Spektrum Satelite Antennas

[Roger_Salmon]

FWIW I always try to mount satellites on the undercarriage bows so that both antennas are in the open.

[EEngineer]

Originally Posted by Bonkievan

Even though I did make that post in jest, the thread did make interesting reading all the same. But surely there is someone out there who can confirm what's going on and have the 'testing to prove it'

It's not like we want the launch codes for a nuclear sub or anything.....sheesh

No problem, Bonk...see below as to how to confirm such testing.

The only aptitude I have is to read the data that a radio IC manufacturer provides.

And Cypress Semiconductor's data sheet specifically indicates that both dipole antenna elements are "active".....

This fact can be independently verified by anyone here, including kenobi, by simply calling Cypress Semiconductor.......toll FREE....and speaking to a CYRF 6926 applications engineer....

Please call 1-800-541-4736 and simply ask for an applications engineer with regards to the CYRF6926 WiFi radio IC.

Perhaps they would even provide data on the effects of "shading" with regards to our satellite Rx mounting arrangements on our helis...

So sorry that this has upset everyone....

FWIW

[Bonkievan]

All good, EE.
It didn't upset me, I am just perplexed as to how such a small bit of electrical 'kit' can have such divided opinions, on how it works, for so long.

I range check mine and have had telemetry to help with Sat placement, but that's about as far as my electronic prowess goes, so I was just trying to get a better understanding

[helibus]

Originally Posted by Roger_Salmon

FWIW I always try to mount satellites on the undercarriage bows so that both antennas are in the open.

Should I ever have the need for one of these satellites, this is what I'd do. And if I can't get both leads in the open, I'd expose the lead on the left. Why? Because I like going with the odds. No thread discussing the two satellite wires ever questions the importance of the left wire. The discussion and debate is always about the viability of the wire on the right. The very discussion is all I would need to cause me to focus on the left wire and spend my time worrying about other things.

The thread is entertaining to my engineering background. Content of the Cypress datasheet and discussion with a Cypress engineer would be informative, but hardly conclusive. So the chip has two antenna pins. Short of Spektrum using a circuit board that came from Cypress (which I doubt), there's nothing Cypress can do to control how their part is used. We don't know that Spektrum talked with a Cypress applications engineer. Or read the datasheet (the design could be a copy). Or that the information translated well into the native language of the designer. Or that the Spektrum designer knew what he was doing. The point is WE DON'T KNOW.

Again, I'd just go with the odds. Verifying with a range check testing various orientations of the heli as best I can. And then going to fly.

EDIT: And if Spektrum did read the datasheet, they very well may have only provided one active element since that is what the reference design in Figure 12 implies. The second RF pin doesn't have an antenna connected to it. Just L2 and C3.

[EEngineer]

You go with the odds....and that's fine...

But, you can't possibly be serious in your speculation that no one read the data sheet
on the CYRF6926 radio IC......to develop a DSMX satellite RX.

How in heck would one be able to understand how the radio IC worked?

By guessing?

Come one...give us a break.

Back to the original point.....both satellite Rx dipole elements are "active"....
as clearly shown by Cypress Semi....

As opposed to the baloney that 1 dipole element is "grounded"....whomever
came up with that....

The good thing is that...in most cases...your satellite will work just fine...as you
have it currently mounted.....and it doesn't matter which dipole antenna
element is "shaded" by the frame sides.....

FWIW

[fjoe]

Here is a great example, look at a yagi antenna. It, according to what is in this thread, only has one "active" element. Do you think it matters if you just got rid of all the other elements?

[EEngineer]

Originally Posted by fjoe

Here is a great example, look at a yagi antenna. It, according to what is in this thread, only has one "active" element. Do you think it matters if you just got rid of all the other elements?

That's a Yagi....a very highly directional antenna system that projects its "beam" in one specific direction.......relative to its axis, as your pic demonstrates.....and conversly, receives the any RF "beam" only when properly oriented......if you remove any elements, it won't work as advertised.

Which makes for a very poor solution for the Rx/Tx antenna system on the satellite Rx(the satellite Rx also transmits data....which allows for the transmission of telemetry data)...
in addition to the Yagi's inherent weight limitations......

And, again, Yagis are not used with 2.4GHz systems....because of its limitations at such frequencies....so why use that as an example...."square peg in a round hole"...."apples vs. oranges"....

As you maneuver your heli in the 3D moves that only you can make......you want an antenna system that is "omni-directional".....that its gain pattern doesn't change...when the antenna orientation relative to the Tx controller varies.....

So it can "hear" your Tx..."loud and clear"....no matter what maneuver you're doing....and....
while doing such maneuvers....your onboard telemetry systems are reliably relaying the data back to the Tx....

This is what the "H-Stub" DIPOLE antenna system does....at 2.4GHz.....by introducing differential RF phase shifts relative from one dipole antenna element vs. its "twin" dipole antenna element...on the other side of the PCB.

This differential RF phase shift....that provides better "omni-directional" reception....
is most practically accomplished by using the width of the satellite PCB to add this
phase shift.....

Both satellite dipole elements are "driven" directly from the RFp and RFn I/O antenna pins(I/O Rx and Tx'ing telemetry)......in "sync"...

As a result, by the width of the PCB....~3/4"....a phase shift is introduced...because "light" travels ~ 1ft/inch.....

Works very effectively!

There's is no way that "shading" can change this well defined effect....

This provides "omni-directional" reception....at ALL orientations...within the limits of the RF range...which is what's required for this antenna system application....at 2.4GHz.

While having both dipole elements "unshaded" by the frame is the ideal condition(for absolute max range), it matters not one iota which dipole element is "shaded"...as I have maintained...and this FACT would be verified by a simple call to Cypress using the TOLL FREE #.

Having tried to dispell this erroneous myth....I will say this...

The connectors used on these satellite Rx's....are connectors used on PCB's in...
non-vibrational environments....most of my issues(one didn't bind, etc.)....were due to
bad connections at the connector.

I use "liquid electrical tape"....obtained at Home Depot or AutoZone...applied after
"plugging" the connector in....to mitigate any vibrations that might interrupt these
connections.

FWIW

[spykez]

Sorry, I need to dredge this up again, but since people in the know are probably watching this, hopefully it won't be seen as too unreasonable.

Just a few questions more.

1. If a SPM9645 sat is a half dipole antenna, ideally then, shouldn't both elements be not shielded vs the prior linked images which only show optimal exposure of one element?

2. What about the long whiskery pair of antennae that say futaba receivers have? Is each one a monopole or a dipole? Also, given they are long and whiskery, doesn't that length actually enable better exposure of the active antennae? Ie is this sort of design inherently better? I don't know about planks but it would seem to me that for heli's with cf and all, these'd be best trailing the arse end of the heli?

3. Similarly what was the final story about the whiskers on the AR7200BX?

Thanks gents!

[ArchmageAU]

Originally Posted by spykez

Sorry, I need to dredge this up again, but since people in the know are probably watching this, hopefully it won't be seen as too unreasonable.

Just a few questions more.

1. If a SPM9645 sat is a half dipole antenna, ideally then, shouldn't both elements be not shielded vs the prior linked images which only show optimal exposure of one element?

2. What about the long whiskery pair of antennae that say futaba receivers have? Is each one a monopole or a dipole? Also, given they are long and whiskery, doesn't that length actually enable better exposure of the active antennae? Ie is this sort of design inherently better? I don't know about planks but it would seem to me that for heli's with cf and all, these'd be best trailing the arse end of the heli?

3. Similarly what was the final story about the whiskers on the AR7200BX?

Thanks gents!

This is just my uneducated opinion, but it works for me.

1) The ideal is both element unshielded if you can manage it. If not, much better results are attained with the "active" antenna exposed with the "ground" potentially shielded by CF.

2) Better or not, my FrSky long antennas perform fine on my heli's. I just ensure BOTH antennas stick out from the frame at 90 degree angles and all seems good. The length gives more opportunity for optimal mounting. On my X5 they are out he arse end, on my 700, they stick one out each side (at the requisite angles).

3) On my 450X (my only AR7200BX heli), the mounted antennas are 90 degrees (one vertical, one parallel to (5mm away, so not touching) the boom). Never had a coverage issue to date.

[spykez]

Yeah, I'm still wondering about the whisker antenna. Are they dipole or monopole. But that's trivia.

I'm beginning to believe that having two long whiskers is going to be theoretically better having than 2 sats as they are more likely to be able to be flapping in the breeze clear of the carbon frame.

Now if I can only convince myself to go get a 14SG.

Btw, are you on archeli as well, I tried to pm / post on that archeli page, no reply. I even pm'ed an admin politely asking whether that article should be amended.

[ArchmageAU]

Originally Posted by spykez

...

Now if I can only convince myself to go get a 14SG.

Btw, are you on archeli as well, I tried to pm / post on that archeli page, no reply. I even pm'ed an admin politely asking whether that article should be amended.

Yes, but rarely on archeli. PM me on there and I receive email.

btw, I use Taranis (REALLY impressed with programming flexibility and RX cost (with telemetry) and RX performance). Went from Spektrum to Taranis. The Orange DSMX module allows me to still fly my BNF blade helis on the same TX.

[spykez]

I was actually trying to reach Costas on archeli. You know that recent debacle on main you yourself somehow got entangled in, unwittingly, spurred me into looking at that issue again as I'd always believed that archeli article.

I'm no electronics engineer, but the more and more I read, the more I believe it is a half dipole and that Costas was probably at least mistaken in that specific point. He wrote a good article all that said, I think perhaps he should revisit this, now that the questions been raised.

Thing is, I don't want to go in and make too many waves, I gues the idea is you don't want to proverbially shit on your own doorstep. Don't want to become the local pariah. hence my pm's there to people. Awaiting replies.

[ArchmageAU]

Originally Posted by spykez

I was actually trying to reach Costas on archeli. You know that recent debacle on main you yourself somehow got entangled in, unwittingly, spurred me into looking at that issue again as I'd always believed that archeli article.
....

EEngineer occasionally goes off the rails a bit, but he does have a solid electronics engineering background.

I have no idea what he was talking about on the main thread with me and DSMX specification. (btw, openly calling someone a liar without proof is usually not a good move. Especially when that someone has a good reputation, a lot of friends, is an admin, would not benefit if it was a lie and is not lying in the first place. ).

When I was using an AR8000 + TM1000 on my X5 I followed the advice from the Archeli article and never had a problem, but I'm not trying extreme range.

I now use FrSky on my bigger stuff and still follow advice from electrical engineers more experienced than me. I range test from all sides after setup, then rely on the telemetry to tell me when signal strength is low.