Yagi for the T3?

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DAllen

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So I basically know nothing about this sorta stuff...I have a Yagi that was given to me and I have no idea what it is good for as in frequencies. I also have a T3 I'd like to connect it to so that it hopefully increases the range. I have several questions:

- Is it worth the time and effort to bring this yagi out to the field with me?
- Is this the right antenna for the job?
- If I do use this antenna with the T3 is there anything else I need to watch out for?

Let me know if you need any dimensions or whatnot. I have a little adapter cord (?) that screws rather nicely into the antenna thingy on the T3.
 

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Use it for ground recovery only. The beamwidth on 900Mhz is pretty narrow. You could test it out with a lower impulse motor and see how it performs but at a long distance that is totally sight unseen, you might not have it pointed correctly to decode the packets. Best to use an omni directional antenna for in flight
monitoring of the 900Mhz trackers. Or lookup a patch antenna as that is a little square antenna that gives some directional gain with a larger beamwidth.
I've used one on a 10 foot pole with success.

Now don't toss that Yagi because if you know where the rocket went. You can take that Yagi and point it in the proper direction as you come in for the final recovery. You'll pick up a signal sooner than a stock antenna and the Yagi increases the ground footprint or your 900Mhz tracker. The rocket is generally in one place once down as long as the wind isn't blowing it. Kurt
 
So here’s another silly question about the t3; I am using a empty prescription bottle to house the Tx and in order to make a secure connection to a quick link or cord I glued a eyebolt on the side of said bottle. It’s about 1.5” long or so. That bolt Is parallel to my Tx antenna ... is that going to screw with the signal back to the receiver or the GPS signals it receives?

I can always get something else to use if the bolt is problematic.
 
So here’s another silly question about the t3; I am using a empty prescription bottle to house the Tx and in order to make a secure connection to a quick link or cord I glued a eyebolt on the side of said bottle. It’s about 1.5” long or so. That bolt Is parallel to my Tx antenna ... is that going to screw with the signal back to the receiver or the GPS signals it receives?

I can always get something else to use if the bolt is problematic.

Can you post a picture? If the bolt is not in the same plane as the antenna it shouldn't be an issue. If it is, you might need to do a good range test before flight. I've found that on ascent, packet pickup can be spotty with the NMEA trackers. On descent, one will get enough positions to effect a good recovery especially after the Main chute is out and the descent rate slows. That's the time to pay close attention. If the venue allows, try to do a higher rather than lower main chute deployment. Altitude can sometimes make up for poor Rf propagation.

First flights, use a lower impulse motor so if there are tracker issues, you can likely do a visual recovery. Once you are confident of your technique, you can really punch it to totally sight unseen land and feel comfortable about a successful recovery. That experience is a really neat one to punch a rocket out of sight, not see any of the events and come up to it with all the recovery laundry out deployed and obviously with a successful deployment sequence.
Been there and done that many times and it never gets old.

If I'm in a mood to watch everything, I use the right motor to do that. If there is standing vegetation, I fly a tracker no matter what. If I want to really punch it,
a GPS tracker and live mapping can really be a blast. Am still trying to perfect it. I'm glad there are so many choices for folks now. Kurt Savegnago
 
Not sure what frequency your antenna is designed for. Not sure what a "T3" is.

You could build yourself a patch antenna which is quite directional. Just search for "goof proof patch antenna" with google. Scale to whatever frequency you want. I have quite a large one for 435MHz.
 
Yes, you want the antenna to be straight. The eyebolt is probably not a problem, but ground test.

Will the pill bottle be dangling from the eyebolt and flopping around? If so, the bottle seems prone to cracking. Would be better to securely tape the bottle to the shockcord, or better yet, put the tracker in an ebay. I treat my GPS like I treat my altimeter. It has a secure home in the rocket.
 
Yes, you want the antenna to be straight. The eyebolt is probably not a problem, but ground test.

Will the pill bottle be dangling from the eyebolt and flopping around? If so, the bottle seems prone to cracking. Would be better to securely tape the bottle to the shockcord, or better yet, put the tracker in an ebay. I treat my GPS like I treat my altimeter. It has a secure home in the rocket.

No, the idea of the eyebolt is to attach to a quick link in the recovery chain and be a secondary element in holding the pill bottle. The primary element will be to thoroughly tape it to the shock cord. So basically the intent is for this Tx to be easily moved from one rocket to another. So moving the antenna straight is going to change how I want to construct this because I want the entire thing - antenna included - protected. hmmmm

Thanks for the info
 
I fly my Missile Works RTx in similar fashion. Unit is stuffed in 38mm body tube taped to shock cord & antenna is curled up. Dozens of flights & never an issue. Have a 2nd RTx in an AV-bay in close proximity to all-thread and again antenna is some what curled up. No issue.
 
I fly my RTX with the wire antenna folded over the RF module, never an issue. Longest recovery was well over a mile away, never lost signal. Not sure what configuration is 'optimal' for it, but I've seen all sorts of curli q pig tails twists, folded overs, and straight outs enough to make me think that, other than right alongside (touching) a metal rod, these little RF units are pretty insensitive to configuration when it comes transmitting their RF.
 
The T3 should have plenty of range (5+ miles) just using omni antennas. I wouldn't mess with a Yagi unless you are flying something very extreme.

I can't tell from the pic exactly what you've got, but it seems like it may be too high-gain and directional for easy rocket use. You want about a 9 dB antenna, which would typically have no more than 5 elements. A patch antenna is probably a better choice, as others have said.
 
The T3 should have plenty of range (5+ miles) just using omni antennas. I wouldn't mess with a Yagi unless you are flying something very extreme.

can't tell from the pic exactly what you've got, but it seems like it may be too high-gain and directional for easy rocket use. You want about a 9 dB antenna, which would typically have no more than 5 elements. A patch antenna is probably a better choice, as others have said.

Use a patch antenna for flight and the yagi to increase the ground footprint. Beamwidth of yagi is too narrow on this band. For sport flying, totally unnecessary but if one is pushing 3 miles and totally sight unseen, a patch can be insurance. Especially if one gets a main at apogee and there's a chance to get it back on a wild goose chase. Don't fold an antenna is a best practice. Sure one mile away, one might get away with it but you never know. Kurt
 
The T3 reports back GPS position, so as long as you have a lock, you should know where it is. How do you maintain lock? Well, that's a good question! The problem is that most of the antennas commonly used are for terrestrial use - on the flat surface of the Earth (yeah, I know...). Rockets don't stay in this plane, and may exceed the footprint of an omni antenna. We had a similar problem when I was working at the Natn'l Severe Storms Lab, tracking various balloon-born research projects (400MHz range). One advantage we had was that the frequency band was restricted, so it was fairly free from interference. I don't know how "clean" the 900MHz band is. I remember we used an omni-style antenna with a modified ground plane that gave higher "look angle", and an in-line amplifier. I'll see if I can dig up the specs on what we used (this was 18 years and several computers ago...). If you're pushing the range of your equipment (for example after the rocket is on the ground), you might actually need two antennas, an omni and a yagi (or other directional antenna) and switch them out.
 
From what I can dig up, an omnidirectional antenna, like a vertical dipole or J-pole, mounted close to the ground will have a high "take off" angle (that is, it's sensitive to things at a high angle above the ground). The higher the antenna is above a ground plane, the lower the take off angle. This explains why some vertical antennas (for example scanner antennas) have downward angled ground plane radials.
 
From what I can dig up, an omnidirectional antenna, like a vertical dipole or J-pole, mounted close to the ground will have a high "take off" angle (that is, it's sensitive to things at a high angle above the ground). The higher the antenna is above a ground plane, the lower the take off angle. This explains why some vertical antennas (for example scanner antennas) have downward angled ground plane radials.
Some antennas are designed with multiple loading coils along the length. That keeps the sensitivity pattern more closely tracking the horizontal plane and makes it less sensitive to changes in the ground plane position and form.

sg7900_e.jpg

An example is the SG-7700 or the SG-7900 here: https://www.diamond-ant.co.jp/english/amateur/antenna/ante_1mobile/ante_mo1_sg.html
That's what I run on the car for 435MHz telemetry reception. Works to 10k' no problems with the TeleMega.
 
Ksaves, what's a decent little patch antenna for the T3 (with wire whip)?

I'm happy with the stock system, but I like to learn and dip my toe in things also
 
Thank you both! I'm guessing there's no inexpensive off the shelf item for this range.

I'll need to burn a favor with one of our club solderers
 
Ksaves, what's a decent little patch antenna for the T3 (with wire whip)?

I'm happy with the stock system, but I like to learn and dip my toe in things also

Ummmm, Look at the recommendations from others here. I bought a $19.95 patch that was recommended by Cris Cerving of EggFinder fame many years
ago. Not available anymore. Has worked well for me. DIY? Look very closely at the designs and see if there is any bandwidth to allow to tuning to other frequencies. If you DIY and tune to one frequency, that will give you maximum performance as long as the transmitter antenna on the EggFinder is optimal.

Now listen, if one is looking to one to maybe three miles distant recovery, I don't think all this balderdash that I and others have espoused is necessary.
If trying to stretch the range in an extreme situation, what has been said about a patch antenna for in flight tracking and a Yagi to increase the ground footprint might help with a difficult recovery. Sport flying? Go to the last known position and as long as it's not a ballistic flight, you'll find the rocket or get a new fix. If it's an unfortunate ballistic flight, you might see the pieces or if it's a 'glass rocket, see the fincan poking out of the ground. Been there, done that. Kurt
 
Thanks for the advice K (and Tony, and O-Top)

I tend to like to learn about things before they're critically necessary. Eventually I'll get along to larger/faster projects, and tinkering around before that happens can only help out down the road.
 
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I need to add....if you purchase one, get the correct polarization. There is linear and left or right hand circular. I use linear, and both construction articles mentioned above (IBCrazy and goof-proof) are linear. Spend a brief period of time with Google and a good drink to learn the differences.
 
Here's a thought...What if instead of using a patch antennna on a pole would the range be increased at all if I just put the T3 on a pole to gain 10-12' elevation? I do realize trees and topography would play a significant factor but am wondering if it might help.

I'm looking for simple and easy things I can do to improve my chances at finding my rocket again. The linear patch antenna looks like a easy peasy option that isn't horribly expensive which could be a fun little add-on to the system. I can see myself walking around the flight line with one of those on a pole doing a bad Gandalf impersonation.
 
Put the T3 on a pole and that would get you more ground footprint with increased line of sight when the rocket is down lower. For under 2miles probably doesn't make much difference for a successful recovery. A patch antenna has higher gain so the system can reliably decode positions at longer range. If I'm not mistaken, the T3 is a 250mW tracker as opposed to the EggFinders 100mW. Raw horsepower can improve performance.
The said, plenty of folks have flown EFs to very high 5 figure altitudes and have had successful recoveries. Just do a search here. What one won't get is a successful decode of every single position. Live data freaks will have to wait for recovery to download data. (With an optional memory sim in the EF case.)
What does happen is once the main blows and the rocket settles down in to a gentler descent, the position decoding improves and that's what counts. It is smarter to blow the main chute a bit higher if the venue allows to take advantage of the better line of sight and improve the initial position reception. It's a tradeoff of course and sport fliers who don't venture above 5 figure heights that often don't need to worry as much.
All this diddling leads to better recovery insurance if something unforeseen happens like a totally sight unseen flight. A smaller rocket doesn't have to fly very high for that to occur. Kurt
 
...I'm looking for simple and easy things I can do to improve my chances at finding my rocket again.

Does your T3 work as is? If so, I would say don't mess with it. There is probably no flight at Three Oaks that could not be found with the stock T3.

I would suggest to brush up on the wonky Bluetooth connected Android apps, instead. In my experience, that is the likely point of failure. I am about resigned to the fact that a laptop base station is a better receiving device for the T3 than the 3 available (that I know of) Android apps.
 
Does your T3 work as is? If so, I would say don't mess with it. There is probably no flight at Three Oaks that could not be found with the stock T3.

I would suggest to brush up on the wonky Bluetooth connected Android apps, instead. In my experience, that is the likely point of failure. I am about resigned to the fact that a laptop base station is a better receiving device for the T3 than the 3 available (that I know of) Android apps.

Yeah, the Android apps leave a lot to be desired - but it works. Can't seem to get the T3 to bluetooth with my lapper but that's probably an issue with my lapper and not the T3. Alrighty I won't mess with the antenna. It is pretty easy to walk around with my little 7" tablet and my T3 receiver as is.
 
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