Best Yagi Antenna for Altus Metrum

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One thing that's not been called out here but I feel worth mentioning is that all of our transmitters (for the most part) are using 1/4 wave whip antennas. These antennas have polarisation, as do yagi antennas. Last year I was tracking a TeleGPS and noticed my SNR was lower than I expected. I could rotate my 5 element yagi 90 degrees to where the elements were in a vertical orientation and my SNR would improve dramatically. I didn't really catch onto what was happening until I got to the rocket. It was in a sea of canola and the chute had caught itself in the canola which resulted in the nose cone hanging off the canola in a vertical orientation. So my transmitter antenna was in a vertical orientation, and turning my yagi to match that orientation improved SNR dramatically.

TLDR, if you aren't getting a good signal on the ground try rotating your yagi 90 degrees.
Oh shoot. Back in the "old RDF days" I saw the "old-timer fliers" rotating their Yagi receive antennas in their hands to try to get the maximum position signal trying to match up the Yagi antenna polarity to the transmitter as a rocket was falling under drogue. I studied to be a Ham radio operator with a "General" license soon after back then and realized what the heck they were doing with my study! Knowledge is power I tell you!
Those oldsters were trying to match antenna polarity so they could get the maximum range out of their RDF trackers of the time by twisting their arms about their wrists right and left. Get a signal peak and follow it down.
Pointing a Yagi is not a problem but getting the polarity right for reception is priceless. Hence, "rotate the wrist." I saw that technique used back in the early 1980's with RDF with the "older rocket guys" and it has stuck with me since. The rich fliers had the Walston stuff and I think there was a "Rocket Tracker" commercial RDF tracker in days of old. Never lost a rocket myself with RDF though I switched to GPS tracking very quickly as it was so more precise. I still use a 900Mhz Yagi antenna to hunt downed rockets on 900mhz GPS tracking as the rocket is not moving and it's easier to aim a 900Mhz Yagi at a downed rocket. I still "twist" my wrist around with my hand held Yagi antenna to "peak" the signal receive input. Gets more position packets in that way more reliably. An attenuator doesn't help for RDF until one gets close to the tracker/rocket position and is not needed for GPS/APRS tracking. There are no 900Mhz RDF trackers as the ground footprint is small at that frequency. Although I found out it's pretty decent with a multi-element 900Mhz Yagi antenna pointing at the presumed rocket position for ground recovery.
I don't care if it's RDF, GPS or APRS tracker. Point a Yagi receive antenna in the direction of the downed rocket and you'll at least know you'll get it back sooner rather than later. The 900 Mhz stuff works fine when the rocket is downed. If it's a GPS tracker and it still has a view of the satellites on the rocket, one will get a final position. A 900Mhz reciever Yagi will tell you sooner rather than later you'll get there as long as you know where to point it. I like that.
For lawn darts, I've witnessed with RDF and GPS tracking that one can get to the "hole" and see the fincan sticking out of the ground. With RDF, if someone was out in the field takig a fix, when a rocket came down, can "cross" the fix lines from the guy/gal out in the field and the flier from the launch site on a map. Can at least salvage motor components and "dispose" of the rocket "trash" stuff and dorked electronics in an appropriate manner after the digging up! Been there and done that myself actually. At least the electronics gave up their lives so I could dig the rocket out of the ground and dispose of the batteries appropriately. Sometimes, only see the fincan sticking out of the ground.
Though I've seen many folks doing RDF by themselves able to "walk a line" out to the last known direction fix and get rocket remains back if the deployment events didn't occur properly! GPS rocket tracking makes it easier. Kurt
 
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An attenuator doesn't help for RDF until one gets close to the tracker/rocket position and is not needed for GPS/APRS tracking.
Often I use my Yaesu VX-8GR to find my rockets via GPS and APRS. But over the past season I landed in the middle of a canola paddock twice. Due to the lack of accuracy of my radio (the inbuilt APRS TNC has a 0.1km resolution) I would often end up RDFing the transmitter once I got REAL close. My 'attenuator' is a combination of slightly detuning my radio and rotating my yagi between horizontal and vertical polarisation. These two things allowed me to use the signal strength meter of my handheld to RDF the transmitter in ~6 foot tall crop. The last time I did it I nearly walked over the rocket as I was pretty much only paying attention to the LCD screen of the radio instead of looking where I was going.
 
Often I use my Yaesu VX-8GR to find my rockets via GPS and APRS. But over the past season I landed in the middle of a canola paddock twice. Due to the lack of accuracy of my radio (the inbuilt APRS TNC has a 0.1km resolution) I would often end up RDFing the transmitter once I got REAL close. My 'attenuator' is a combination of slightly detuning my radio and rotating my yagi between horizontal and vertical polarisation. These two things allowed me to use the signal strength meter of my handheld to RDF the transmitter in ~6 foot tall crop. The last time I did it I nearly walked over the rocket as I was pretty much only paying attention to the LCD screen of the radio instead of looking where I was going.
An audible beeper can be your friend…
 
Oh shoot. Back in the "old RDF days" I saw the "old-timer fliers" rotating their Yagis in their hands to try to get the maximum position signal trying to match up the Yagi antenna polarity to the transmitter as a rocket was falling under drogue. I studied to be a Ham radio operator with a "General" license soon after back then and realized what the heck they were doing with my study! Knowledge is power I tell you!
Those oldsters were trying to match antenna polarity so they could get the maximum range out of their RDF trackers of the time by twisting their arms about their wrists right and left. Get a signal peak and follow it down.
Pointing a Yagi is not a problem but getting the polarity right for reception is priceless. Hence, "rotate the wrist." I saw that technique used back in the early 1980's with RDF with the "older rocket guys" and it has stuck with me since. The rich fliers had the Walston stuff and I think there was a "Rocket Tracker" commercial RDF tracker in days of old. Never lost a rocket myself with RDF though I switched to GPS tracking very quickly as it was so more precise. I still use a 900Mhz Yagi antenna to hunt downed rockets on 900mhz GPS tracking as the rocket is not moving and it's easier to aim a 900Mhz Yagi at a downed rocket. I still "twist" my wrist around with my hand held Yagi antenna to "peak" the signal receive input. Gets more position packets in that way more reliably. An attenuator doesn't help for RDF until one gets close to the tracker/rocket position and is not needed for GPS/APRS tracking. There are no 900Mhz RDF trackers as the ground footprint is small. Although I found out it's pretty decent with a multi-element Yagi antenna for ground recovery.
I don't care if it's RDF, GPS or APRS tracker. Point a Yagi receive antenna in the direction of the downed rocket and you'll at least know you'll get it back sooner rather than later. The 900 Mhz stuff works fine when the rocket is downed. If it's a GPS tracker and it still has a view of the satellites on the rocket, one will get a final position. A 900Mhz reciever Yagi will tell you sooner rather than later you'll get there as long as you know where to point it. I like that.
For lawn darts, I've witnessed with RDF and GPS tracking that one can get to the "hole" and see the fincan sticking out of the ground. Can at least salvage motor components and "dispose" of the rocket "trash" stuff and dorked electronics in an appropriate manner! Been there and done that myself actually. At least the electronics gave up their lives so I could dig the rocket out of the ground and dispose of the batteries appropriately. Sometimes, only see the fincan sticking out. Kurt
 
An audible beeper can be your friend…
Also, if you're on a budget, these are quite good

3 element Yagi antenna
For a 900Mhz base station tracker. A flat panel antenna gives decent gain. 15 years ago when I bought mine, they were cheaper. Example here: https://www.showmecables.com/l-com-...MI2IuAkuaD_QIVCfTjBx36VwkUEAQYBCABEgIfevD_BwE
Mounted mine on a pole to get it off the ground and try to generally point it at the rocket in flight. Rarely lose a position while the rocket is in the air with 900Mhz stuff. I'll try to post a picture of it. Obviously can't go out to the recovery site easily and switch to a handheld 900Mhz Yagi to do so.
As mentioned, I track on the 70cm band too and have capability to do APRS on 2 meters. Have Arrow Yagis on 70cm and 2 meters too.
900Mhz is adequate to find sport rockets though and I'm glad folks don't have to be licensed Hams to do so. Getting a Ham Tech license is not so hard and opens up other bands one can use. Kurt KC9LDH
 
WARNING: Mid-level nerd-speak from an "oldster" amateur radio operator INCOMING!

1/4 wave whip antennas.

Vertically polarized antennae need to be vertical for best transmission range.

This is why @RocketDestroyer in post #16 uses a circular polarized antenna.
This has a 3dB loss

A 3dB loss is a 50% power reduction. I don't think I am willing to do that with a milliwatt transmitter.

A Uda-Yagi antenna at the receive station is a no brainer. As covered, you can change its polarization from horizontal to vertical or anywhere in between just by rotating the elements from parallel to the horizon to perpendicular to the horizon or anywhere in between.

Simply no contest on gain over dipole... Simply adding a reflector adds a ton of gain (2-element). Adding directors adds MORE gain! But the law of diminishing returns and antenna boom length and size dictate that the number of elements reaches the absurd somewhere before 10.... For us... about 7 max. You can have a 2-piece boom to make transport and storage easier. Just have to make sure the driven element and the reflector are on the same piece. Bigger diameter elements are better up to a point... same law of diminishing returns.

"Problem" with standard Yagis is the reflector is a single slightly longer element behind the driven element. So the antenna receives and transmits off the BACK END rather well, enough to confuse you if you are not careful. IF you add a plane or corner reflector spaced properly from the driven element (or use your body), you will stop/reduce signal off the back end while increasing gain yet again. This would make the antenna bigger, heavier, and harder to store unless it broke down into multiple pieces... 4 or so.

I have the 3-element Arrow. That will work for 90% of all flights and for general direction finding. I plan to add the 7-element Arrow for high altitude and tighter beam width for hunting on the ground WITH the 3-element. Will have an adjustable attenuator on the big Yagi. I don't think I will add a corner reflector unless some need presents.

What is important to me is that whatever receiving antenna I use, I want the receiver, etc. to mount ON the antenna like Altus Metrum does it!

So, the RECEIVING station is not really the main issue IMO. We can build an antenna system that is second to none with amps and attenuators, etc.

The REAL need is to look at the antennae on the transmitters in the rockets.... The ones that are soldered wires are barely passable and not very durable.

Rubber Ducks are ONLY really useful IMO IF they are specifically tuned to 70cm and not a compromise for 2m/70cm. We can't afford to compromise a small antenna on a tiny power level transmitter. We need 100% of the power to LEAVE the antenna for the universe, not bounce back and forth in the traces.

Oh yeah, rubber ducks are (imo terrible compromises) usually well shorter than the length of a quarter-wave element and thus use matching elements (coils and such) to make the antenna APPEAR electrically long enough at the expense of transmission efficiency. Better to use a non-loaded whip like we use on the cheap Chinese HT radios.

So, IMO you need to put a quality antenna connector on the board and use a length of quality 50 Ohm coax, like LMR-100, properly terminated on both ends to get the antenna OFF the board.... Antennas get hit, flipped around, have mass.... That is bad for the pads/traces to which the connector is soldered.

Better to use a cable and remote mounted antenna..... Especially if the rocket tube is metal or carbon fiber.... Antenna ideally would be externally mounted where the rocket body cannot shield the signal. ALL materials attenuate radio signals.... some more than others.
During ascent and descent, we can creatively get the antenna in a place to transmit effectively.

It is after touchdown that we can improve rocket recovery percentages a LOT.... Problem? Most of the time, the vertically polarized antenna is laying on the ground horizontally.... incorrect polarization, no elevation, and more than half the transmit signal being shot directly into the ground.

Get that antenna up off the ground even a little bit and your reception will improve significantly. Get that antenna off the ground a bit AND turned vertically, and you will get a MUCH, MUCH better signal reception area around the rocket.
I am working on a number of potential solutions for the airframe antenna system.

One solution would be to make the avbay/coupler in a DD system the substrate for a full DIPOLE antenna.... A dipole is a balanced antenna that doesn't need to rely on a ground plane (especially the tiny ones available to flight computers/trackers). Groove the coupler in a fashion that you can implant two quarter wave antenna elements into the outside of the coupler and glue in place. Or, fix the avbay into one of the long body pieces and put the dipole along the body piece, and connect it to the avionics gear with a small LMR-100 cable. Will work on the way down as a vertically oriented dipole, and on the ground as a conventional horz. dipole and MAYBE have up to body tube diameter elevation.

Gotta figure out how to get the antenna off the ground or at least standing vertically wherever it is mounted.
You can use the best receiving station in the world, but you will reach a point where you can't make it better easily or cheaply.
THAT is when you HAVE to start looking at the transmission system.

And it is a SYSTEM on both ends. Apologize.... I could talk antenna design for..... forever.
 
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practical experience, I have never lost data from my TeleGPS, using a simple 2m/70cm magmount on the car.

Usually it's good enough to get data with the rocket on the ground. But as noted, change to a directional antenna like a 3 or 5 element Yagi for close in direction finding.

In the way that rocketry is a central hobby, it leads to many other fascinating things. Get a Technician amateur license, and join a local club doing foxhunts. It's a lot of fun and will really hone your rocket tracking skills.
 
A standard whip antenna will be fine up for receiving APRS telemetry in flight. It's the 'on the ground/final position' packet where having a yagi provides benefit. I've helped recover rockets at Black Rock before where I was using my VX-8GR and my mate was using his. Only difference was I had a 5 element yagi whereas he was using the standard whip that came with the radio. I was able to get a 'on the ground' packet a lot earlier than he was solely due to the yagi. It helps, but basically only on the ground.
 
Groove the coupler in a fashion that you can implant two quarter wave antenna elements into the outside of the coupler and glue in place.
Just remember that an antenna taped/glued to the airframe doesn't see air as the dielectric. It partially sees fiberglass (don't put it near carbon fiber). The higher permittivity means the antenna needs to be a different length than in free air. You can use a cheap VNA (search this forum for "nano vna" threads) to tune the antenna to its new surroundings very easily.
 
So do you need two yagi antennas in your launch box, with "slightly" different configurations depending on your flight & site conditions?
With some additional influence from the antenna arrangement in the rocket?
 
So do you need two yagi antennas in your launch box, with "slightly" different configurations depending on your flight & site conditions?
With some additional influence from the antenna arrangement in the rocket?

Practically, no. Don't worry about it.

If you're a ham and want to nerd out, go ahead. For example, sometimes (3 day rocketry campouts) I also bring a cross polarized 2m/70cm dual Yagi, and separate HT, for satellite work. And HF antennas. And ...
 
My Moxon was an experiment. I wanted an antenna that I could just set up and forget about. I didn't to have to worry about having to point it in the best direction during a flight. Was it successful? Moderately so. I was intended to have about 6 dB of gain overhead with a similar loss of gain on the horizon. I also liked it because it has an excellent front to back ratio. Plus, I just like to experiment building antennas so it was a win/win for me. It does pretty much what I expected but frankly, a simple wire vertical antenna preforms about the same for my flights which are all under 20,000 feet.
Here is the plot from a typical flight. Vertical antenna in the nosecone of the rocket fed by a TeleGPS and a vertical ground plane antenna about 6' high. It was made from a coax connector with four drooping radials. The receiver was a TeleDongle connected via USB to my laptop.
Vertical.PNG


For comparison here is the Moxon on the same flight. The receive antenna in this plot is the Moxon at about 6' off the ground. The receiver in this case was a TeleBT connected to my phone via Bluetooth.
Moxon.PNG

The Moxon has a slightly lower RSSI on the pad as the rocket is on the horizon of the antenna where the antenna has negative gain and the vertical's main lobe is pointing at the rocket.
The Moxon has a slightly better signal at apogee and the vertical does better as the rocket descends down near the horizon. Both antennas lost the signal once the rocket was on the ground. I have in one case been able to pick up the rocket on the ground by simply picking up the Moxon antenna and pointing it in the direction of the rocket.
The one disappointment was that I was expecting to see fewer deep drops in the RSSI data with the Moxon as compared to the Vertical but this doesn't seem to be the case in practice.
So overall, I have enjoyed building and experimenting with the Moxon antenna but for the average user, as pointed out by CLS, just go with the vertical antenna. You don't have to have data all the way up and down, the main goal here is to recover the rocket. Even just one data packet received near the ground will get you close enough to either find the rocket or start picking up new data from the rocket on the ground. There is really no need to use convention RFD techniques for a GPS locator. It tells you where it is.
For the TeleGPS I just use a quarter wave piece of wire for an antenna. You don't really need anything fancy. I did have a nice 432 antenna and SMA connector on the TeleGPS until I had a hard landing and the antenna and connector snapped off the TeleGPS. I do support the wire with a thin piece of bamboo. Since then I haven't broken off any more SMA connectors.
I use the vertical because it is light weight, simple and as an unbalance antenna is directly matches the unbalanced output of the TeleGPS.
Just for fun, here is a picture of the Crossed Moxon antenna. The phasing and matching sections of coax are hidden inside the antenna.
20230206_192428.jpg

Sorry, I didn't mean to rattle on for so long. Hopefully some will find this of interest.

PS I had a broken wire inside the antenna last fall and lost the data from the rocket when it launched. My trusty Yaesu VX-8GR saved the day. There was a small hill behind the flight line and from there I was able to get a data packet from the rocket using the rubber duck antenna on the radio. Well, actually it would have saved the day. About the time I got the handy talkie working I received a call from another rocketeer who had found my rocket and gave me directions to recover it. Good thing I put my phone number on the rocket.

PPS The Moxon loop makes a great RDF antenna due to it's very good front to back ratio. If you need a bit more gain, just add a director in front of the Moxon loop.
 
Vertical antenna in the nosecone of the rocket fed by a TeleGPS and a vertical ground plane antenna about 6' high. It was made from a coax connector with four drooping radials.
Can you post a photo of the ground plane antenna? So folks can see what we're talking about. I'm wondering how you fit it in the nose cone.

Excellent stuff!!
 
This is just my way of installing the TeleGPS into the nosecone. There are lots of other ways that would work just as well if not better. Experiment and have fun. If it's not fun you are doing something wrong.

I believe that the TeleGPS and most other trackers depend upon the circuit board to act as the ground plane of the antenna. I just try to help it out a bit by providing a bit more surface area. I mount the TeleGPS to a piece of copper clad PCB board that is connected electrically to the ground of the TeleGPS. I don't really know if it makes a difference, I've never done any testing to confirm if it does. I just assume (hope) that it does.

Here is a quick drawing of how I typically put the TeleGPS into the nosecone.
20201208_173138.jpg

And the actual unit during construction. You can see the copper foil on the PCB. You can also see the bamboo skewer that supports the wire antenna.

View attachment 562144

On this unit I had more room so I have a USB bulk head connector on the bulk plate so I don't have to take the unit apart to connect my computer to the TeleGPS. That's the heavy black cable in the photograph.

Here is a closeup of the TeleGPS on another system that I built for a smaller diameter rocket.
View attachment 562145

Finally, here is a picture of the drooping ground plane receive antenna that I use. It is a quarter wave vertical with little gain. Antenna gain here wouldn't really be helpful. No doubt a magmount antenna on the roof of the car would work fine too.

20230208_075749.jpg

It is made from an SMA bulkhead connector, a round piece of metal about the size of a quarter and some wire. It was cheap to make but works quite well.

I'm sorry for hi-jacking the thread which is supposed to be about the best yagi antenna for the Altus Metrum products. Since I like to build my own stuff I recommend the WA5VJB cheap yagi antennas. You can add as many directors as you need. For a commercial antenna the little Arrow antenna is hard to beat.
 
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If you want more gain for the ground antenna something like this might be the ticket. It consists of 4 yagis with 33 elements each and is steerable in azimuth and elevation and had about 26dBi gain. Sadly it was taken down about 5 years ago.
QSL Front.jpg
 
:) This antenna was for EME and Tropo but I have also done the satellite thing back in the days of Oscar 6 up until AO-13. Wish we could have had another bird like AO-13, it was amazing.
 
It's pretty incredible what can be done with a SDR, relatively small offset dish (sub 1 meter), and a homemade helical feed these days. I regularly demod/decode polar orbit weather sat transmissions (NOAA, MetOp, and Meteor) as well as GEO birds like Elektro-L and Fengyun-II. It's good fun.
 

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:) This antenna was for EME and Tropo but I have also done the satellite thing back in the days of Oscar 6 up until AO-13. Wish we could have had another bird like AO-13, it was amazing.
I remember a flier who erected a portable tower as a base station at the launchsite to track his 70cm band Beeline GPS tracker! Even I thought it was overkill as I didn't think his rockets would drift that far!:oops:
 
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