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Tracker antenna strain relief concerns

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Conway Stevens

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Ive been looking at alot of the mouinting of various trackers. Featherlight, Eggfinder, Missileworks, Altus, BRB and others and how current manufactures or nose/avbay or shockcord mounted units. I have yet to see abny of them offer any support for the antenna. How do these not damage the tracker and antenna mount? this may not be as big of a deal on wire whip but on the extended range antennas that are more solid mount I would be concerned with the jolt at the end of recovery or a whip around of the nose cone/shock cord to have high potential for damage to these units due to such. Is anyone making or adding support for this? love to see your examples. Or if you feel no concern id be curious why.
 
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watheyak

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I guess I'm in the "no concern" camp. Mine have usually been in nosecones. I've used BigRedBee, Altus Metrum and Featherweight.

If the ejection (or flight anomaly) creates so much force that it causes the antenna becomes detached, you've probably got bigger problems than antenna being detached.
 

Conway Stevens

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I guess I'm in the "no concern" camp. Mine have usually been in nosecones. I've used BigRedBee, Altus Metrum and Featherweight.

If the ejection (or flight anomaly) creates so much force that it causes the antenna becomes detached, you've probably got bigger problems than antenna being detached.

Thank you for the input Scott. Guess im basing my post off of other potential concerns ive heard possible. Seems like at times we try to prepare for things that are possible. Currently I have an Eggfinder and a Featherlight. Studying for my HAM to get into the Altus and BRB ham bands I also use an RDF tracker at times. But I believe in the case if the added larger antenna Cris from Eggtime has recommended strain relief. Just wasnt sure as Iv not used one yet and most I see dont either.
 

Voyager1

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You will see in some of the posts describing tracker mounting that some people use support for their antennas. This is probably more significant for the heavier manufactured monopoles. There are examples of people employing 3D printed stems attached to a baseplate the tracker is installed on, or even a F/G bulkhead with a hole to support the monopole about halfway along its length, even for the simpler stiff wire or thin brass rod antennas.

For the shorter monopole antennas I’ve not worried about supporting them. However, the longer ones probably should be supported.

If your tracker is mounted in the nosecone you have less to worry about. However, if you mount the tracker in your avbay with the antenna mounted off the outside of one of the the bulkplates protruding into the chute compartment, as some people do, then you really should secure the antenna because it could be damaged by the shock cords or tethers.
 

OverTheTop

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Any of the stick antennas or ones that screw onto the SMA or RP-SMA need support. The lever arm will amplify any forces from the flight or recovery and stress the solder joints on the connectors. Solder is a good conductor but not good mechanically. It will likely crack. You would also be relying on the bonding of the copper pads to the PCB stubstrate. Give them a holiday and apply strain relief.
 

Conway Stevens

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Any of the stick antennas or ones that screw onto the SMA or RP-SMA need support. The lever arm will amplify any forces from the flight or recovery and stress the solder joints on the connectors. Solder is a good conductor but not good mechanically. It will likely crack. You would also be relying on the bonding of the copper pads to the PCB stubstrate. Give them a holiday and apply strain relief.

That's some of the input around I've received but searching upon it yielded no real data shared that was of large consensus. I personally would have to Agree with you. We constantly talk about forces that we put things under all the time. But how about when your main deployment occurs and the chute inflates fast and snaps the nosecone in an awkward or rapid jolt. The only support is the solder joint of the SMA connection to take the brunt of that. I use stick type screw on antenna on every tracker I have. I'd prefer to not have loss of signal or broken tracker. Would fastening something as simple as a mounted stir stick to the sled and wire tie the antenna to the stick be enough? I would think it would be strong and rigid enough.
 

OverTheTop

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But how about when your main deployment occurs and the chute inflates fast and snaps the nosecone in an awkward or rapid jolt.
Many times the deployment forces have been underestimated, on both amateur and commercial rocketry.

I would think that just supporting the distal end of the stick antenna would be sufficient. If you support it all the way along the support material becomes important and has the potential to detune the antenna a little. You really just want to increase the resonant frequency and reduce the lever moment.
 

Conway Stevens

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Almost like a standoff part way down that has a ring around the antenna. Fiberglass or printed plastic? To keep it whipping from the midway point to the end area?

As long as it's not a metal?? Would it affect the tuning of the antenna? Wood, plastic, Fiberglass?
 

QFactor

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The pictures are from a new build. So this rocket hasn't flown yet. It's a head-end deployment, so I could not put the tracker in the nose cone like I usually do. This is a T3 tracker, and the clips holding the antenna are from the local hardware store. They are used for wiring harnesses in cars. Amazingly they were the perfect height for the stand-offs I used on the T3. Usually I have a bulkhead, with a small countersink and nut, at the antenna threads to hold the top end of the T3's board. The clips have adhesive pads on the bottom. The T3 was tested to see if there were any interference issues; long hikes thru the neighborhood & subdivision carrying the AV bay. T3 worked fine.

IMG_0355.JPG IMG_0362.JPG
 
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QFactor

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Here are pictures of my T3 tracker mount that goes in a nose cone. This has flown on many a flight in my EZI-65. No problems with the antenna not having any support along its length. The antenna is 4.75" long.

IMG_0366.JPG IMG_0369.JPG IMG_0370.JPG
 

TonyL

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I dropped a featherweight GPS tracker and a Big Red Bee from about 20kft, and both antennas suffered a bit. I pushed the Featherweight antenna back mostly straight and potted the two broken legs on the SMA connector. It seems to have about the same antenna performance from the reported signal values. Since then I make more of a point of staking the antenna with hot glue. The Big Red Bee was more properly repaired.

Qfactor's clamps to the board are similar [and a definitely overkill for what is strictly necessary], but I just put a dab of hot glue about 1/3 down from the tip. It is only the antenna's unsupported weight that needs restraint as the board supports the end already. One could try potting the SMA connector to the board, but that seems like minimal improvement for the work involved. I like hot glue because it is easy enough to apply and remove, especially if one keeps the tracker on the same sled most of the time.

br/

Tony
 

g.pitts

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Ive been looking at alot of the mouinting of various trackers. Featherlight, Eggfinder, Missileworks, Altus, BRB and others and how current manufactures or nose/avbay or shockcord mounted units. I have yet to see abny of them offer any support for the antenna. How do these not damage the tracker and antenna mount? this may not be as big of a deal on wire whip but on the extended range antennas that are more solid mount I would be concerned with the jolt at the end of recovery or a whip around of the nose cone/shock cord to have high potential for damage to these units due to such. Is anyone making or adding support for this? love to see your examples. Or if you feel no concern id be curious why.
Conway,

If you have a wire antenna, there really isn't a lot of mass there, but what is your design criteria - specifically the G-force of your flight? Here's what I designed for the Featherweight tracker that I plan to use in the nose cone of my upcoming (I hope) L3 attempt, and if you have interest I'd be happy to share the files with you - or anyone for that matter.

<edit> I have a similar design for the Eggfinder as well.

Regards,
Gene

IMG_4113.jpg
 
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g.pitts

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Any of the stick antennas or ones that screw onto the SMA or RP-SMA need support. The lever arm will amplify any forces from the flight or recovery and stress the solder joints on the connectors. Solder is a good conductor but not good mechanically. It will likely crack. You would also be relying on the bonding of the copper pads to the PCB stubstrate. Give them a holiday and apply strain relief.
Well stated! Solder is not intended to be used as a mechanical connection - only as an electrical connection. I also worry about the possibility of hitting a point of resonance (paranoia?). For that reason, and the ones you've stated, I secure my antennas.
 
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Conway Stevens

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Conway,

If you have a wire antenna, there really isn't a lot of mass there, but what is your design criteria - specifically the G-force of your flight? Here's what I designed for the Featherweight tracker that I plan to use in the nose cone of my upcoming (I hope) L3 attempt, and if you have interest I'd be happy to share the files with you - or anyone for that matter.

<edit> I have a similar design for the Eggfinder as well.

Regards,
Gene

View attachment 444212


Gene

thats awesome. I like it. I have featherweight tracker and the Eggfinder with the sma connected screw on connection antenna added. Plus plan to be adding further tracking options. Most of what im doing is minimum diameter flights. There is potential for higher g forces applied as well as I feel on recovery from ejection, the recoil of recovery harnesses, chutes that open under whatever conditions that create an almost abrupt slow down, or even when landing on the hard ground. the Sma soldered connection wasn't ment for physical support of this I feel.


I would greatly appreciate the files if you don't mind. Thank you. And good luck on your L3. I'm sure you will nail it. enjoy the day of it. Was one of my funnest flights when I did mine.
 

Adrian A

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Any of the stick antennas or ones that screw onto the SMA or RP-SMA need support. The lever arm will amplify any forces from the flight or recovery and stress the solder joints on the connectors. Solder is a good conductor but not good mechanically. It will likely crack. You would also be relying on the bonding of the copper pads to the PCB stubstrate. Give them a holiday and apply strain relief.
The SMA connectors used on the Featherweight GPS wrap around both sides of the board so that forces on the connector go into the fiberglass of the board rather than stressing the solder. I have gotten repair requests after a crash breaks the brass connector, but I've never seen the solder fail by itself.

Giving the antenna a cradle on your sled for support like Gene showed above is a good idea (and I have sometimes done that on my own rockets), but it would probably only help for the kind of crashes that are going to cause other damage first.

I have had two deployment failures that resulted in ripping the tracker off of the bay, and the tracker landing by itself (with battery still attached) in the dirt. In both cases the antenna was fine because I tracked right to the bare tracker, though IIRC at least one of them may have been using a wire whip.
 
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cerving

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I second Adrian's assessment, I've also seen broken legs on brass RP-SMA connectors. I'd MUCH rather see the legs on the connector break under stress instead of the solder joints... otherwise it would probably lift the antenna pads off the PC board, which would be bad.

With a wire whip or flexible wire, this really isn't an issue, however the external antennas are definitely an upgrade from a plain wire.
 

Conway Stevens

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I second Adrian's assessment, I've also seen broken legs on brass RP-SMA connectors. I'd MUCH rather see the legs on the connector break under stress instead of the solder joints... otherwise it would probably lift the antenna pads off the PC board, which would be bad.

With a wire whip or flexible wire, this really isn't an issue, however the external antennas are definitely an upgrade from a plain wire.

Do you recommend a support for these external antenna? As like the one Gene or others utilize?
 

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Conway,

Let me tell you what I've done with a wire whip on a Wildman Jr. rocket. I stick my Beeline GPS in the forward part of the ebay on a carrier that has the deployment electronics aft which consists of a Raven II altimeter. I've lined up a hole on the forward bulkhead of the ebay so the wire antenna sticks up into the main chute bay.
So, o.k. under G forces the main chute will go aft and squish the antenna right?

Weeeeelllll, You know the cardboard tubes that contain the Aerotech wired igniters? I simply put a bit of removable clay around the antenna/bulkhead interface for a gas seal. I then slide the cardboard tube (that contained the igniter) over the wire and use clay and tape to hold the cardboard stent over the wire antenna at the bulkhead interface. I do use a micrometer to measure the wire antenna and choose a drill bit that will make a hole that will just let the wire go through the forward bulkhead. The removable clay or putty is more than enough for a gas seal.

Sure, the wire may be bent a little bit one side to the other but the antenna stays straight and not smushed down. It will track just fine via Rf. I've had no trouble with the low powered BLGPS at a couple of miles out though once it's down, the signal fades out.
No big deal as I have the last known position locked, go to it, get a new fix when I get closer and recover the rocket. Works like a dream.

Errrrrr, um, I did fly the rocket one time on a lower powered motor that I knew would keep it in sight without the stent and I can testify the wire antenna will get "smushed" and crunched down!
Signal was lost after launch but rocket came down in sight so recovery was no big deal. I thought the wire would get pressed against the inside wall of the tube, stay more or less straight but I was way wrong. At least I was smart enough to test it with a lower impulse motor to keep the rocket in sight for recovery. I straightened the antenna and brainstormed what to do.

After the main chute charge blows, if the cardboard stent is lost no big deal as one has a ready supply of more.
Actually, I've never lost a stent and they don't catch fire from the momentary flash. When they wear out, I replace them from a ready supply of cardboard tubes from my AT motor igniters.
It's a very easy remedy when ones rockets don't have enough room in the nosecone for a tracker bay.
Unless AT changed the tubes, mine are thick walled and strong. Make real nice stents to keep wire antennas straight inside main chute bays. The cardboard is radio-lucent.
Make sure the main chute bay is not painted with metallic paint as I've had it attenuate the signal terribly on the 400mhz Ham trackers. I don't know about the 900mhz stuff and I'm not going to try to find out how they behave with metallic paint.

As an aside, one could use a stent with an Eggfinder using a wire antenna. Just have to have an ebay that has enough room for the tracker, batteries and deployment electronics.

Best of luck,
Kurt Savegnago (also known as KC9LDH on hf)
 

Tech 68

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I bought a six inch extender cable with appropriate SMA mating connectors for my EggFinder/Antenna, put a service loop in it and secured it and the antenna with "zip ties".
 
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