Reach RTK | alternative GNSS combinations for time mark logging

us DJI pilots would love that flight time.

owing to @VanavaraDigital endorsement i have purchased the BT560 L1 spiral antenna and this cable: https://www.unmannedtechshop.co.uk/product/reach-mcx-male-to-sma-female-antenna-adapter-cable-50cm/
When I get results I will let you know how the spiral performs compared to the patch antenna. Cycle slips aren’t much of a problem after my vibration isolation efforts, but I’m looking for better SNR values as i think BeiDou and Galileo reception could be stronger:

The best way to use BT-560D for L1 Reach M+.

Thank you for the input! Now I understand why I had more and more problems with cycle slips.

When we talk about vibration we have to consider that I’m flying in strong wind. More wind and gusts cause more vibration. I think it is hard to compare flights with different amounts of wind.

I guess you fly in Danmark with a lot of wind too, would you share images of youre setup und youre SNR results?

A part of my cycle slips are connected to a vibrating motor (DOA) which I have to replace.

Do you recommend to shorten the antenna cable? Which tools and adpters do you use, can you recommend some?

I’m very interested in the results! And thank you very much for the SNR data visualization, its always good to have a reference!

If you have good results with the antenna I will buy one from @VanavaraDigital/Konstantin.

Hey @tobias-dahms ,

Results of the spiral antenna are good, as can be seen on the following plot. UAV was on the ground, among trees, until 00:35. From there you can see it clear right up. BeiDou Geo satellites (C01-C04) are now tracked properly and are useful for processing, whereas before they were a cycle-slip mess. There is still directionality evident in the SNR, but is not enough to matter.

Thank you @VanavaraDigital for your antenna recommendation. I have better tracking and saved about 15g weight. I appreciate your participation in the forum.

3 Likes

Hi, you are welcome)

Yesterday I made L1/L2 tests.
Results are there: AShot - new way for integration of Reach M+ to DJI Phantom 4 adv | pro

Great, thank you very much @wsurvey! I will try it too! Can you send me a picture of how you mounted the antenna? Where did you buy your BT-560D?

@VanavaraDigital Konstantin, I would like to buy two (or is there a special discount for 3 or 4?) of your or the BT-560D antennas. What would be the delivery time?

I think I found a suitable cable:
https://www.minipc.de/de/catalog/il/2613?gclid=EAIaIQobChMIiIOo9e275QIViK3tCh0J7gBvEAQYBCABEgJBPfD_BwE

Tobias,

As for antenna shopping, I just go to ali express and search for ‘bt-560d’, and buy the cheapest one. That’s how I’ll get my next one. I will convert the second unit as soon as I can based on my test.

As for mounting, I bought some 25x25x1.5mm L-shape aluminium extrusion, cut a small piece, drilled a 6.5mm hole for the antenna, drilled 2x2mm holes for mounting to the timber mast, and strengthened the mount with 2-part epoxy.

1 Like

That one looks really like the Emlids L1/L2 antenna for the M2 unit…
Whats the idea around the antenna shape?

1 Like

It also looks like this waterproof, airtight, durable, smellproof stashjar:
stash_jar

but I digress…

1 Like

Close but no sigar for you :wink::sweat_smile:

Its a half hollow cylindrical antenna.
Edit: That pdf was old…

Edit 2: In depth from Ublox https://www.u-blox.com/sites/default/files/products/documents/GNSS-Antennas_AppNote_(UBX-15030289).pdf

2 Likes

How many SNR do you think you could get from a backfire resonant quadrifilar helix DIY coathanger antenna?

Very cheap to build, but you might spend too many hours of labour making and testing different tunings.

1 Like

I would go for a 3d printed version. I guess someone already made it… .

https://www.researchgate.net/publication/275828209_The_Basics_of_Quadrifilar_Helix_Antennas/figures?lo=1

Cool, thank you Nick!

So no groundplane. I will have to make something which improves my vibration issues. I guess I will try something like moongel.

I am guessing the design will help people like @Luke_Wijnberg in a banking situation. Would be cool to see some comparison.
Anybody got some intel about this?

2 Likes

Tallysman single frequency = 105 $
https://www.digikey.com/product-detail/en/tallysman-wireless-inc/33-HC771-28/1526-33-HC771-28-ND/10473742

Tallysmann multi frequency = 274 $
https://www.digikey.com/product-detail/en/tallysman-wireless-inc/33-HC975-35/1526-33-HC975-35-ND/10473744

Looks like the helix antenna can be used with or without ground plane.

Helix antennas can be designed for use with or
without ground plane. If a helix antenna is
designed without ground plane it can be tuned
into such to show a more omni-directional
radiation pattern as shown in Figure 22.
Although we can determine an axial ratio close to
9 dB between zero degree and 90 degrees
elevation, which compares to the patch antenna,
the back lobe of the helix generally degrades
much smoother and does not show any
sensitivity at the –180 degree direction. In
contrast, the back lobe of a patch antenna
depends very much on the size and shape of the
ground plane.

Yes, thank you. I think groundplane is the wrong term, these groundplanes we use are RF noise shields I guess.

1 Like

No, no groundplane anymore.

The antenna vibration is supposed to be mitigated by the antenna mast being pressed into a 3mm piece of sorbothane stuck to the side of the P4. It is the material that kept coming up when i was searching for ‘best shock absorbing material’

2 Likes

Sorry to ruin the party but aren`t you introducing a flexed vibration ( like a tuning fork) ? Or you might have solved it some how, but hard to tell from the picture
Edit: Your wooden pole might be stiff enough to counteract that, of course

3 Likes