Radio question
10-15-2010 | 03:37 PM
#26
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From: Garland, TX
RE: Radio question
ORIGINAL: shanet75
Thanks for the input. I have a Sig bipe that is a pain to get the wing off so I would probably keep one in there and I could switch the receiver out in the others. I was looking at the 6exa 2.4 and never considered the 7c. I'll check them out.
Thanks again
Thanks for the input. I have a Sig bipe that is a pain to get the wing off so I would probably keep one in there and I could switch the receiver out in the others. I was looking at the 6exa 2.4 and never considered the 7c. I'll check them out.
Thanks again
The receivers are not that much more expensive and you only need one. I've never understood the reason for needing two receivers in a plane.
10-15-2010 | 04:31 PM
#27
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From: Bend,
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RE: Radio question
ORIGINAL: carrellh
Shane, I think this comment
is criticizing the Spektrum brand for needing multiple receivers in one model, not sugessting that you buy one receiver and move it from plane to plane.
ORIGINAL: shanet75
Thanks for the input. I have a Sig bipe that is a pain to get the wing off so I would probably keep one in there and I could switch the receiver out in the others. I was looking at the 6exa 2.4 and never considered the 7c. I'll check them out.
Thanks again
Thanks for the input. I have a Sig bipe that is a pain to get the wing off so I would probably keep one in there and I could switch the receiver out in the others. I was looking at the 6exa 2.4 and never considered the 7c. I'll check them out.
Thanks again
The receivers are not that much more expensive and you only need one. I've never understood the reason for needing two receivers in a plane.
I never mentioned a brand name...........I merely stated my opinion.....and that's all it is..........it is not a criticism.........that I've never understood the necessity for satelite receivers when there are brands out there that do not require that. To me, it takes up extra space, extra wiring and why go to that trouble when there are brands that operate just fine with one receiver. There are lots of folks that go the other way and that is their opinion and it is probably right for them.........I was just offering food for thought.
10-15-2010 | 06:07 PM
#28
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From: Dubbo, New South Wales, AUSTRALIA
RE: Radio question
G'day
Why use more than one receiver?
Have you ever listened to FM radio in a big city. Sometimes the signal bounces off the reflective surfaces and the reflected signal cancels the direct signal and you get what is called "the picket fence effect". That is, the signal strength increases and decreases greatly over short distances because of the reflections. The result is a sort of chopped sound from the radio. It fades in and out over short distances. The same effect can be heard with UHF transceivers in a reflective environment - the signal fades in and out rapidly as you drive along. You get a sort of FFFFFT FFFFFFT FFFFT sound as the muting circuit in the radio cuts in and out.
The same thing can happen with any radio transmission and the higher the frequency, the closer together are the cancellations or nulls as they are called.
So, one solution to a fading in and out signal is to use "diversity tuned receivers". This is a system where two or more receivers are joined together by a diversity system which picks the strongest signal from the receivers to process and send on to the decoder. This system is used in high end FM radio receivers intended for cars and also by the military where they need rock steady reception particularly for data.
This is the reason for the two receivers in some Spektum systems. It is a "belt and braces" approach to minimising the signal cancelling problems caused by multipath reflections which are very common with high frequency radio transmissions.
If you are out in the middle of a paddock where there are no reflecting surfaces then it is probably not necessary but if there are metal buildings or large car parks or metal grain silos etc etc, then it starts to make sense.
Why use more than one receiver?
Have you ever listened to FM radio in a big city. Sometimes the signal bounces off the reflective surfaces and the reflected signal cancels the direct signal and you get what is called "the picket fence effect". That is, the signal strength increases and decreases greatly over short distances because of the reflections. The result is a sort of chopped sound from the radio. It fades in and out over short distances. The same effect can be heard with UHF transceivers in a reflective environment - the signal fades in and out rapidly as you drive along. You get a sort of FFFFFT FFFFFFT FFFFT sound as the muting circuit in the radio cuts in and out.
The same thing can happen with any radio transmission and the higher the frequency, the closer together are the cancellations or nulls as they are called.
So, one solution to a fading in and out signal is to use "diversity tuned receivers". This is a system where two or more receivers are joined together by a diversity system which picks the strongest signal from the receivers to process and send on to the decoder. This system is used in high end FM radio receivers intended for cars and also by the military where they need rock steady reception particularly for data.
This is the reason for the two receivers in some Spektum systems. It is a "belt and braces" approach to minimising the signal cancelling problems caused by multipath reflections which are very common with high frequency radio transmissions.
If you are out in the middle of a paddock where there are no reflecting surfaces then it is probably not necessary but if there are metal buildings or large car parks or metal grain silos etc etc, then it starts to make sense.
10-16-2010 | 01:08 AM
#29
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RE: Radio question
We have had several unexplained radio malfunctions at our field. Some of the reason may be the communications towers or radar stations nearby. We have seen high dollar name brand 2.4 radio systems fly away for no explainable reason despite all systems functioning normally when the plane was recovered. Ihave had one crash due to a radio intereference problem on 72mhz.
10-16-2010 | 02:03 AM
#30
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From: Dubbo, New South Wales, AUSTRALIA
RE: Radio question
G'day
There are some places where it is just best not to fly RC planes. I used to fly at a field which was below a hill (we called it a mountain because Australia is not very tall) on which there were over 200 transmitters of various sorts from VHF and UHF TV transmitters, FM radio transmitters and lots of gigahertz phone and other links. One of the phone links ran through one end of our field and every now and then, people would have problems with radios when flying in that area.
If a RF receiver of any sort gets hit with enough RF energy out of its band, there can be problems. Possibly this was what was happening at our field but without a spectrum analyzer and a list of the frequencies present, it is very hard to say just what is going on.
The other problem we have had at our field is people playing with model cars using aircraft radios near the flying field. This is almost impossible to stop.
I have been lucky (touch wood) so far. I have used 29 Meg FM, 36Meg AM and FM and PCM and now three different types of 2.4 Gig (Spektrum, Hitec and Fly-Dream) and have not had any serious problems yet. My worst problem was recently at a fly-in. I was flying on 36 Meg and kept getting hit by someone else's radio. It was enough to make me land the plane in a wheat field. No damage.
The only 2.4 Gig problem I have seen was with some early Extreme Link 2.4 Gig gear. Two similar sets were flying and one shot the other down. The software has since been upgraded and there have been no problems since.
Our gear keeps getting better but it is and never will be totally fool proof. Fools are too darn clever.
There are some places where it is just best not to fly RC planes. I used to fly at a field which was below a hill (we called it a mountain because Australia is not very tall) on which there were over 200 transmitters of various sorts from VHF and UHF TV transmitters, FM radio transmitters and lots of gigahertz phone and other links. One of the phone links ran through one end of our field and every now and then, people would have problems with radios when flying in that area.
If a RF receiver of any sort gets hit with enough RF energy out of its band, there can be problems. Possibly this was what was happening at our field but without a spectrum analyzer and a list of the frequencies present, it is very hard to say just what is going on.
The other problem we have had at our field is people playing with model cars using aircraft radios near the flying field. This is almost impossible to stop.
I have been lucky (touch wood) so far. I have used 29 Meg FM, 36Meg AM and FM and PCM and now three different types of 2.4 Gig (Spektrum, Hitec and Fly-Dream) and have not had any serious problems yet. My worst problem was recently at a fly-in. I was flying on 36 Meg and kept getting hit by someone else's radio. It was enough to make me land the plane in a wheat field. No damage.
The only 2.4 Gig problem I have seen was with some early Extreme Link 2.4 Gig gear. Two similar sets were flying and one shot the other down. The software has since been upgraded and there have been no problems since.
Our gear keeps getting better but it is and never will be totally fool proof. Fools are too darn clever.
10-16-2010 | 09:03 AM
#31
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From: Bend,
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RE: Radio question
With all due respect the FAAST systems do not seem to have this problem because they do not "link and lock" on to a frequency, they just continue to frequency "hop" so if they detect interference they just hop to another frequency.
10-16-2010 | 05:37 PM
#32
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RE: Radio question
ORIGINAL: mike109
G'day
There are some places where it is just best not to fly RC planes. I used to fly at a field which was below a hill (we called it a mountain because Australia is not very tall) on which there were over 200 transmitters of various sorts from VHF and UHF TV transmitters, FM radio transmitters and lots of gigahertz phone and other links. One of the phone links ran through one end of our field and every now and then, people would have problems with radios when flying in that area.
If a RF receiver of any sort gets hit with enough RF energy out of its band, there can be problems. Possibly this was what was happening at our field but without a spectrum analyzer and a list of the frequencies present, it is very hard to say just what is going on.
The other problem we have had at our field is people playing with model cars using aircraft radios near the flying field. This is almost impossible to stop.
I have been lucky (touch wood) so far. I have used 29 Meg FM, 36Meg AM and FM and PCM and now three different types of 2.4 Gig (Spektrum, Hitec and Fly-Dream) and have not had any serious problems yet. My worst problem was recently at a fly-in. I was flying on 36 Meg and kept getting hit by someone else's radio. It was enough to make me land the plane in a wheat field. No damage.
The only 2.4 Gig problem I have seen was with some early Extreme Link 2.4 Gig gear. Two similar sets were flying and one shot the other down. The software has since been upgraded and there have been no problems since.
Our gear keeps getting better but it is and never will be totally fool proof. Fools are too darn clever.
G'day
There are some places where it is just best not to fly RC planes. I used to fly at a field which was below a hill (we called it a mountain because Australia is not very tall) on which there were over 200 transmitters of various sorts from VHF and UHF TV transmitters, FM radio transmitters and lots of gigahertz phone and other links. One of the phone links ran through one end of our field and every now and then, people would have problems with radios when flying in that area.
If a RF receiver of any sort gets hit with enough RF energy out of its band, there can be problems. Possibly this was what was happening at our field but without a spectrum analyzer and a list of the frequencies present, it is very hard to say just what is going on.
The other problem we have had at our field is people playing with model cars using aircraft radios near the flying field. This is almost impossible to stop.
I have been lucky (touch wood) so far. I have used 29 Meg FM, 36Meg AM and FM and PCM and now three different types of 2.4 Gig (Spektrum, Hitec and Fly-Dream) and have not had any serious problems yet. My worst problem was recently at a fly-in. I was flying on 36 Meg and kept getting hit by someone else's radio. It was enough to make me land the plane in a wheat field. No damage.
The only 2.4 Gig problem I have seen was with some early Extreme Link 2.4 Gig gear. Two similar sets were flying and one shot the other down. The software has since been upgraded and there have been no problems since.
Our gear keeps getting better but it is and never will be totally fool proof. Fools are too darn clever.
Wonderful post Mike and right on
John
