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From: "Da Man"
Subject: Re: Single wire FM antenna
X-Newsreader: Microsoft Outlook Express 5.50.4807.1700
Date: Fri, 03 Jan 2003 08:53:46 GMT
NNTP-Posting-Date: Fri, 03 Jan 2003 04:53:46 AST
"Kevin McMurtrie" wrote in message
> In article ,
> "Phil Allison" wrote:
> >"mook johnson" wrote in message
> >> I have an FM receiver (75MHz) that has an antenna tuned to
> >> of the wavelength of the carrier.
> >> From what I've read, 5/8 would be better.
> >> This receiver only needs to work over a short range (~1000 feet max)
> >> fairly strong transmitter nearby (~1 watt).
> > ** 1000 ft range is not needed with a RC car since you cannot
> >control what you cannot see. A range of 150 feet is about normal. Your
> >is unlikely to be of 1 watt RF output either.
> Aren't you quite the troll here.
Yes, he really seems to be.
> 75MHz RC systems are commonly used for 1/10 scale race cars. I used to
> have a super-modified Tamiya Falcon that did 40 to 50 MPH. Driving it
> in anyting less than a 300 foot radius was just tedious tire burning.
> It had a range of 900 feet at full throttle and over 1000 feet at light
> throttle. (I checked my favorite driving spots on Mapquest to get the
I have a simular R/C device - a boat, and it will easly do 1000 feet, and at
high speeds. The large nitro engine powered ones are half retarded.
Some people have clamed to get over 100 MPH out of a specally designed 2 or
3 foot ELECTRIC powered boat that hovered across the water, with the prop
the only thing in the water!
150' at anything above 40 MPH will go by increadably fast.
To the OP
You can calculate the antanna length. I have not really done much with
antannas, but 5/8 wavelength should give you 2db more field stregth on
TRANSMIT, 1/4 and 1/2 wavelength antannas being optimal for both
transmitting and reciving. Not sure about 1/8 wavelength antannas.
Use a 5/8 wavelength on the transmitter, and be exact as possible. Use Coax
up to the antanna.
Also look at pirate and ham radio websites. There is a wealth of info on
some of those.
> The transmitter power for those is 0.25 to 0.75 Watts.
> To the original poster, find out what the factory antenna length is.
> The receiver module is pre-tuned for _exactly_ that length. Some
> companies will re-tune and match a transmitter/receiver pair for a small
This can be done yourself (and you can find out how to use it) if you have
accsess to a SWR (Standing Wave Ratio) meter used to tune antanna systems,
and you can figure a way to hook it up (will likely require disasembly of
the units). People with CB sets often used these, but the frequencys may be
differnt, so they may not work/be accurate.
> 1000 feet is doable.
> Do a Google search for RC hobby web sites.
> >> This is for an R/C car controller
> >> Could someone explain the performance differences between 1/8,1/2 and
> >> wavelength single line antennas?
> > ** Make the Rx antenna longer if you like but why do you want
> >range ?
That could very well decrease range.
> > .............. Phil
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