wings

When using dual receivers, is it necessary or recommended to separate the receivers and antennas by a certain amount? Or does it not matter? I'm referring to 72Mhz.

krayzc-RCU

My Feedback: (31)

I have my ant. almost beside each other and the reciever are on each side of the plane.

BuschBarber

My Feedback: (2)

I have seen some setups where the antennas go out diagonally, in a V. I have never used dual Rx's. but others do. A good Range Check should help determine if the antenna arrangement is working.

krayzc-RCU

My Feedback: (31)

it really should not matter since the signal is the the same channel

A.T.

A large number of experiments have been run testing dual receivers for buddy and back up systems. in many instances severe interference or glitching was encountered if the antenna were run close and parallel to each other. Separate aerials as far apart as possible and at different angles to each other. Further information available under sub section "Receiver - FAQ, guides and aids to best reception.." at
Alan's Hobby, Model & RC FAQ Web Links
Regards
Alan T.

Star7

To amplify the good advice from Alan; multiple receivers (or diversity systems with multiple antennas) are aimed at preventing signal loss due to shadowing from an object (eg engine or battery pack) and polarization issues. At higher frequencies like the 2.4 Ghz range, the polarization of the receiver and transmitter antenna makes a significant difference. They should idealy match but that is impossible while a model is cavorting about. So best to orient antennas orthogonal (90degree) to each other to cover all possible polarization combinations. For shadowing, it is best to get the antennas as far away from the motor and battery as feasible and preferably separate them from each other. That way, when one is shielded, another is receiving.....Obviously, keep an eye on CG while you do this!

wings

Thanks star. But what you are talking about is for spread spectrum radio equipment. Two receivers are (or antennas for FASST) are used because the 2.4Ghz signal gets blocked by solid objects such as the engine or landing gear etc. Not an issue with 72Mhz.

I'm talking about 72MHz dual receivers for redundancy. (nothing to do with shadowing in this case)

I was more concerned with any type of interference from having two receivers too close.

I am kinda thinking along the same lines as krayzc-RCU.

I don't quite understand how there would be interference if both receivers are receiving the same signal. How would the signal interfere with itself?

But what do I know? That's why I am asking

Star7

OOOPS! I am sorry, obviously I did not read closely enough. I have no RC experience with dual receivers in that application. I suppose that you might get some noise coupling that would provide a mixed mode interference....if that happens, it might be just as bad with power and ground leads as for antennas. At least with power and ground, you can twist the wires to minimize common mode interference and use a ferrite torroid. Can't do that for antennas obviously. sorry! shot my keyboard off out of turn

krayzc-RCU

My Feedback: (31)

Wings,

This is what my set-up looks like and its not one of those pretty picture set-up like you see some of the guys post. This set up have worked well since 2002 on the 40% Extra no issues what so ever and like I said in an eailer post these ant are very close shoot just look at the pics.......

wings

Don't be sorry, I appreciate you taking the time to respond. Just wasn't what I was lookin for that's all.

wings

Thanks Crazy,

Wow, that's a nice lookin bird! I am guessing you did your homework before taking a chance with that airplane. I think that answers my question.

I appreciate it!

Matt

Star7

The conversion scheme of a receiver mixes an internal signal (from an oscillator) with the signal feed to present the original two signals and their sum and difference. This is necessary to get the signal feed frequency down to a lower value for filtering, processing and demodulation. The difference frequency, from this mixer, is the new signal passed down the line in the receiver and is far enough away from the other three signals that it is easy to filter them out. The problem is that the oscillator signal will be radiated by the receiver and could overload its neighbor. This is how the feds in the UK can tell if you have a TV operating without the proper number of license taxes paid....they use a receiver to listen for the little transmitted signal from your TV (too much time on someone's hands). So you really really don't want two receiver antennas lying side by side because the mixers from each will overload the other and cause desensing. Sorry, I am really into this crap and sometimes can't stop myself. Yep, separate the receivers if feasible and run the antennas at 90 degrees to minimize coupling. sorry I will now crawl back into my hole

wings

Smart People are cool!

A.T.

I should have guessed you own big birds, great photos. I neglected to mention sub section "Giant Scale, Large RC models, Twins & Multi Engines" on my web page. Unfortunately, even The Wayback Machine can no longer retrieve the two good posts on RCU by Anne-Marie Cross, then Product Support Manager for Great Planes, of how she and her husband installed dual RX and warning to separate RX antenna at differing angles.
Another good reference is
RC Installation for Large Models
Who is keith Mitchell? - check his 33% Hawker Hunter
Regards
Alan T.
Alan's Hobby, Model & RC FAQ Web Links

G.E.G.

My Feedback: (1)

I guess what started this is that I have a GP Pitts Special that I wish to use one receiver for the upper wing and right elev. A second receiver for the lower wing and left elev. The receivers will be about 5in. apart while each ant will run down eather side of the fuse. and double back on it self parallel about a inch apart in a plastic tube. The other ant. will do the same on the other side after looking at crazys pic I feel safe in running this set up. I'd like to thank wings for starting this thread and all of the responces.If my set up does not work, as soon as I quit crying, I let everyone know.

krayzc-RCU

My Feedback: (31)

yeah baby! I run two different Ultimate both on one receiver and dual y-cords. The only dual set-up I have is the Extra as it use so many servos 6 total for wings and 4 total for elevators + 2 rudder and lots of battery power

PS your set up will work u will be suprised at how often someone will give advice from the start of the convo "I heard", " I think" "I would not"

G.E.G.

My Feedback: (1)

Thanks krazy. Nice looking birds. Right now I'm running four servos on the wings two on the elev. one on the throttle, one on the choke, one on the engine kill switch, one on pull pull on the rudder and one for the pull pull on the tail wheel. This is just something I wanted to do. Again thank you for your reply.

Javier Garcia

You can look the "ABC receivers" article in www.acteurope.de

They make diversity systems (two receivers that interchange their information) in two differents frecuencies. Multiplex now make this type, and JR/Graupner too.