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R/C rx antennas

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Hi all.

I´m studying the best way to mach an antenna for our needs. I read Mr.RC-Cam´s article in this way and found it very interesting but I should make some thoughts.

I think we should include in our measurements the video gear and all placed in our plane. The idea of getting rid of the esc and the gas servo and placed instead a small voltimeter is good.

For a starting point I think we should consider some advanced math and see how the brand has chosen the serial inductor on the antenna. Where the value of the inductor comes out with this:

L=350/[2PI x F x tan (360º x h/wavelenght)]

Where:

F= Frecuencie in Mhz

h= Antenna´s lenght

wavelenght= v(wave propagation speed) / F(Mhz)

By putting the inductor value we should know the teorical appropiate lenght of the antenna for a 1/4 wavelenght for example.

In addition to this I think it should improve to make a dipole of a 1/4 wavelength that in 35 Mhz is 2.14m.

What do you guys think about this thoughts?

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What do you guys think about this thoughts?

How about this: Install a 1/4 wave length aerial (or as close as you can get to that). And apply careful tweaks to the Rx's antenna matching transformer. For extra credit, install a counterpoise 1/4 wave element to the Rx's RF ground. I do realize this is a burden at 35Mhz, so if your model is small then I will concede that this is not a practical solution.

In a nutshell, the results you get with any antenna tweaking will depend on many factors. Prepare to perform a lot of tests to determine what works best in your installation.

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How about this: Install a 1/4 wave length aerial (or as close as you can get to that). And apply careful tweaks to the Rx's antenna matching transformer. For extra credit, install a counterpoise 1/4 wave element to the Rx's RF ground. I do realize this is a burden at 35Mhz, so if your model is small then I will concede that this is not a practical solution.

In a nutshell, the results you get with any antenna tweaking will depend on many factors. Prepare to perform a lot of tests to determine what works best in your installation.

Installing a 1/4 wave lenght aerial would interfere the inductor all receivers have. Probably the inductor is not needed right?

Anyway what do u think about including the video gear for our test?

I know is hard to match a good antenna for a specific instalation, but I think it worth, you could get up to 2 times more range than the "stock" range.

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Installing a 1/4 wavelength aerial would interfere the inductor all receivers have. Probably the inductor is not needed right?

That is why I mentioned tweaking the antenna matching transformer (it is the "inductor"). Not all Rx's have the adj coil, but the older designs often do.

However, even if yours does not have one to adjust, I believe you will find that range on many R/C rx's will increase as you lengthen the antenna. If necessary, you can trim the aerial in 1 inch increments until best range is found. Have you tried that yet?

Anyway what do u think about including the video gear for our test?

The video gear may affect range. So, range tests should be performed with the video gear too. Frankly, most everything will affect range, including the layout of the servos, the R/C wiring positions, EMI noise from the ESC, antenna placement, bad karma, and more. The Rx's design is critical too.

but I think it worth, you could get up to 2 times more range than the "stock" range.

I agree, that seems very possible with a optimized installation. But, not as easy as it sounds on small models.

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That is why I mentioned tweaking the antenna matching transformer (it is the "inductor"). Not all Rx's have the adj coil, but the older designs often do.

I think I had a language problem there :huh:

However, even if yours does not have one to adjust, I believe you will find that range on many R/C rx's will increase as you lengthen the antenna. If necessary, you can trim the aerial in 1 inch increments until best range is found. Have you tried that yet?

I haven´t tried anything yet, I thinking about the best way to make my measurements in the most realistic way.

I would use the formulae to make a theorical aprox of the optimal lenght. After that I would use your method with the video gear installed and transmitting.

If I have time enough I would make a range test at my flying field with all this. This is a good way to ensure that the lab data are ok.

After all I´ll make the dipole soldering a 1/4 wavelenght to receiver´s ground.

By the way, soldering an extension to the stock antenna would be harmful for antenna performance?

Sorry about my english, is not as good as I´d like

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After that I would use your method with the video gear installed and transmitting.
Do you mean you will monitor the Rx's RSSI output? If so, be aware that the RSSI can appear to show a strong RF, even if the RF is essentially interference from unwanted sources. During my tests, I deliberately shut down all the local electrical equipment in the area so that the R/C RSSI data was not corrupted by it. In other words, the RSSI might be affected by the strong RF carrier from the video transmitter. So, it would be wise ensure that is not the case during your tests.

By the way, soldering an extension to the stock antenna would be harmful for antenna performance?

A quality soldered connection will not affect RF performance.

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Do you mean you will monitor the Rx's RSSI output? If so, be aware that the RSSI can appear to show a strong RF, even if the RF is essentially interference from unwanted sources. During my tests, I deliberately shut down all the local electrical equipment in the area so that the R/C RSSI data was not corrupted by it. In other words, the RSSI might be affected by the strong RF carrier from the video transmitter. So, it would be wise ensure that is not the case during your tests.

Ok then I will do the lab test with the video gear OFF but installed in the plane or the prototype.

Thanks all your help is great :)

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Well I got to work on this, first problem where is the rssi in my cheap E sky 6 channel receiver? I figure out that it was on there (see the picture) but not sure, the voltage seems to be affected with the conditions (transmitter on, adding a servo etc). Could you please take a look at the picture and confirm me?

post-6-1170009839_thumb.jpg

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RSSI is on pin 12 of the 31136 IC. You should look at the mfg IC data sheet for details to the filter cap that is required.

Keep in mind that the Esky Rx's are not high performance (they are low cost designs). Not the best to use if you expect reliable long range.

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RSSI is on pin 12 of the 31136 IC. You should look at the mfg IC data sheet for details to the filter cap that is required.

Keep in mind that the Esky Rx's are not high performance (they are low cost designs). Not the best to use if you expect reliable long range.

RSSI is on pin 12 of the 31136 IC.

Sorry about that, is the same component than in your special project.

You should look at the mfg IC data sheet for details to the filter cap that is required.

Now I do have the mfg IC data sheet, but I don´t understand what are you trying to say with the filter cap that is required, probably again a language problem here ;)

I know is a cheap receiver but I´m starting with it becouse if I burn something it wouldn´t be too expensive :D

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If you look at the data sheet you will see that a capacitor is required on the RSSI output. The data sheet shows the value.

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