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Rf Attenuation with black filament wound nosecones?

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ksaves2

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This is a question: Anyone notice Rf attenuation or decreased reception range with a rocket that uses a nosecone mounted tracker in a black filament wound nosecone?

Reason I ask is I've heard that carbon black might be used as a pigment in the epoxy to give it the black color. Might be some Rf attenuation there even if carbon fiber filaments weren't used in making the nosecone..

I have a black 4 inch diameter NC for a project and one for a 38mm MD rocket. I might have to take more time for a range check before flying.

I've had the misfortune of signal loss due to metallic paint with a 70cm GPS tracker in two rockets. The one fortunately landed within sight and the other had a deployment failure and was lost for 18 months.
Very sick feeling when no signal is heard and am trying to avoid that situation. In fact, the one that landed within sight went a little over 10,000' AGL and Mach 1 on an L1400. It's the only GPS tracker flight that
I've ever seen under chute. All the dozen or so other flights were small screamers that totally disappeared that were only seen to have performed well when I walked up to them and saw the recovery systems deployed
properly while lying on the ground after the flight.

Kurt Savegnago
 

watheyak

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I've used a 70cm Beeline GPS in a black filament wound nosecone with no issues.
 

llickteig1

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What someone needs to do is to put two trackers of the same type with new batteries in a rocket - one in the NC and one taped to the shock cord. See if the NC one is attenuated.

For that matter, it would be an easy and repeatable test on the ground. I would lay the trackers at the same height on a couple buckets (i.e. off the ground) and see if the NC one is attenuated. I would do this at ever increasing distances. You can track a L&L transmitter at probably a mile that isn't laying on the ground on flat terrain.

Do the black tubes potentially use carbon black for coloring, too?

We could give this a try at AIRFest - there's a fair amount of flat ground at The Rocket Pasture. ;)
 
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Titan II

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What someone needs to do is to put two trackers of the same type with new batteries in a rocket - one in the NC and one taped to the shock cord. See if the NC one is attenuated.

For that matter, it would be an easy and repeatable test on the ground. I would lay the trackers at the same height on a couple buckets (i.e. off the ground) and see if the NC one is attenuated. I would do this at ever increasing distances. You can track a L&L transmitter at probably a mile that isn't laying on the ground on flat terrain.

Do the black tubes potentially use carbon black for coloring, too?

We could give this a try at AIRFest - there's a fair amount of flat ground at The Rocket Pasture. ;)
This is some info on the black "profusion" tubing:

http://www.rocketryforum.com/archive/index.php/t-27782.html
 

dixontj93060

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Absolutely had trouble with the old Profusion offerings. Luckily was able to debug when first noticed during prep and turn my BRB around allowing antenna to extend aft out of the bulkhead. Beyond that have never had problems with regular FWFG nosecones of any color including black.
 

Xrain

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I haven't had problems with signal levels on black wound nosecones. If they are using carbon black as a pigment it's only used in 1-2% mix with the resin, which shouldn't be enough to cause much attenuation issues. I'd suspect it's likely that other configuration problems would be at fault for people who have had issues with it (RF is funny like that).
 

rms

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No issues for me either, 430 meg signal from regular power Big Red Bee gps, full quieting for the round trip including landing up to 1.7 miles away. Flown to as high as 17,000' ish a couple times using a couple different black filiment wound nose cones containing the transmitter, worked great.
 

ksaves2

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This is some info on the black "profusion" tubing:

http://www.rocketryforum.com/archive/index.php/t-27782.html
Thanks for the post/link TII and all the replies. I was a part of the thread back then. Subsequent to that, I had seen a post where a person did have a problem with a Profusion nosecone with a 900Mhz tracker. Since folks have posted experiences with 70cm/420-450Mhz trackers and not had problems, I can either test my 900Mhz ones rigorously or use my BLGPS or Tele-GPS. The phenomena can be frequency dependent. I had that demonstrated when I failed to receive packets from two metallic painted rockets with BLGPS low power trackers. One rocket went missing for 18 months before I received the remains and the other one came down within "eyeshot" after an outta sight flight to 10k. One packet received at altitude but I half-heartedly did a download
attempt on the Beeline GPS for the .kml file. To my surprise, it had a six to eleven satellite lock the entire flight. The metallic paint blocked the transmitted Rf but was transparent to the incoming satellite signals! In fact, since I had the BLGPS set to
auto shutoff when the battery voltage got low, I didn't bother to turn it off until I broke the rocket down when I got home. The .kml showed the flight plus the track to the pizza restaurant we went to after the launch. The .kml showed the parking lot
position. Kurt
 

dford

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Kurt,
Have you made any profound discoveries using 900mhz?

Has anyone else?
 

ksaves2

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Kurt,
Have you made any profound discoveries using 900mhz?

Has anyone else?
I had a ballistic flight with an EggFinder I posted in another thread. I only received one or two packets while the rocket was low on the up side and only one position 40' above the ground before impact. I have it detailed in another thread.
The rocket came towards me but in a parallel track out in the field. The flight was totally unseen and stupidhead here undercharged the motor deployment charge. I wouldn't have known where to look except that one position "beep" was
plotted on the map just before impact. I proceeded to the point on the map and the fincan was sticking up out of the ground. Broke the black profusion nosecone digging it out of the ground and bought a Wildman replacement that is not profusion.

I did a "roof test" of the Eggfinder tracker in the nosecone. A roof test is me putting the nosecone on top of my tabletop chimney on my single story home. I still had a strong signal at 1/4 mile so I figured it was good.

If the profusion nosecone didn't attenuate the signal, it might be that the doppler effect of the ballistic flight made it so the GPS couldn't get a lock. Generally after a successful apogee event either main or drogue the positions starts coming in.
since my rocket only slowed to terminal velocity before it hit might be a position was decoded and sent from 40 feet up. The rocket was closer to me than it was on the pad. So I don't know if it was the nature of the ballistic flight or
the fact that the Profusion attenuated the signal and I received that one position before it hit because it was much closer to my receive position.

Some have said they've flown EggFinders in the Go Devil 38 with no trouble. I still don't know what happened here. Gotta fly some more. Kurt
 
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OverTheTop

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Got a Madcow Go Devil 54 kit a while back. Just put the NC in our EMC test chamber at work to measure the effect of the black filament-wound NC on the transmitter signal. Spectrum analyser showed that with the NC the signal getting out was 1dB less than just a bare. The effect was real.

I was using low power (25mW) RDF beacon on 433.9MHz.

For the cost of 1dB drop in signal I won't be worrying about moving my telemetry elsewhere in the rocket. Nose is good for me.

Keep in mind that this result is for the Madcow 54mm black f/w f/g NC only, with a sample size of n=1. YMMV.
 

ksaves2

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(Inserted from above) Got a Madcow Go Devil 54 kit a while back. Just put the NC in our EMC test chamber at work to measure the effect of the black filament-wound NC on the transmitter signal. Spectrum analyser showed that with the NC the signal getting out was 1dB less than just a bare. The effect was real.

I was using low power (25mW) RDF beacon on 433.9MHz.

For the cost of 1dB drop in signal I won't be worrying about moving my telemetry elsewhere in the rocket. Nose is good for me.

Keep in mind that this result is for the Madcow 54mm black f/w f/g NC only, with a sample size of n=1. YMMV.[/QUOTE]
______________________________________________________________________________________________________________________________________________


I thought so! I have replaced some of the N/C's with colored ones some of which a translucent enough for the LED's of the enclosed device to be seen. Some pics here:
21000002.jpg

I think the key is using a nosecone that doesn't have carbon black in the resin. This would mean that the black "Profusion" tubing could have the same phenomena.
1Db might explain why I didn't see anything on a 900Mhz GPS tracker in the prior nosecone on that Formula 54 except just before impact. A range check with these two cones I purchased from Wildman was satisfactory.

Too bad it's not possible to test at 33cm (the 900Mhz band) 1.25M (the 200Mhz Walston/Com-spec et al) and 2M Ham band. The 900Mhz band is going to be
ubiquitous because of the no license required.


If this attenuation is across the board, it might be overcome with more Rf power output but it will impede one who is operating at the extremes of their system.

Kurt
 
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manixFan

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..For the cost of 1dB drop in signal I won't be worrying about moving my telemetry elsewhere in the rocket. Nose is good for me....
That's good info, thanks for testing the nosecone. I agree the drop isn't enough to really warrant a change unless you are really pushing the tracker to the limits of it's normal distance.

FWIW, I've used the Marshall trackers in several black nosecones with no recovery issues, even to +20K'.


Tony
 

mpitfield

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I have launched my CF Tomach, which has a black 5:1 FW/FG nose cone with a titanium tip, to 17,AGL using the TeleGPS as well as a Comspec AT-2B and both tracked fine. Good information to know that there is a difference on the black ones.
 

OverTheTop

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1Db might explain why I didn't see anything on a 900Mhz GPS tracker in the prior nosecone on that Formula 54 except just before impact.
I doubt it, unless there is a much greater effect on the higher frequency.

If this attenuation is across the board, it might be overcome with more Rf power output but it will impede one who is operating at the extremes of their system.
Correct. 25% more Tx power will negate 1dB of loss.

Decibels is a logarithmic scale. Usually peoples' brains don't instinctively handle logs well. In human terms your ear will barely be able to tell if something is 1dB louder or softer. 3dB is double or half volume.

The effect of 1dB actually depends on how much signal level you have to spare in your system, which includes things like antenna gain, feedline losses, noise margin on the Rx, etc...
Incidentally, the same loss would possibly be achieved by two or three connectors in the antenna feedlines (Tx or Rx), just as another perspective.

As an example, my TeleMega system at 21k' currently has a remaining margin of about 5-6dB. 1dB will not affect the link. If I want more range I can build a bigger antenna with more gain.

I will be fitting the TeleMega to my black NC and not losing any sleep over it.

Summary:
1dB higher signal is not worth worrying about
2dB higher signal is worth having if you can get it
3dB higher signal is definitely worth the effort to get

If I can scratch up a 900MHz ISM-band Tx I can quickly repeat the test. Stay tuned :wink:
 

cerving

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A higher gain antenna on the receiver can easily make up 1 dB. The one that we sell for the Eggfinder receivers is 3 dB, it essentially doubles the range. I have seen rubber ducky antennas that go up to 5 dB, they tend to be fairly large with a narrower beamwidth of course. Your link budget is dependent on a lot of things: The transmitter's power output in dBm, the transmitter's antenna gain, the free space loss (which is dependent on frequency and distance), cable losses, the receiver's antenna gain, and the sensitivity of the receiver itself. There are a lot of calculators for this out on the Internet, but you'll need to get the specs on your hardware to accurately calculate it.
 

ksaves2

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I doubt it, unless there is a much greater effect on the higher frequency.


Correct. 25% more Tx power will negate 1dB of loss.

Decibels is a logarithmic scale. Usually peoples' brains don't instinctively handle logs well. In human terms your ear will barely be able to tell if something is 1dB louder or softer. 3dB is double or half volume.

The effect of 1dB actually depends on how much signal level you have to spare in your system, which includes things like antenna gain, feedline losses, noise margin on the Rx, etc...
Incidentally, the same loss would possibly be achieved by two or three connectors in the antenna feedlines (Tx or Rx), just as another perspective.

As an example, my TeleMega system at 21k' currently has a remaining margin of about 5-6dB. 1dB will not affect the link. If I want more range I can build a bigger antenna with more gain.

I will be fitting the TeleMega to my black NC and not losing any sleep over it.

Summary:
1dB higher signal is not worth worrying about
2dB higher signal is worth having if you can get it
3dB higher signal is definitely worth the effort to get

If I can scratch up a 900MHz ISM-band Tx I can quickly repeat the test. Stay tuned :wink:
Great, The fact that I had a ballistic flight might have been part of the issue that is did not receive any positions until just before it hit. The rocket distance-wise was closer to me when it went in than it was when it was on the pad. It hit out in the field away from me but due to the rocket size, no one saw it come in. The one or two "terminal" positions were enough to get me to the rocket with the fincan sticking out of the ground. It was pretty deep too! Kurt
 
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