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Receiver shootout (part 1)

Old 03-08-2004, 12:11 AM
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XJet
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Default Receiver shootout (part 1)

Today I compared the sensitivity of three RC receivers: The Hitec RCD3500, the Hitec 555, the FMA M5

In each case, the receiver was attached to a freshly charged 600mA 4.8V receiver pack and a single non-digital servo.

It was mounted 30 inches above the ground and the antena wire was run horizontally (at right angles to the direction of the test transmitter) for 2/3 its length, then vertically for 1/3 its length.

The transmitter was a Hitec Eclipse with Spectra module.

All receivers were on Channel 23 (72.250MHz).

During the testing, the transmitter voltage remained between 9.6V and 9.8V and the antenna was kept fully collapsed. The transmitter was also kept at the same height above the ground and at the same orientation to the receiver throughout the testing.

The tests were conducted at a distance of more than 200 yards from any structure, underground or overhead wiring or other factors likely to influence the results.

Here's how they stacked up:

Hitec RCD3500: max range - 101 yards
Hitec 555: max range - 94 yards
FMA M5: max range - 65 yards

Notes:

The servo response degraded gradually with both Hitec receivers as they approached the limits of their operating range. Significant servo twitching was noted some 10-15 yards before all control was lost.

The FMA M5 stopped abruptly at the limit of its operating range with no twitching. A small amount of slugishness was noticed 5-6 yards before all control was lost.

Summary:

The FMA M5 has "S.M.A.R.T" decoding designed to reject corrupt data frames and this facility clearly works as advertised when the signal level drops to the point where noise impinges on the received signal.

However, I was disappointed that the FMA M5 has only 65% of the range offered by the Hitec receivers.

I was contemplating using the M5 in a large model but now I'm not too sure. Certainly it's a huge advance on the "park flyer" single-conversion receivers and their limited range and given it's ultra-light weight and small size would make a great alternative to these.

I have subsiquently flown the FMA M5 and noticed no problems, albeit this was in a small plane that ventured no more than 200 yards from the transmitter with its antenna fully extended.

The next round of testing involves subjecting all three receivers to burts of impulse noise, off-band signals and frequencies designed to produce 2IM and 3IM products.
Old 03-08-2004, 07:24 AM
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CafeenMan
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Default RE: Receiver shootout (part 1)

I had a 555 in a plane that was very colorful and had control of it until I couldn't see it any more and lost the plane. That's all I need to know. I can control it as far as I can see it. I haven't used the other rx's you tested.
Old 03-08-2004, 07:54 PM
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Lynx
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Default RE: Receiver shootout (part 1)

Those ranges might be usefull, but only if they're consistant with more than just 1 of each receiver. Otherwise you can't see how variable the manufactor's process's are. You'd have to test 10 of each, preferably not from the same batch to come up with usefull numbers.
Old 03-08-2004, 10:20 PM
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XJet
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Default RE: Receiver shootout (part 1)

Yes, it would be very useful to establish the variance within receivers of the same brand/model -- however my budget doesn't stretch to that. Of course if any manufacturer want's to lend or donate units for the testing I'd be happy to comply :-)

That would be even nicer when it comes to testing the interference rejection capabilities -- given that there are now several manufacturers offering receivers which, they claim, offer the benefits of PCM when used with regular PPM transmitters.
Old 03-09-2004, 07:37 PM
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Lynx
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Default RE: Receiver shootout (part 1)

Unless you can aford said benchmarking technics you can not say anything for or against any transmitter, receiver, or modulation method or signal processing technic of any system =) Unless it is of course your own person experiance, in which case you can say anything you well please about anything you damn well please =>
Old 03-09-2004, 07:55 PM
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Default RE: Receiver shootout (part 1)

Regardless of any benchmarking "technics", the data is useful and worth having. Its just one more real world data point that can be used with other data collected. I'd much rather have some metrics than none, and he at least tried to reduce the outside influences as much as possible. Until someone comes up with a large budget to do it right, I'm more than happy to have data like this rather than simple opinions based on uncontrolled testing.
Old 03-09-2004, 09:03 PM
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XJet
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Default RE: Receiver shootout (part 1)

ORIGINAL: Lynx
Unless you can aford said benchmarking technics you can not say anything for or against any transmitter, receiver, or modulation method or signal processing technic of any system =) Unless it is of course your own person experiance, in which case you can say anything you well please about anything you damn well please =>
I'm not saying *anything* against *anything*. As I've pointed out, all of the receivers tested would provide adequate range and sensitivity when used for controling the average RC model.

One would also hope that modern manufacturing methods and procedures would ensure that the variance within any particular sample of a company's receivers of the same model would be minimal.

In respect to the test method, the simple method used has an awful lot of *advantages* over throwing a receiver on the test bench and measuring its sensitivity with a well calibrated RF signal generator and is almost certainly going to give more useful "real world" data.
Old 03-10-2004, 01:05 PM
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Rodney
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Default RE: Receiver shootout (part 1)

Lynx made some good points, unless you have a representative sample number, the tests are next to worthless. Also, if tests were made with the transmitter antenna down, the self heating in the transmitter will continually increase as the heat builds up due to high SWR which results in decrease power output with the units first tested getting the higher powered signal. To be a valid test, the antenna must be fully extended on the transmitter or a calibrated RF meter used to be sure a constant RF output was generated. I do not want this to throw cold water on your test, the effort is commendable and I hope you continue to persue more testing. Just be aware of the possible pitfalls that can lead to errouneous results. Please don't let this discourage you and do continue to report any additional tests. Our hobby needs more people who question and test for results.
Old 03-10-2004, 02:19 PM
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XJet
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Default RE: Receiver shootout (part 1)

I'm well aware of the variables -- and the transmitter was "rested" for 20 minutes between tests so as to ensure that the operating voltage and RF output was equal.

The results are the average of three sets of tests performed in different order -- since there's always the possibility that some external RF may have impinged on the test area (although a scan was done before and after each test and no such signals were detected).

As for the sample-size -- yes, it would have been nice to have a larger number of each make/model of receiver to check but unless manufacturers are willing to ante-up sample units then this is beyond the budget allocated to these tests.

And in some ways it's better that manufacturers didn't provide sample units as there's always the risk that the units supplied would be carefully tuned and checked to make sure they had performance levels greater than that likely to be obtained in an "off the shelf" unit.

While it's true that the testing method may introduce some variance due to the variables you have mentioned, this variance would be nowhere near the 50% difference in range noted between the FMA and Hitec equipment.

Once again I should reitterate that all the receivers tested provided adquate range for normal RC model flying -- but the Hitec appear to offer 50% more headroom.
Old 03-10-2004, 02:48 PM
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Default RE: Receiver shootout (part 1)

ORIGINAL: Rodney
Please don't let this discourage you and do continue to report any additional tests. Our hobby needs more people who question and test for results.
Ditto. I love this type of info when done is a systematic and methodical way. Its much better than just believing what the manufacturer decides to tell us since we have nothing else to go on. XJet was smart enough to reduce the variables as much as he could within the limits imposed on him. It would be nice if he had 10 or 15 of each units, while the proper equipment for testing. Short of that, I think he did a credible job with what he had, and I would encourage him to do more.

ORIGINAL: XJet
While it's true that the testing method may introduce some variance due to the variables you have mentioned, this variance would be nowhere near the 50% difference in range noted between the FMA and Hitec equipment.
The only issue is that the FMA receiver could be a bad receiver. Considering the large discrepancy, it wouldn't hurt to test another FMA receiver to see if they both are reduced 50%. That would at least reduce the probability substantially. BTW, I am willing to send you a couple receivers I have in the shop if you need some additional receivers to add to the mix, and have a JR or Futaba transmitter to use. I will want them back however [>:] (note the bold and italics!!)

Did you also use the same crystal for each receiver, or did each receiver have its own crystal? That could be another potential source of the large variance.
Old 07-09-2008, 10:35 PM
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FLYBABY6
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Default RE: Receiver shootout (part 1)

I've always wondered without actualy trying the limit, about how far does a typical fm radio transmit? i have a lazer 6 and the new suprieme IIs reciever both high tech and 4.8v 11mah bat for the reciever and slow realistic plane manuvers(patern). how far can i fly out befor its lost? and is it the same distance over head? sorry if this is dumb. noob....
Old 07-10-2008, 08:16 AM
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Default RE: Receiver shootout (part 1)

It's very likely that your system will be able to control your model way past the point of your being able to see it clearly in any direction .

Karol

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