Garmin Astro

I am going to invest in a Garmin Astro tracking device.

After a quick search, I see there are a couple different models available (220 & 320). Is there a specific model that makes better sense for rocketry?

Also, I am soliciting any additional advice from experienced users...

• Do you simply remove the wireless transmitter from the dog collar and toss the collar? Or, do can you just buy the transmitter?
• It’s hard to tell from the sales materials how large the transmitter is. What size E-bay can accommodate this?
• What is the best technique to secure the transmitter to the rocket?
• What else do I need to buy up front? Is the Garmin Portable Antenna necessary?
• Any other tips / suggestions?

Thanks

We had a Garmin Astro for the dogs, it came with the 220 handheld and the DC-20 collar, we then added a DC-30 collar for the 2nd dog.

Our experience was that this system is semi useless as soon as the dogs go into trees, or over a hill. Every time we used it, we found some severe "line of sight" problems. ie, if the dog/transmitter and your handheld receiver are not in direct line of sight of each other, you will lose signal, or at best you will get updates every 30 seconds. The docs state that it should update once every 5 seconds, I found this actually happened about every 8-10 seconds.
After a month of ownership and use/testing, we decided that the system wasn't all it was made out to be. Lacking in a variety of areas. It went back.

For rocketry tracking I see a problem both with the time it takes to update the handheld unit (average 8-10 seconds) and the 'line of sight' issues.

That was about 9 months ago, since then I have read a few articles that all state that the aerials seem to be the main problem, and that upgrading to aerials with better gain might help with the 'line of sight' problem.

Right now I am looking at options to save me HPR's from disappearing into sage brush. This means that I will be looking for another tracker of some sort. After my disappointment with the Garmin I am looking at the BRB 900 from Big Red Bee. This retains for about $420 including the upgrade to data logging and LCD display on the handheld. It means that I will have to use another handheld GPS system to get me to the Co-ords, but I have a $80 Garmin that is used for GeoCaching that will do perfect for that.

All the guys in our club using the Astro love them! 99% of the rocket's flight is "line of sight", so I don't see why that'd be an issue. If you take the last gps reading you received before it touches down and goes out of sight, you're probably within a few yards of the final touchdown point. I have 2 DC20's (yet to fly them), but am going on the recommendation from club members.
-Ken

The Astro (and Rhino) both use MURS for telemetry. This is limited (by law) to 2watts transmit power. As such, the performance will only be as good as the antenna. A handheld yagi would solve and problems and should keep you receiving within a couple miles in most terrain. Check out: https://www.arrowantennas.com/sub/arrowiiyagi.html Either the 146-3 or 146/437-10 would work excellent with the latter also supporting standard uhf trackers.

MURS is intended for short-range local communications. Antenna height is limited to 20 feet above structure or 60 feet above ground, whichever is the greater. [47 CFR 95.1315] https://home.provide.net/~prsg/murs_faq.htm

Bob

bobkrech said:

MURS is intended for short-range local communications. Antenna height is limited to 20 feet above structure or 60 feet above ground, whichever is the greater. [47 CFR 95.1315] https://home.provide.net/~prsg/murs_faq.htm

Bob

Click to expand...

Actually the more relevant portion of Part 95 here would be 95.2303(b) that states that MURS operation is not authorized onboard aircraft in flight. The thing to remember here is that we are talking about an intermittent telemetry transmission that would last less than one minute above altitude thresholds in a radio service that no longer requires licensing because the FCC was unable to enforce licensing requirements thus causing them to defer to "license by rule" on MURS the exact same way that they did with 11 meter CB years ago. So, is it totally compliant with current regulations to utilize MURS to track a rocket in flight? Not exactly but at the same time you are HIGHLY unlikely to cause harmful interference and it is even less likely that you would ever see an enforcement action.

csoechtig said:

I am going to invest in a Garmin Astro tracking device.

After a quick search, I see there are a couple different models available (220 & 320). Is there a specific model that makes better sense for rocketry?

Also, I am soliciting any additional advice from experienced users...

• Do you simply remove the wireless transmitter from the dog collar and toss the collar? Or, do can you just buy the transmitter?
• It’s hard to tell from the sales materials how large the transmitter is. What size E-bay can accommodate this?
• What is the best technique to secure the transmitter to the rocket?
• What else do I need to buy up front? Is the Garmin Portable Antenna necessary?
• Any other tips / suggestions?

Thanks

Click to expand...

i purchased and have flown the astro 320 with the dc40 and had no problems. the unit is a perfect solution if you want to simply find your rocket, it does not collect much data as it reports location every 5 seconds. the collar is easily removed by removing 2 screws. i have heard there can be problems with some altimeters if the transmitter is to close. i mounted mine in the nose cone which is atleast 24 inces from my altimeters. i made a bracket that the 2 screws that held the transmitter to the collar can be attached to.
the unit works right out of the box. like stated above, the line of site is not an issue until the rocket lands.
feel free to pm me if you have any other questions or need dimensions of the dc40.

Hello,

I purchased a Garmin Astro 320/DC40 at Christmas time from Amazon.

I've used successfully since then to recovery 2 rockets per launch date so that about 4 flights a month. The Astro 320 will point to the direction and distance of the rocket. I've download Sat images to show actually site terrain.

I'm using mostly on the rolling hills at LUNAR, may lose lock briefly as I walk up and down hills but last known location/direction is display and lock regained as I close in on the landing site. At SARG a flat field no problem at all. Garmin says Astro 320/DC40 has ~7 miles range.... but I've not had more that 1/2 mile away so far, no problem at this distance.

I removed the orange collar but left the plastic case for protection. Due to the size I use only in nose cone of 4 inch rockets like Wildman Vindicator, Dark Star, Wild Thang, etc. I can fit in my 3 my Wildman Dual Deploy nosecone and ebays of my Performance Rocketry 1/2 Scale Amraam but tight. It will not fit in small diameter rockets. DC40 weights 147 grams.

I wrap foam around the DC40 and fill the empty space in nose cone with bubble wrap to keep DC40 from moving around.

Can use Astro 320 as general purpose GPS for hiking, etc. too.

Ask if I missed one of your questions.

Last weekend a friend of mine flew one to mach 1.8 and 30200 ft, and as far as I know, it never lost lock going up, down, or on landing. It showed us that it was 2 miles north, then 1.6 and so on. Updated very quickly for the price.

One thing of note, as a dog tracker, it will not measure the altitude (go figure).

Thanks for the feedback! I believe I will pull the trigger on the 320 with dc40.

I figured I would find room in the AV Bays. However, I like the idea of mounting it in the nose cone. I am curious how you are modifying the cones to accommodate the Astro. For example, I plan to use the Astro in LOC builds with 4" dia polypropylene nose cones.

1. Where do you cut and insert the device?
2. If you cut out the bottom section, how do you secure the main shock cord to the nose cone?

Thanks!
Chris

csoechtig said:

Thanks for the feedback! I believe I will pull the trigger on the 320 with dc40.

I figured I would find room in the AV Bays. However, I like the idea of mounting it in the nose cone. I am curious how you are modifying the cones to accommodate the Astro. For example, I plan to use the Astro in LOC builds with 4" dia polypropylene nose cones.

View attachment 80043

1. Where do you cut and insert the device?
2. If you cut out the bottom section, how do you secure the main shock cord to the nose cone?

Thanks!
Chris

Click to expand...

I would caution against putting the DC40 in the Alt bay. I use RRC2s so I touched base with Missile Works prior to installing the unit and Jim confirmed that the RRC2 MAY have false readings due to the power of the transmitter. He was not sure how far apart the unit should be from the altimeter but thought it should be at least 2'. I've kept mine 2' away and had no problems. Not sure about other altimeters but I read in the post below that certain components are/can be affected:

https://www.rocketryplanet.com/forums/showthread.php?t=8455&highlight=garmin+astro

I tried to do some ground testing with light bulbs attached to the altimeters but never got the unit to show a false reading.

Can't help with mounting the unit in a plastic nosecone as the rockets I fly the unit in are fiberglass and I make the bulk plate removable to mount the unit inside. I've heard of people attaching the unit directly to the shock cord. You could fabricate a nomex/kevlar bag to protect it, attach it directly to the nosecone anchor point and drill a hole in the base of the nosecone for the antenna to run through.

edwinshap1 said:

One thing of note, as a dog tracker, it will not measure the altitude (go figure).

Click to expand...

The DC40 does measure and report elevation and the readings have been pretty close to the altimeter readings. You'll just need to adjust it for AGL figures based on the elevation of the range.

Scott S said:

You could fabricate a nomex/kevlar bag to protect it, attach it directly to the nosecone anchor point and drill a hole in the base of the nosecone for the antenna to run through.

Click to expand...

Thanks Scott - you read my mind. I was thinking the exact same thing.

I attach by DC30s dirtectly to the shock cord. I have removed the collar. I feed my shock cord through a kevlar sleeve. I then place the ASTRO in the sleeve and zip tie both ends. It has neve come out. I will take pictures at our next launch to post.

cwbullet said:

I feed my shock cord through a kevlar sleeve. I then place the ASTRO in the sleeve and zip tie both ends.

Click to expand...

Now that is an excellently elegant solution for this application. Protective and secure.

--Lance.

llickteig1 said:

Now that is an excellently elegant solution for this application. Protective and secure.

--Lance.

Click to expand...

I double the sleeve at the ends and use a double zip tie method. 1 under the double over fold and one securing the fold. The inside ties are protected from hot gas just in case.

Here's how I secured my Garmin DC30 in one rocket application:

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