14-06-2011, 10:59 AM
Your right Gaz you do get what you pay for,
I brought two orange receivers the other day just to give them a go on my depron foamies and get my good spectrum receivers back for other projects.
We will see how they go I haven't has a chance to try them yet.
But when you test radio gear thoroughly it's not just a matter of sticking an RX in a tin.
Signal loss is not linear for a start, In a perfect world it falls of by the cube root of the distance or something like that, you can get all sorts of other effects too like shadowing and multi path, even the sun can get angry and mess with things. You can get more or less gain depending on how things are placed relative to others in your model, so comparing distance like that is pretty crude at best. It's OKish but you must be careful when interpreting the results.
To do a better range check you've got to set it up in the model with the motor going all servos plugged in and with the all the wiring that you'd use in the plane. Then you need to drive out and have line of sight you also need to hold the tx as you would when flying.
Antenna's don't have the same range in all directions, a 1/4 wave dipole like you have on the RX and TX drops off markedly as they are orientated end on to each other. This is why a nice diversity system on the receive end (satellite receiver) works much better.
The longer dipole which is what I think he had on that spectrum receiver would have more gain but a narrower field pattern. The field pattern would look something like a pancake rather than a doughnut. So orientation would be more critical with this one. For instance if you fluke the orientation in your test it might well give you an exaggerated estimate of your real range.
If the receiver has the ability to choose between two antenna's ie the one with the best reception this is called diversity. I think that the spectrum receivers do this nicely. I'm not sure how good the signal processing is or how far they've gone with it but I think it's possible to do signal processing and error correction in such a way you can use multi path signals to extend range as well. I'm not sure if they use this technique tho' as it'd need a heap of processing power
If you have nice digital signal processing rapid diversity and redundancy built into the signal and clever error checking all working for you. Then you can extend your range a lot with out upping the power of the TX. I'm not sure just how fairly this will show up in a tin can test.
I'm not poo pooing the guys technique at all, I think it's a good idea but it's also good to realize that there are other factors and it's a complicated system your asking to be evaluated with a very simple test.
Just like you say Gaz, you do get out, what you put in, this holds true for testing methods as well.
I brought two orange receivers the other day just to give them a go on my depron foamies and get my good spectrum receivers back for other projects.
We will see how they go I haven't has a chance to try them yet.
But when you test radio gear thoroughly it's not just a matter of sticking an RX in a tin.
Signal loss is not linear for a start, In a perfect world it falls of by the cube root of the distance or something like that, you can get all sorts of other effects too like shadowing and multi path, even the sun can get angry and mess with things. You can get more or less gain depending on how things are placed relative to others in your model, so comparing distance like that is pretty crude at best. It's OKish but you must be careful when interpreting the results.
To do a better range check you've got to set it up in the model with the motor going all servos plugged in and with the all the wiring that you'd use in the plane. Then you need to drive out and have line of sight you also need to hold the tx as you would when flying.
Antenna's don't have the same range in all directions, a 1/4 wave dipole like you have on the RX and TX drops off markedly as they are orientated end on to each other. This is why a nice diversity system on the receive end (satellite receiver) works much better.
The longer dipole which is what I think he had on that spectrum receiver would have more gain but a narrower field pattern. The field pattern would look something like a pancake rather than a doughnut. So orientation would be more critical with this one. For instance if you fluke the orientation in your test it might well give you an exaggerated estimate of your real range.
If the receiver has the ability to choose between two antenna's ie the one with the best reception this is called diversity. I think that the spectrum receivers do this nicely. I'm not sure how good the signal processing is or how far they've gone with it but I think it's possible to do signal processing and error correction in such a way you can use multi path signals to extend range as well. I'm not sure if they use this technique tho' as it'd need a heap of processing power
If you have nice digital signal processing rapid diversity and redundancy built into the signal and clever error checking all working for you. Then you can extend your range a lot with out upping the power of the TX. I'm not sure just how fairly this will show up in a tin can test.
I'm not poo pooing the guys technique at all, I think it's a good idea but it's also good to realize that there are other factors and it's a complicated system your asking to be evaluated with a very simple test.
Just like you say Gaz, you do get out, what you put in, this holds true for testing methods as well.
“The knack of flying is learning how to throw your machine at the ground and miss.”
"When once you have tasted flight, you will forever walk the earth with your thoughts turned skyward, for there you have been, and there you will always long to return." ~Leonardo Da Vinci