Getting rid of all-thread

I don't usually disagree w/ folks ; but if someone has a 10k+ backyard w/ recorded data, I'm all ears.

If someone is saying " at 50ft no difference was detected w/ off-the-shelf consumer hardware " then yes, the measurement error was likely far larger than the allthread attenuation.

We've tracked rocket many MILES away with the tracker in close proximity to a central all-thread....
To quell your disbelief and before you do all these hand-stands, let's flip it back at you, where is your data that the all-thread IS a problem?

Along the lines of what John D. said....what do you think radio towers are made of, cardboard and Kevlar?

dhbarr said:

I don't usually disagree w/ folks ; but if someone has a 10k+ backyard w/ recorded data, I'm all ears.

If someone is saying " at 50ft no difference was detected w/ off-the-shelf consumer hardware " then yes, the measurement error was likely far larger than the allthread attenuation.

Click to expand...

Ok, that's fair. But it sounds like you have no data to support your position. Also RF and antenna theory doesn't support your position either.

All-thread cannot attenuate. It can distort the radiation pattern but does not absorb appreciable energy. Paper airframes(especially with moisture content) and FG will attenuate far more than all-thread.

Now all-thread can detune the transmitting antenna if its really close or touching it, but that is only is a factor if the antenna was properly tuned in the first place. But with our hobby trackers and such with wire antennas on questionable ground planes it is likely that the antennas are already mismatched to some degree. The presence of all-thread is just as likely to improve the tuning of the antenna as detune it.

I honestly want to know where I may have gone wrong.

So, let's narrow and specify the question(s) just to make sure we're all talking about the same thing.

I assert: a metal object close to an TX antenna isn't good for someone trying to RX a signal from same. Thus one allthread would have less attenuation than two, given equal distances from the TX.

I hear: one or two allthread close to TX should have less effect than a cardboard tube as measured at the RX.

Note that I am -NOT- trying to be difficult or put words in anyone's mouth: I have projects for which I want to tradeoff engineering constraints.

Before I go try to educate myself by reading forum pages, ham primers, & experimental data : am I asking a good question?

dhbarr said:

I assert: a metal object close to an TX antenna isn't good for someone trying to RX a signal from same.

Click to expand...

Correct. A metal object close to a TX antenna does not do any good.

dhbarr said:

Thus one allthread would have less attenuation than two, given equal distances from the TX.

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Again, allthread does not attenuate the signal. If it happens to reduce the signal strength in one direction, it will increase signal strength in another direction. Radiative energy is conserved.

dhbarr said:

I hear: one or two allthread close to TX should have less effect than a cardboard tube as measured at the RX.

Click to expand...

Perhaps, but other factors especially antenna polarization mismatch of the tx and rx antenna will be a much larger contributor to signal loss than the electrically floating (ungrounded) metal in your electronics compartment.

dhbarr said:

Before I go try to educate myself by reading forum pages, ham primers, & experimental data : am I asking a good question?

Click to expand...

Yes this is a common concern for those who fly radios for the first time. After that you will discover its not a concern anymore....

You haven't seen any cell phone towers where the antennas are mounted 1/2 to 3/4 up the tower?

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Remember these are typically phased-array antennas, I am guessing mostly facing away from the mast or supporting building :wink:. They would be designed for having the metal close behind. Having the three sets of antennas on a mast gives the cell tower 360deg coverage. Each antenna only covers about 120deg though, and the front-back ratio keeping interference from other towers down.

FredA said:

We've tracked rocket many MILES away with the tracker in close proximity to a central all-thread....
To quell your disbelief and before you do all these hand-stands, let's flip it back at you, where is your data that the all-thread IS a problem?

Along the lines of what John D. said....what do you think radio towers are made of, cardboard and Kevlar?

Click to expand...

Yes but the radiating elements don't parallel the tower support.

Listen, if you have decent power output, sure you can track from a suboptimal installation. If going with 100mW in the 33cm band one might want to pay attention so they can squeeze as much range out the the system.

Doing a 1 watt or more tracker (Byonics had some small single board 8 watt APRS trackers if one could loft the battery) depending on the frequency, two pieces of all-thread aren't going to matter.

Where's the data. Do a range check and that will get you your data. If your installation won't track as far with all thread than in free air one needs to assess whether the compromised system is "good enough" for their purposes.

Kurt

What about eye nuts? One threaded rod (instead of the usual 2) and an eye nut at each end, in place of the U bolt or eye bolts. Load is thru the rod, and not transferred to plates & such. Only real issue is securing them in place so they don't unscrew in flight.

The 'strap-thru-the-AV-bay' is a pretty neat idea.. I like that..

One all-thread and a pair of eye-nuts are is all we ever use.
Drill a hole through the ends of the all-thread and insert a cotter pin to eliminate the possibility of an eye-nut unscrewing.

dr wogz said:

What about eye nuts? One threaded rod (instead of the usual 2) and an eye nut at each end, in place of the U bolt or eye bolts. Load is thru the rod, and not transferred to plates & such. Only real issue is securing them in place so they don't unscrew in flight.

The 'strap-thru-the-AV-bay' is a pretty neat idea.. I like that..

Click to expand...

I used this type system on my L3 cert rocket, using 3/8" B7 grade all-thread with eye-nuts on each end so that shock load stresses were straight line through the recovery harnesses, for the sled I used aluminum rods as strength was not an issue. One eye-nut was threadlocker'd and the other had a jam-nut inside the eye.

I was going to go with this for a larger diameter rocket :

https://www.eplastics.com/Plastic/fiberglass-threaded-rod-and-nuts/FIBERGLASS_BOLT-375

But decided it would be more beneficial to glue a bulkhead in one side, fixed - and do a CR at the other end of the coupler and have the sled mount to a bulkhead like a nosecone avbay .

Still looking for a smaller 54mm or punisher type header solution as both of mine seem not to scale down at all .

Kenny

ksaves2 said:

Yes but the radiating elements don't parallel the tower support.

Click to expand...

ksaves2 said:

Where's the data. Do a range check and that will get you your data. If your installation won't track as far with all thread than in free air one needs to assess whether the compromised system is "good enough" for their purposes.

Kurt

Click to expand...

Data.

https://www.rocketryforum.com/showt...er-antenna-what-happens&p=1532410#post1532410

Conclusion: I'm not worried.

Yep - as I said, a solution looking for a problem.
All-thread works and it is easy.
Why do handstands for no good reason.

[I do get that some of you like the self abuse aka "a challenge"....whatever floats your boat]

Buckeye said:

Data.

https://www.rocketryforum.com/showt...er-antenna-what-happens&p=1532410#post1532410

Conclusion: I'm not worried.

Click to expand...

Valid for that system plus the BRB900 is at 250mW output. As I've said power can overcome a less than ideal installation. Try it with a ham band BRBGPS and a 16mW tracker and see what you get? Oh, and use some rattle can Rustoleum metallic paint
while you're at it for good measure to paint the tube. Tell me if you get your sight unseen rocket back. Ground testing in the open can be encouraging but not fool proof. Been there, done that.

If one is going to try to apply the above test to their own situation with different equipment best of luck. (Unless the power output is more then one has more leeway to screw up.)

Fred it's not self abuse. If the all thread happens to interfere with the propagation, one could be in for a surprise. Depending on power, output, frequency and length of the passive radiators, the all-thread can interfere and that is certainly more likely with a lower powered tracker. Personally, I prefer to optimize the install for the best performance to increase the chance of recovery for completely sight unseen flights. If one gets a visual on the descending rocket with a tracker, 2/3'rds the work is done
with a GPS tracker and half the work is done with RDF. Piece of cake to get within the ground footprint no matter what type of installation if one sees the direction they need to go.

If you prove a particular installation works, fine for you and I hope your future designs work too and don't leave you with you scratching your head when a rocket goes missing. In the end, horsepower trumps all as long as it doesn't interfere with one's
deployment devices. Been bit a few times there myself. Kurt

Kurt,

Understand optimization.
Also understand leaking EBay's allowing BP residue to nuke you avionics or weakly held Ebays being pulled apart by deployment forces.

You DO ground test your setup and see if you can track it at a distance....right?

If you've got a build technique that is KNOWN not to suffer from any issues then go for it.
Otherwise you are flirting with danger for no upside.
Make sure you aren't creating problems by trying to eliminate a non-problem is all I'm saying.

ksaves2 said:

Valid for that system plus the BRB900 is at 250mW output. As I've said power can overcome a less than ideal installation. Try it with a ham band BRBGPS and a 16mW tracker and see what you get? Oh, and use some rattle can Rustoleum metallic paint
while you're at it for good measure to paint the tube. Tell me if you get your sight unseen rocket back. Ground testing in the open can be encouraging but not fool proof. Been there, done that.

Click to expand...

This test was with the Gen 1 BRB900, which I believe was less power than 250mW. Oh, now I have to add metallic paint to my tests? When does it stop? The topic is all-thread, not paint. If you've been there, done that, then the onus is now upon you to provide the data.

Try it with a ham band BRBGPS and a 16mW tracker and see what you get?

This is our primary tracker.
Usually wrapped in a little bubble wrap and stuffed into NC's that have a central all-thread.

We track and FIND rockets that go out of sight all the time -- easily over 100 recoveries - some never seen coming down.

This is a non-issue people.

FredA said:

You DO ground test your setup and see if you can track it at a distance....right?

Click to expand...

Well, Kinda.

Not being much of a radio guy, what is an effective way to do a ground check?

First let me say, I have broken all the "rules" and still had success. I've even had a Telemetrum right next to the all-thread with 2 90 degree bends in the antenna AND only partially sticking out of a carbon fiber airframe and still had no problems.

But, Fred's comment got me thinking. Especially in the less-than-ideal situation I just mentioned, decent ground testing would have certainly put my mind at ease before the flight. Being that the signal essentially is lost once the rocket is on the ground, I have always figured there was no way to do a good long distance ground check. I have to admit, my actual ground check is surely seriously lacking to non-existent. Perhaps I've just been lucky in the past.

By the way, I've also made a few all-thread-free av-bays, just not for the reasons discussed here.

First let me say, I have broken all the "rules" and still had success.

Click to expand...

It all comes down to link budget. There is a certain amount of headroom available in the signal transmitted, over and above what is actually required for reception of the data at the Rx. As long as you have enough signal for the reception to be effective all is good.

Anything sub-optimal then takes away from this headroom and nibbles the link budget down. The amount of spare link budget usually determines the effective range of your tracking (all other things being equal). If you fly higher you need more overhead available in the link budget.

So, things don't have to be perfect when you put them together. There can be RF absorbers local to the antenna. There can be kinks in the antenna. The antenna can be not the right electrical length (ie wrong frequency). As long as there is still space in the link budget you can still track.

When link budget is exceeded then the link breaks. Since you are the designer of the system, you have control over when that happens.

watheyak said:

Well, Kinda.

Not being much of a radio guy, what is an effective way to do a ground check?

First let me say, I have broken all the "rules" and still had success. I've even had a Telemetrum right next to the all-thread with 2 90 degree bends in the antenna AND only partially sticking out of a carbon fiber airframe and still had no problems.

But, Fred's comment got me thinking. Especially in the less-than-ideal situation I just mentioned, decent ground testing would have certainly put my mind at ease before the flight. Being that the signal essentially is lost once the rocket is on the ground, I have always figured there was no way to do a good long distance ground check. I have to admit, my actual ground check is surely seriously lacking to non-existent. Perhaps I've just been lucky in the past.

By the way, I've also made a few all-thread-free av-bays, just not for the reasons discussed here.
View attachment 310683View attachment 310684View attachment 310685

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I have done and do radio tracking 'ground' tests. I set them on the ground in my front yard and then go for a bike ride. I've tested various things, trackers, GPS, different manufactures, inside electronics bays, outside electronics bays, next to al-thread etc. Yes, being on the ground does not give the best signal but I can or can't tell the difference with this type of testing.

On a side note: I received and old rocket radio tracker from a buddy of mine just before he passed away. I set it out to see how well it would do. Jump on my bike and headed to the street and house that my other trackers "made it to". I still had a very strong signal and got tired of riding my bike and came home and jumped in my truck and head off. This particular Tx was easy 4 times the distance as my other Tx. To bad they're not made any more!

Tony

FredA said:

Kurt,

Understand optimization.
Also understand leaking EBay's allowing BP residue to nuke you avionics or weakly held Ebays being pulled apart by deployment forces.

You DO ground test your setup and see if you can track it at a distance....right?

If you've got a build technique that is KNOWN not to suffer from any issues then go for it.
Otherwise you are flirting with danger for no upside.
Make sure you aren't creating problems by trying to eliminate a non-problem is all I'm saying.

Click to expand...

What I do Fred is button up the ebay and put it on the roof of my single story house. Specifically on my table top chimney. Sometime I've done the bare tracker and then with it in the ebay. I'm paranoid as I was burned by metallic paint once.
Do a range test and I do have obstructions to contend with but if I have any doubts about it, I'll go to an open field and set the bay on top of a ladder or something to at least get it off the ground.

I was burned 9 years ago due to not performing an adequate range test and will not do that again. One rocket recovered because a visual was had when it came back from 10k and one was lost due to recovery failure and Rf couldn't get out of the rocket due to metallic paint.

I understand your point about the non-problem side. The 250mW and higher power trackers have more resistance to installation foibles. The low powered trackers do not so beware. Besides range testing, flying with a lower powered motor that is likely to keep the rocket coming down within sight the first time is a good idea and I do that now with first flights generally. If someone is new to this, I highly recommend it 'cause it doesn't do any good
to lose a tracker on the first flight due to technical difficulties. Kurt

I've been kicking around some ideas for building an avionics bay without all-thread. That way I can simply mount my GPS to the sled without worrying about interference, and I wouldn't have to worry about a bulkhead-mounted antenna getting damaged during recovery. (That's happened to me twice so far.)

I'm thinking of attaching the sled to the bulkheads and running a length of kevlar through the bay with loops on each end to serve as attachment points for the recovery harnesses. The kevlar would be simply tied to the center of the bay. get rid from rat poison. I'll try to draw something up when I get home in a few hours to better show my idea.

Has anyone ever done something like this before? Or are their other alternatives?

Click to expand...

I didn't this before but Idea is great and now thinking to do!

When we first started out we would have somebody drive the tracker in the NC and dump it across the valley.
Then we would go hunting.

Now we don't even bother....we know we can find it anywhere.

At our Brothers, OR launch site rockets always, and I mean always land between the sage brush and lie on the ground.
They go over the hill or down in the valleys.
As long as you can get a little elevation you can find them.
I've stood on the roof rack on my van or drive up to the top of the hill to get that first beep from the beacon.
Once you hear a beep, just one, you know you will be on it soon.

We only really use the 16mW BRB beacons - can locate them miles away without having a clue where they went down.
I do like to turn up the beep rate so you can swing the Yagi faster, but that's it. The high power beacons actually make it HARDER to find the rocket. In the sage, you can walk right past a rocket that's 10 feet from you. Too much power and you can't locate a thing when close.

The Playa at Blackrock seems to suck up RF. There you need to be a little more diligent in your search pattern and hopefully get a general direction while it is still in the air. That is where the higher power BRB's come in handy. But we've yet to loose a rocket there, knock on wood.

I'm thinking of attaching the sled to the bulkheads and running a length of kevlar through the bay with loops on each end to serve as attachment points for the recovery harnesses. The kevlar would be simply tied to the center of the bay. I'll try to draw something up when I get home in a few hours to better show my idea.

How do you plan to seal the ends?
The hole where the strap goes though the bulkhead will be a problem.
The lack of tension on the end caps will allow them to leak.

You end up with BP residue on your electronics and possibly damage the barometric sensor from the pressure from the charges.

If you glue to Kevlar it will break at the glue joint.

FredA said:

One all-thread and a paid of eye-nuts are is all we ever use.
Drill a hole through the ends of the all-thread and insert a cotter pin to eliminate the possibility of an eye-nut unscrewing.

Click to expand...

Holy crap why didn't I ever think of this. Thanks Fred!

https://www.mcmaster.com/#general-purpose-eye-nuts/=165z77a

in case you were curious!

Here's what one of my typical EBay ends look like: (sorry, older picture)

View attachment 310722

This was BEFORE we found the Eye-nuts.
Now substitute an EyeNut for the UBolt.
Only issue is that you can't put the swivel onto the Eyebolt, so that gets sewn to the other end of the TN that's permanently sewn onto the Eye-Nut. Then I put heat-shrink over the first ~10 inches of TN to protect it from the BP blast.

I'll have to take a more up to date picture and post it here....maybe later today.

FredA said:

I'm thinking of attaching the sled to the bulkheads and running a length of kevlar through the bay with loops on each end to serve as attachment points for the recovery harnesses. The kevlar would be simply tied to the center of the bay. I'll try to draw something up when I get home in a few hours to better show my idea.

How do you plan to seal the ends?
The hole where the strap goes though the bulkhead will be a problem.
The lack of tension on the end caps will allow them to leak.

You end up with BP residue on your electronics and possibly damage the barometric sensor from the pressure from the charges.

If you glue to Kevlar it will break at the glue joint.

Click to expand...

I've been sitting back and enjoying the conversation here. I'm new to most of this, so it is incredibly informative. I realized that I never posted a schematic of my idea, so I drew something up while waiting to have my tire repaired this morning. Sorry this is so ugly, but maybe you will see what I was originally considering.



I was planning to plug the holes for the harness to pass through the bulkheads with sticky tack. It makes a mess, but it has worked for me before.

In light of the conversation here, it sounds like this new design is probably overkill. I'm using an Eggtimer TRS, and from what I understand, it isn't as powerful as the BRB systems that you guys are using. I have tested my system in my yard but always with the antenna mounted outside of the bay. Has anyone tested the Egg stuff with the antenna near the all-thread? If not, I'll give it a try whenever I find some spare time and report back.

Sled glued into couplers. Bulkheads glued in to ends of couplers. No all-thread.