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Dual receivers cause reduced range?

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Old 02-08-2003, 05:01 AM
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aviti
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Default Dual receivers cause reduced range?

I am looking at running dual JR 945 receivers for my 33% Edge. I am considering this for the ease of wiring and the redundancy. I have however read posts that indicate that the dual recievers can cause reduced range in certain circumstances. JR confirms this possibility on their forum.

Has anyone out there experienced this problem while running dual receivers?
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Old 02-08-2003, 01:26 PM
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Default Dual receivers cause reduced range?

I run dual rxs on all my research planes (about 20) and I have never experienced any problems. The rx antennas need to be run in a non-parallel orientation to each other. The best way is a difference of 90 degrees in orientation but often that is difficult.

I run one antenna along the base of the fuse while second antenna runs to the tip of the vertical stab. The antennas are then not in a parallel plane.

Elson
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Old 02-08-2003, 04:45 PM
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Default Dual REceivers

Get 2 Deans or other type whip antennas and install them on the turtledeck or rear fuselage at 90 degrees to each other.
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Old 02-08-2003, 05:00 PM
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Default Dual receivers cause reduced range?

You really don't need to RX's in a 33%-35% model or even in a 40% model... Redundancy is a function of eliminating a perceived problem, adding a second RX simply does nothing to address this other than introduce new variables for failure and reduced range... It's well documented... There are hundreds of modelers successfully using two RX systems.... It's a viable concept, there are some considerations as have been mentioned by other's.

The simplest thing that you can do that will add true redundancy without adding to failure probability, is to install two batteries and switches...

Receiver's rarely fail in todays world... Typical reasoning for dual RX's is to distribute the power-load of 14 servos, eliminating the need for wyes and using up channel ports in a single RX install.
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Old 02-08-2003, 05:39 PM
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Default Dual receivers cause reduced range?

Michael - I am now leaning towards the 1 receiver setup. In over 20 years of flying I have never had a receiver fail. I will run the 2 batteries and switches though. I have several other questions. I have read many posts on these issues but they are worth bringing up again I think. Using just one receiver would make the wiring a little more complicated as I will be using 8 digitals for the control surfaces, one servo for throttle and one for ignition cutoff (my fist gasser so not sure how the ignition cutoff works). What is the best way in your opinion to gang the servos for the ailerons and rudder? I was simply going to use the matchbox which would also solve the problem of not enough reciever ports. Would it be safe to run all 4 aileron servos through one channel of the receiver using the matchbox? I have been using a matchbox for elevators on a 25% Cap without a problem, but I have read the posts where some people say they are having problems with matchboxes locking up. If you don't use a matchbox, it is extremely difficult to gang servos without them fighting, correct? I have been studying all of these issues for many months but it is difficult to get a definitive answer (and there is obviously more than one right answer in many instances).
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Old 02-08-2003, 06:55 PM
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Default Dual receivers cause reduced range?

There are two different strategies which are very different is dealing with the electronics on board our RC airplanes. These are 1) minimizing the probability of failure and 2) planning for failure.

The use of a single rx with dual switches and dual batteries are in the category of minimizing the probability of failure by duplicating the components most likely to fail. However, if the rx fails, all is lost. The weak pt in this system is the single rx and the rx operates on a single frequency.

The use of dual rx with independent battery systems and each rx controlling each side of the plane is in the category of planning for failure. If any component within one of the rx systems fails, the plane can be landed on the 50% control provided by the second rx. The probability of both systems failing is very small. The weak pt is this system is that both rxs are on the same frequency.

Using dual rxs, I have survived every component failure possible in my university research fleet without a crash. The additional cost per air frame of a dual rx setup is less than $100 compared to the number of dollars invested. If the plane is worth a $1000, the second rx is only 10% additional cost with the benefit of being able to save the plane with any failure except frequency interference.

For me, the decision is a no-brainer

Just my experience.

Elson
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Old 02-08-2003, 08:19 PM
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Default Dual receivers cause reduced range?

I like your reasoning. This subject has been argued with great point for either single or dual receivers. The cost is not my concern as the additional $ is nothing compared to the overall project for a 33% aerobat. It seems about half the people like 2 receivers for a 33% project and the other half like 1 receiver. When you go to 40%, more people sway to using 2 receivers. I wish it were more cut and dry what to do here, but it isn't! Keep the comments coming!
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Old 02-09-2003, 04:35 PM
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Default Dual receivers cause reduced range?

Having had at least 3 rx failures in my 20 years of flying I am a strong advocate of a dual Rx setup in some of my more valuable planes. I have not had any range reduction but I follow the "non parallell" antenna tecqnique descibed here.
Arguments against dual RX's state that adding an extra one inreases the probability of failure which is true. However, the probability of simultaneous failure is very low. If you doubt the soundness of redundant systems/components, look at full size aircraft and the numerous "back up" items carried. Dual magnetos, dual engines, back up pumps, dual or triple hydraulic systems, etc. the list goes on and on. :-)
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Old 02-10-2003, 03:16 AM
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Default Dual receivers cause reduced range?

Originally posted by aviti
I like your reasoning. This subject has been argued with great point for either single or dual receivers. The cost is not my concern as the additional $ is nothing compared to the overall project for a 33% aerobat. It seems about half the people like 2 receivers for a 33% project and the other half like 1 receiver. When you go to 40%, more people sway to using 2 receivers. I wish it were more cut and dry what to do here, but it isn't! Keep the comments coming!
The biggest single reason people started to run two receivers in the first place was to distribute the current load. Today, most people that use two receivers try to justify it with redundency.

With today's technology, a receiver failure is a rarety.

Your better off to not run any servos on the receivers directly period. Let the receiver receive, and then distribute the signal. and power the servos with its own battery.

I have yet to use any redundency in my plane, but I do my homework with proper maintenance and good installation.

If you need redundency, then use two Transmitter, because that can go also.

Oh yes, isolate the servos from the receiver with no electrical connection between the two.
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Old 02-10-2003, 03:11 PM
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Default Dual receivers cause reduced range?

Aerografixs. I must respectfully disagree with several of your points.
First, let me state that my objective in using dual Rx's is to reduce the chance of a single point failure in the on board system causing loss of control of the aircraft. The 2nd Rx is used in conjunction with a split servo arrangement and separate batteries and switch's for each Rx.

Now to my disagreements:

1. Parallel rx/servo/battery/switch schemes have been around for a long time and pre-date the use of a dual rx to split the current. I my self have used this scheme in several large airplanes for years and have done so purely for reliability considerations. It has nothing whatsoever to do with current splitting

2. New technology has improved reliability to a degree but by no means has it eliminated failures. On of my most recent failures was a new MPX 9 channel IPD rx from an MPX 4000 system. I also had a failure in a brand new Tx.

3. Separate batteries for the servos and Rx actually decrease system reliability from the point of view of a single point failure causing loss of control. With this scheme you have two batteries, but the failure of either one will cause loss of control. A parallel battery arrangement allows the failure of either battery without loss of control

4. One of my failures was caused by a component in the system that failed at elevated ambient temperature but worked at room temperature, a problem like this is very difficult to detect how carefully you inspect or install your equipment.
Careful maintenance and inspection is no guarantee that you will not be the victim of a random failure of a component in the Rx. or elsewhere.

5. I install my Rx's wrapped loosely in thick foam, watch my antenna routing, be careful not to place stress on wires, secure my foam pack in the fuse, do frequent range checks, check voltage before every flight, etc, etc, etc. I take pretty good care of my fleet and am mildly resentful that you would imply otherwise.

6. I agree, transmitters do fail, but a dual Tx arrangement is much more difficult and complex than a dual rx. One was marketed several years ago for the old Kraft systems. If one was available today I would look be interested in it.

7. I can see that the addition of a fiber optic link would help with problems arising from voltage drop and induced noise in long servo leads but, exclusive of those issues, I do not see it guarding against loss of control due to a single point failure. Quite the contrary, the optical couplers themselves add complexity and additional components to the system.

A parallel system is not something I use in all planes. It is only used where the plane is particularly valuable to me and when it is large enough to carry the extra weight. It has saved at least one plane for me and is well worth the extra time and expense.
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Old 02-10-2003, 03:24 PM
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Default Dual receivers cause reduced range?

Originally posted by JLLayton
. I take pretty good care of my fleet and am mildly resentful that you would imply otherwise.


.
You should not be resentfull at my statement, as it was not directed at anyone in particular, it was only meant as a general statement,

Just because someone has money and only fly's large scale, doesn't make him an expert in the field of maintenance or proper installation. On the other hand, there are a lot of real experts with only small aircrafts.

So don't be resentfull, it wasn't meant for you by any means.

This guy came up to our IMAA gathering flying a 40% with a DA 150. Everybody revered him as the expert. He was a very good pilot, but when I assisted him with a battery problem, I was flabergasted to see the innered of his airplane, it was the work of a uninformed newbie at best.

Someone tried to point to him some very dangerous installation but was disregarded by others by saying "what do you know with your small airplanes"... Beleive me, he knew....
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Old 02-13-2003, 11:46 AM
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Mark Bowman
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Default Dual recievers

In using dual recievers doe it matter if they are ppm or pcm?
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Old 02-13-2003, 12:50 PM
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Default Re: Dual recievers

Originally posted by Mark Bowman
In using dual recievers doe it matter if they are ppm or pcm?
As long as you don't mix them, either two PPM or two PCM but not one of each. and that is because your transmitter will only transmit in one or the other but not both at the same time.
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