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  1. #1

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    TWO ANTENNAS REQUIRED!

    A Reprint from my 'Other Site', but still worth the read.

    Yes! it was my plane.


    Now I had a β€˜Exciting Experience' This weekend!

    I was enjoying a great Flight with my 50cc Extra 300 and as I was getting into position for a landing I lost contact with the plane! It went into a slow spiral down and I had NO Control! (Yes I was three mistakes high and I needed two of them!)

    After a terrifying few seconds – the plane started to answer to commands again and I was able to bring it home in a hasty and not too pretty fashion.

    Thirty minutes later I had screwed up my courage and took off for a second flight. It was GREAT, lots of loops and spins – then I set up for another landing in the same location… YEP! I lost control again! And sure enough I regained control after a few seconds and brought it home shaken but safe…

    TECHNICAL DETAILS?
    Hitec 2.4GHz system - Optima 7 Receiver – Single antenna.
    1 - Two 2000ma batteries on a 'BATSHARE' parallel system for the Receiver and a third 2000 ma battery for the engine. All are new this year and were fully charged on the Thursday the flight was on Sunday. No Flights since charging.
    2 - Antenna is mounted parallel to the main Fuse.
    3 - Wooden Prop, Aluminum Wing tube and CF Landing Gear.
    4 - Servos are not digital - all are new (1 year old) and there are six servos of different sizes (depending on the function)

    I have had 4-6 flawless flights on this plane and this glitch was a first time event - it has been suggested that I rebind the TX - RX, plus I plan to reposition the Antenna.

    After all was said and done I think I know what happened…
    As I went out to set up for the landing the single antenna was in the β€˜RF Shadow’ cast by the engine (DA50R) and I lost the signal – the Hitec System requires 2-3 seconds to β€˜Reacquire’ contact and in that time you can do nothing but pray…

    So my solution is to swap the Optima 7 for an Optima 9 receiver – the O9 has TWO antennas and the differing placement of the antennas should remove/solve this problem.


    FYI
    I have six other Optima 6 Rxs and I have not had any such problems before… but they are all in smaller AC.

    *******
    Well Guys;

    I had a Optima 9 just sitting around so I loaded it onto the plane and did the BIND. (Now I have TWO antennas- one in the original position and the second is on the other side of the plane mounted vertically!)

    To answer some of the normal questions;
    -Yes I have flown at this location before (my home field),
    -Yes I have done this approach before with the same AC...two weeks ago - no problems,
    -Yes I have flown multiple other AC here on 2.4 with no such problems,
    -The Antenna WAS oriented along the axis of the fuse - away from the engine and batteries and not near any servos but within 8" of the CF Landing gear.


    I just read a footnote in the Hitec manual that recommends the dual antennas of the Optima 9 for LARGER AC due to the power, Carbon fibre and big engines etc.

    BUT
    I have flown plane in this pattern at least six times before...
    *******

    The Extra Lives to fly another day!

    The sky was clear and the winds were right down the runway so it was a good day to go flying!

    Although a little tense I took the Extra up and had a wonderful 6 minute flight that took me all over the area - then the landing approach from the west... NO PROBLEMS!

    As I said previously; I changed to the Twin antenna Optima 9 and... went flying!

    I had Five flights 5-10 minutes each without incident, I was practicing my landings / Touch & Go and other than the normal dumb thumbs - all was good!

    So I'm calling this one SOLVED! Big airplanes need TWO Antennas!

    OK back to the workshop everyone!
    It\'s Time to Kick the Tires and Light the Fires!

  2. #2
    raptureboy's Avatar
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    RE: TWO ANTENNAS REQUIRED!

    What type of battery? Nicad, NmH, lipo? Nicad and NmH can lose quite a bit of power over 4 days, but your problem sounds like it was solved with the receiver. I use airtronics and they have 2 attennae at right angle to each other. No problems yet in 3 years in all sizes of planes. Glad to see you beat the devil 2 times
    If what you believed to be true was false would you want to know the truth?

    "You shall know the truth, and the truth will set you free".

  3. #3

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    RE: TWO ANTENNAS REQUIRED!

    My question would be..............After the first incident, WHY WOULD YOU TRUST YOUR 50CC TO THAT JUNK???

    So you're saying that a smaller sized bird isn't worth as much as your 50 cc, so it's ok to risk them??

    Not trying to start an argument here....trying to understand your illogical decision to trust ANY bird to a system with obvious brownout issues and flaws!!
    RC MANIAC-PRO BRO 1900-AMA# 95841

  4. #4
    speedracerntrixie's Avatar
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    RE: TWO ANTENNAS REQUIRED!


    ORIGINAL: RC MANIAC119

    My question would be..............After the first incident, WHY WOULD YOU TRUST YOUR 50CC TO THAT JUNK???

    So you're saying that a smaller sized bird isn't worth as much as your 50 cc, so it's ok to risk them??

    Not trying to start an argument here....trying to understand your illogical decision to trust ANY bird to a system with obvious brownout issues and flaws!!

    While I agree that an investigation should have taken place before another flight. I can attest that the A9 is not junk. I have hundreds of flights with mine using both the Optima 9 and 7 channel receivers. The airplanes include 50cc aerobatic, electric pattern. full house composite sailplane and nitro powered pylon racers.

    I do use the dual antenna 9 channel RX with the gassers as gassers tend to have more potential for RF issues. Everything else has the 7 channel single antenna and no issues


    This is NOT a brand issue!


  5. #5

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    RE: TWO ANTENNAS REQUIRED!

    Thank you Trixie for your comments, the Maniac seems to have issues with Electronic brands that he disapproves of...

    After having had so many good flights with my entire fleet I had no issues with my Radio - as to that AC - trust me - I spent the entire break period checking out the AC and controls it was all working, the only final test was another Flight... which was successful - until I duplicated the conditions EXACTLY!

    Same altitude, Quadrant and Approach equaled the same loss of contact and then re-establishment of control. A quick confirmation of the fault WITH A CALCULATED RISK.

    Let's face it -the entire hobby is based around calculated risk - it is often a gut wrenching experience to Maiden an AC - but we do it anyway...

    Some three months later after numerous successful flights, I felt I should share this Two Antenna Solution with the folks on RCU. Take it for what it is worth - and have nothing but Happy Landings.
    It\'s Time to Kick the Tires and Light the Fires!

  6. #6

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    RE: TWO ANTENNAS REQUIRED!

    I was having some trouble with my DX8 and along with the positive input came the negative name calling that dosent help anything....Its like you are stupid to have purchaced that brand and should have knowen better...Thank you for bringing this to our attention...Maby an aircraft or two will be saved because of this information......And that is worthwhile in my mind .
    Ken , Biker BC Cub Brother #6 Ultra Sport Brother # 100 Tiger Club # 7 Pulse Brother # 1 Sig Brother # 58 Top Flight Brother # 9

  7. #7
    kenh3497's Avatar
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    RE: TWO ANTENNAS REQUIRED!

    It may have been as simple as repositioning the antenna to vertical at the top of the fuse???? In any case you did the safe thing buy switching out to the 9 channel RX. I'm happy you had success and thank you for sharing.

    I just purchased a new Hitec A9 and can not be happier. It replaced my old JR X-347 converted to 2.4 with a Spectrum module. I never had any issues with that set up but wanted a more capble TX and I got a smoking deal on the A9 with 4 RX's. One 9ch, two 6 ch and a Minima 6E.

    Ken
    Sent from my Dry-Erase-Board


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