 
tacaruth said:
I am interested in building a tracker and have a question about the transmit antenna. Would this antenna look similar to an elt antenna? I would like to install my tracker in a removable location in the baggage compartment of my RV-7A. The antenna sold by byonics is roughly 18" inch long whip. Is this the best antenna for a portable unit? My thought is to have it removable/portable so I can take it with me when I go backpacking, hiking, etc. I realize that a rubber-duckie antenna is not very good but would it be workable? The rest of the stuff is very portable. According to byonics, a 9V alkaline battery would run the system for about 9 hours. When in the plane, I would have a socket to plug into for airplane power.

Thanks,
Tom RV-7A N175TJ Flying
Click to expand...

Very good question!

(Warning: layman's explanations to follow (because that's what I am); electrical engineers and radio experts please keep your snickering to yourselves...or jump in with better explanations :) )

Please keep in mind as you read this response that my experience with APRS is very limited. Hopefully Pete and others with APRS rigs will chime in with more input.

Yes, the antenna may indeed look very much like an ELT antenna....or it may look very different. There are many different types of antennae and they each have various physical mounting requirements and radiation patterns.

The typical ELT antenna is some version of a 1/4 wave whip. If it contains no circuitry that allows it to be shorter than 1/4, it will be approximately 23" since this is 1/4 of the radio wavelength at 121.50 Mhz.

We are using 144.390 for the trackers, and 1/4 wave is about 19.45". This is the number I used when constructing the 1/4 whip I installed on the bottom of my plane.

tracker-5.jpg


For a whip antenna to work most effectively, it needs a "ground plane" or artificial earth. In our case, the aircraft airframe serves as the ground plane. A whip with a good ground plane will usually be much more efficient than one without a ground plane. That is one reason why the rubber ducky on a handheld transceiver doesn't work as well as a ground plane antenna (the short element works against it as well).

So, the 18" whip that Byonic sells (why is it 18" instead of 19.45"?) will load the transmitter just fine, but the radiated signal will not be as good as it would if the antenna was working with a ground plane.

I have been very happy with the performance of the whip on the bottom of the fuse. Pete Howell will hopefully jump in to provide his input about using a J-pole antenna in the wingtip of his plane.

By the way, I see no reason why an ELT antenna that is designed to be mounted on the exterior of an aircraft shouldn't make a fine tracker antenna if it is trimmed slightly to optimize it for 144.390 Mhz. I have a nice little ELT antenna that I'm going to try in place of the whip to see how it performs. A SWR meter is used to tune the antenna for maximum performance at a particular frequency.

Don't know if I answered your question fully, but maybe this will get the discussion rolling.
 
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18 inch vs 19 inch whip

Sam,

The Micro-Trak whip antenna is shorter than 19 inches for two reasons: 1) The RF path from the module to the end of the board adds about an inch to the RF path, and 2) Experiments with the spectrum analyzer showed that thats the length that worked best for 144.390 and 144.800 (The European frequency for APRS) frequencies. My antenna design, like my new power supply module, is the result of literally dozens of minutes of extensive R & D in what my friends call "the bat cave". In all seriousness, the design was intended to be cheap and effective: I stole the basic idea from those toy RC cars at Radio Shack....For the gentleman looking for a more robust antenna for portable use, I suggest something like the Diamond R77 dual band whip. He is also less likely to put his eye out.

Pete's antenna is going to have 3dB gain over a whip, effectively doubling your effective radiated power. I would suggest glassing Pete's antenna into the wingtip, and going to a an external whip for going walkabout. Adding a "rattail" ( a 19 inch long strand of wire ) to hang off the antenna connector is a good way of increasing the effectiveness of the whip antenna, although its not pretty.

Best Regards,

Allen R. Lord
VHS/Byonics
 
VHS said:
Sam,

The Micro-Trak whip antenna is shorter than 19 inches for two reasons: 1) The RF path from the module to the end of the board adds about an inch to the RF path, and 2) Experiments with the spectrum analyzer showed that thats the length that worked best for 144.390 and 144.800 (The European frequency for APRS) frequencies. My antenna design, like my new power supply module, is the result of literally dozens of minutes of extensive R & D in what my friends call "the bat cave". In all seriousness, the design was intended to be cheap and effective: I stole the basic idea from those toy RC cars at Radio Shack....
Click to expand...

Thanks for the reply, Allen, I was confident you had a very good reason for the "under-size" antenna, I just didn't know what it was. :)

Once your regulated power supply emerges from the bat cave, I'll probably get it and an amp on the way to the skunk works. By the way, is there any reason why the amp should or should not be located adjacent to the tracker? The MicroTrak-300 is doing a fine job in the air, just thinking a little more power might make it possible to get hits at very low altitude.
 
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Micro-Trak with amp

Sam,

There is no reason to have the amp distant from the transmitter. I usually use either a double male SMA adaptor or a 1 foot patch cord ( I bought a bunch of nice ones surplus for .99 each from HSC Electronics. I should have bought a few thousand.....) In addition to the RF link, you need a a short jumper to trigger the amplifier gate. I have sent Byon the first bunch of Power supplies. If you would like one, send me your mailing address. Sending you a few bucks in parts is the least I can do for getting me all this publicity in the experimental world!

Now I know all us RF guys are supposed to say that power is unimportant, and that what is really important is antenna gain and height, but who are we kidding? Size does matter! 10 watts beats the heck out of 300 mW's.


Allen
 
Wingtip J-pole

Hi Guys,

I am having good luck with the J-pole in the the wingtip. The prototype J-pole was not tested or tuned at all, but seems to work pretty well. This antenna design would ideally would be installed vertically, so curling around the front of the wingtip is a compromise. I have hit digipeaters 160 miles out, so it does works.

I do think I get a bit of signal blanking from the airframe, so a few packets are lost depending on the direction of flight. This is not an issue with a belly whip.

The J-pole, driven by Allen's 8 watt retina scorcher should hit digis from coast to coast and keep the cabin warm like a microwave....;):p A sample environmental impact statement will be sent with every order.....
 
8 death dealing Watts of power!

Pete,

I have an experimental 30-40 Watt Micro-Trak, but it might cause sterility, mutations, and spontaneous human combustion if used in an aircraft....:)
I just saw a post on another board asking if it was safe to be exposed to a 300 mW signal in a cockpit, so I guess I should be careful joking about this!

Allen
VHS
 
I have a couple of questions to finalize my design. Allen has recommended a 15" Diamond antenna from the following website.

http://www.rfparts.com/diamond/srh77ca.html

Would this antenna work as a baggage compartment antenna in an RV-7A? I would probably mount it on the bulkhead that goes behind the seats with it sticking up towards the canopy.

Does Byonics sell these? If not, then where to buy?

Thanks for all the help.
Tom, RV-7A N175TJ Flying
 
Another Data Point

I put my tracker in my Cessna 150 until the RV is done. Bought one of the Byonics whip antennas. Taped up inside of windshield. Tried it out yesterday and got OK performance until my 9V battery died. Got one hit on the ground and the next one on climb out. A HAM friend noted that I did not have a ground plane and suggested that I attach about an 18" wire under the jam nut (ground) on the SMA connector and stretch out across glare shield. I plan to give that a try next. Also plan to power off aircraft power through cigarette lighter jack.
Alan Jackson
 
Counterpoise

Hi Alan,

That wire is known as a counterpoise and acts kinda like the ground plane.(I think) it creates a simulated 1/2 wave whip and should perform better - let us know how it works.

It might just be that the 150 is too fast to track:p....... We all flew sluggers and and they are great trainers for RV's:)
 
N316RV said:
I put my tracker in my Cessna 150 until the RV is done. Bought one of the Byonics whip antennas. Taped up inside of windshield. Tried it out yesterday and got OK performance until my 9V battery died. Got one hit on the ground and the next one on climb out. A HAM friend noted that I did not have a ground plane and suggested that I attach about an 18" wire under the jam nut (ground) on the SMA connector and stretch out across glare shield. I plan to give that a try next. Also plan to power off aircraft power through cigarette lighter jack.
Alan Jackson
Click to expand...

Good to see you in the air, Alan!

N3216V.jpg


Looks like you hit a repeater 41.8 miles away before the battery gave up the ghost. :)

Does flying the C150 mean you have to monkey with the beacon interval??? :D

Stations which heard N3216V directly on radio over the last 48 hours:
W4GPS-7 5.2 miles 211° 2008-03-08 12:56:44
K4GIG-7 41.8 miles 215° 2008-03-08 13:02:00
KE4ROC-7 9.3 miles 279° 2008-03-08 13:02:30
N4BK-7 5.6 miles 243° 2008-03-09 17:34:38
 
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Another Antenna question

I too have a Microtrak 300 on order and have an antenna location question. I am of the pre-novice category (taking the Tech test this weekend) and need all the help I can get.

I am thinking about mounting the Byonics whip antenna in the engine compartment mounted to the firewall and extending forward. Any thoughts about whether this will work?
 
DickF said:
I too have a Microtrak 300 on order and have an antenna location question. I am of the pre-novice category (taking the Tech test this weekend) and need all the help I can get.

I am thinking about mounting the Byonics whip antenna in the engine compartment mounted to the firewall and extending forward. Any thoughts about whether this will work?
Click to expand...


Dick,

Not a good idea to mount the antenna in that location. The reason is this, too much metal up there. The close proximity to the engine ETC., will cause a higher than normal SWR (Standing Wave Ratio). A high SWR will adversly affect the RF moduel possibly causing overheating and or destroying the device. Antennas work better in a non metal environment. As in the wing tip or on the belly of the craft. If installing in tip area I would mount it to the outboard rib for a good ground plane. Verticaly polarized would again be the best way to mount the antenna.

I'm planning on installing a 2 Meter rig with the antenna on the belly and the APRS antenna behind the 2 Meter antenna.

Good luck

John H. KQ4FT
N194JH RV-9
N5810U Cherokee
 
Ryan's J-Pole Antenna - Performance Report

Well I received Ryan's J-Pole Antenna today and plugged it into my Microtrak 300. I have never been able to hit a digi from my house before with the little wire antenna that comes with the Microtrak. But I WAS able to hit the nearest digi (about 6 miles away) with Ryan's antenna. Not very scientific, but it IS promising!;)
 
Thanks John!

Given the info from John I will also be mounting the antenna on the belly. I already have 2 com antennas and a marker beacon on the belly so I'm sure I'll need to pay close attention to the spacing.

What is the minimum separation needed for the Micro-Trak 300 antenna relative to the marker beacon and comm antennas?
 
APRS antenna placement

tacaruth said:
I am interested in building a tracker and have a question about the transmit antenna. Would this antenna look similar to an elt antenna? I would like to install my tracker in a removable location in the baggage compartment of my RV-7A. The antenna sold by byonics is roughly 18" inch long whip. Is this the best antenna for a portable unit? My thought is to have it removable/portable so I can take it with me when I go backpacking, hiking, etc. I realize that a rubber-duckie antenna is not very good but would it be workable? The rest of the stuff is very portable. According to byonics, a 9V alkaline battery would run the system for about 9 hours. When in the plane, I would have a socket to plug into for airplane power.

Thanks,
Tom RV-7A N175TJ Flying
Click to expand...


If you place the antenna in the baggage area the aluminum structure will block a good share of the signal. I would definately place the aircraft APRS antenna on the exterior of your RV7 and run coax to the baggage area to connect to the unit if you go this route. The antenna would likely work best on the belly of the aircraft with as short a coax run as possible to the transmitter.

While backpacking you could use a rubber duck antenna if you wanted but a better bet would be something like a quarterwave antenna or one of the larger flexible HT antennas designed for 144-148Mhz.

The math to determine 1/4 antenna length for a given frequency is 234 divided by the frequency in Mhz. Multiply this number by 12 to get length in inches.
234/144.39Mhz = 1.62 x 12 = 19.44"

Brian
KF7TG
 
Check's in the mail!

Noah said:
Well I received Ryan's J-Pole Antenna today and plugged it into my Microtrak 300. I have never been able to hit a digi from my house before with the little wire antenna that comes with the Microtrak. But I WAS able to hit the nearest digi (about 6 miles away) with Ryan's antenna. Not very scientific, but it IS promising!;)
Click to expand...

Noah - glad it works! I'll let Ryan know.
 
APRS antenna from Aircraft Spruce

Here is the antenna I've used as a COM antenna on my plane for the past eight years. It has held up fine and performs very well. It would make a capable APRS antenna at a reasonable cost:

AV-534.jpg


http://www.aircraftspruce.com/catalog/avpages/av534.php

If you want to optimize it for 144.39, it could be shortened ~2", or really dialed in with an SWR meter. Mounted on the belly of the plane it should be a great APRS unit. It is basically a store-bought version of the home-made antenna I use:

tracker-5.jpg




Here is an interesting antenna, I have one but have not yet tested it:

pointer-ant.jpg


It is an ELT antenna that is only 12" long, mounts in a 1/2" hole, includes a BNC connector, and sells for about $70. I suspect a very slight trimming in length would put it in the 2-meter band.
 
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External whip antennae

All of the Aircraft external antennae I have seen links to are just1/4 wave whips. Antenna gain is measured against the standard of a quarter wave whip, an antenna that is said to have no "gain". Essentially, you have a piece of wire 1/4 of a wave length long ( An APRS transmission has a nominal wavelength of 2 Meters-so 1/4 wave is....you guessed it...1/2 Meter. Guys testing for your Tech license, you will see this material again!

Pete's antenna is a dipole. It has two quarter wave elements. One balances the other out, and allows more power to be communicated through the antenna, in fact, as much as twice as much power. ( or 3 dB- I will try not to get too technical. The rule for all of you taking the test ham test is that every three dB you add is twice as much power. You will see this material again!)

If you are just going to use a plain whip in a fiberglass aircraft, you may as well just fasten it to the transmitter without any cable. This will eliminate the power loss you would lose from the feed cable resistance.

Better yet, if you are going to use a quarter wave whip, add a counterpoise.
If I could add an optimal counterpoise to your aircraft antenna, I would use a 36 inch pizza pan on the deck, with the antenna mounted through it. This may not be feasible,(duh..) but you could add copper tape laid out in a cross shape on the deck, with the bulkhead connector going through the center. From the center,each end of the cross should be about 18 inches long. ( about 5% less than the actual wave length. If you can't get a a full cross or a pizza pan in there, use one piece of copper tape ( aluminum will work too) just use one piece. Or you could buy Petes' ladder cable dipole antenna and not drill any holes in your fuselage.....

Does a 3 dB whip improve your performance? Oh you betcha! In order to double your maximum distance, you would need to quadruple your energy output. (inverse square law of energy?) So you can do two things to increase range. 1) More power ( Micro-Trak 8000 FA has 10-12 Watts output) and/or 2) use an antenna with gain, not just a pretty whip antenna.

Allen
VHS
 
VHS said:
If you are just going to use a plain whip in a fiberglass aircraft, you may as well just fasten it to the transmitter without any cable. This will eliminate the power loss you would lose from the feed cable resistance.
Allen
VHS
Click to expand...

FIBERGLASS??!???? YEEECH!

Allen, all RVs are good 'ol metal airplanes. :)

(We will excuse the extreme insult since you are a radio guy.......and design really good trackers) :D :D
 
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Fiberglass vs metal

I deeply apologize to your airframes and expect that since they are made of metal, they will make excellent ground plains!

Allen
VHS
 
VHS said:
I deeply apologize to your airframes and expect that since they are made of metal, they will make excellent ground plains!

Allen
VHS
Click to expand...

Allen, our airframes sincerely accept your gracious apology and they look forward to bouncin' the Micro-Trak beacons all over the fruited....uh....plane. :D :D
 
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Different Idea

How about putting the antenna in the gear leg fairings. Would one in each leg better? If this is a good location, what type of antenna would be best?
 
cguarino said:
How about putting the antenna in the gear leg fairings. Would one in each leg better? If this is a good location, what type of antenna would be best?
Click to expand...

Charlie,

I've never tried putting APRS antennae in each gear leg fairing, but several years ago I did experiment with a homemade COM antenna (made out of RG-58 coax) in one gear leg fairing. The results were underwhelming to say the least. Guess I couldn't get the antenna element far enough away from that big chunk of dense steel to keep it from being detuned severely.

But hey! We're experimenting here so give it a try and let us know how it works! :)
 
So how about the idea of two antennas? I see the truckers use two almost as a rule. Also, how does the gear detune the antenna. I would of thought it would act as a ground plane if anything. I was more worried about it being directional. That's why I was thinking two. One in the front of one gear fairing and one in the back of the other.
 
Do I get this right?

Am I understanding this correctly?

Are you folks saying that Pete's dipole antenna, in the fiberglass wingtip, even though not vertically polarized, is better than an external whip antenna (18") with the alum. airframe as groundplane?

Roger Evenson, Tucson, AZ
7A, building
 
Maybe Not Better

Hi Roger,

I don't know about better, but it seems to work pretty well. Here is the breakfast run today:

ANE-EAU-CBG-ANE

2003894562193808603_rs.jpg


We had good coverage even on the ground at ANE, EAU, and CBG.

The design goals for the J-pole were ease of construction and install, reversibility, good performance and modest price. I think we did pretty well against all the goals. The J-pole allows a clean, reversible(no holes) install in the wingtip. We hit digis pretty well, and my twins (with my help) will make you one for $20. Will it beat a 1/4 wave whip for all out distance, I'd have my doubts - Maybe Sam and I should do a cage match flyoff........

I have my antenna mounted so it curves around the front of the airfoil, to give it a bit of verticality(is that a word?).

When I need some extra APRS punch, I just point the -9A straight up and let the awesome power of the O-320 do its thang) (that was a joke).......
 
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Gain vs Orientation

While a J-pole will give you a couple of dB gain over a 1/4 wave, orientation does matter. Cross polarization (horizontal vs. vertical) will give you a 20 dB loss (theoretically it's infinite, but 20 dB is much closer to reality).

Polarization Mismatch Loss (dB) = 20 log (cos (theta))

deg___dB
15.0 | 0.3
30.0 | 1.25
45.0 | 3.0
60.0 | 6.0
75.0 | 11.74

The other thing to consider is the way gain is achieved. There's no such thing as a free lunch. An isotropic radiator radiates equally in all directions. A quarter wave vertical has a cone of silence directly overhead (if it's mounted vertically) A vertical antenna with a 3dBd gain shifts more of the power towards the horizon and as a consequence will have a bigger cone of silence directly off the end of the radiating element. Now if you don't mount it vertically, where are you putting all of your power?

Here's the best pic I could find on the net:


verticalradpats.jpg


It appears to be using a linear scale vs. the more common log scale so its a bit stretched out horizontally, but you get the concept.

Paige
 
revenson said:
Am I understanding this correctly?

Are you folks saying that Pete's dipole antenna, in the fiberglass wingtip, even though not vertically polarized, is better than an external whip antenna (18") with the alum. airframe as groundplane?

Roger Evenson, Tucson, AZ
7A, building
Click to expand...

Roger, I think Allen's assessment of the dipole vs the whip was skewed by his misunderstanding of the construction of our RV aircraft. Allen was under the impression RVs are constructed of fiberglass which would provide good options for correctly orienting the dipole.

Obviously, with a metal aircraft, most of those options don't exist. I can't think of a location in an RV that would allow the vertical installation of a 50" antenna inside the airframe. Pete's installation is a compromise and it works well not because the antenna is performing to its full capabilities but because the antenna installation is satisfactory for airborne use. The physical characteristics of the dipole make it very easy to install in our limited options. Next time I have the cowl off N399SB I'm going to glue a Ry-pole in the lower cowl just to see how that works.

Theoretically.......the external 1/4 wave whip would be superior to an antenna folded up inside a wingtip, and an experienced ham who is familiar with my plane told me he couldn't imagine an antenna better suited to my plane than the external whip on the belly of the airframe. Guess that is why our COM antennae look the way they do. :)

But it doesn't really matter as long as both installations work satisfactorily. In a different thread Allen stated the 8 watt MT-8000 and Micro-Amp can tolerate a SWR of 20:1 so we are in no danger of cooking any equipment due to a less than ideal antenna installation.

In regard to Paige's post, I think I've seen the result of the null off the end of the whip. On one flight, the local iGate that had been capturing the beacons was blanked as the plane was turning and the antenna was positioned with the end of the whip pointed at the iGate. Fortunately a digipeater 140 miles "to the side" of the whip picked up the beacon and tracking was not interrupted.

Rich in Denver just completed his first flight in the metro area, had the dipole taped to the canopy and enjoyed nearly perfect tracking on 300mw (are we in the process of putting the "congestion problem" to bed?). So it appears the antenna issue is easily handled by options readily at hand. Fortunately we have antenna solutions that are proven to work well.
 
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Certified plane - any antenna ideas

Any good antenna ideas for a certified plane that I don't want to drill any antenna mounting holes in?

My Tiger has a glass wing tip almost identical to the early RV4/RV6 tips...

Or a rubber ducky taped to the rear window? I don't think any of the windows can take a full dipole..

gil A - got KE6HAP after the Northridge quake... my FIL (WB6UPA) over 100 miles away knew more that the news radio...:rolleyes:
 
Or a rubber ducky taped to the rear window?
Click to expand...

Radio Shack used to sell something like this:
http://www.scannerworld.com/content/product/model/ANT73

ant73.detail.jpg


The 25-1200 MHz coverage they show for the included rubber duck is obviously not a transmit spec. Chances are the SWR is below 20:1 (max SWR for the little 300mw units everyone is using), but you might want to use an antenna designed for 2M.

Definitely a compromise, but altitude is your friend.

Paige
 
Well I have almost completed getting an APRS system ready to go. All that's left is taking the test, and mounting the antenna.

I acquired an old Comant COM antenna (CI-122) since I wanted one that looked like any old standard antenna with a streamlined base. When I contacted Comant (and Rami) about shortening the antenna for use at 144.39Mhz, both companies said their antennas incorporated matching networks and that if I shortened the antenna that these coils and capacitors might prevent the antenna from working well, and both suggested buying their high priced antennas made for that range.

So, I tore into this old antenna and ripped out the guts of all the coils so that all I had was a nice base, and a metal whip. My next step is to cut the whip, and then solder back on a BNC connector and then I'm ready to go.

The question is, from the above thread, it sounds like there is some length that is given up within the transmitter traces...like maybe almost an inch. (Refer to the posts regarding 18" antenna length) And then of course, there's the theoretical 1/4 wave calculation of roughly 19.45" that I could go by. So if maybe Allen or someone could comment, where would be the ideal place to cut this antenna off to make it as roughly accurate as possible....for us anal folk? I'd like to do the best I can, anyway.

I had some SMA connectors for RG-400, so I used a scrap of RG-400 about 18" long and made an antenna cable that is SMA to BNC. Now I just have to put my BNC connector back on the antenna. There IS a small 1" wire lead soldered to the inside tip of the Comant antenna, and I'm assuming that I should count that length into the equation as overall antenna length. On the other hand, the antenna rod is partly inside of the streamlined base of the antenna, which is metal.....so perhaps some of that should NOT count, as it can't effectively radiate or receive when it's shielded by the metal base? So should I measure from the tip? Refer to http://www.comant.com/prodpages/ci122.html
for the look of the antenna.


Care to comment?

Tim
 
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Antenna length

Tim,

On the MT-300, when you have an antenna mounted directly on the unit, the approximately one inch of RF path on the board is nominally subtracted from the antenna length, which is why the cheapie Micro-Trak whip is about 18 inches long. When you remote the antenna, the trace on the board acts less like a radiator, allowing you to use an antenna more closely cut to the theoretically perfect length. I suggest going slightly longer and trimming it down if necessary. (For the truly power mad, you can use a Wattmeter and trim the antenna to optimum length while using a PC to force a test tone.) If you want power, buy the MT-8000 FA! I think its safe to say that the consus of he group is that at altitude, 300 milliwatts is plenty, but on the ground, its not so hot.

Allen
VHS
 
Thanks for that answer, I figured I'd start with cutting it to the theoretical length, and leave it at that until I can either see good results, or get some real method of testing like you suggested. I guess I'll know pretty soon how good it works!
Tim
 
The poor antenna...

...that I have taped to the rear window of my Tiger works quite well in the flatter Eastern US states...

http://www.mail2600.com/cgi-bin/track.cgi?call=N12GA&days=7&hours=0&tiny=1&elim=0

Wasn't too good at 2500 ft AGL in the Roswell or El Paso areas (go back another days track) , but that may be due to lack of ground stations...:)

All I have is the cheapest Byonics antenna that is a fine wire taped to my rear window.

Quite good performance considering.....

gil A - in rainy Burlington, IA - for some reason, I wan't transmitting from MO to IA....:(
 
Byonics MT8000FA antenna 90-degree adapter

What is the name of the mini cable connector that connects the Byonics whip antenna to the tracket unit? It looks gold plated. I would like to get a 90-degree adapter so that my tracker unit (in project box) can sit on top of my airplane's pane and have the antenna stand vertically. Thanks!

Mike
 
Pete, Thanks for the SMA connect info. Order one and then saw that my local Radio Shack sells them. Oh well.

I have been testing my MT8000FA in a project box sitting on top of my panel with the Byonics whip antenna taped at the end to the windscreen. It is not far from my head - a foot and some inches. Is this thing safe to operate with the antenna that close to me?

Mike
 
J-pole ant. question

Antennae question.
I plan on installing my j-pole in my wingtip along with the tracker and gps. One little package plus mount the antennae. Have not seen pics of a j-pole in a wingtip.
Any chance there would be conflight against a magnotometer, marker beacon, vor, com antennae, strobes, nav, landing light etc etc etc?

Wavelength and frequencies are magical and I know less than zero about how they might all play together.
Thanks
 
Kahuna said:
Antennae question.
I plan on installing my j-pole in my wingtip along with the tracker and gps. One little package plus mount the antennae. Have not seen pics of a j-pole in a wingtip.
Any chance there would be conflight against a magnotometer, marker beacon, vor, com antennae, strobes, nav, landing light etc etc etc?

Wavelength and frequencies are magical and I know less than zero about how they might all play together.
Thanks
Click to expand...

Welcome to APRS, Kahuna! :)

Take a look at the APRS sticky "Airplane Tracker" to see Pete Howell's rig mounted in the wingtip:

http://www.vansairforce.com/community/showthread.php?t=26797

Very unlikely you will have problems with the tracker talking to your other gizmos. Of course it would probably be best if you mounted it in the tip that has the lowest antenna population, and be sure you make a test flight with your glideslope receiver, etc before blasting off into the thick stuff. But I don't recall hearing of a tracker being impacted by strobes, transponders, etc.

It is indeed magic but fortunately the genies are pretty cooperative with our APRS efforts. :)
 
Ive ordered all my stuff. Im right in the middle of deep dive annual where Im changing out a bunch of stuff. Timing is great.

Wingtip install is best for me. Its easy for me to get direct power out there. Im using a spare switch in the cockpit cause i MUST be able to turn this thing off for low level activity. This little monster could get someone in trouble if not careful:rolleyes:

Ill take pictures and report my activities. Im using this as a safety device more than anything. I travel cross country quite a bit and normall file to get into the system so family knows where I am. This will give me the freedom to just launch VFR and go without regard to being in the system for tracking.

I look forward to geeking out with it. Thanks to all you guys for laying the ground work.
 
Wingtip mounting works but can couple into "stuff" ...

Kahuna said:
Ive ordered all my stuff. Im right in the middle of deep dive annual where Im changing out a bunch of stuff. Timing is great.

Wingtip install is best for me. Its easy for me to get direct power out there. Im using a spare switch in the cockpit cause i MUST be able to turn this thing off for low level activity. This little monster could get someone in trouble if not careful:rolleyes:

Ill take pictures and report my activities. Im using this as a safety device more than anything. I travel cross country quite a bit and normall file to get into the system so family knows where I am. This will give me the freedom to just launch VFR and go without regard to being in the system for tracking.

I look forward to geeking out with it. Thanks to all you guys for laying the ground work.
Click to expand...

I mounted mine in the left wingtip of "PapaJuliette". Did not have another wire there that was convenient so I used the nav light power as others have.

The thing that I noticed is that there **IS** some coupling into the NavAid autopilot servo that is mounted out there in the wing (or is it the head unit in the cockpit?).

When the APRS transmitter fires and the sutopilot is on, there is a very slight turn to the left I think in my case. Not bothersome but noticeable if you are paying close attention.

I can also hear a little in the radio but did NOT get any complaints while flying CLOSE some some of my friends during practice for OSH. Did NOT have it on during the "actual event".

Contact me "offline" for some interesting info about "formation tracks".

James
 
configuring a wingtip tracker without removing the wingtip

Kahuna said:
Ive ordered all my stuff. Im right in the middle of deep dive annual where Im changing out a bunch of stuff. Timing is great.

Wingtip install is best for me. Its easy for me to get direct power out there. Im using a spare switch in the cockpit cause i MUST be able to turn this thing off for low level activity. This little monster could get someone in trouble if not careful:rolleyes:

Ill take pictures and report my activities. Im using this as a safety device more than anything. I travel cross country quite a bit and normal file to get into the system so family knows where I am. This will give me the freedom to just launch VFR and go without regard to being in the system for tracking.

I look forward to geeking out with it. Thanks to all you guys for laying the ground work.
Click to expand...

Mike, something I've considered if ever doing a wingtip APRS install is a way to easily program the tracker. I haven't spent a lot of time thinking this through but why couldn't you put an 1/8" stereo mini-jack (TRS connector) in the underside of the tip and wire it to the serial in-out of the tracker? This would allow you to fiddle with the programming without having to remove the wingtip. (plug tip to tracker pin 2, ring to pin 3 and sleeve to pin 5). Just take the laptop to the plane, power up the tracker, plug in the config cable, and tweak the tracker as desired.

The GPS needs to vacate the data "in" pin of the tracker during config, and this could be handled by wiring the jack to disconnect the GPS when the plug on the config cable is inserted into the jack. If the jack was located way up under the wingtip it should be nearly invisible, and a little rubber plug could be fabbed to keep water out of the jack.

You said you wanted to geek out.............. ;)
 
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Yes Sam you are exactly right.
Would require a special plug.
Who knows what the nomenclature on it would be? You know SPST or what ever?

Oh and I received my antennae from Ryan Howell today. He sent the antennae before I even sent him the check. Guess he figures he knows where to find me:)

Now who knows a plug that will do the trick here?
 
Kahuna said:
Yes Sam you are exactly right.
Would require a special plug.
Who knows what the nomenclature on it would be? You know SPST or what ever?

Oh and I received my antennae from Ryan Howell today. He sent the antennae before I even sent him the check. Guess he figures he knows where to find me:)

Now who knows a plug that will do the trick here?
Click to expand...

Looks like your local Radio Snack could fix you up:

http://tinyurl.com/5mgns8

You want the type of jack that is used in audio applications where the speaker is disconnected when the plug is inserted. Put the GPS data feed in the "speaker" circuit so the GPS data gets disconnected from the tracker when the config cable is plugged in.

I believe circuit "D" is what you will find in the common "stereo audio" version of the TRS connector. This connector will disconnect the left and right speakers when the headphones are plugged in. You only need one "speaker" circuit for the GPS data line.

Phone_jack_symbols.png


Digi-Key should have a higher-priced unit, and no doubt your local avionics shop will have a closed-circuit jack in their parts bin. But hey! We're cheap! Go with the Shack. ;)

Here is how I'm seeing this circuit:

tracker_cable.jpg


Be sure you apply peer review! (I worked in the yard this afternoon and may have gotten too hot.....mainly check to be sure I got the null part of the circuit correct)

WARNING! I haven't tried this mod, but so far don't see why it wouldn't work.
 
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yes ths will work just fine. Good drawings Sam.

Im going to mount the plug in the wing tip trailing edge support rib. Move the aileron, plug in jack, geek out.
 
I have rigged the test harness for the jack and it works. Plug in jack, opens the gps connection, closed serial connection from computer. Perfect.!
stereojack.jpg
 
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