dwaynenancy

My Feedback: (62)

I have several of the named receivers and I am trying to determine what type of modeling are they designed to be used in, aircraft, helicopters, etc?

Dwayne

BarracudaHockey

My Feedback: (11)

http://www.spektrumrc.com/Products/D...odId=SPMAR7600

7 channel airplane reciever

AndyKunz

They're a cross-over product. The AR7600 is a DSM2 receiver with an (and it's unique in this) optional remote receiver. The remote makes sure this is a good aircraft receiver, but the small base size and 7 channels means it's ialso deal for helicopters, which are typically flown much closer to the pilot than planes.

Andy

dwaynenancy

My Feedback: (62)

I was told by the "powers that be" that this was strictly a helicopter radio and it was not suitable for airplanes. I don't fly helicopters and I do fly airplanes.

fizzwater2

My Feedback: (61)

I think "the powers that be" are wrong.

I've been flying a 7610 (the DSMX version of the RX) in a plane, works like a champ. I use the DSMX satellite with it.

Len Todd

I have seen a couple AR 7600 in local planes. As Andy inferred; If you fly in close you do need the Remote Rxer. If you want more range, you have the option to add the Remote. I think it was a great marketing idea. We can get an excellent Rxer for the Heli or park fliers w/o paying for the remote. When we get tired of crashing helis and switch back to planes, you just add the remote if you find you need the range of have a lot of conductive materials onboard, etc.. It works for both. Only thing is, it is NOT DSMX.

BarracudaHockey

My Feedback: (11)

Just a note to dispel any misunderstandings about range.....

A single reciever has just as much range as a reciever with a remote. What it lacks is path diversity to over come shadowing from components that may come into the RF path like ESC's, motor's or the like.

BuschBarber

My Feedback: (2)

+1

Len Todd

Actually, getting away from "shadowing" is only one advantage of multiple Rxers. Another advantage of a remote Rxer is to improve antenna polarization. If you have a Rxer horizontally polarized and the transmitter vertically polarized, you just lost 30 dB of your signal (e.g. Knife Edge flight with a Rxer antenna positioned vertical when upright.). A three (3dB) loss is 50% of your signal. So a 30 dB loss is very significant.

With a remote Rxer positioned cross-polarized to the other Rxer, you increase your overall Rxer's ability to maintain the same polarization as the transmitter, thus increasing your range. If you have three Rxers, you even further improve your odds of maintaining a similar polarized Txer to Rxer path. In the above Knife Edge flight example, can you imagine the signal loss if the tip of the cross-polarized Rxer antenna is pointing directly at the Txer?

Planes that fly "way out there" (e.g. Jets & Giants) typically have multiple remote Rxers. Planes that fly "in your face" do not typically need them. The remote Rxers give them that additional range. With three Rxers properly positioned, you can typically have at least one Rxer properly polarized with the Txer. If you have a lot of conductive material to deal with, 4 Rxers may be needed to maintain a properly polarized path that is not shadowed by something on the plane.

By the way; Only one Rxer is used at a time. When the Rxer Control Unit (my choice of words) switches to another Rxer, that is when it records a Fade on the Rxer that has just become weaker than the one it just selected, which has the stronger signal. We always used to call that "voting."

AndyKunz

That's not how the remote receivers work, Len. It doesn't switch based on voting - all receivers are used all the time, each generating the same message. As long as any one delivers a message, it will be used. If any one does not deliver a message (nothing about strength) it will be recorded as a fade.

Andy

Len Todd

I knew I would finally get it out of you. I just have to keep trying.So we are not voting on RF signal strength.

Questions, ...

if a Rxer does not deliver a message but one other Rxer did provide a message this records a Fade on the Rxer that did NOT provide the message?

If a Rxer delivers a message but the checksum is wrong or the message is incomplete, it records a Frame Loss?

If none of the Rxers delivers a message, then a Hold is recorded? Or is the Hold RF based?


Why would the Spektrum want to process the same signals from each Rxer? Seems terribly inefficient, especially when you have 3 or 4 Remotes. If say, ... 3 remotes provide data, is there a precedence (e.g. use the first good frame and trash the rest as long as the frame used had the right checksum, etc.)? If you are not voting on RF signal strength, then it seems like the processor has to have some sort of precedence to sort out the redundant data. After all, how can it take all the data for all remotes simultaneously and why would the developers waste time decoding redundant data?

How can one answer create so many new questions, eh?

AndyKunz

Maybe you've been reading the wrong forums for the explanation. I've explained it a number of times, probably most on the RCG Radios forum. If you really want an answer quickly, you need to change forum!

If a remote does not deliver a message, that's a single antenna fade. Note that if you remove a remote, you won't see fades reported and it will restart at 0 when you plug it back in because the remote was power-cycled.

A remote will not deliver a message if it got a bad check. That will also be a fade.

If no remote delivers a message for the same frame, that counts as a frame loss.

A Hold is when 43 consecutive frame losses occur.

Stop thinking so analog!!! This is a digital world now! The base doesn't process signals, it processes messages. (Yes, in an academic sense these are "signals" but it doesn't help to think that way. By differentiating them as "messages" most people comprehend it better).

Computers are horribly inefficient. We throw thousands of transistors at a problem that could often be solved with a few caps and resistors.

There doesn't need to be a precedence. The computer can receive data from all the remotes "simultaneously" and store it all in separate buffers, one buffer for each remote receiver. Then all it needs is to do is pick any buffer that was just updated and use the data (because all buffers have the exact same message content in them).

People coming from an analog world have a real problem comprehending the fact that signal strength has no correlation to delivered message quality in a digital world. Remember PCM? You either had perfect control or no control at all. With FM you could tell when you were glitching. In that regard all the modern 2.4gHz systems are more like PCM. Signal strength doesn't matter.

Easily, by not searching first

Andy

Len Todd

Just trying to figure out what is going on inside the "black box." For those of us who have built RF equipment from scratch, it is kind of frustrating not knowing what is going on inside them. Thanks for your explanation and time!

I suppose if I had time to surf around all the related forums, I would be a grounded pilot.But, I will look into the other forum.