# Marco Polo Tracker - Great Bang for the Buck

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#### BSNW

##### Well-Known Member
So I finally put my Marco Polo to use this weekend. In a word, it proved itself very worthy for rocketry use. I first loaned it to a friend who put it in his 5.5" kit on a K600 ex motor. I established a link to the tag before launch and the receiver kept a lock on it all the way up to around 2500 feet and all the way back down. I was encouraged that it maintained the lock between the tag and receiver.

I then put it in my PML Ariel for a slightly higher flight. Unfortunately, it did land in waist-deep soybeans about 3/4 of a mile away. I got in my car and drove to the edge of the field. In doing so I was actually going farther away from the tracker. I momentarily lost signal when I went behind a metal barn, but quickly regained signal when I came out past the building. I had to park my car pretty far away and began to track. All I can say is it walked me right up to the lost rocket. All I had to do was follow the arrow and % signal on the receiver. I would have never found it or taken hours to find it in the beans.....I was elated. I have lost rockets in soybeans and we all know how well they swallow up large rockets!

Talking to a guy at the flight line he told me he loaned his to a guy at a Tripoli-Mid Ohio launch for his L3 flight. He had a GPS and a Marco Polo. Guess he lost signal on both after launch. He looked for hours for his rocket. At long last, it was the Marco Polo that found this guys rocket in a wheat field! I guess he drove up the road a bit until it picked up the signal, then walked up to it.

The Marco Polo transmitter will send a signal for up to 3 weeks....plenty of time to find your rocket in crops, grass, thicket, etc. All I know is it works out of the box and is extremely affordable. A couple guys at the launch told me they are ordering one.

For MOST people this product is more than adequate. It was also very fun to track my rocket.....I truly recommend this tracker.

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#### Scott_650

##### Well-Known Member
I get both sides of this discussion - Kurt’s points are valid, if you’re spending the money anyway just spend a bit more, get your ham license and have a system that takes advantage of all the resources available and you’ll always find your rocket. OTOH, Andrew has a solid viewpoint - your initial cost is pretty much fixed and for most people who fly rockets the Marco Polo setup solves over 80% of their problem - finding a rocket in crops, grass, nearby woods, etc. If I had put a MP unit in my Estes MAV Saturday at the NOTRA launch I could’ve walked right into the bean field and picked up my rocket. A full on amateur radio/GPS tracker would’ve been overkill to find a rocket I tracked down but was swallowed up by the soybeans. If I was a HPR flyer and launched high altitude rockets on wide open ranges it could be well worth the cost/effort for a full system. As a LPR/MPR guy finding my model rocket in the corn with a simple RDF tracker might be worth the investment. Great discussion!

#### BSNW

##### Well-Known Member
I get both sides of this discussion - Kurt’s points are valid, if you’re spending the money anyway just spend a bit more, get your ham license and have a system that takes advantage of all the resources available and you’ll always find your rocket. OTOH, Andrew has a solid viewpoint - your initial cost is pretty much fixed and for most people who fly rockets the Marco Polo setup solves over 80% of their problem - finding a rocket in crops, grass, nearby woods, etc. If I had put a MP unit in my Estes MAV Saturday at the NOTRA launch I could’ve walked right into the bean field and picked up my rocket. A full on amateur radio/GPS tracker would’ve been overkill to find a rocket I tracked down but was swallowed up by the soybeans. If I was a HPR flyer and launched high altitude rockets on wide open ranges it could be well worth the cost/effort for a full system. As a LPR/MPR guy finding my model rocket in the corn with a simple RDF tracker might be worth the investment. Great discussion!

I also don't mean to keep repeating myself but this unit already has proven itself on at least one high altitude flight at a TMO launch where the rocket did go high and was recovered a number of miles away and over rolling terrain.....and after there was a LOS (which was recovered).

I don't understand any other situation (in rocketry ) that falls out of this type of scenario. I also don't understand why if it works in a mid-power rocket going to a respectable altitude it would not work in a high power rocket going a bit higher and land further away. The principles in play are the same.....distance, terrain, etc. With this unit all one has to do is re-establish a (potential) loss of signal and track.....do not the other, more "advanced" systems do the exact same thing? If this works in a wide-open field, why would it not work on the "playa of the Gods"? Or on the rocket prairie of Kansas? Again, a person has 3 weeks to re-establish a lost signal.

IMO I think the Marco Polo lacks the "Cool High Power Rocketry-Advanced Electronics-From a Rocketry Vendor" mystique (for now).

If so, I don't mind, as it seems like it can track with the best of them in 99% of the time for 99% of rocketeers...for much less money. I think a lot of questions and dare I say doubts...would be answered if folks try it. I also invite others to read the testimonials for others who have actually used it.

If I am showing my ignorance here, please forgive me

I would imagine there are far more planes and drones that have flown away or gotten lost over the same types of distances and terrain than rockets, as there are far more plane/drone folks than rocket folks. From what I hear from that group, they love it.

Andrew.

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#### Tim Crabtree

##### New Member
All I can add here is some clarification of how the Marco Polo system works.

Both the handheld "Locator" and the remote "Tag" are transceivers with two-way communication capabilities. If the tag is powered up but the locator is off or in idle then the tag wakes up once every 10 seconds and scans the 50 frequencies used by the system for RF power. If nothing is found that matches the hopping pattern that is unique to the individual tag, then the tag goes into deep sleep for 10 seconds and then repeats the scan. The tag can do this for up to 15 days on a charge.

If the locator is "paging" a tag it is sending out data packets with synchronization information on a secession of channels which are, once again, unique to the tag being paged. A packet, or data frame, contains a payload of 6 bits which are encoded and forward error corrected into 24 bits to allow an 80% packet decode rate with a received SNR of 6dB. Each repeating set of data frames are organized in a "superframe" structure containing 53 frames, 1 frame is reserved for receiving the response of the tag being paged, the other two are reserved for transmission and reception of data to/from up to 7 other tags that have already had communication sessions started. Each of these tags is assigned a specific superframe to communicate with the locator in a "hyperframe" structure that consists of 16 superframes. Half of the superfames are dedicated to a single selected tag that is being tracked once every 4.7 seconds the remaining superframes are assigned to individual tags that are being "monitored". Much of this is designed to support other applications outside of rocketry, such as monitoring the proximity of 3 dogs and 2 cats and sounding an alarm if any of the animals exceeds an individual boundary that is established for them. The air protocol allows the locator to maintain communications with the 3 dogs and 2 cats while paging a 3rd cat and locking its tag into an unused superframe in the hyperframe. Once communications are established, the locator can select any tag to be the "active" (tracked) tag where it receives commands and responds on every other superframe or return the active tag to monitor status where it receives commands and responds on only one designated superframe in the hyperframe. The locator can also command tags to go back to idle status and then page and assign different tags to the idle superframe. Tags effectively have a 24-bit address (16M unique tags) and can be individually selected, even though the address is never sent over the air, in either direction, in normal operation.

I only drag you through all this because many people see or hear what Marco Polo does and they automatically think they know how it does it. Yet I doubt that anyone would have guessed the above explanation, which only covers the data communications, not the direction finding.

Back to this problem domain; a tag must, of course, be powered on before flight. When in the idle mode the tag only cycles its receiver on once every 10 seconds to listen for transmissions from a locator. So in idle mode the tag does not transmit any RF energy and can be co-located with any other RF transmitters or receivers used during flight. This is popular with drone users since they have often have multiple RF links running during flight. The tag can also be activated by the locator before or during flight and once locked into a tracking session with the locator it will receive and respond to commands from the locator once every 4.7 seconds, the locator will then measure the RSSI and compute the angle of arrival of the signal for display after each communication. Each tag transmission is 50 msec in duration on a pseudo randomly selected frequency repeating every 50 transmissions. Thus the dwell time on any one frequency is 50 msec once every 4 minutes. If you have telemetry that would suffer interference from the tag's transmissions (or the locator's, since it is basically doing the same thing on the ground) then I would leave the tag in idle. In most cases I would suspect that you would start the tracking session before launch and track the rocket during descent so you have a bearing from the launch point to guide you in a search. if the signal is lost when the tag in on the ground then the handheld locator will enter searching (paging) mode and reestablish communications when you get within the ground-to-ground range of the system. Getting to higher ground helps a lot when trying to establish communications, even standing on the bed of a truck makes a noticeable difference. We have military customers that track payloads ejected from high flying drones, I think they do have GPS coordinates as a starting point. All I know is that they tell me they "have never lost one yet."

Tim Crabtree

#### Scott_650

##### Well-Known Member
About a third of all this only makes sense to me as it connects to the other 2/3 of the info - in other words I can “logic” out how it fits together but I’d never be able to explain the science of how it works

But I find it all fascinating - spent a hunk of my afternoon down the rabbit hole reading about frequency allocations, history of amateur radio, strengths/weaknesses of all the variations of LF and HF frequencies, impact of RDF aircraft navigation...dang, this is one of the reasons I LOVE this hobby!

Thanks to Andrew, Tim, Kurt for a fun session of skull sweat !!

#### Buckeye

##### Well-Known Member
BSNW, Congrats on your successful tracks. It is a rush when your device leads you to your rocket! Nobody is calling your baby ugly though, so no need to be offended. There are several tracking technologies out there, each with pros and cons. The Marco Polo is a nice addition to the space.

Personally, I like numbers and I like maps, so I go for GPS. Unregulated GPS, to be exact.

#### BSNW

##### Well-Known Member
BSNW, Congrats on your successful tracks. It is a rush when your device leads you to your rocket! Nobody is calling your baby ugly though, so no need to be offended. There are several tracking technologies out there, each with pros and cons. The Marco Polo is a nice addition to the space.

Personally, I like numbers and I like maps, so I go for GPS. Unregulated GPS, to be exact.

However, I was indeed not offended. I was a tad frustrated...yes....as I was trying to explain that the very things I was being told it could not do....I actually experienced and was told (already) that it could do. Either way, it's all good. I am sure as this catches on with more rocketeers people will be surprised as to is capabilities and like the affordability and ease of use.

I know and respect the many other options out there. But that was not my point. I just felt (maybe incorrectly) that this product was initially being dismissed for its perceived limitations in lieu of actual observed performance. This was the source of my frustration.

Thanks!
Have a great day all.

#### Handeman

##### Well-Known Member
TRF Supporter
This is certainly much more complicated and technically dependent on the technology working than a simple RDF system. The price point is good, but I find the difference between this and a GPS system not much different when it comes to dependency on the technology working. Certainly it preserves battery life way past what a GPS locator would have transmitting packets every few seconds. I still don't think it would out last the simple RF burst from a true RDF transmitter as far as longevity. Of course with the RDF, the directional detection is all up to the user. An experience user can detect apogee ejection if the system is set up right.
Certainly worth considering as a tracking system.

#### Tim Crabtree

##### New Member
This is certainly much more complicated and technically dependent on the technology working than a simple RDF system. The price point is good, but I find the difference between this and a GPS system not much different when it comes to dependency on the technology working. Certainly it preserves battery life way past what a GPS locator would have transmitting packets every few seconds. I still don't think it would out last the simple RF burst from a true RDF transmitter as far as longevity. Of course with the RDF, the directional detection is all up to the user. An experience user can detect apogee ejection if the system is set up right.
Certainly worth considering as a tracking system.
Man, you guys know your stuff. Way different than the woman with 5 cats that says, "Oh, does this use radio signals? Is that why it didn't work well when I was standing between 2 dumpsters in the school parking lot?" Or, "Red LED? You mean the red light? Why didn't you just say red light???"

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