are receiver antennas a specific length on purpose?

[iamsuperbleeder]

As the title suggest, are receiver antennas a specific length coming from the receiver itself so they are more or less "tuned" to the frequency needed? Like a CB antenna on a 1:1 vehicle? Or are they the length they are just because, well, that's the length they are, for no real specific reason.

The reason I ask is because I plan on putting a whip antenna on my SCX10 made from a length of guitar string, and I was thinking about actually soldering the receiver's antenna wire to the base of it, so the antenna would actually be functional. But in doing so, I'm obviously going to be changing the antenna's overall length.

Would I have any bad side-effects from doing this? Maybe good, like a little extended range? (not that that's really needed, since I tend to stay only a few steps behind my crawler anyhow )

Thanks!

[MRCCRAWLER1.9]

i believe this is not possible with a guitar string because i believe there are 2 small wires in that wire. one for sending, and one for receiving. hopefully someone else will clear this with you.

Yes, RX wires are purposely set to be a certain length, too short or too long, and it will disrupt how the RX and TX communicate between each other causing glitching.

[JeremyH]

Originally Posted by iamsuperbleeder

As the title suggest, are receiver antennas a specific length coming from the receiver itself so they are more or less "tuned" to the frequency needed? Like a CB antenna on a 1:1 vehicle? Or are they the length they are just because, well, that's the length they are, for no real specific reason.

Yes, just like your CB that is tuned to integer value of standing waves per length of the antenna, these too should not be shortened or lengthened....

[iamsuperbleeder]

cool, glad I asked before I hack up the antenna wire

thanks fellas!

guess the little whip antenna will be purely for looks

[squatch71]

I don't see a rhyme or reason to it though..I have a JR RS300 adjustable channel AM recievers. two of them have a length of about 15"...the other one is about 35", and no one can explain why. They all work the same...great.

but yes, don't cut it...if you do you loose distance that you can be away from your rig.

[HndsWthtShdws]

Antenna lengths are derived using waveform length. Antennas are generally some factor of 1/4 of the wave length. A 75 mhz radio wave has a wavelength of 12.48 feet.

Ideal 75mhz antenna sizes would be
1/4 wavelength = 37.44"
1/2 wavelength = 6.24'
1 wavelength = 12.48'



This is also why CB antennas come in the lengths they do. a 102" whip is meant to be mounted on a 6" spring, for a total of 108" and 1/4 wavelength.


The average person installs their radio and coils all that extra wire neatly somewhere out of the way right? If you have a little know how you might even coil it in a figure 8 fashion. All that extra wire is not functioning as a proper antenna. Only the bit that sticks straight up does. Cutting the antenna while having a full antenna tube should not hurt anything.

If I was in your shoes, I would unsolder the existing antenna wire and solder on a new wire with an eye terminal. Bolt the whip onto something plastic with the eye terminal. You could possibly see a range decrease but I predict everything will function 100% if your within 100 yards or so. Just to be safe make the whip+new wire equal to 18.72 inches (1/8 wavelength). If performance is not to your expectations solder the old wire back on.

"I believe there are 2 small wires in that wire. one for sending, and one for receiving." I would like to correct your beliefs. Its a standard multi strand wire. The transmitter antenna sends, the receiver antenna receives. Neither does both. I'm not familiar with telemetry systems which might.

[MRCCRAWLER1.9]

Originally Posted by HndsWthtShdws

"there are 2 small wires in that wire. one for sending, and one for receiving." is absolute horse shit. Its a standard multi strand wire. The transmitter antenna sends, the receiver antenna receives. Neither does both. I'm not familiar with telemetry systems which might.

No need to be an a-hole bout it. I am not familiar with the old Am/FM, but i was thinking it could have been a 2.4ghz kind of wire that is Co-axial, which is what spektrum uses in their receivers.

also i did not straight up say that "there are..." i said "i BELIEVE..."

[HndsWthtShdws]

Wasn't intentional or nothing.

Are you a woman? They've been calling me a-holes all my life.

[Stregone]

2.4ghz antennas are coaxial. The actual antenna is the part at the tip where the outer shielding is removed.

[MRCCRAWLER1.9]

Originally Posted by Stregone

2.4ghz antennas are coaxial. The actual antenna is the part at the tip where the outer shielding is removed.

ah i see, thanks for clearing that up

[AreCee]

Originally Posted by Stregone

2.4ghz antennas are coaxial. The actual antenna is the part at the tip where the outer shielding is removed.

Not all 2.4GHz receiver antennae are coax.

All of Spektrum's fisrt DSM weren't coax; SR300, SR3000, SR3500, SR3001.

Now their second generation of DSM2 receivers are coaxial; SR3100, SR3250, etc.

The SR3000 comes with an 8.5" antenna wire which can be shortened to 3.6" exactly according to their instructions. I haven't read all the manuals but I think that was the only DSM receiver that you could shorten the wire. I do know that the SR300 and SR3500 come with the 3.6" antenna wire.

[Stregone]

Originally Posted by AreCee

Not all 2.4GHz receiver antennae are coax.

All of Spektrum's fisrt DSM weren't coax; SR300, SR3000, SR3500, SR3001.

Now their second generation of DSM2 receivers are coaxial; SR3100, SR3250, etc.

The SR3000 comes with an 8.5" antenna wire which can be shortened to 3.6" exactly according to their instructions. I haven't read all the manuals but I think that was the only DSM receiver that you could shorten the wire. I do know that the SR300 and SR3500 come with the 3.6" antenna wire.

Interesting, I did not know that. I got back into r/c after a long hiatus a little while after the first gen of 2.4ghz radios were released, so I never saw any of those.

[iamsuperbleeder]

well this would have been on a stock Axial AR-2 receiver that come in the SCX10, if that helps at all