I had problems with the range on my FMA FS8 recievers. Their range limit seems to be 3/4 mile in the air compared to several miles for JR and Futaba recievers[:@] I have two FS8 units, so I know its not just a defective reciever... I have also read some other threads about limited range of the FS8 units. After some pretty extensive testing, I found that the range problem can be solved on the FS8 by adding a reciever preamp . The FS8 reciever just is not sensitive enough by itself and the range was much less than my 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 from my JR, I put the same preamp on my JR reciever but that did increase its range at all. It appears that the JR reciever is sensitive enough already and the preamp just does not help it...

The only bad part to this whole thing is that the preamp requires 12 volts and is rather large [X(]... So that makes it hard to use this in most RC planes. Any suggestions on how I can increase the sensitivity of these FS8 receivers ??? Attached is a picture of my Preamp Solution....

The FS8 has been air tested to over 5 miles in the OUTLAW system and we demoed 3 miles ground-to-ground on Wednesday with a Futaba 9CAP and 800 mw output. The range of FS8 is very far beyond visual range at 72 MHz.

One possibility is a transmitter that is probably way off frequency. It may work with your JR radio because it is broadband enough to tolerate the error.

We could test your FS8 receivers for proper tuning or even check your transmitter calibration, if you like. Please call Tech. Support at 301-668-4280.

Thanks for the reply greg That is awesome, I hope I can get that kind of range from mine [X(] I will take you up on your tech support offer I love the FS8 and would not use anything else if I can get the range I need out of it, maybe it is my transmitter module that is causing the problem [&:] I am using a JR PCM 10X


BTW, I have the 50 MHZ FS8, acutally two of them and a CP4 also Would you expect the same range with the 50 MHZ unit as you got on the 72 MHZ unit ??

Thanks

JettPilot

Yes, the range should be the same for both bands.

Let me check with Engineering to see if there are any known issues with a JR PCM 10X.

One other question for you Dave, the antenna on every RC reciever I have ever owned is 39 " which is 1/4 wave at 72 MHZ... But all the manufacturers also use a 39 inch antenna on their 50 MHZ receivers even though 1/4 wave at that frequency is about 55 inches... Im guessing its just easier to use an antenna from stock than make special ones for 50 MHZ. Is there any reason I should not leinghten the antenna to 55 inches on my 50 MHZ FS8 [sm=confused.gif]???

The more I think about your explination of narrow bandwidth of the FS8 and the possibility that my Transmitter may be a bit off frequency the more it makes sense[sm=idea.gif]. I will be sending my TX module and recievers to you to be tuned together ASAP. Thanks for the great support and I will also be buying a couple flight recorder units as soon as I get my range problem fixed

I fly a JR and Futaba 9CAP amongst others. Our standard qual validation is to fly to as high an altitude as our test pilot can see and that is way beyond my line of sight (Howie has eagle eyes) then collapse the transmitter antenna and fly as you normally would fly. We use the on board recording feaure to confirmt that only a few frames are ever missed and there are no glitches.

Everyone should have the output spectrum checked for their transmitter every two years. Unfortunatley, checks of transmitters of all makes in out facility (the check is at no cost except that you pay the shipping) for buyers of our receivers show many brand new transmitters off by as much as 1500 hz. Beyond 800 hz, any FMA receiver is narrow band enough to let you know. Of course this means we almost never get any reports of interference. The FS8 with the fail safe has been demonstrated to fly through interference caused by turning on a second JR 10X on frequency. Since you live in Sterling, just half an hour away, come see us and we will check that rascal for you.

Here is the response from FMA Engineering on the FS8 range.

1) conduct range test in accordance with the "full range test" procedure in the manual. That is, use only the RX, a battery pack, and only one servo. Put the RX on a non-conductive surface approx 2 feet off the ground. Run the RX antenna up a dowel rod. Range should be at least 200 feet with TX antenna collapsed. More likely range is 300 to 600 ft.

2) If range is O.K. in the above test, but still short in the airplane, consider installation issues. Re-route antenna. If you have long extensions, consider installing our 605SB on long extension channels.

3) if problems persist, best support will be provided if you return the RX along with the TX. We will test frequency accuracy and reset JR transmitter at no charge if it is found to be off frequency. We will also check the tuning on the FS8 RX. Customer is required to pay return shipping.

Range for 50 MHz will be slightly less than 72 MHz because antennas are not as effective.

I am fortunate to live in the area where FMA is located, and I drove up to their Facility at Frederick Mayrland to take them up on thier offer to tune my transmitter for free. I got there and their tech guy Howard was very friendly and started testing my transmitter right away. It turns out that my transmitter was quite a ways off frequency and over modulated [:@] Howard carefully adjusted my radio to the point that it was dead on frequency and modulatoin. While I was there Howard also checked and tweaked both of my FS8 recievers for optimum performance and also gave me lots of good advice.. For example to use an opto isolator on my large plane where ALL the servo leads are over 48 inches [X(]

The transmitter tuning fixed the problem. Today I collapsed the transmitter antenna while the plane was 600 feet in the air (measured) , and while it would go into fiailsafe intermittently, I had full control of the airplane and could fly around just fine. With the antenna up, my previous range issues were gone The FS8 reciever gave me better performance and rejection of the interference from my onboard video transmitter than my JR reciever does.

I also bought the flight recorder module while I was there, and its really neat to be able to see exactly what was going on with todays tests. The FS8 reciever has so many neat features that I will eventually replace ALL my recievers with FS8 units. There are very few companies that would help out thier customers to the extent that FMA does, which is just icing on the cake

Thanks Guys,

JettPilot

Greg,
perhaps you can advise. Would like to use ppm in a large gas plane and am considering acouple of your 8 channel rxs on seperate frequencies using the german act dual rf unit. Have heard of problems with certain txs being a bit off tune and having probs. Being in the UK do you have any suggestions for curing this problem should it occur?
cheers
Robin

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Has FMA fixed the FS8 receiver so it will work with my Futaba 9Z synthesized transmitter module?
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Answered by PM.

[email protected]

Currently, the only receivers we manufacture that is compatible with the Futaba synthesized equipment is our Fortress series receivers (201FM72 and 202FM72). For an explanation, please read the following:

1) Frequency synthesis is the method whereby a transmitter can be "programmed" to work on any R/C channel; not just one like normal transmitters.

2) With some synthesized systems, the circuit that "locks" on to a frequency does not, by nature, like to change frequencies.

3) When you have FM type transmitters, the very nature of FM modulation means the frequency is constantly shifting back and forth.

4) A PCM system will spend equal amounts of time above and below the center frequency when it is modulating.

5) A PPM system (normal FM like our receivers), spends half as much time above the center frequency as it does below.

6) If the synthesized circuitry for Futaba transmitters is modulated by PCM it will run on frequency. If it then receives PPM data, it might not run on frequency.

7) Our understanding of the technical issues regarding the Futaba synthesized transmitters leads us to believe that Futaba modified the standard PPM modulation scheme defined in the late 60's so that it would spend equal amounts of time above and below center frequency.

8) When the output from these transmitters is fed into a normal PPM receiver, the receiver cannot properly "decode" the altered signal unless either extra componentry is added, or the normal PPM receiver circuitry is fine-tuned to work with the Futaba synthesized output.

If a fixed frequency module is installed into the Futaba transmitters, it outputs normal PPM data and will work with all of our receivers. In our attempts to satisfy the market with smaller and smaller equipment, we have felt it is not beneficial to design our equipment to work with this peculiar transmitter. The FMA Fortress series receivers do operate normally with the Futaba synthesized transmitters, but they are larger and more costly to manufacture.

Hi Greg,

I'm new to helicopter and wonder the FS8 Flight Systems can replace the gyro in the heli.