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Old Nov 12, 2010, 01:38 PM
USA: LakeGeorge, New York
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Question
Will increasing antenna wire Lenght increase RC-Rx range?

Hello,
I have a Futaba PCM reciever (168DP),

1. will adding another 39" of wire to the existing
reciever antenna wire increase range?
I'm afraid if I go out too far, my servos' will lock out....
(I don't have OSD)
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Old Nov 12, 2010, 02:22 PM
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Norway, Hordaland, Bergen
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Yes, most likely.


See chart, this is rssi voltage vs distance(meters), from a 35MHz Futaba PCM receiver (don't remember model).

Blue line is original antenna length, the other is longer.


Megafluffy
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Old Nov 12, 2010, 03:05 PM
USA: LakeGeorge, New York
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I have 72mhz.....
is it the same for 35mhz?
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Old Nov 12, 2010, 03:16 PM
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Generally yes. In theory there are certain specific lengths that could reduce the
range, but in practice, longer seems to almost always be better.

ian
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Old Nov 12, 2010, 03:52 PM
USA: LakeGeorge, New York
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Daemon,
I don't want to reduce range....
will the doubling the original length the perfect solution?
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Old Nov 12, 2010, 04:15 PM
RCPlaye
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suscribed
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Old Nov 12, 2010, 04:19 PM
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Mega,
Do you have the lengths as a % of the original?

It looks like the Black line is about optimum.
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Old Nov 13, 2010, 04:25 AM
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Hi all,

Yes doubling the length will be good.

On 35MHz original length is 1/8. I have also tested 1/2(pink) 5/8(yellow) 3/4(green) 1/1(black), I haven't tested 1/4 yet.
The red one is 1/2 that was a bit to long.

But as you can see, doubling from 1/2 to 1/1 is not worth it, minimal signal increase, but big weight and drag increase (at least on 35MHz, ant is about 8m).

Megafluffy
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Old Nov 13, 2010, 05:32 AM
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Can you test 1/4 length?
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Old Nov 13, 2010, 06:19 AM
Stuart
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Quote:
Originally Posted by Megafluffy View Post
Hi all,

Yes doubling the length will be good.

On 35MHz original length is 1/8. I have also tested 1/2(pink) 5/8(yellow) 3/4(green) 1/1(black), I haven't tested 1/4 yet.
The red one is 1/2 that was a bit to long.
Well most RXs seem to use 1M/39" as a handy length, there is no reason for it to be deliberatly 1/8th Wavelength. In any case 1/8th wavelength at 35.2mhz is 1.125M. Plus I have a 40MHZ Corona, it has a 1M antenna also, figure that out.

The graph is very good info, but I suspect you would have had the same progression (some lengths better than others) if you had ignored wavelength and teseted, 1M, 1.5M, 2M etc.
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Old Nov 13, 2010, 07:21 AM
Chris R
United Kingdom
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Cutting off a old antenna wire and solering to my antenna on corona receiver double my range with transmitter antenna down.
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Old Nov 13, 2010, 07:46 AM
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The problem with increasing the lengths is that the receivers dont use a tuned antenna and they have coils on the input og the rx. This means as the antenna length increases the impedance goes too far out loosing performance instead of gaining it
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Old Nov 13, 2010, 02:37 PM
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Quote:
Originally Posted by Guntars View Post
Can you test 1/4 length?
Hi,

Sorry but it will not happen anytime soon... I have the same enemy as everybody... TIME... Wont let me do everything I want, and have to do.

But I guess it would be just below 3/4.. Good improvement, but not as good as 1/2. But this is just my guess.


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Old Nov 13, 2010, 02:42 PM
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Quote:
Originally Posted by Coyote64 View Post
The problem with increasing the lengths is that the receivers dont use a tuned antenna and they have coils on the input og the rx. This means as the antenna length increases the impedance goes too far out loosing performance instead of gaining it
Prove it.

Every actual test I've ever seen (and people have been doing them for decades now)
shows increased signal strength and longer range with longer antennas on
72Mhz and 35Mhz Rxs. I've never seen one actual lose performance, although
it is theoretically possible.

ian
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Old Nov 13, 2010, 03:01 PM
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Quote:
Originally Posted by Coyote64 View Post
The problem with increasing the lengths is that the receivers dont use a tuned antenna and they have coils on the input og the rx. This means as the antenna length increases the impedance goes too far out loosing performance instead of gaining it

Hi,

I know this is true for transmitters. But for receivers, good match is not so important. This you can see in my tests, where the antennas with the highest impedance, has the best results (1/2 and 1/1).

Maybe the input impedance for the receivers is higher than the the antenna they are supplied with?

All antenna length tests has an average of 6-10 inputs for each distance.
(because of this, it takes long time to do this tests)

Megafluffy
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