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AM Tx as buddy-box to FM Tx??

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Old 02-15-2003, 03:50 AM
  #1  
strato911
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Default AM Tx as buddy-box to FM Tx??

Has anyone here ever tried using an AM Tx as a buddy-box together with an FM Tx? I have a Futaba Attack4 (T4NBL) I would like to use as a buddy box with my Hitec Focus6. Although the Attack4 doesn't have a trainer port, I have located the PPM signal. If I make my own cord, using the signal in the picture, is this likely to work with my Focus6?
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Old 02-15-2003, 05:12 PM
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Default AM Tx as buddy-box to FM Tx??

If I'm not mistaken Hitec and Futaba use opposite shifts in their TX's so that probably wouldn't work, unless you fed the output through a CMOS inverter which would probably clean up the signal as well.
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Old 02-15-2003, 05:26 PM
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strato911
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Default AM Tx as buddy-box to FM Tx??

Sorry Lynx, but I think you are mistaken. Research has shown that they both utilize negative shift. That is why Futaba and Hitec are compatible (unless you order the Hitec w/ +ve shift for Airtronics compatibility).

My main question is if the PPM signals are compatible, since I recall reading that the signal length per channel MAY differ between AM and FM.

Here's a screen capture of the PPM signal from the Hitec Focus 6 trainer port for comparison.
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Old 02-16-2003, 05:33 PM
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Default AM Tx as buddy-box to FM Tx??

Hi strato,

Just try it!! Just try to connect your AM-radio to your FM-radio. If your PPM?-signal of slave transmitter does not exceed 5 volt, there will be no harm to your master transmitter. The worst that could happen is that it's just not working. I'm very curious about this item. Perhaps will try it myself with an old 27Mhz Mag Gregor (UK-made) AM transmitter (first finding the code modulated signal (PPM?).

Give me some news if any trial, in order to mention it in my website.
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Old 02-16-2003, 10:08 PM
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Default It works!!!

I just did a quick test with a temporary hook-up, and it worked!

Surprisingly enough, the servo reversing switches on the Attack4 (slave) didn't have any effect.

If anyone else wants details where to tap a Futaba Attack4 (T4NBL-72) to get the PPM signal, private message me for the details.
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Old 02-18-2003, 10:13 AM
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Default AM Tx as buddy-box to FM Tx??

My club has several "Buddy Boxes" made from older AM transmitters in this way.They are hardwired at the "Buddy Box" end,and have a plug to connect to the Master transmitter.You might want to double check your connection point, I believe that the sevo reversing should work.
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Old 02-18-2003, 04:35 PM
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Default AM Tx as buddy-box to FM Tx??

Originally posted by KB9STD
You might want to double check your connection point, I believe that the sevo reversing should work.
I'll check again - it was just a quick 5 minute test without a proper plug on the "master" end. It could be that I have tapped it prior to the reversing switches though. If the reversers don't respond, I'll scope it again to see if I can get them working too.
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Old 02-25-2003, 03:22 PM
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Default AM Tx as buddy-box to FM Tx??

Originally posted by strato911
I'll check again - it was just a quick 5 minute test without a proper plug on the "master" end.
Any progress?
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Old 06-11-2003, 05:58 AM
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Default AM Tx as buddy-box to FM Tx??

Hi,


I am just trying to see how to use my old Futaba Attack-4 AM Tx
to control FMS simulator, which is basically the same problem as to try to use it as a "buddy box".

From the look of the circuit board, I suppose that the IC is the doing the actual encoding. So I searched on the net and found that this CD8081N is the same thing as the NE5044.
Datasheet here: http://www.mh.ttu.ee/risto/rc/electronics/ne5044.htm

From that datasheet, I suppose that this is the output ie pin 11
that we shoudl be after.
I had a very quick try last night but the signal did not quite look like I expected. Is this really PPM?

I will try again with a proper setup (did not feel like getting the Iron out last night) and let you know what I find.
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Old 06-12-2003, 06:48 AM
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Default AM Tx as buddy-box to FM Tx??

Hello again,


Took the soldering iron out last night and... made it!
I got the PPM signal out and now I am using my Tx with FMS.
However to get it to work I had to use the Mic input and get the
level rather high so that it saturates and get "nice" square signals.

Anyway the conclusion is: this can be done.
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Old 07-18-2003, 04:32 PM
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Default AM Tx as buddy-box to FM Tx??

hi vpersiani,

I would love to have any details on how you got the Futaba Attack 4 transmitter to work with FMS. Did you end up connecting to pin 11 of the IC you mentioned? How did you connect to the PC? Any information would be greatly appreciated, since I'm trying to do exactly the same thing as you!
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Old 07-19-2003, 01:34 PM
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Default AM Tx as buddy-box to FM Tx??

Hi superchicken,


Yes I got the signal out of pin 11 and plug it into the PC.
You need to really saturate the input so I could not get it done with the line input but it was OK with the Mic input.
Then I use a driver called smart propo (http://www.sekiriki.jp/smartpropo/index-j.html) which gives me a .dll file to install in the same directory as FMS.

After that you need to play with the Mic volume to get stable readings in FMS.

Having said that, it works fine on my desktop, but I could not adjust for stable readings on my laptop (maybe it understood that this was not for work! ;-)). There seems to be an electronic circuit on the Mic input which adjust the level to avoid saturation!

In any case, you should be able to get the signal into the PC and see the readings moving in FMS, even if you have difficulties adjusting the level.

Let me know how far you get, I will be happy to help if I can.

Good luck
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Old 07-31-2003, 07:00 PM
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Default AM Tx as buddy-box to FM Tx??

Thanks for the info-- unfortunately that smart propo dll doesn't work with my computer running WinXP. It made the FMS program crash! But that's still helpful info, about where to find the PPM signal. I guess I'll need a serial adapter to go from there.
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