Range of dual conversion receivers
01-29-2005, 08:07 AM
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Range of dual conversion receivers
can anyone tell me if there is any advantage to a dual conversion receiver when it comes to longer transmitting ranges for a airplane?
Thnaks.......John
Thnaks.......John
01-29-2005, 08:22 AM
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RE: Range of dual conversion receivers
John
There is a good article regarding this at http://www.classicaero.com/berg/berg.php
Safe flying!
There is a good article regarding this at http://www.classicaero.com/berg/berg.php
Safe flying!
01-29-2005, 11:30 AM
#3
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RE: Range of dual conversion receivers
It is not whether or not its dual conversion that determines range, it is the receiver sensitivity. Both dual conversion and single conversion receivers can (an usually are) be equally sensitive. However, many of the park flyers are delivered with receivers that have far less sensitivity than your standard brand receivers, probably intentionally due to the lack of need for great range with the small and slow flying models.
01-29-2005, 01:49 PM
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RE: Range of dual conversion receivers
Are we limited in range by sensitivity or by noise? At HF, range is generally limited by noise (atmospheric and man made noise, not receiver noise). At microwave frequencies range is limited more by receiver sensitivity. 72 MHz is sort of in the middle.
01-31-2005, 04:55 PM
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RE: Range of dual conversion receivers
Are we limited in range by sensitivity or by noise?
I am a bit confused why transmitter and receiver manufactures don't publish specifications on their equipment. At least I have never seen any. That way we can compare receivers and transmitters intelligently.
I would also like to see an article that compares receiver specifications. And then puts the receiver and transmitter on test equipment and report the findings. I hear guys often mention that one type of receiver works better than others especially in these domes when there are a lot of electric flyer's, flying in close to each other. Lets see some real specs!
02-01-2005, 07:22 PM
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RE: Range of dual conversion receivers
The magazine editors will tell you that nobody is interested in what goes on inside of our radios.
02-01-2005, 07:43 PM
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RE: Range of dual conversion receivers
The magazine editors will tell you that nobody is interested in what goes on inside of our radios.
Regarding radios, I see enough questions being asked in these forums to justify several articles on transmitters and receivers. And I do not mean functionality of transmitters; I mean how good are they at doing what the manufacture claims.
An article that I certainly would like to see is an article that rates receivers. We all know that certain receivers are better than others, especially in crowded environments. I hear the phrase “getting hit†frequently. Why is that? Why are certain receiver designs less likely to be “hit†than others? Why don’t we learn about the pro and cons of different receiver designs? Which receivers are best at rejecting adjacent channels and which are not? I could keep going but guess you catch my drift.
I personally know the information that I would learn from such articles would make me a more knowledgeable consumer. I also bet if manufacture XYZ starts to see his receivers in the group flagged as “Most likely to have problems when someone is on the adjacent channel†or “These receivers do poorly with gas ignition systemsâ€, that XYZ will improve their product.
Does everyone care, nope, but I bet a lot do.
02-02-2005, 03:17 AM
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RE: Range of dual conversion receivers
ORIGINAL: P47 Jug - Al
An article that I certainly would like to see is an article that rates receivers.
An article that I certainly would like to see is an article that rates receivers.
Hitec Supreme "dumb" FM/PPM -- as a benchmark
Hitec QPCM -- as a benchmark
Berg 5 DSP II
Berg 6 DSP III
FMA M5
Sombra Shadow 1 (synthesized)
Polk Seeker (synthesized)
A full range of tests has been conducted, evaluating a wide range of performance areas such as sensitivity, selectivity, intermod/cross-mod resistance, out-of-band rejection (including images), interference rejection (impluse, burst, constant carrier, modulated carrier), same-frequency signal rejection, operating voltage range, performance with long servo extensions, compatibility with various popular transmitters, etc, etc.
The Hitec Supreme and Q-PCM receivers have been included to provide benchmarks against which the performance of this new generation of "smart" (DSP/TSR) receivers can be compared.
Are DSP/TSR receivers *really* much better than plain old PPM/FM units?
Does PCM really provide the ultimate in interference rejection?
The results may surprise many people!
As you can imagine, there's a *lot* of work involved in producing something this comprehensive in a manner that meets the needs of the lay-person and those who want information at a more technical level so it's taken almost three times longer than I'd originally anticipated.
However, the work is almost complete and I'll be publishing the results as soon as I've got some responses from the various manufacturers whose equipment is being compared and once I've knocked all these notes and test-results into some human-readable form.
02-02-2005, 08:19 AM
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RE: Range of dual conversion receivers
A full range of tests has been conducted
I like all the different evaluations you have performed. It sounds like it must have been exhaustive to do. If feedback is good, are you planning to do a follow-up using other receivers, JR, Futaba, etc.? I hope so.
If you are free to say, where will this article be published?
Thanks again for the heads up on a forthcoming article.
Al
02-02-2005, 08:57 AM
#11
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RE: Range of dual conversion receivers
The magazine editors will tell you that nobody is interested in what goes on inside of our radios.
It is important to understand how the frame data is protected from corruption.
1. Is the data protected?
2. What techniques are used to protect the data?
3. Why does a hard over occur on some receivers with a turn on?
4. How many bad frames are required to instigate failsafe?
5. What is being done to protect against the ever-increasing number of park flyers?
Bill S
02-02-2005, 11:55 AM
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RE: Range of dual conversion receivers
ORIGINAL: XJet
Such an article is on its way and evaluates/compares the following receivers:
Hitec Supreme "dumb" FM/PPM -- as a benchmark
Hitec QPCM -- as a benchmark
Berg 5 DSP II
Berg 6 DSP III
FMA M5
Sombra Shadow 1 (synthesized)
Polk Seeker (synthesized)
A full range of tests has been conducted, evaluating a wide range of performance areas such as sensitivity, selectivity, intermod/cross-mod resistance, out-of-band rejection (including images), interference rejection (impluse, burst, constant carrier, modulated carrier), same-frequency signal rejection, operating voltage range, performance with long servo extensions, compatibility with various popular transmitters, etc, etc.
The Hitec Supreme and Q-PCM receivers have been included to provide benchmarks against which the performance of this new generation of "smart" (DSP/TSR) receivers can be compared.
Are DSP/TSR receivers *really* much better than plain old PPM/FM units?
Does PCM really provide the ultimate in interference rejection?
The results may surprise many people!
As you can imagine, there's a *lot* of work involved in producing something this comprehensive in a manner that meets the needs of the lay-person and those who want information at a more technical level so it's taken almost three times longer than I'd originally anticipated.
However, the work is almost complete and I'll be publishing the results as soon as I've got some responses from the various manufacturers whose equipment is being compared and once I've knocked all these notes and test-results into some human-readable form.
ORIGINAL: P47 Jug - Al
An article that I certainly would like to see is an article that rates receivers.
An article that I certainly would like to see is an article that rates receivers.
Hitec Supreme "dumb" FM/PPM -- as a benchmark
Hitec QPCM -- as a benchmark
Berg 5 DSP II
Berg 6 DSP III
FMA M5
Sombra Shadow 1 (synthesized)
Polk Seeker (synthesized)
A full range of tests has been conducted, evaluating a wide range of performance areas such as sensitivity, selectivity, intermod/cross-mod resistance, out-of-band rejection (including images), interference rejection (impluse, burst, constant carrier, modulated carrier), same-frequency signal rejection, operating voltage range, performance with long servo extensions, compatibility with various popular transmitters, etc, etc.
The Hitec Supreme and Q-PCM receivers have been included to provide benchmarks against which the performance of this new generation of "smart" (DSP/TSR) receivers can be compared.
Are DSP/TSR receivers *really* much better than plain old PPM/FM units?
Does PCM really provide the ultimate in interference rejection?
The results may surprise many people!
As you can imagine, there's a *lot* of work involved in producing something this comprehensive in a manner that meets the needs of the lay-person and those who want information at a more technical level so it's taken almost three times longer than I'd originally anticipated.
However, the work is almost complete and I'll be publishing the results as soon as I've got some responses from the various manufacturers whose equipment is being compared and once I've knocked all these notes and test-results into some human-readable form.
02-02-2005, 12:05 PM
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RE: Range of dual conversion receivers
Here is part of the note I got from G. Banks of RC Report:
"After reading your article twice, I have to agree with you about being too technical. I learned something from it, and I thought long and hard about whether or not to share that with everyone, but after asking a lot of the local guys, it seems that many want to now the best servo in each class, but few care about how, why, and what's going on inside. People may complain about ARF airplanes taking over, but no one complains about RTF servos! So, I'm going to decline your offer to write these servo articles."
I have tests of about 20 servos of various make if anyone is interested.
"After reading your article twice, I have to agree with you about being too technical. I learned something from it, and I thought long and hard about whether or not to share that with everyone, but after asking a lot of the local guys, it seems that many want to now the best servo in each class, but few care about how, why, and what's going on inside. People may complain about ARF airplanes taking over, but no one complains about RTF servos! So, I'm going to decline your offer to write these servo articles."
I have tests of about 20 servos of various make if anyone is interested.
02-02-2005, 12:16 PM
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RE: Range of dual conversion receivers
I wonder if there is enough market to support a specialty magazine aimed at the technically oriented RC audience. There used to be such a magazine for hams called "Ham Radio". It is no longer in print but was very popular while it lasted.
02-02-2005, 04:36 PM
#15
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RE: Range of dual conversion receivers
The biggest problem with evaluation of receiver sensitiviy, noise rejection etc. is the very expensive equipment required to do a valid test. This is not something you can do in your garage or basement. An anochoic chamber is almost a necessity as well as expensive test gear. Random testing in real life situations is very imprecise and depends on to many variables to be valid. However, the manufactures should have done these tests and the data could be made available if they are willing to provide it.
02-02-2005, 05:35 PM
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RE: Range of dual conversion receivers
Right! And VHF anechoic chambers are few and far between, and cost millions.
The thing to do would be to remove the antennas and make coaxial connections to the receiver and transmitter. Of course, some might say this would cast doubt on the validity of the test, but what else can one do?
The thing to do would be to remove the antennas and make coaxial connections to the receiver and transmitter. Of course, some might say this would cast doubt on the validity of the test, but what else can one do?
02-02-2005, 06:44 PM
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RE: Range of dual conversion receivers
Accurate absolute sensitivity tests *can* be difficult with the type of front-end used by many RC receivers (losely coupled untuned lengths of wire) but relative tests are far simpler.
Since my article is a "shootout", I've created a lot of side-by-side video-footage in which the performance of the different receivers can be visually observed as they're all subjected to the same levels of signal, interference, etc.
It's interesting to watch, for example, how they respond when levels of high RF noise are introduced (the servos connected to some receivers remain rock-solid, while others also in frame gyrate wildly). Similarly, I've done a "range check" shot where the receivers (each driving a single servo) are visible in the foreground, while the transmitter is walked away in the background. As the range increases you can see some receivers/servos stopping long before others and some lose the signal far more gracefully than others.
Naturally comprehensive tests were also made to ensure that the receivers operating in close proximity to each other did not adversely affect each other's performance in any way.
Since my article is a "shootout", I've created a lot of side-by-side video-footage in which the performance of the different receivers can be visually observed as they're all subjected to the same levels of signal, interference, etc.
It's interesting to watch, for example, how they respond when levels of high RF noise are introduced (the servos connected to some receivers remain rock-solid, while others also in frame gyrate wildly). Similarly, I've done a "range check" shot where the receivers (each driving a single servo) are visible in the foreground, while the transmitter is walked away in the background. As the range increases you can see some receivers/servos stopping long before others and some lose the signal far more gracefully than others.
Naturally comprehensive tests were also made to ensure that the receivers operating in close proximity to each other did not adversely affect each other's performance in any way.
