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Jul 24, 2005, 08:32 PM the skies...
Cats Eyes's Avatar

The Planelocator thread

This thread will be a sort of review and documentation of the planelocator, a radio frequency tracker for lost model planes, manufactured by Communications Specialists, Inc. I'll start with a review of what I received, and the testing that I am doing of the system in an attempt to determine how effective it will be. Please feel free to post questions and/or comment if it's relevant to either the planelocator itself, or other, similar devices or systems.


Due to all the posts regarding lost models, and my own loss (briefly) of my Slow Stick in a bean field last fall, I have been looking for a suitable method for tracking a lost model for some time now. My knowledge of RF (both technical and regulatory) is somewhat limited and I didn't want to spend a lot of time right now learning the ins and outs, getting a HAM license etc.

In the thread Lost Models... what do we really need?, Vince53 suggested the planelocator. While I thought this was a little on the expensive side, it seemed to be what I was looking for, and it didn't seem like anything cheaper might come along any time soon. So I ordered it.

First Looks

(Note: if this sounds familiar, it's because this is basically a re-post of my initial "review" that I posted on the Lost Models thread)

From first impressions, unpacking the box, I have to say that I'm very impressed. The receiver looks very well made and rugged. The instruction manual (which you can view on-line if you're interested) is very clear and well illustrated. They supply you with everything you need and then some. They throw in three rubber caps to cover over the battery in the transmitter, three extra transmitter antenna wires of varying lengths, scads of extra nuts and lock washers (to hold the antenna wires on the transmitter), and even a nut driver!

The receiver itself is a rugged-looking aluminum box, with a BNC connector on the top for the "rubber duck" and directional antennas (included with the receiver). The included 9V battery fits in a clever little tray on the bottom. The transmitter is very small and light, and they supply two batteries (supposed to last 30 days of continuous use). The on-board weight breaks down like this:

Transmitter.................3.8 g
Battery.....................2.9 g
Antenna wire & connectors...0.6 g
Rubber cap..................1.0 g
...................Total....8.3 g

Note that the rubber cap is optional, but probably advisable, especially if you're flying over a swamp!

Attached is a photo of what comes in the box if you order just the receiver and one transmitter. I actually ordered two transmitters and a sheet of extra batteries (not shown).

A - Directional antenna
B - Receiver
C - Instruction manual
D - Non-directional "rubber duck" antenna
E - Transmitter with 4" antenna wire installed
F - Extra (longer) antenna wires (three)
G - Batteries (two)
H - Rubber caps
I - Extra nuts and lock washers (lots!)
J - Nut driver

From first impressions, this seems like a very solid, well-made and professional product.
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Jul 24, 2005, 08:36 PM the skies...
Cats Eyes's Avatar
First test, July 24, 2005

This first test was just to see how effectively I could locate the transmitter, without worrying too much about how "good" at test it was in the sense of being a fair approximation of the kind of search I'd be up against in a "real" lost-model situation.

I asked my wife to hide the transmitter near a country road, but left it up to her where along the road that would be. The logic was that, usually when a plane goes down, you have a bearing on it when last seen, and can be fairly sure it is near a line drawn from your pilot station to the last sighting. (This, obviously, wouldn't work if the plane were lost in a cloud.)

For a bit of visibility, I placed the transmitter in an empty margarine tub. My wife dropped me at a corner left to hide the transmitter. After about 20 minutes, she returned and the search was on.

When I first powered up the receiver, I couldn't get a signal at all. (Looking at a map later, I saw it was at least 1.5 miles from the hidden transmitter, so this is hardly surprising.) I got in the car and drove along the road, leaving the receiver on. After a time, the receiver started picking up the signal. I don't remember exactly when I first noticed it, but I don't think it was more than about 500 ft. from where the TX was hidden. This will bear further investigation, as the range is supposed to be a mile. However, they do mention that the range is considerably diminished inside a vehicle. I plan to do some more testing to see exactly what the range is.

After driving for a short while the signal began getting weaker again and I pulled over to the side of the road and continued on foot. I made a "360" and determined that the signal was greatest back the way we'd come so I proceeded up the road in that direction. I began walking up the road and observed that the signal was getting noticeably louder. Several times I stopped to do a 360. Most of the time this indicated I should proceed the way I was going, however, at one point the signal direction seemed to be off to the side of the road. I debated what to do at that point, thinking that the TX was hidden off the side of the road at that point. However, I decided to keep walking back on the road just to see if I could "triangulate" the TX location a bit better. As I continued to walk, however, the signal got louder still and no longer indicated it was off to the side.

A little ways further, there was a parking area for a nature trail. As I passed it, the signal seemed the loudest I'd heard yet, and diminished as I walked past it. A 360 at that point indicated that the signal was coming from opposite the parking area. A trail lead off on the other side of the road and I proceeded down that.

The signal continued to get louder, and at one point I had to switch from "long" to "medium" range on the receiver to avoid overloading it. I actually narrowed down the location of the TX to within about 10 feet or so fairly quickly, but took another 5 or 10 minutes to actually locate the TX in the underbrush. At less than 20 ft. or so, the receiver seemed to get confused about the directionality. After going back and forth within five or ten feet or the TX, I eventually found it. My wife had done a pretty good job of hiding it!


Generally, I am pleased that the TX was located fairly quickly. I don't know that it wasn't a 100% fair test as I knew it was hidden fairly close to the road and/or an accessible trail. However, the exercise did point out a few interesting aspects.

1. The direction at which the signal is loudest is generally fairly accurate, but at times can be off by as much as 90 degrees. I would conclude therefore that any particular reading should not be considered necessarily very accurate, and one should take a number of readings at a number of locations when determining direction.

2. Signal strength proved to be a fairly good indication of the distance to the target. The "art" of RDF (Radio Direction Finding) seems to consist of combining indications from both the direction and signal strength data, taken at a number of locations.

3. Close-in work (less that about 20 ft.) tends to be a bit troublesome. This should generally not cause problems -- if you are within 20 ft. of your model you should be able to see it! However, the inclusion of an audible alarm is probably of some utility. It should shorten the time to locate the model after one gets to within about 100 ft. or so.

4. More tests will be necessary to determine the outside range. I don't remember well enough when the signal first appeared, and at any rate it was within a vehicle, so this information would not be conclusive anyway.

Further reading

Here is a partial list of "lost model" (and solution) threads:
Stay tuned for further testing in the days to come...

-- Kevin
Jul 25, 2005, 06:33 AM
Registered User
ViddyFlyer's Avatar
Excellent post Kevin. I'm looking forward to the results of your maximum range testing.

Having recently lost my modded Slow Stick AP plane and new Casio EX-Z750 hindsight has me thinking, "Why didn't I check-out RF based locators?" I'd checked out audio devices and even conceived adapting a marine emergency strobe light. Simple answer is that I'd never seen a post on that type of system and I was too "simple" to think about searching myself.

And, then there WAS the other mindset deficiency, "Oh, It'll never happen to me."

I'm destined to return to the air with Casio #2, but plan to keep it on a much shorter "leash." The cause of my loss was that I was flying too far out. As I slow turned to do one more pass over my target a little farther out the altitude of the plane stayed about the same, but it dropped lower on the horizon. Instead of appearing on the other side of the upper branches of a distant oak it disappeared. Hoping for a flash reflected from the setting sun I flared up and tried turning toward me. A half hour later I was still flaring up to the left. How long did the invisible plane respond to my sticks? What direction did it end up going? How long did it go? The huge area it went down in is heavily forested foothills. Lots of tall pines and oaks on posted private property. I drove the few roads looking and posted "Lost Plane - Reward" signs. Now it's just nagging memory and darned expensive lesson.

So, is a $250 investment in a Planelocator good sense insurance? The $125 Co-Pilot was intended as insurance to save me from another uncontrolled spiral. But I also bought it for major benefits of slow mellowed flight characteristics and much improved percentage of level AP horizons.

The Planelocator website mentions joint use through a club use, but I'm solo! Kevin would you consider renting your receiver? If needed I could "wire" a deposit and cost of overnite express. Upon return to you in good condition you keep $50 for your effort and return the rest. Would that work for you?
Jul 25, 2005, 07:28 PM the skies...
Cats Eyes's Avatar
Thanks, Viddy

Sorry, the range testing will be a couple of days. Another heat wave just blew through here -- seems like the fifth or sixth this summer! I should have something by late in the week or the weekend at the latest.

As to the "why" people lose planes, just blaming it on "flying too far out" is to my mind too simplistic. What is "too far?" When I lost my plane in a bean field, I had in fact flown farther out and lower to the horizon on that very flight, and felt fairly comfortable with it. The trouble started when I was coming back. It was a combination of wind rotors coming off a line of trees and dying batteries (shouldn't have been flying that long). There are many reasons people lose planes even though they are flying well within their "comfort zones."

Your average sport flier has no reason to venture into areas where loss of plane is likely, it is just us AP nuts that want to fly in crazy areas, or want to push it just a bit to get that perfect shot. If you vow that you'll only fly your plane where you're 100% guaranteed to make it back to your landing zone, IMO you're not likely to get much interesting AP done.

So I think "risking" the plane is, to a certain extent, a "given" in AP. There is in fact much you can do to minimize the risk (on-board devices, flying practices, etc.), but sooner or later, if you fly enough AP missions, you're probably going to lose a plane. So the next question becomes, what can we do to maximize the possibility of retrieving it. Hense this thread, among others.

Another point of discussion might also be what to do when you lose sight of your plane. Even with an RF or other type of locator aboard, it will still be very useful if you can identify the location where it came to rest as accurately as possible. They say the Planelocator's range is a mile, so you still have to be sure you can get within a mile of your plane just to get started. With only an audible alarm, your range will probably be more like 100 yards maximum.

I have heard that full up elevator and full left or right rudder will put the plane into a spiral that will have a fair sink rate (thus not be blown too far away from the point of last sighting) but will not come down so quickly that it would cause a lot of damage (to the plane or bystanders). A shallow, straight glide is probably not a good idea, as it could take the plane miles away. Perhaps others could comment on that.

As to "renting" the receiver, I would be open to it except I'm in Canada and mailing the thing across the border and back could be a bit of a pain. Perhaps you could find someone closer to home. Maybe the RCAPA or some other organization should invest in one? Maybe you could even contact the manufacturer, Communications Specialists, Inc., about setting one of their units aside as a rental?

-- Kevin
Jul 25, 2005, 07:47 PM
Old Timer
California Condor's Avatar
The Walston retrieval systems though more costly work for miles, the Free flight modelers have been using them for years, and have found models miles away even in metal buildings, I have personal knowledge of this. I am in no way connected with them, just share a flying field where they are used.
Jul 26, 2005, 10:31 PM the skies...
Cats Eyes's Avatar
The Walston has been mentioned by a number of people. They generally have good things to say about the system. It is somewhat difficult and frustrating trying to research it, as they don't have appear to have a web site and there is almost no information available about it on the web. The only info I've ever seen about it is here:
(Several links at the bottom of the page to scanned GIFs of some literature. I have no idea how up-to-date it might be. )

I'm glad to hear they at least have an e-mail address!

Looks like at a minimum you're talking $399 for the receiver, $135 for the transmitter, and $79 for an antenna, for a total of $613

A little out of my range, but I suppose it is worth considering if it will more-or-less guarantee that you'll find an errant aircraft.

Hey, why don't you buy one and write up a review?

-- Kevin
Jul 26, 2005, 10:42 PM
Old Timer
California Condor's Avatar
I guess I am one of those who believes he is not going to loose a model. (actually I have lost several in my 70+ years of flying them, only one permanently).
The walston system is essentially the same as used to track animals,
Jul 27, 2005, 02:05 PM
Registered User
ViddyFlyer's Avatar
Yeah Kevin, risking it has been a BIG (expensive) part of my whole first year of RC flying. I'd venture to say that if you had bought Hobby Zone stock on the day I got my first Aerobird you'd have made a killing!

Windsurfing, a 12 year past passion, always was a learning process and constant evaluation was necessary to gauge improvement. Pushing it to my "edge" meant I got wet a lot. I was never great at it, but always enjoyed the risk and the challenge. Seems the challenge still is to experience the thrill of flying and not get "soaked!"

Darn! Yeah again, I see shipping your Planelocator receiver from Canada would be impractical. Maybe a stateside solution will appear? HELLOOOO?

As far as heat waves ... it's pushing well over 100 here again today. So I "hear" you on that one too. My solution, a kayak, is racked on the car. Just need to load eats and trout gear and I'm off enjoy a cool afternoon at alpine Silver Lake at 7000ft. Now that's high flyin!
Jul 27, 2005, 04:24 PM
Registered User
Check out this site:

Here's a transmitter glued to an insect!
Aug 01, 2005, 12:58 PM the skies...
Cats Eyes's Avatar
Second test, July 31, 2005

I was out at the flying field yesterday and took the opportunity to do some more testing of the planelocator. The purpose of this test was establish range information for this system, i.e. how far away from a lost model one would have to be to lose the signal entirely, and how effectively one could locate the model if a weak signal could be received.

I placed the transmitter, with the little 4" antenna that comes attached, on a rock about 12" off the ground. I turned on the receiver and began driving. By 0.2 km (kilometer = 0.62 mile) the signal in the car was very faint, and by 0.5 km it was lost. Out of the car, the signal was somewhat better, however by 0.7 km, I could not pick up a signal.

This was rather disappointing, to say the least. They say the range is over a mile. It still works well if you can get within about km, but there are situations where that might be a problem. I started thinking seriously about taking them up on their 30-day no-questions-asked return policy.

As mentioned, the receiver comes with a 4" antenna (just a piece of stiff wire) attached. They also supply three other antenna wires in (roughly) 8", 12" and 18" lengths. So thinking I might get better range with the longer antenna, I put the 18" wire on the transmitter.

The difference was apparent right away. The signal even in the car persisted for over a km. The range out of the car was way up. The signal remained usable up to about 2 km (over a mile). At that distance, I had to listen carefully to hear the signal, but it was enough to give a direction.

I did not have enough time to test the intermediate antenna lengths. Given the results of this test, I think I'll be using the longest wire at all times. I may even run some tests with even longer wires to see if I can boost the range even more.

Here is a chart made from my field notes. The Distance, Signal, Meter and Dir. refer to observations made out of the car with the ignition off. In car was in the car while driving (slowly!). Distance is in kilometers, with miles in parentheses. The meter on the receiver has 10 divisions, and the Meter column is the meter deflection for each "blip" from the transmitter, with the meter at about half-scale. The Dir. column is how accurate the directionality information was.

Some other interesting observations:
The range in the car was much reduced compared to the range outside the car. Even when I got a signal in the car, I could not get any reliable direction information. I found I got the best directionality by moving away from the car (turned off) and holding the antenna pointed directly away from my body, then making a full circle. I found it also important try the antenna both horizontal and vertical as that could make quite a difference in the signal strength.

I found both the audio and the meter to be useful. When the signal was very weak, there was no meter deflection, but I could pick up changes in signal strength by listening to the sound. In stronger signal situations, the meter gives a good indication of the exactly direction where the signal is strongest.

The "rubber duck" antenna, as suggested in the instructions, can be used for "close-in" locating. It is not directional, so you don't have any direction information, but I found the signal strength to be a fairly accurate indication of the distance to the target. This worked well even in the car, where the direction information was scattered.

  1. Size matters. The short antenna is to my mind almost useless. Range with the longer antenna is over a mile.
  2. Directionality remains surprisingly good, even in very faint signal situations. If you can get a signal at all, you should probably have your plane found in short order.
  3. Signal in a vehicle is much reduced, and the directionality is scrambled. The best approach is to turn off the car, get out and do a "360" with the antenna pointed away from you.
  4. For "close-in" work, distance-to-target (signal strength) can be used reliably, as well as directionality.

I would conclude therefore, based on these tests, that with the 18" transmitter antenna, this system should be sufficient to locate your lost plane under almost any conceivable circumstance. If you have maintained visual contact until the plane goes down over the horizon, you should have a good enough idea where it came to rest to be able to locate it in short order. In situations where it's location is not as well known (if the plane is lost in a cloud and never seen again for instance), I would think a systematic search should be able to put you within range of your plane eventually. If you get any signal at all, you can get pretty good direction information from it, and from there you're pretty much home free.

All my AP missions from here on in will have one of these on board!

-- Kevin
Aug 03, 2005, 02:10 PM
Registered User
ViddyFlyer's Avatar
GREAT testing and reporting Kevin ... THANKS again!

RE: Antenna
My ancient recollection of antenna tuning for US amateur radio transmitting is that a couple of meter devices are used. A SWR (standing wave ratio I think) meter is used at the "back" of the transmitter inline with the antenna coax to help adjust radio/antenna system for maximum radiated power. How this type of tuning adjustment is carried out for a tiny transmitter like the planelocator I don't know. As for antenna adjustment itself the length is often varied to obtain the best SWR reading. At higher transmit frequencies the amount trimmed off the antenna wire for tuning may be just fractions of an inch. The manufacturer would have to be consulted for this type of tuning.

For actually "looking" at the power output from a transmitter a field strength meter is the tool used. One memory of using this device is moving it around a transmitting antenna to determine the pattern of stronger or weaker lobes. The planelocator receiver functions as a field strength meter so I should think it would give good indication for testing the best antenna wire "mounting" placement. Hummm ... My concern / question here is how to properly position the antenna on the plane and then confirm good performance. Could I tape the wire to my Slow Stick's aluminum fuselage? ... could it be strung along side parallel to the plane's receiving antenna? Or???
Aug 03, 2005, 08:03 PM the skies...
Cats Eyes's Avatar
Thanks, Viddy

Your observation about the antenna length is interesting. The supplied antennas seem to be discrete multiples of the 4" length. I'm not sure if that's significant. I was thinking that they were "tuned" multiples of half-wavelengths, but at 220 MHz the wavelength is 1.36 m, so that doesn't make a lot of sense.

I remember using a SWR meter and a "match box" (basically an autotransformer with a tuned circuit on the output) years ago when I was into CB radio. (Never got into the HAM stuff.) I don't think you could do anything like that with these little transmitters. There's no coax; not even really a "ground" connection, other than the transmitter's case.

As you say, the planelocator's receiver has a field strength meter built-in, which would be useful for measuring relative field strengths. I hadn't really thought about the placement of the antenna on the plane. I must do some experimentation on that.

I would think placing it next to the Slow Stick's (aluminum) fuselage would not be a good idea, as it would tend to "short out" the transmitted signal, wouldn't it? Placing it next to the receiver's antenna would result in a very strong coupling into the receiver. They say it won't interfere with the receiver's operation, but why chance it? I am thinking now about possibly stringing the antenna out the wing and in fact mounting the transmitter underneath the wing near the root.

Speaking about grounds, another thought that occurs to me. Maybe the transmitter's case (which I presume is the "ground") can be attached electrically to the Slow Stick's fuselage and the antenna wire run perpendicularly to it (out the wing for instance). Any ideas if that might work?

At any rate, for my purposes I am quite happy with the 1-mile range. I will have to confirm that is still present when the transmitter is mounted on the plane. If so, I'm inclined not to spend too much time trying to eek more range out of the setup. The only scenario I can see where you'd need more range than that is if you've "specked out" way up high (not something I'm doing) and lose sight of it.

The bottom line for me is to just make sure I have the transmitter on the plane and working for every AP flight. If that means compromising the range a bit, then that's the risk I'll take. If the range is only a half-mile, it will take longer and require a more systematic search to find the plane, but the plane will most likely still be found. I'll worry about "tweaking" for maximum range when I get some spare time.

-- Kevin
Aug 04, 2005, 01:49 AM
Registered User
ViddyFlyer's Avatar
Roger dodger 10-4 good buddy! You wern't packin one of them slightly less than legal ole linears between that good ole coax and moonraker now were yah? (Heheheh .. you can take the 5th) I CBed for a couple years before practicing Morse and testing for the "ticket" which all went for naught when hobby cash got gobbled by computers.

We seem to share enough knowledge of this antenna tuning stuff to make for interesting questions. Does the maker of the planelocator offer mounting and placement tips. I did glance at the manual, but have other online chores before I can refer back to it. Wing placement sounds good to me.
Aug 04, 2005, 06:55 PM the skies...
Cats Eyes's Avatar
Actually, my CB days were in my teens, before I even had a job, so the whole thing was done on a shoestring. Couldn't afford a "linear" or a moonraker (although I knew plenty of people running either or both). I think I did the whole thing for under $70. I bought a second-hand 40-channel mobile unit; designed and built the power supply from stuff I had "floating around" and stuck a homemade dipole antenna in a tree. The SWR meter was a demo unit I picked up for half price from rat shack. I wound the "match box" coil myself and used a variable capacitor scrounged from a defunct transistor radio. Kind of amazing it all worked as well as it did. I used to talk to a guy 35 miles away fairly regularly.

Oops! Sorry for the digression/reminiscence. Where was I?

Oh, yeah. Mounting tips. The only information I could find in the manual is on page 6:

The PT-1B ELT should be installed in the fuselage of your plane. Tape or tie wrap it so it is attached securely. If your plane is composite or has a metal skin, try to trail the antenna outside the fuselage. This may require a longer antenna attached to the PT-1B antenna mounting stud. The PT-1B is extremely crashworthy and waterproof.
Not much there. I think this is the one area where the documentation is rather lacking. They don't mention the severely limited range from using the shorter antenna. You would think that the way it's mounted on the plane (especially in the presence of other metal components) would greatly affect range as well, but there is little about this other than suggesting routing the antenna outside the fuselage in the case of metal skin. There has to be more to it than that!

Unfortunately, I'm going on vacation soon, so will not be able to do any more testing for a few weeks. Presumably anyone purchasing the system can do his/her own testing using the field strength meter built into the receiver to ensure that any particular installation has similar radiated power to the transmitter in free air.

-- Kevin
Aug 04, 2005, 08:04 PM
Registered User

Did you range check your plane with the Planelocator installed and transmitting?

Just to make the above question clear: Did you verify that using the Planelocator does not reduce your normal range check distance?


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