SOLVED - Tx / Rx Issues

[goldfishrock]

Hi Guys,

I was wondering if anyone out there can advise on the best placement of antennae after changing the stock receiver. I recently changed the stock receiver and transmitter for a Futaba 8J with a R2008SB Receiver. Everything has been working fine however I am experiecing a range issue.

The problem I’ve been seeing is that most of the time the P2 works as expected and then I climb it to approx. 250m and lose control .Needless to say the first time this happened my heart stopped until I saw the failsafe kick in (IOSD shows it in the bottom left of the FPV monitor). Once it came down to about 150m I was able to gain control and land it.

I opened it up and repositioned the antennae, this time placing one down the front leg and one out along one of the arms, maintaining that 90 degree separation they talk so much about. It flew four times faultlessly yesterday including a 300m ascent over my head then just before the sun went down yesterday. I made sure all batteries were fully charged and flew it once more, this time losing it at 250m over my head, again. Once again, saved by the Failsafe which descended it to about 200m where I took control back and landed.

I am interested to hear if you guys think it’s an antennae position issue of whether the Tx / Rx could be faulty. Either way, Obviously I am reticent to fly it anymore until I can be sure the problem has been addressed.

 

[ianwood]

Re: Tx / Rx Issues

Directly over your head is tricky in terms of signal. The dipole antenna on your transmitter works best when the broad side is facing towards the P2. If you have the tip of the antenna pointing towards the P2 as might be the case when flying directly overhead, your range will be a lot less. So if you want to go straight overhead, best to position the antenna to keep the tip perpendicular to the P2. Imagine it as a giant doughnut radiating from your antenna (z):

As for the P2 itself, keep your FPV TX antenna as far away from the RX antennas as possible. Some people put both antennas pointing down in the legs which will probably give you best horizontal range but having one horizontally on the underside may be good for when you're mostly overhead.

 

[goldfishrock]

Re: Tx / Rx Issues

Thanks for that Ian, that does make sense.

I think what's thrown me is that on several occasions I flew it 3x higher than I did this time using the stock Tx/Rx and after fitting what I believed to be a superior radio system, I started to get the problem.

The Antenna in the Futaba 8J is internal so I presume it points stright up when I hold the handset in the 'normal' position.

 

[ianwood]

Re: Tx / Rx Issues

Thanks for that Ian, that does make sense.

I think what's thrown me is that on several occasions I flew it 3x higher than I did this time using the stock Tx/Rx and after fitting what I believed to be a superior radio system, I started to get the problem.

The Antenna in the Futaba 8J is internal so I presume it points stright up when I hold the handset in the 'normal' position.

Hmmm, maybe someone with an 8J can chime in.

 

[EMCSQUAR]

Re: Tx / Rx Issues

Actually the Futaba T8J has 2 antennas at the top of TX (towards handle) & Ian is correct about being directly over yourself. I have same set up and my Futaba rx is planted to side of NAZA and one antenna runs down front leg, the other lays across in front of NAZA. Local shop where I bought my Futaba warned me to keep antennas away from compass cable and FPV trans and to keep a space between NAZA and Futaba Rx.

 

[goldfishrock]

Re: Tx / Rx Issues

one antenna runs down front leg, the other lays across in front of NAZA

Is that the same leg that the CAN-BUS connector is on? This is how mine was setup before; I had no joy that way so moved the antenna from the front of the Naza and placed it straight out down one of the arms.



Since this was taken I have moved the Rx about 6mm away from the Naza but was still having the problem.

It was recommended by another forum to try a range check using the functionality on the 8J... I then wondered if it was possible the the Tx was stuck in 'Power Down' mode. I'll check when I get home.

Thanks for the advice so far.......

 

[goldfishrock]

Re: Tx / Rx Issues

Time for a rethink and redesign. The problem continued at irregular intervals and after asking the question on some other forums it seemed that most thought it was antennae placement. After a little digging around I found that Futaba do an extension 400mm antenna (Part (UK): P-RA2-4G/400 (US): HSP79766) that replaces the stock 100mm.

I replaced mine and decided to give maximum exposure decided to place them as low as possible on the legs where they were as far away from all the motors and lecky bits and pieces. One is pointing straight down and the other horizontally from front to rear.

I did move the CanBus connector to the rear leg opposite the compass to free up the front legs.

So far things are good…. I’ve not experienced anymore signal dropout and los of control so hopefully, problem solved.

 

[HELICOP]

Re: Tx / Rx Issues

Directly over your head is tricky in terms of signal. The dipole antenna on your transmitter works best when the broad side is facing towards the P2. If you have the tip of the antenna pointing towards the P2 as might be the case when flying directly overhead, your range will be a lot less. So if you want to go straight overhead, best to position the antenna to keep the tip perpendicular to the P2. Imagine it as a giant doughnut radiating from your antenna (z):

As for the P2 itself, keep your FPV TX antenna as far away from the RX antennas as possible. Some people put both antennas pointing down in the legs which will probably give you best horizontal range but having one horizontally on the underside may be good for when you're mostly overhead.

Did you say "giant donut"? Yummy.

 

[skeeter]

Re: Tx / Rx Issues

Time for a rethink and redesign. The problem continued at irregular intervals and after asking the question on some other forums it seemed that most thought it was antennae placement. After a little digging around I found that Futaba do an extension 400mm antenna (Part: P-RA2-4G/400) that replaces the stock 100mm.

I replaced mine and decided to give maximum exposure decided to place them as low as possible on the legs where they were as far away from all the motors and lecky bits and pieces. One is pointing straight down and the other horizontally from front to rear.

I did move the CanBus connector to the rear leg opposite the compass to free up the front legs.

So far things are good…. I’ve not experienced anymore signal dropout and los of control so hopefully, problem solved.

Still humming along OK?

Can't seem to get a line on those extension antennae. Grrrr... In the US anyway.....if anybody knows a place with them, please post it! Otherwise, I'll try to get them from the UK....

And.... How do they connect to the RCVR?

Thanks!!

 

[goldfishrock]

Humming along perfectly. I've not had a single reoccurance of the 'loss of signal' problem I experienced. It seems that placing the antenna tips anywhere near the ESCs causes the problem. I've flown it significantly long distances away to prove it's working well.

I've done a little digging and in the US it seems those antennae have a different part number (I'll amend my other postings carrying the UK part number to reflect the US version too). Have a look around for HSP79766. In the UK they are advertised as either 400mm extensions or BOAT ANTENNAE (so don't worry if you come across that terminology). I'm sure if you still draw a blank a quick call to the Futaba Service Line over there may yeild results?

As for fitting them, that hardest part is, once again, undoing all those screws to get into the P2! The Futaba Receiver opens up easily by just pushing in the little plastic lugs on one side and removing the top cover. The board is easily removed and you'll see that the antennae are attached using the standard antenna plug that most receivers use (including the P2 itself). There a couple of small rubber grommits you have to remove from the old ones and fit to the extensions but there is nothing to it.

If you need a hand just let me know.

 

[Jdacal]

Thanks for that tip Goldfishrock. Just ordered a set from proshophobbies, showed one in stock. Hopefully its not the same one everybody that read your post ordered. :lol:

 

[skeeter]

Grrrrr!

 

[goldfishrock]

hahahaha.... Sorry skeeter

Aparently in the US, Hobby Services can supply

http://www.hobbyservices.com/

 

[Arseniaa]

Re: Tx / Rx Issues

Time for a rethink and redesign. The problem continued at irregular intervals and after asking the question on some other forums it seemed that most thought it was antennae placement. After a little digging around I found that Futaba do an extension 400mm antenna (Part (UK): P-RA2-4G/400 (US): HSP79766) that replaces the stock 100mm.

I replaced mine and decided to give maximum exposure decided to place them as low as possible on the legs where they were as far away from all the motors and lecky bits and pieces. One is pointing straight down and the other horizontally from front to rear.

I did move the CanBus connector to the rear leg opposite the compass to free up the front legs.

So far things are good…. I’ve not experienced anymore signal dropout and los of control so hopefully, problem solved.

I had a quick question for the 400mm wires they are very very long, where do you put the rest of the wire? Inside the body? I'm trying to figure out how you did what you did because the wires I just got from Futaba are very long and go out significantly long than your photos.

 

[goldfishrock]

Just coil the excess wire and stick a little electrical tape to hold the coil. It'll sit quite happily either ontop of the NAZA or you can put them at the front of the P2 in the gap infront of the mainboard. As long as those exposed tips are outside and away from electrical interference the rest of the cable is shielded so is fine inside.

Don't kink or fold the cables though!

 

[ginsonic]

Just coil the excess wire and stick a little electrical tape to hold the coil. It'll sit quite happily either ontop of the NAZA or you can put them at the front of the P2 in the gap infront of the mainboard. As long as those exposed tips are outside and away from electrical interference the rest of the cable is shielded so is fine inside.

Don't kink or fold the cables though!

The active antenna for 2.4GHz have 3 cm. It's a standard. The rest of 37 cm from 400mm antenna are inactive (isolated).

So can use any shorted extension. On market can find 150-300 mm extensions, too.

Longest extensions are good to keep active antenna far away from electric interferences.

 

[goldfishrock]

Longest extensions are good to keep active antenna far away from electric interferences.

Exactly. I figured that the best place away from the electrical interference was on the base of the legs. Also means that (as long it it's level or above you) there will always be at least one antenna that isn't obscured by the Zenmuse.

 

[ginsonic]

Longest extensions are good to keep active antenna far away from electric interferences.

Exactly. I figured that the best place away from the electrical interference was on the base of the legs. Also means that (as long it it's level or above you) there will always be at least one antenna that isn't obscured by the Zenmuse.

I saw that your both antennas have horizontal and parallel orientation. I talk about active part of antenna. How i know best results are for one vertical and one horizontal (90 degree orientation).

 

[goldfishrock]

I saw that your both antennas have horizontal and parallel orientation. I talk about active part of antenna. How i know best results are for one vertical and one horizontal (90 degree orientation).

No, not quite.

This one is horizintally along the base of the leg (you can make out the antenna tip just before the centre strengthener in the leg).




And this one is vertically down the leg (the tip of this is enclosed in the antenna tube)




So in this configuration they do maintain the recommended 90° separation and maximum expose away from electrical interference.

 

[tylerng]

Thank you goldfishrock. I had loads of issues with the T8J dropping out at 250 - 300m. I took your advice and got me the same 400mm antenna and just finished the install in the same way you did! I hope I can do > 1km as a test just so I have more confidence doing some flybys..

btw, my antennas are exposed/without a sleeve. do you think it's ok that way? where did you get the orange tube from?