(19-Apr-2017, 08:44 AM)unseen Wrote: S-parameters are measurements that describe how well an antenna works at various frequencies. (See: http://www.antenna-theory.com/definition...meters.php)

I have the equipment to test and measure these parameters, but it uses SMA connectors for all the various connections, so I'll need to find a good way of adapating from the connector that's used on the removable FrSky antennas (often called u.fl or IPX) to an SMA connector so that I can connect the antenna under test to my test equipment.

Once I can do that, I can generate a bunch of graphs that look like this:



If I create such graphs for both the long and short antennas, we can see how they work at the different lengths. Maybe there's a surprise waiting for us in the results?

When? this is really interesting 

(22-Apr-2017, 12:41 PM)sevet Wrote: When? this is really interesting 

I have to wait for the connectors that I've ordered from China to arrive before I can start so you'll have to contain your enthusiasm for a while.

Looking forward to the results of this, Unseen!
I'm using an FrSky XM on a micro build - I know it's not supposed to have very long range, but mine seemed uncharacteristically short - checked the length and it measured at 36mm.

Cut it down to 31mm - still seems pretty crummy ... and I'm now realizing that 33mm was probably the correct length - ho hum. Shoulda just gotten the XM+ and made it work. The range on that is absurd (coming from someone who never flies beyond a few hundred meters. On that, the rssi never really dips below like 85% ... on 3mw for my tx).

(24-Apr-2017, 02:26 AM)CesiumSalami Wrote: Looking forward to the results of this, Unseen!
I'm using an FrSky XM on a micro build - I know it's not supposed to have very long range, but mine seemed uncharacteristically short - checked the length and it measured at 36mm.

Cut it down to 31mm - still seems pretty crummy ... and I'm now realizing that 33mm was probably the correct length - ho hum. Shoulda just gotten the XM+ and made it work. The range on that is absurd (coming from someone who never flies beyond a few hundred meters. On that, the rssi never really dips below like 85% ... on 3mw for my tx).

The manufacturer specifies the range of the XM receiver as "> 600m". That hardly qualifies as "not supposed to have very long range" does it?

What kind of range are you getting? Actual range is very much about how you have placed the antenna on the craft and even such simple things like how the antenna on your radio is oriented with respect to the receiver antenna. If your radio only outputs 3mW, you're already asking a lot of the receiver, especially if where you fly has lots of other signals on the 2.4GHz band.

(22-Apr-2017, 02:46 PM)unseen Wrote: I have to wait for the connectors that I've ordered from China to arrive before I can start so you'll have to contain your enthusiasm for a while.

Chine? So next month then haha 
As much as I like this on my build thread, this deserves it's own thread IMO...
Just put a link here if you do open one please.

(24-Apr-2017, 09:16 AM)sevet Wrote: Chine? So next month then haha 
As much as I like this on my build thread, this deserves it's own thread IMO...
Just put a link here if you do open one please.

Once I get what I need to do the testing, I will be starting a thread for it.

I have a feeling that the testing will end up being quite complicated.

(24-Apr-2017, 08:37 AM)unseen Wrote: The manufacturer specifies the range of the XM receiver as "> 600m". That hardly qualifies as "not supposed to have very long range" does it?

What kind of range are you getting? Actual range is very much about how you have placed the antenna on the craft and even such simple things like how the antenna on your radio is oriented with respect to the receiver antenna. If your radio only outputs 3mW, you're already asking a lot of the receiver, especially if where you fly has lots of other signals on the 2.4GHz band.

Ah, sorry, thank you for the response. Let me clarify a few points:

Indeed, >600m seems just fine on paper. "not supposed to have very long range" - is from user experiences claiming that the range isn't as advertised ... some claim it does a lot better without the presence of VTX's.

My tx is a Devo7e with a 4-in-1 with an adjustable antenna.  3mw was an accident ::derp:: I usually run at 100mw.
I''ve tried a variety of different orientations, but I seem to get drop outs within 50-75m but that's with a lot of trees and stuff in the way; I have a 200mw vtx, and it offers crystal clear video before the 2.4ghz starts to fade, so it can't be that bad. I have other rx's advertised at 400m that also fade before the 200mw VTX hits its limit, but the video clarity is prettttttttttttty snowy at that point.

One thing that I noticed is that the rx requires the fine tuning below -10 - but beyond that - it'll bind and report very similar rssi readings all the way down to the max adjustment (-125?).  So... I'm just doing with 70 for now.

I strip back a little more and try again.

I've been having similar problems with LemonRX diversity satellite receivers recently. I've used them on many builds before and had no problem getting out to over 250m. On a few recent builds though, I've had no more than 30m range, even from my Devo 10.

In both cases, I'd been forced to de-case the receiver because the build was so tight. Swapping to an FrSky receiver solved the problem in both cases.

Naked receivers are always going to be more susceptible to external RF interference and even a plastic case means there's at least some distance between the receiver and other electronics. The tiny little XM and XM+ receivers are easier to position so that they have a little 'personal space' and I think that's more to do with them solving my problems on a tight build than any particular edge in RF performance.

If you can re-position the XM, it's worth a try to see if it helps.

(24-Apr-2017, 11:41 PM)unseen Wrote: I've been having similar problems with LemonRX diversity satellite receivers recently. I've used them on many builds before and had no problem getting out to over 250m. On a few recent builds though, I've had no more than 30m range, even from my Devo 10.

In both cases, I'd been forced to de-case the receiver because the build was so tight. Swapping to an FrSky receiver solved the problem in both cases.

Naked receivers are always going to be more susceptible to external RF interference and even a plastic case means there's at least some distance between the receiver and other electronics. The tiny little XM and XM+ receivers are easier to position so that they have a little 'personal space' and I think that's more to do with them solving my problems on a tight build than any particular edge in RF performance.

If you can re-position the XM, it's worth a try to see if it helps.

Verrrrrrrry interesting.  I'll try that!
Tricky to find space on this runt though:

(26-Apr-2017, 11:15 PM)CesiumSalami Wrote: Verrrrrrrry interesting.  I'll try that!
Tricky to find space on this runt though:

Clean build man. I like

(26-Apr-2017, 11:15 PM)CesiumSalami Wrote: Verrrrrrrry interesting.  I'll try that!
Tricky to find space on this runt though:

Is that a 3D printed Hoverbot nano?

(27-Apr-2017, 02:22 AM)Drone0fPrey Wrote: Clean build man. I like

Thanks! It's a fun little quad.  Had to redo the top to this cleaner look after mangling a TX02 in small crash. Blew out a regulator somewhere....  Grabbed a FX758 that I had around from an old brushed project and was back on track! The TX02 is so weird ... it takes vin to the vtx side and steps it up to 5v, passes that to the camera, and then the camera steps that down to 3.3v and sends that back to the vtx. I wonder if that's just a noise filtering thing...

(27-Apr-2017, 08:04 AM)unseen Wrote: Is that a 3D printed Hoverbot nano?

I didn't originally plan for it come out that way (started this project before the 1103's even came out) .... but yeah ... there are enough similarities (and inspirations from their designs) that I did contact the Hoverbot folks to ask if they'd like me to refrain from posting files and links to buy the carbon base.  I don't believe that there are any IP issues - but mostly just wanted to offer because they seem like a great member of this community that created a stellar product (also at least two of them are still college students).  But they did give me the green light.

This hack job of mine doesn't hold a candle to their quad but for those that want to tinker ... could be fun.

If you're interested: http://www.thingiverse.com/thing:2276767

Cool!

The prop guard system on the Hoverbot is a really neat design and they're great guys to give you the green light on this. A big pat on the back to you as well for seeing the issue and doing the right thing.

Coincidentally, I just received a package from the USA yesterday...



So now I really do have to get my 3D printer put back together so that I can print a camera mount for it!

Yeah - I thought it was nice of them, too. I'm not looking to turn a profit or develop a product. But I did want to share my work.

OOooOOOOoOooOoO very nice. It's such a good design - i'm sure you'll love it.
Personally, after building my shoddy facsimile, I realized that I may actually prefer the wider arms for separate ESC's to keep the stack super low. Enjoy!!!

Since you're not in the US. Might I suggest scanning the arm links for future printing? They're supposed to be tough, but they're also supposed to be crumple zones ...

I will be building this with separate 6A ESCs to keep the stack low. All that will be in the stack is a Piko BLX and a micro FrSky compatible receiver with telemetry. That way I can avoid having to add an OSD to keep an eye on the battery.

I'll have look at duplicating the arm links for 3D printing. The details on them are quite fine but I can manage 0.1mm resolution on my printer so it should be OK. I'll be printing them in PLA though as my hot end can't go up to the temperatures needed for nylon.