FS8 Copilot - Good and Bad

[JettPilot]

I have just started test flying my UAV and have run into a real problem with the FS8 copilot. The sensitivity of the reciever is so bad that it start to lose the signal and is going into fialsafe at 1/2 mile range at an altitude of 1000 feet. I am able to get the plane back every time by holding my transmitter the air and the signal imporves enough to make the turn and get it closer, but it very consistantly loses signal at 1/2 mile. I am using a JR PCM 10X transmitter, which is top quality with good output, so that is not an issue.

I have seen others fly RC planes miles away using standard transmitters and RC receivers, even cheaper ones. I really like all the computer features, flight recorder, and and the FS8 does an excellent job of keeping the aircraft level while allowing control and want to keep using it, but this is unusable with its current range. I am going to put a preamp on the receiver and see if that improves the range, if not I will have to go back to the old less capable FS4 which does not have a built in reciever ....

I FOUND MY PROBLEM, SEE THE LAST POST IN THIS THREAD FOR COMPLETE RESULTS :)

IT WAS MY TRANSMITTER BEING OFF FREQUENCY...


...

[mlbco]

I don't know what RF issues you may have going on in your plane, but one very easy trick to try is increasing the length of your reciver antenna. I would try adding 1 foot of additional wire to the end where it trials off from the airframe. Receiver antennas are not highly tuned and often benefit from increased length, especially if it gets the antenna more clear of the airframe.

Steve Morris

[JettPilot]

Increasing the leintgh of the antenna would definately help, and I may try that.... but,

There is obviously a very big problem when the reciever starts losing the signal at 1/2 mile, I think the sensitivity of the FS8 receiver is just bad, and it will take more than adding some antenna to solve it. I will try the preamp and hopefully that will work, I will post my results.

What kind of range are the rest of you guys getting with stock JR and Futaba receivers getting ?????

[Medve]

You may also want to try adding wire to your TX antenna. Same length that is going up, clip to the antenna and let it hang down. I have seen this solution advertised in HAM magazines, called a Tiger Tail. It is supposed to complete the other half of the dipole.
Haven't tried it, just an idea.

[JettPilot]

Adding wires to the antenna is a great idea :) I am hoping to get this FS8 reciever at least up to standard RC range with the preamp, then with better antennas maybe I could improve it to 5 miles or more :D

I have an 80 watt amp for my transmitter, but I dont want to have to use that every time I fly :mad:

[sesat]

80W amp?


Ram.

[JettPilot]

I meant .8 watt amplifier, with a better vertical antenna for the transmitter :p

[vpatron]

Have you checked the RX crystal? It might work well enough close in but lose sensitivity because the RX could be off frequency.

-Vince

[sesat]

Vince, what equipment do I need to check the center frequency and spread of a crystaL?


Ram.

[JettPilot]

Have you checked the RX crystal? It might work well enough close in but lose sensitivity because the RX could be off frequency.

-Vince

Yeah, I have two fo them and the results are about the same, so im sure its not an isolated problem.... :(

[JettPilot]

I got my Preamp today :D I will wire it up and do some tests and post my results !

[vpatron]

The easiest is to swap crystals. I guess he's done that.

For spread, you'd have to use a test oscillator circuit. This will have an adjustment to test the "pullability" or Q of the crystal. You usually make your own oscillator. I've never tried this.

The way I've done it in the past when I was an RF engineer was to make a loop of wire maybe 3/4" diameter, solder to a thin coax pigtail connected to a spectrum analyzer. I then use this to "sniff out" signals. You'll pick up the local oscillator which will be the desired RX frequency plus the 455 kHz IF frequency.

I also used this to sniff out digital circuits to see what RF "hash" the radio section could be faced with. I found one spare gate accidentally not grounded that was oscillating on its own and causing an RF spur.

Regards,

-Vince

Vince, what equipment do I need to check the center frequency and spread of a crystaL?


Ram.

[vpatron]

Yeah, I have two fo them and the results are about the same, so im sure its not an isolated problem.... :(

Ok, good.

A few other folks have found that their ESCs produced enough RF hash that when placed close to the receiver, it reduced their range. Since ESCs have microcontrollers, they do produce some RF noise.

Try putting the ESC away from the RX and away from the antenna.

I can't believe that you get only 1/2 mile range. Even a cheap GWS RX can do better... :)

-Vince

[JettPilot]

I dont have an ESC, my UAV is has a G-45 for power :D Ignition noise is not a problem as the reciever is 22 inches away from the engine, and I use the stock magneto ignition on the zenoah which produces very little noise anyways. Those battery powered electronic ignotions are really bad for noise, but I dont use that. The video transmitter is 48 inches away from the reciever and antenna and powered by a seperate battery. I have covered all the RFI bases pretty well...

1/2 mile was the absolute limit, at that range (measured by GPS) it was constantly going into and out of failsafe and I had to hold the radio vertical up in the air to get enough control to make the turn and bring it back :eek:

I have read a couple things about the FS8 reciever being horribly short on range, I just hope the preamp fixes it :) Its in the plane now and I will probably test it out tomorrow.

[SOCADJE]

I am looking Into Buying A FS8 system.....I cannot find other threads about the FS8 being Horribly or even somewhat short on Range..... Can you Please Direct me to the Info From others on their trouble with the FS8?....that you Mention in this thread...I would like to study this issue more before buying.... THX...

[vpatron]

Jett, I don't know what a G-45 or a zenoah is but man, it sounds like a sweet system... :)

I hope that the preamp works, but I don't know. Gain is one of the easiest and cheapest things to add to a radio design so I don't know why they would skimp say 25 or 50 cents on that.

Where cheap radios skimp on is filtering. The steeper the filter skirts (higher order), the bigger and more expensive it gets.

Have you tried other channels? The RC band is interleaved with paging and train radios or something like that so maybe in your area there is one of these next to the channel you're using.

Regards,

-Vince

I dont have an ESC, my UAV is has a G-45 for power :D Ignition noise is not a problem as the reciever is 22 inches away from the engine, and I use the stock magneto ignition on the zenoah which produces very little noise anyways. Those battery powered electronic ignotions are really bad for noise, but I dont use that. The video transmitter is 48 inches away from the reciever and antenna and powered by a seperate battery. I have covered all the RFI bases pretty well...

1/2 mile was the absolute limit, at that range (measured by GPS) it was constantly going into and out of failsafe and I had to hold the radio vertical up in the air to get enough control to make the turn and bring it back :eek:

I have read a couple things about the FS8 reciever being horribly short on range, I just hope the preamp fixes it :) Its in the plane now and I will probably test it out tomorrow.

[vpatron]

JettPilot, I sure hope an FS8 works at full-range and your range problem is specific to your setup because I just bought one!

I won't be home to try it until Labor Day.

-Vince

[CenTexFlyer]

Hmmm.... we have a couple FS8's running in electric wings and have had no problems with range at all. And there were times *I* was worried about turning around and coming back! It has always been a rock solid performer for me and I depend on it help me out when I'm shooting photos. I don't believe that I've ever had it go in failsafe mode on me at any time. Of course, I live out in the country so maybe there's alot less interference out here, but I always end up with a few "missed packets" when the flights done, just not very many. Oh yes, and I'm using a Hitec Eclipse with the Spectra module.

CTF

[SOCADJE]

Ok Jettpilot..You mentioned your Experiences with the bad Of FMA FS8 CoPilot...and the thread states THE GOOD AND BAD.....SO..Any Good Things to SAY?

[birdman11787]

Seems to me that puts you at about 2800 feet away and my guess is out of sight for most RC models. That receiver was designed for RC models flown by your average hobbiest..... not for piloting UAVs beyond visual range.

[kd7ost]

not for piloting UAVs beyond visual range.

Maybe so as far as the manuacturer is concerned. But, this being the UAV section, we carefully push the limits and share experiences. We find out how well it really works. 2800 feet is certainly well within see and avoid abilities.

Dan

[JettPilot]

Hi Guys,

At 1/2 mile, my very large plane (1500 square inch yellow) is very hard to see, its right at the limit even with 20/20 vision. If you are flying normal sized airplanes in visual range, then you will never fly that far and not notice any range problems. If you fly the FS8 on large planes to the outer visual limits (1/2 mile), you will start to have problems and it will go into failsafe alot. If you went further you would not get it back. I had my plane go into failsafe 7 times on my 1/2 mile flight just trying to get it turned around, holding the transmitter vertical to get a little better signal etc... I tried this many times with always the same result... I use a JR PCM 10 X transmitter, top of the line stuff.

From what I read from others, standard name brand receivers will work for miles with a standard transmitter. 2thdr did a 2.2 mile flight with a standard futaba radio, and azza went to over 30,000 feet with a standard futaba setup also. So the only thing I can say is that the FMA FS8 has substandard range. I hate to see this, because its a WONDERFUL unit with lots of neat features, I am 110 % happy with the FS8 except for the range :(

The preamp experiment ended in a minor crash :mad: . I hooked the preamp to the FS8 reciever and connected it to the computer and did the noise and signal streingth tests. Everything looked good and range checked ok, so I flew it and it was fine for several minutes flying overhead and around the pattern, i tried it with the antenna pointed toward airplane, away from it etc etc....with no problem, as I started to get far away it started going into and out of failsafe at 1/3 mile, I managed to get it turned around and back to the runway, but turning short final it started going into and out of failsafe again many times, (it does right descending power off circles in failsafe) and I let it circle once and got it lined up again on final, but at about 30 feet it hit fialsafe again which took it into its programmed right hand descent into the bushes. There was no electronics damage ( I still had video and a GPS position even after the crash :p ) but the fuselage got busted up so now I have a repair job on my hands.

It seems strange that all was well and then everything went bad 5 minutes into the flight and that even on short final it was still going into failsafe. There is the possibility that someone could have turned on a transmitter on my frequency. I suspect because I asked my wife to bring me the frequency pin while I set up.. She came back and told me the channel 6 pin was gone and that someones card was in the slot :eek: After setting up I go to the board and my channel 6 pin is now there. I have NEVER seen anyone on my channel before , but my wife always gets the correct pin for me, so its not like she just couldnt find it.... Could someone have accidently shot me down? Its very possible considering the circumstances, but im not sure. I will now have time for some more extensive ground testing with the FS8 and preamp.

I think that when I repair the UAV though, I will use a JR dual conversion reciever and the FS4 even though it has less features :( .....

Attached is a picture of the UAV before the crash :)

[kd7ost]

My methodology is a little different. Equipment wise I use a Futaba 8 Channel PCM transmitter with stock receiver. I also use an 8 channel optical isolator from EMS Jomar. I have my receiver operating off of a 1200mah AA nimh pack. This lasts just about forever. On the Opto-isolator side I have two 5 cell AA nimh 2400 mah packs into a EMS Jomar battery backer. This gives me a measure of secure system redundancy as well as level shifts the 3.3 vdc Futaba PCM receiver pulses to full voltage. (Not needed except for inputs to PIC chips) You may also use servo buffers to level shift. I have enough battery power to last for 8 hours of flight. Gas is different. Only enough for 1 hour.

I have a Garmin geko 201 GPS and a PDC-10 onboard on the rudder. I have a pico alt E onboard for the Elevator altitude control. I have a Co-pilot on-board employed in roll axis only. (It's employed all the time) Before flight, I always put my location into the GPS as a waypoint and then tell it to "goto". Now, if a failsafe situation occurs for any reason, the devices I mentioned are enabled by the PCM receiver and the plane comes back to me and loiters overhead giving me time to analyze the situation and take appropriate action.

I am also very fortunate that I have many places to fly that are not AMA fields and that even if my plane could fly off, it won't make it to civilization before the fuel runs out. I count my blessings for the space I have here in the high desert.

I don't know how far I can fly with a standard RC system. It varies depending on a number of factors. I fly see and avoid with full RF LOS to my UAV at all times. I have ventured to the edge. You can tell because the AV camera tilts up to see ahead, and the plane begins an immediate turn to come back to you. PCM or similar by itself doesn't do much in these situations unless you use it to enable other devices. Devices that have a measure of programmable intelligence.

I haven't reset the GPS trip data in the platform since it was installed in the new plane this last spring. It now reads in excess of 1000 miles covered. These are all test and photo flights that again, are all with Pilot in control, Via commercial RC system LOS, see and avoid with a few, "Whew, glad that GPS and PDC-10 are there" moments.

Thats the way it works for me in my little world. :)

Dan

[SpinDoctor]

Sounds like you need to add a little rudder into your failsafe programming, so your plane can circle back when the signal is lost.

Instead of range testing the FS8 at the risk of your plane, why not install a standard rcvr on the same channel, in parallel with the FS8; using the FS8 to record hits.

Pete

[evermax]

Jett,
I have only had a few flight with the FS8 and have the same feeling.
I often have failed range tests on the ground and have yet to figure whats up.
I have moved my BlackWidow 1watt, further away but fs8 still seems weak as far as ground test signals. And only have test flown it with the Fialsafe lit when returning.
I am new to the fs8 and working on another plane thats going to be fulltime home for it.
Have you come across anything that has helped?
FYI I using a Futaba 9CA Trans. With a bunch of Gear, (BW reciever, 5" lcd, and nicads attached to it.) Sure that doesn't help, New rig will remove and seperate all that from the trans.

Thanks
Evermax

[JettPilot]

After some pretty extensive ground testing, I found that the range problem can be solved on the FS8 with a reciever preamp :) . The FS8 reciever just is not sensitive enough by itself and the range was much less than my top of the line JR reciever. After putting this preamp on my FS8 reciever (pictured below), the range was increased to almost exactly match what I could get with my JR.

Thinking that might get even more range, I put the same preamp on my JR reciever but that did not do me any good :( It appears that the JR reciever is sensitive enough and the preamp just does not help it...

The only bad part to this whole thing is that the preamp requires 12 volts.. Wanting to use my reciever battery for this, I put in this DC to DC converter that steps up 4.8 volts to 12 volts. It works like a charm, and the whole setup draws about 10 milliamps :p But, this little jewel is what cause my crash :eek: When I put this next to my reciever in ground tests, it totally wiped out the signal on both my JR and FMA recievers :mad: I still want to use this, so I am going to get some torrid cores and shield this thing and see if I can cure the RFI.

[JettPilot]

Upon further testing, putting the receiver preamp on the FS8 works very well. I get all the range with the above pictured setup that I get with my JR receiver :D What I have not been able to solve is the RFI from this little step up DC to DC converter :( I completely wrapped it in copper that was grounded to the system ground and put a ferrite choke on the leads, and moved it two feet away from all other electronics and it STILL wiped out my radio at a very short range :mad:

I have two DC to DC step down switching regulators on the same airplane and they do not cause me any problems, but for some reason that step up regulator puts out a ton of RFI that I cant get rid of...

[vpatron]

Hi Jett, that's really surprising and actually dissapointing of FMA, actually. What this indicates is the front-end noise of the FMA is quite high so the additional preamp helps out. Knowing this, it also means that they did not already add an internal preamp (an LNA -- low noise amplifier) to improve the overall receiver perfomance, or if they have, its performance is inadequate. Man, for the price of the receiver, I thought they would at least add an LNA.

Can you get an amp that can work off 4.8V directly? Being hams themselves, the Hamtronics folks might be friendly enough to show you how you can modify the bias circuits to run off 4.8V if it is possible (and I would guess it is).

Regards,

-Vince

[JettPilot]

Yeah, it is dissapointing that FMA didnt make the reciever part of that better :( ... The FS8 is such a neat unit with so many features, I would really like to use it :p . I have heard a growing number of people on the forums start to complain about short range with the FMA reciever. Looking at the cheapness of some of the FMA conponents its very obvious that they were working very hard at saving a few dollars in manufacturing costs... :mad: So its not a suprise that they came up with a substandard reciever. I would have much rather paid more for the unit and had good quality parts and reciever performance :rolleyes:

The built in voltage regulator in the preamp is an 8 volt unit, I already thought of bypassing that... But contacting them is a good idea and they may have a way to run it off 4.8 volts that I had not considered. Thanks for the advice :D

JettPilot

[vpatron]

I'm fairly certain it would only need some changes in the biasing resistors. The question is whether they'll give that info... :) Good luck to you!

-Vince

[JettPilot]

I'm fairly certain it would only need some changes in the biasing resistors. The question is whether they'll give that info... :) Good luck to you!

-Vince

Great advice, actaully there is 8 volts going to the drain of the FET, but it might still work at 5 volts. I just emailed the company as asked them... Why didnt I think of that :o

[vpatron]

Jett, If you don't get a reply from them AND you can get a hold of the schematic, post it here and I'll see what I can figure out. It's been many years since I've designed amps but what the heck, I'll take a whack at it... :D

Besides, I still have my FS8 in the box and having second thoughts so if the preamp works really well, maybe I'll do that and open the box.

-Vince

[JettPilot]

I wrote a post about my FS8 range problems on the FMA factory support forum, and the guys from there told me that the FMA reciever is very narrow band compared to standard RC recievers, and that if my transmitter was off frequency the FS8 would reject the signal more quickly than a stock JR reciever would. FMA checks transmitters for free for those that have purchased FMA receivers. I live in the area where FMA is located so I drove up there yesterday to take them up on thier offer. When I got there their tech guy Howard started on my transmitter right away, and found it to be way off frequency and overmodulated pretty badly. Howard carefully tuned my transmitter and also tweaked my recievers for dead on accuracy. Howard also suggested that I run an opto isolator on the plane as ALL my servo leads on my UAV are over 48 inches ! The FS8 does not always like long servo leads... So on Howards advice, I put the opto isolator in line even though the FS8 worked ok without the opto isolator...

In flight testing today, the FMA receiver performed very well even with a strong video transmitter onboard :p I flew at an altitude of 600 feet (measured) and collapsed my transmitters antenna, and while the FS8 would get into an intermittent failsafe, I had full control of the model and could fly around with no problem. With the antenna extended control of the UAV was perfect.

It seems that the FMA reciever is very narrow band and will reject a transmitter that is off frequency, where the wider band JR recievers will more easily accept an off frequency signal (this is bad :mad: ).

When I run my strong video transmitter on my plane ( 5 watts :eek: ), the FMA FS8 reciever rejected interference better than my JR reciever does and gave me better range :) I dont need the preamp on the FS8 anymore :p I now have two FS8 recievers and will eventually replace all my recievers with FS8's due to the performance and all neat features they have :)

While I was there I bought the data recorder for the FS8 and its really neat. I can see signal streingth to the reciever, voltage, control position, airplane attitude, etc, etc. :D The FS8 has lots of really neat features... The incredible support that FMA gives its customers is icing on the cake.

JettPilot

[icebear]

Thanks for the update Jettpilot!

That definitely answered my latest question re my first UAV. I ordered my FS-8 today!

Just one more question - the opto isolator helps when you have long servoleads I understand. Would it also be helpful when you have a lot of other gear connected, i.e. Picopilot, GPS, etc installed in the plane? I suppose the opto isolator goes between the receiver and the servos, but could you also use the Opto isolator between for instance the Pico and the Rx?

/Icebear

[JettPilot]

You could use the opto isolator between the FS8 and any device. My FS8 flew without the opto isolator, but after Howard recommended it I had one sitting in a box that I wasnt using so I stuck it in there to avoid any possible problems in the future.

Other devices will tend to act as isolators, my AP4 definately would NOT work with long servo leads, but when I connected it through another device, any device, they act as servo buffers and it would then work. Of course the opto isolator is best.

I wired my opto isolator so that it just passes the battery power through to the reciever. I dont want to have two batteries and two switches, thats just a bigger chance for failure...

I am running a Jomar Products 8 channel opto isolator, Dan recommended it and im very happy with the way it works.

[icebear]

Thanks JettPilot!
I was wondering about the need of an extra power source but you already answered that one too...
I'll look up the Jomar - saw that FMA had one too (4 ch - $39.95).

Icebear

[vpatron]

Jett, Great info. Thanks! I will open my FS8 package. :D

Yes, I heard the same thing about Berg receivers: very narrow band and subject to off-frequency TX. Hitec is near me, so I stick with their stuff for this reason.

-Vince