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Range of dual conversion receivers

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Old 01-29-2005, 08:07 AM
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big tree
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Default 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
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Old 01-29-2005, 08:22 AM
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Default RE: Range of dual conversion receivers

John

There is a good article regarding this at http://www.classicaero.com/berg/berg.php

Safe flying!
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Old 01-29-2005, 11:30 AM
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Rodney
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Default 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.
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Old 01-29-2005, 01:49 PM
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Default 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.
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Old 01-31-2005, 04:55 PM
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Default RE: Range of dual conversion receivers

Are we limited in range by sensitivity or by noise?
At 72mhz, both man made and atmospheric noise can have an effect along with receiver sensitivity. There are also other specifications which all play a part.

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!
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Old 02-01-2005, 07:02 PM
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Default RE: Range of dual conversion receivers

The magazine editors will tell you that nobody is interested in what goes on inside of our radios.
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Old 02-01-2005, 07:22 PM
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Default RE: Range of dual conversion receivers

The magazine editors will tell you that nobody is interested in what goes on inside of our radios.
Had they asked me, I would have told them I was interested in meaningful Tx & Rx specs. FWIW, my cordless phone, stereo, and TV set all have technical specs in the back of the user guide. And these items are bought by technically challenged consumers. So, it seems to me that the R/C mfg's could do the same for R/C'ers, especially since many of us have technical backgrounds.
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Old 02-01-2005, 07:43 PM
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Default RE: Range of dual conversion receivers

The magazine editors will tell you that nobody is interested in what goes on inside of our radios.
Are you in agreement with magazine editors that we don’t care? I would guess most fliers do care just as they care about different kinds of engines. Magazines have rated various engine characteristics. And I as a reader then can make my decision on what is best for me.

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 systems”, that XYZ will improve their product.

Does everyone care, nope, but I bet a lot do.
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Old 02-02-2005, 03:17 AM
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Default 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.
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.
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Old 02-02-2005, 08:19 AM
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Default RE: Range of dual conversion receivers

A full range of tests has been conducted
XJet, this sounds very interesting!

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
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Old 02-02-2005, 08:57 AM
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Default RE: Range of dual conversion receivers

The magazine editors will tell you that nobody is interested in what goes on inside of our radios.
There are a large number of very smart people in the hobby. And the vast majority is interested in the result of what goes on inside of the radio. No I am not interested in how an electron gets from one circuit trace to another trace.

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
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Old 02-02-2005, 11:55 AM
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Default RE: Range of dual conversion receivers

ORIGINAL: XJet

ORIGINAL: P47 Jug - Al
An article that I certainly would like to see is an article that rates receivers.
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.
Where do you plan to publish?
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Old 02-02-2005, 12:05 PM
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Default 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.
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Old 02-02-2005, 12:16 PM
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Default 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.
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Old 02-02-2005, 04:36 PM
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Default 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.
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Old 02-02-2005, 05:35 PM
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Default 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?
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Old 02-02-2005, 06:44 PM
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Default 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.
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