Franco2fly

That's kinda my thought as to how the Dongle works as well.  Now if we persue that line of logic, the GPS drop outs could be more due to the position I have the STi unit than I previously thought.

I wonder what would happen if I moved the iPhone from inside my coat (I usually drop it Dongle side down into a top shirt pocket) to a Belt holder where the STi is in a different orientation ( say length wise )

Another test would be to download the GPS data from the DX8 to Google maps and see if the DX8 data has drop outs in the same locations...

Oh boy we have some testing to do here.


KKKKFL

JohnB96041

I think it takes a link between the Tx and Rx before the tm1000 can transmit to the STI module. Try it. Get everything running and then turn off the Tx. The link is broken and the STI signal will be lost.

Franco2fly

I don't believe the TM1000 knows what devices are listening, it just has to have the Ack/Nak between the DX8 and the TM1K... but there is obviously some interaction that we don't understand.

I sure would like someone to compare the data that is displayed on the iPhone to GPS data that is collected in the DX8 (using google maps)... This would tell me if data was lost ormasked before being senton the downlink.

KKKKFL

Len Todd

There is no Ack/Nak. The TM-1000 is broadcasting the data without error checking. If there were Acks (error checking) there would not be any lost telemetry data. Once the link between the Plane's "control surface Rxer" and the DX8 is established, the TM-1000 broadcast of data is enabled. As I understand it, that link essentially turns on theTM-1000. When it is on, it is broadcasting.<o></o>

As I understand it, the DX8 and the STi are independently receiving the TM-1000's broadcasted signal, like two different cars going down the road listening to the local music station. The cars do not acknowledge (Ack) the fact that the music is being received or not. You run your car out of the broadcaster's range and you do not get the music, etc. You run around in the fringe of that broadcaster's range and you only get part of the music. We were discussing what affects the range of the signal broadcasted by the TM-1000 and what could possibly cause that range to be intermittently shortened.

As far as testing, for any test to be a good test, eliminate as many variables as possible. I would start with the STI on a table next to the area you are using the DX8, with the STi’s antenna/STi oriented as it would be when you typically use it. In your pocket or near your body, the STi could be negatively impacted. When I use handheld radios I typically get them off my belt and out in front of my face, etc. When I am in the fringe areas, I get the radio up in the air and away from my body, especially when receiving. And, I use a heck of lot more power than what is used in the RC world. Once you eliminate as many variables as possible, then do the test. Record the result. Then change some of the variables, one at time, back toward how you would like to use/hold the device during normal flying and determine and record each change's impact.

You know, there is another effect I previously eluded to but did not fully explain. If the STi is too close to the DX8, the “control surface signals” sent by the DX8 could actually overload the front-end of the STi's receiver thus block the TM-1000’s broadcast. This could preclude the STi from receiving the data also. I left that one out of the discussion because the GPS data loss described seemed to fairly intermittent. But after thinking a bit more on the subject, depending on where the two devices are located and how the antennas are oriented, the physical distance between the two devices could cause “Rxer front-end overload.” This is another variable that could be "in-play" here.<o></o>

Bending over with the STi in a shirt pocket or temporarily moving one or both of the devices around as we fly could be a factor causing the effect to be intermittent. Without knowing the actual frequencies used at the time, the RF power levels, antenna gains, receiver sensitivities, RF filtering in the Rxer design, etc., etc. this would be a hard one to technically figure out. But, a simple controlled test could prove/disprove if there actually was a potential effect. Move the STi closer to the DX8 when operating a plane’s control surfaces and see if there is a distance at which the STi starts losing data. If you do this for several minutes, you should account for the DX8 potentially changing frequencies a few times during the test. Again, I am not sure any of us know how often the frequency changes. Depending on the STi’s design, one specific frequency could have an impact and another frequency in the same band may not (another RF variable). Consequently you would want to run the test operating the control surfaces of a plane and receiving the TM-1000’s broadcasted signal for a while (e.g. 5 minutes.) while moving the STi closer and farther away from each other. Kind of a crude test. But, it should identify the effect, if it exists.

Franco2fly

That said,
once link between the plane and the DX8 is established, then the TM1K links and so does the STi...  I should be able to turn off the DX8 and still have the TM1000 sending data, albeit only the STi device listening...  I think it was czorzilla that said that the STi data stops...

I'll go test this later this afternoon.

KKKKFL

czorzella

Franco, I didn't say that STI data stops....also I have never tested turning off the TX while keeping the STI running, but I'd say that one doesn't interfere with other. Anyway, this testing is really easy to accomplish and I'll give it a try when I get home later on tonight.

Perhaps it is important to mention that I never left the phone close to my body while flying; I always like to lay it down on top of a bench near by with the STI interface pointing towards the sky, but one day happened that I left the phone about 65' (20 meters) from me and it actually received the telemetry data.

Franco2fly

Ok,
Just ran that test...
Don't know who to credit,but it is true...  you can have everything all locked and working with read outs from STi...  the second you pull (shut off) the DX8, the STi drops link needles disappear...  So there is SOME relationship between the STi and the DX8..  The TM1000 must have some working relationship with the airborn receiver that if link is lost the TM shut down the sending of data.

I'll go try with a second model just to make sure.

KKKKFL

Franco2fly

Test 2  Turn off receiver but leave DX8 on and leave STi application running...

This was interesting... I got everything up and running made sure the readings were coming, ie wiggled sticks and watched voltage reports.. all working as predicted..watch temps move.  after a couple seconds I thought I would reverse the process, ie leave tx and STi running shut down receiver...

What happened was the needles disappeared on the STi HOWEVER, the link light on the STi stayed lit...  It was like the STi was receiving data from the DX8 not the TM1000 and since the Receiver and TM1000 had no power there was no data to display, but the STi thought it had link....


Very interesting..


KKKKFL

czorzella

Cool!!! These results are the answer to several of our questions.

Franco2fly

I'm not sure I would go that far...

It does seem to indicate that the STi is linked to the DX8 and not to the TM1000. Let see if Mister Todd has any ideas given these findings.

This would also make the GPS drop out be in both the DX8 and the STi, since it looks like the STi is some how getting the data from the DX8 and not from the
TM1000. Any lost "real time" data going to the DX8 is gonna be missing in the STi as well.

KKKKFL

AndyKunz

I answered these questions ages ago, when we first introduced telemetry.

The DX8 talks, the rx listens. The TM1000 listens, too. Then it talks, when it knows the DX8 is silent. The DX8 listens, the STi listens for the TM1000.

If the TM1000 doesn't hear the DX8, it doesn't talk, but the DX8 and STi still listen for it.

The TM1000 has less range as both rx and tx than our standard receivers, by design. This way you can know that you're getting out of telemetry range (the tx will tell you, if you turn on alarms on the Flight Log). The STi antenna is confined and probably not nearly as sensitive as the DX8 (acting as rx), and when you put it up against your body, it's even less able to hear the TM1000.

Andy

Franco2fly

That explains the link light inside the STi staying on. Also gives a hint as to moving the iPhone out of my inside jacket pocket to improve reception

Len Todd

Well said Andy. I like the way you can be so brief and get the message across!

Franco2fly

So, to summarize..

Best Aircraft reception, place a satellite receiver with antennas in vertical plane, and main rx antennas in horizontal plane. For the TM1000 I am going to use a cocktail straw (available at any Mickey 'D's") poke it through the belly of the plane at a 45 degree angle and feed the TM1K antenna out. (in my RV-4 last night, I made this change and approximately the last 4 inches are now through the body.  Question here, the last inch is exposed wire, is this the actual antenna, or is the antenna the entire wire as soon as it leaves the module case?).    Now there are no "end point" dead zones. 

As for the iPhone and STi,  I sure would like to get an extension cable to plug into the bottom of the iPhone that was about 24 inches long.  The iPhone could stay inside my coat top pocket, and the cable could run out along my collar and up to my Ball cap where I would plug it into the dongle and then velcro the STi dongle to the outside of the hat band.  Velcro'ing the whole iPhone up there is just a little TOO geeky even for me...

Another option would be the use of wireless technology to get the audio to my ear from the iphone which could be placed on a stand nearby any of the flight line stations.  This is an expensive way to go, and I do not know anyone that has broken the code as to which bluetooth devices would actually work.  At a minimum, this approach is gonna cost a "C" note.   I've also thought that clipping the iPhone holster to a jacket that has epulets so that the dongle faced out away from my body  (kinda like the setup the police use where they clip the microphone up near a lapel) could be an option...  Bottom line here is that it needs to by out and away from my body for best reception of the TM1000 signal.

Will take some of these ideas to the field tomorrow and let folks know how I make out.


KKKKFL

AndyKunz

The Apple extensions are available and yes, that would help.

Using a BT audio is probably a bad idea. You're talking about putting a second 2.4g transmitter in close proximity to your telemetry receiver - perfect way to make sure you don't get good telemetry reception.

Andy

Franco2fly

Would there be concern were I to clip the iPhone to the handle of the DX8? It was a passing thought, but I dismissed it favoring the lapel clip approach instead. Another idea revolved around those armband things you see joggers use to listen to music while running.KKKKFL

AndyKunz

To the antenna?!?! Bad idea! Arm band might be better than chest pocket.

Andy

Franco2fly

Not the antenna, the silver handle..  doesn't matter I discounted that approach early on, just too close to the Transmitters antenna.  Joggers arm band seems good, I also bought a belt clip case that allows the iPhone to be tilted.  You can clip to your belt, but twist the holder so that the phone is parallel to the ground.

I'll try both this weekend


KKKKFL

Len Todd

Remember that the closer you get to the DX8 the more potential there is to overload the STi's Rxer. But if time domain multiplexing is being used, theoretically separation distance between the DX8 and STi should not be an issue precluding receipt of telemetry data. That being said; there are limits to everything. Testing would be a good idea though.

I attached a few more thoughts about telemetry data loss and lack of documentation, etc. that Andy's above statements initiated.

czorzella

Franco,
Concerning the iphone cable extender, maybe this one will do: www.radtech.us/products/procable-30pin-dock-extender

Andy,
As for placing the iphone near the antenna, I fully understand the consequences and that is why Ialways place my iphone away from the transmitter. My question:Is there a minimum recomended distance between the TX and STI to assure that one doesn't interfere with the other? Reason being is that if required distance is short enough, perhaps we could use one of those transmitter trays for FPV to hold the Iphone above the TX and antennas about 8 inches (20 cms.).

Franco2fly

From my past "tester" experience, I really like to maintain  the same configureation and limit as many of the variable as possible.  That said, I can report that the data losses WRT GPS are ALL in the same orientations and same locations at the same field...  Most testing of the GPS has been done with my 1/4 scale RV-4 where the TM1000 antenna runs from just under the leading edge of the wing back to just behind the trailing edge.

The other plane that I have used is my RussiaStik...  same exact orientation, and curiously, same location of drop out, however, the drop out areas were smaller  (gives rise to the"Mask" theory)

If you envision a race track in front of your position on a flight line, I always lost the GPS data when doing a landing approach where I would make a left turn on to a base leg (facing East, and looking to my left). The GPS tracking arrow would not reappear until almost touch down, so it was absent for a good bit of the final approach after dropping out on the turn to base.  The electric plane seemed to regain GPS sooner.  There were also drops off to my right but these were of much shorter duration...  The difference here is that at that end of the race track I was always at a higher altitude... (80 feet on the landing approach for a start...  other end of the runway I'm between 200 and 300 feet.)


I'll post a picture and explain where I see the drop if that helps making some evaluations.


KKKKFL