Economical NDB modroc tracker.

Here's an economical Non-Directional Beacon tracker for modrocs if one is a Ham.

https://www.jbgizmo.com/page30.htm

For $15.00 I built a couple but haven't done a real world test yet. 400 yard range on the ground is pretty good so if one has
an H/T and a 3 element yagi might not risk much $$$$. (I did a site search here but didn't see any other posts pertaining to this)

I'd say seal it with urethane, wrap some wadding around it, tie the antenna/counteroise along the shockcord so it gets deployed with the chute and have fun. Kurt

I'm not sure I would call 400 yds a good range, especially since that is several feet above ground. If it lands in a hollow, you might have to be within 50 ft to pick it up. That doesn't seem like something I would want to put in my HPR rockets.

Maybe I'm spoiled by our clubs Walston. It has a 20 mile range in the air and 2-3 miles on the ground, if there are no hills in the way. It isn't what I'd call economical though if you have to buy it yourself.

I did say modroc and $15.00 is not so bad. Combine it with a 3 element Yagi and I think it would be serviceable. A standard Beeline NDB is 16Mw and works reasonably well. One needs to get a good bearing and proceed in that direction. A "sight n' go" feature on a Garmin handheld GPS is helpful here. Point it down the antenna and lock the bearing to be able to walk a reliable line.

Yes the 50mW in the 1.25cm band that the Walston operates in would work better simply due to the higher power but how much do you pay for just the tracker? Something akin to $100.00. And then there is the SSB/CW mode proprietary receiver that's required, $400.00 or more?

I've been burned with a high powered tracker (>50Mw) dorking deployment electronics and having less than a nominal flight twice. More power is not necessarily better. 2 watt Garmin dog trackers are notorious. Some deployment devices are more resistant than others. Having a more sensitive receive end is a workable solution.

If you get yourself an EggFinder, you can have GPS tracking and not have to worry about getting a bearing. Point to point recovery for $120.00. Kurt

ksaves2 said:

Yes the 50mW in the 1.25cm band that the Walston operates in would work better simply due to the higher power but how much do you pay for just the tracker? Something akin to $100.00. And then there is the SSB/CW mode proprietary receiver that's required, $400.00 or more?

If you get yourself an EggFinder, you can have GPS tracking and not have to worry about getting a bearing. Point to point recovery for $120.00. Kurt

Click to expand...

The Walston is not cheap. You're right, the receiver is at least $400 and models go up over $600. The transmitters are over $150. Our club happened to get a setup used and allows club members to use it. It really is an excellent system. It does take some experience and has a learning curve. It's not too hard to get good at DF with that system.

My question on the EggFinder and other GPS systems. Do you have to have a good in-flight signal from the system during the whole flight? What happens if you don't pick up the signal after launch? Is there a data signal that can be picked up from long range that can guide you to where the rocket is if you didn't receive anything during flight?

That is one of the things I like about the Walston DF system. I don't have to track it during flight. I can wait until it has landed and then pick up the signal and hunt it down.

"My question on the EggFinder and other GPS systems. Do you have to have a good in-flight signal from the system during the whole flight? What happens if you don't pick up the signal after launch? Is there a data signal that can be picked up from long range that can guide you to where the rocket is if you didn't receive anything during flight?"
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If you don't receive anything if flight with any tracker, you have a problem. A GPS tracker will give you packets before you launch. You must follow instructions with any unit you use and must avoid metallic paints. A ground range check should be done with any tracking system you use when it is installed in the rocket.

At altitude, range is quite far even with low power as long as the device has power and the antenna is a reasonable design.
As the rocket gets lower, you'll receive a "last known packet" and when you get to that position, if you don't see the rocket, you generally
will get a new packet that will take you to the rocket.

With my 16mW Beeline GPS tracker, I can open up the squelch on my H/T and can hear a faint packet coming in even though it can't be decoded. I at least know the tracker is functioning and generally this occurs from a 1/2 mile or more away on the ground. I proceed closer and a new packet is decoded for a final position. Then walk right to it. I've done Beeline GPS tracking and not flown my EF's yet. The technique will be the same.

Folks have received packets to 13000 feet last I heard with the EggFinder. No commercial GPS tracker will give you packets during mach flight but as soon as the speed drops, they'll start to come in on descent.

To extend range with the EF get a patch antenna that is recommended in the documents and is generally economical:
https://www.streakwave.com/itemdesc.asp?ic=ARC-PA0910B01&eq=&Tp=

Kurt

I guess that does answer my question. If you don't get any packets after launch, and assuming it is still transmitting, you can pick up something if you get close that will lead you to the location. You're not SOL if you miss the "last known packet".

Handeman said:

I guess that does answer my question. If you don't get any packets after launch, and assuming it is still transmitting, you can pick up something if you get close that will lead you to the location. You're not SOL if you miss the "last known packet".

Click to expand...

The receiver locks that last received packet in the display whether you use this or a Beeline GPS APRS tracker. With a Ham Radio APRS tracker,
the packets are different than those out of the non-licensed trackers in format. The radio receiver is a heck of a lot more expensive. The only advantage at best is the datastream can be sent to a Garmin 60Cs, CsX or 78 handheld and navigation can be done in realtime on the map. (Or a laptop but that is hard to take portable to the rocket.)
The EF can do that trick to a degree with the Android app "GPS rocket locator". If one wants a map of their location, they have to have an internet connection or the device will just give the two points and a line to follow. That's all that's needed to find the rocket anyways.
GPSRL can be squirrely at times but the lat/long can be pulled off the display of the EF LCD and input into any handheld mapping GPS
to navigate to the rocket. It's not automatic but it works.
Recover one rocket that has pricey electronics onboard and the EF pays for itself in one flight. In order to achieve that with the Ham Radio Equipment, one needs to recover 3 to 5 pricey rockets. When I say recover, I mean a flight where the rocket disappears without a trace except the information one sees from their tracker. I've had that happen twice so far with the BeelineGPS tracker. Wouldn't have had any idea where to even start a search. By reading the display, one can tell the drogue is out and when the main is out and deployed even without a visual.
All in all, an individual will feel more comfortable with outta sight flying. Doesn't eliminate trees and lakes but at least gets an idea where to look.

What about RDF? Yeah that works but for really distant flights one can only hope they get close enough on their bearing line to pick it up again. Can waste a lot of time in that endeavor. If one wants to put up more projects, they have a better chance of going directly to the rocket, get it and go one to launch the next one. Kurt

I have used the RDF with the Walston and on our field, only had one flight that was "lost" and gave no return while at the flight line. A walk to the top of the nearest hill got a signal and it was easily tracked down after that. The terrain wasn't easy, but following the signal was.

I don't know much about the ham world so the acronyms you use like APRS, EF, and GPSRL are only guessed at and I don't know what they mean. I suspect many other reading this don't understand either.

I understand the principle of GPS tracking and that it send constant data packages with its current position, but I don't know the details or understand what happens when things go wrong as they often do. I'm comfortable with the RDF equipment I use and have been very successful. I don't know if I would be as successful with GPS trackers.

Handeman said:

I have used the RDF with the Walston and on our field, only had one flight that was "lost" and gave no return while at the flight line. A walk to the top of the nearest hill got a signal and it was easily tracked down after that. The terrain wasn't easy, but following the signal was.

I don't know much about the ham world so the acronyms you use like APRS, EF, and GPSRL are only guessed at and I don't know what they mean. I suspect many other reading this don't understand either.

I understand the principle of GPS tracking and that it send constant data packages with its current position, but I don't know the details or understand what happens when things go wrong as they often do. I'm comfortable with the RDF equipment I use and have been very successful. I don't know if I would be as successful with GPS trackers.

Click to expand...

APRS = Automatic Packet Reporting System

GPRSRL = "GPS rocket locator"

EF = Egg Finder

DF is a heck of a lot better than nothing. I've witnessed lost rockets that had trackers where one simply couldn't get a fix. Hear a weak signal but can't find it. Also had a presumed situation where the rocket may have core sampled, weak signal heard and no remains found.

If a rocket is not traveling a long distance away sure it can be helpful. With APRS tracking (GPS tracking) in the ham band one could use
a Yagi and attenuator to localize a weak signal that can't be decoded but it is not likely going to be needed as one can walk right to the last
position packet. As one gets close to that position, new packets come in marking the final place. If the rocket is withing 2 to 3 miles, the last known packet received is likely very close to the final resting place unless the wind is blowing it along.

Kurt