Fiberglass threaded rod to avoid RF attenuation

I'm thinking about RF tracking.

I understand that threaded rods that typically hold AV bays together may decrease RF range.

I'm wondering about using fiberglass threaded rod instead. I wonder if anyone has tried it, and what kind of strength I can expect from fiberglass rod in this application.

Ari.

E.g. this page https://www.fibergrate.com/media/3834/designtrod.pdf lists "Ultimate Thread Shear" at 1,200 lbs for 3/8-16 rod and 2,400 lbs for 1/2-13

Ari.

I've been using a nylon 1/4 x 20 all-thread in my HP nosecones to avoid the attenuation of the RF signal from my tracker. Before using this nylon all-thread, I put it through several stress tests. I was satisfied that it could withstand all possible scenarios at the conclusion of my tests. I've been flying them this way for about two years now with no failures. Note: I have never used them in the Av-bay, only in the NC.

Thank you for your datapoint Walldiver. I wonder if you use nylon rod with nylon or metal nuts. Also, where you buy yours.

Ari.

Have you seen this thread? https://www.rocketryforum.com/showthread.php?124167-AV-bay-all-thread/

iter said:

Thank you for your datapoint Walldiver. I wonder if you use nylon rod with nylon or metal nuts. Also, where you buy yours.

Ari.

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I have flown both ways, using metal nuts and other times nylon nuts. Is this question because you feel the metal nuts might cause a problem with the RF signal?

One way around the allthread issue it look at the threads that show aft facing bulkhead antennas. Or could even use a short segment of coaxial cable to an antenna with a screw in bulkhead socket. Zip tie the thing to the shock cord. Nylon all-thead for a nosecone tracker sounds good as Walldiver 7 has proven.
I wouldn't count on it in an Ebay that has to pass-through the recovery forces from the shockcord eyebolts but I could see where it could be workable for a
nosecone tracker where the mass could be kept low. I would be extra careful not to overdo the powder charge though. Kurt

Why would a floating (ungrounded) metal rod attenuate the RF? Where does the energy go?

jderimig said:

Why would a floating (ungrounded) metal rod attenuate the RF? Where does the energy go?

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RF attenuation is a well known and undisputed scientific reality.

When the RF signal passes though solid objects, some of the signal power is absorbed. Attenuation can vary greatly depending upon the structure of the object the signal is passing through. Some materials are more "RF Transparent" than others. Metal in the barrier/object greatly increases the attenuation of the signal.

scsager said:

RF attenuation is a well known and undisputed scientific reality.

When the RF signal passes though solid objects, some of the signal power is absorbed. Attenuation can vary greatly depending upon the structure of the object the signal is passing through. Some materials are more "RF Transparent" than others. Metal in the barrier/object greatly increases the attenuation of the signal.

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Well I learn something new every day. Up to this point I thought metal reflects RF....

I suspect that nearby conductors set up reflections that either mess up the antenna pattern (so the signal isn't going where intended), or change it's impedance. An impedance mismatch is going to suck up lots of signal, with less being radiated. Not attenuation, per se, but still less energy at the receiver.

N8OKM

Charles_McG said:

I suspect that nearby conductors set up reflections that either mess up the antenna pattern (so the signal isn't going where intended), or change it's impedance. An impedance mismatch is going to suck up lots of signal, with less being radiated. Not attenuation, per se, but still less energy at the receiver.

N8OKM

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Perhaps, but I would like to see real data, like someone set up a tracker in a avbay with a threaded rod and one without and see if there is any noticeable signal strength or range difference. I fly trackers ALOT and I never had a problem with a tracker in a bay filled with all sorts of metal including threaded rod, other electronics, wires, ubolts, nuts etc.

In fact, my big nuisance is TOO much signal requiring an ATTENUATOR on the receiving end so my S meter isn't railing when I am a 1000 feet from the rocket.

I am show me the data guy, not a hand-waving guy. Respectfully.

I was going to run a rp-sma extender cable with bulkhead mount on my new punisher with the av bay in the nosecone.

It comes with aluminum av bay lids which i assume is just as bad as the all thread..or could it be used as a ground plane for the shorter, single pole antenna ?

Kenny

I am with John on this one.
I have never seen great attenuation from metal support elements.
Now carbon wraps over the antenna section can pose issues.
It is very easy to test it by running a bench test with your setup.
As all setups are different it may or may not reduce your range from 30 miles to 25 miles etc.
And would that really matter??
More data is best for the whole community as we can all use the data.
So let us know.
Even lurkers are looking for more data.

Kenny,
Use it as the ground plane to extend your range.

rdh8 said:

I am with John on this one.
I have never seen great attenuation from metal support elements.
Now carbon wraps over the antenna section can pose issues.
It is very easy to test it by running a bench test with your setup.
As all setups are different it may or may not reduce your range from 30 miles to 25 miles etc.
And would that really matter??
More data is best for the whole community as we can all use the data.
So let us know.
Even lurkers are looking for more data.

Click to expand...

I understand that the effects vary greatly with the ratio of metal objects and antenna wavelength. If you're transmitting in the 6-meter band, 4" of allthread may have a very different effect on your transmitter than the 900 Mhz on which EggFinder transmits.

Ari.

For a couple of my rockets where I put the GPS in the nose cone, I do something like this. Another uses a body tube instead of the plastic. Also, the one does have an aluminum bulkhead, but it did not appear to have any effect on transmission (that was noticeable).

iter said:

I understand that the effects vary greatly with the ratio of metal objects and antenna wavelength. If you're transmitting in the 6-meter band, 4" of allthread may have a very different effect on your transmitter than the 900 Mhz on which EggFinder transmits.

Ari.

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seems like an easy thing to figure out. Mock up your eggfinder with a couple althread rods around it and go find some open space. And go for a walk. See how far away you can get before you loose the signal. Go back remove the all thread and repeat your walk.

Or you can do something like the attached photo. That is a 54mm LOC plastic nose cone. The plastic end cap is held one with screws.


Tony

If you are doing your DD properly, what's the farthest away from the launch site you think your rocket may come down?

My question is: what is the original, unimpeded signal range, and then how much do you lose from attenuation? Like Robert said, if the range is 30 miles and you only get 25 miles, who needs that? If the range is 10 miles and you only get eight, so what?

Now, if the range is five miles and you only get one, that could be a problem.

Metallic, non grounded, threaded rods could serve as directive/reflective elements, depending on frequency of operations and distances from the radiating element, but I am with JD on this, as from an operational viewpoint I doubt you would ever experience a significant issue with it. Even multiple element antenna arrays with significant forward gain (which 2 threaded rods would never be) radiate off the sides. Also, with shorter wavelength, higher frequencies you tend to get more reflections.
Bottom line, the signals will get out just fine!
The same can certainly not be said in the case where a metallic, etc airframe surrounds the radiating element.
The one factor you should consider, especially with higher power transmitters (ie 100 mw units) would be potential interference with other on board electronics if mounted in close proximity to them in an ebay.
I keep my outputs lower (ie 9 - 12mw) which is plenty of a signal for most applications. More is not necessarily better...
Greg

I originally put my Eggfinder in a FWFG nosecone with a 1/4" allthread down the middle of it. Tried it out on the ground and could get about 50 ft. away before loosing signal. Rebuilt the N/C with a plywood bulkhead and kevlar strap for retention and the range improved to over a quarter mile. After many flights with an Eggfinder, you can expect several miles of range while in the air, my best is 18,000 ft, and around a half mile on the ground, depending on which antennas you use.



Don't even think about putting this in a carbon fiber tube, I did that with a CSI tracker beacon and couldn't get a signal 10 yards away.

I don't use carbon fiber, and I have found my rocket more than 3/4 mile away. I have the BRB900. Its specs are:

Transmitter Dimensions: 1.25” wide x 2.85” long, excluding transmit antenna.
Antenna: Reverse Polarity SMA, 3dbi gain approx 4.25” long
GPS Module: u-blox Neo 6Q. Altitude and speed may exceed 18,000 meters or 515 meters/second, but not both.
RF Transmitter: 250 mw 900 Mhz Spread Spectrum.
Receive Current : 115mA
Transmit Current: 315mA
Power supply: Single cell Lithium Poly battery (3.5 to 4.2 Volts)

Can anyone with electronics savvy translate those specs into a transmission range?

Bat-mite said:

I don't use carbon fiber, and I have found my rocket more than 3/4 mile away. I have the BRB900. Its specs are:

Transmitter Dimensions: 1.25” wide x 2.85” long, excluding transmit antenna.
Antenna: Reverse Polarity SMA, 3dbi gain approx 4.25” long
GPS Module: u-blox Neo 6Q. Altitude and speed may exceed 18,000 meters or 515 meters/second, but not both.
RF Transmitter: 250 mw 900 Mhz Spread Spectrum.
Receive Current : 115mA
Transmit Current: 315mA
Power supply: Single cell Lithium Poly battery (3.5 to 4.2 Volts)

Can anyone with electronics savvy translate those specs into a transmission range?

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I have a little "electronics savvy" but all you need is an internet connection to their webpage for range. Says 6 miles with the provided antenna, and twice that if you use a yagi. Problem with the yagi is it's very directional, if you can't see the rocket, you won't know where to point it.
It has more than twice the power output of the Eggfinder, a measly 100 mw compared to the 250 mw on your system. Since I'm getting more than 3 miles with mine, yours could easily be more than twice that. Of course, conditions during flight will have an effect on that. I think BRB also warns against metal parts near the transmit antenna though.

I hadn't looked at their site recently, but several years ago I got my ham licence to use their Beeline GPS system. Found the Eggfinder instead and saved a bunch of money. Now it looks like BRB has reworked their BRB900 to compete with the Eggfinder. Nice system and you don't need the license to use it. Did you get the LCD screen?

Yeah, I got the package. Expensive, but, for me, easier than getting a HAM license.

So, six miles, even if a metal allthread knocks it in half, is three miles, and I seriously hope I never come down that far away.

Wayco said:

...

Don't even think about putting this in a carbon fiber tube, I did that with a CSI tracker beacon and couldn't get a signal 10 yards away.

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What if we wrap our All Thread in Carbon Tube ? Hmmm

Kenny

KenRico said:

What if we wrap our All Thread in Carbon Tube ? Hmmm

Kenny

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That might work Kenny, just don't bring it to Eagle Eye, you will never find it.

tfish said:

seems like an easy thing to figure out. Mock up your eggfinder with a couple althread rods around it and go find some open space. And go for a walk. See how far away you can get before you loose the signal. Go back remove the all thread and repeat your walk.

Or you can do something like the attached photo. That is a 54mm LOC plastic nose cone. The plastic end cap is held one with screws.

Tony

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I remember you tracking this at Snow Ranch! Are you coming to Dairy Aire Tony?

Ari.

Bat-mite noted a thread I had started earlier. The GPS receiver on my Eggfinder has no issue with the allthread in my AV bay. In the AV bay, in the rocket, in the house, it still picks up at least 6 satellites. I ended up getting an RP-SMA extension and mounting my antenna in the AV bay lid. Should have plenty of range that way. I put the antenna on the aft bulkhead so that I hopefully get the best signal while the rocket is on the way up. I'm not to worried about reception on the way down, since it'll no longer be inside the rocket a short distance from a motor casing.

Tonimus said:

Bat-mite noted a thread I had started earlier. The GPS receiver on my Eggfinder has no issue with the allthread in my AV bay. In the AV bay, in the rocket, in the house, it still picks up at least 6 satellites. I ended up getting an RP-SMA extension and mounting my antenna in the AV bay lid. Should have plenty of range that way. I put the antenna on the aft bulkhead so that I hopefully get the best signal while the rocket is on the way up. I'm not to worried about reception on the way down, since it'll no longer be inside the rocket a short distance from a motor casing.

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When I first flew a Beeline GPS 70cm in a metallic painted 3 inch Wildman with an L1400, no Rf packets were received after the rocket left the rail. I didn't do
an adequate range test!! But.... I successfully got the thing on the rail without activating the G-Switch and was able to download a perfectly fine .kml file
after the flight. The paint didn't affect the GPS signal reception but sucked up the 70cm Rf energy. Was fortunate the rocket came down within sight.

I believe the metal all thread and batteries can parallel the tracker board but not be in parallel with the antenna. Aft facing antennas, bulkhead mounts and remote antennas with a short shrift of coax cabling get the job done and are fair game.

You know, a Yagi antenna is a well thought out arrangement to "direct" the Rf to one's advantage. I can comprehend how a parallel chunk of random metal can have a devious effect on transmitting efficiency. Sure, if one is not going to fly farther than they can throw a 16 inch softball, do whatever you want. Me, I will confess to the "blind appeal to authority" and their view of the science when it comes to optimizing a tracking system. Kurt

iter said:

I remember you tracking this at Snow Ranch! Are you coming to Dairy Aire Tony?

Ari.

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Yes, I'll be at Dairy Aire. I'll be doing some s4 stuff with a couple of High Schools.

I'll be sure to bring some Nomex.

Tony