on an RF note... Anteannas and such...
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Dear James:
As far as anteannas go you will want to go with an
anteanna that approaches the *true* length of either
5/8 or 1/4 wavelength for the frequency you are
transmitting at for lowest losses. Generally speaking
a rubber duck anteanna will have a higher loss because
what they do with a rubber duck is wind a loading coil
at the base to simulate a longer anteanna length. This
longer anteanna length is what provides the 52 ohms
necessary for most impedance mathing situations. There
are some cases such as in the microwave region where a
rubber duck anteanna is actually the size of 1/4 or
5/8 the wavelength in which case the loss would be the
same. What really matters as far as anteannas are
concerned is how high up they are.
On another note lately i have been reading many
inquiries on how to improve the transmitting distance
of an rf module. The key to this would be to go to
www.rfparts.com or www.motorola.com and look up the
little rp power amplifier modules. Take for instance
the M57721M which can be found at www.rfparts.com.
This module provides a bandwidth of 400-450 mhz. For
10 mW input you can get 7 Watts output. It has class
AB bias point and costs $31.30. From my experience 7
watts of rf power can go somewhere around 5-10 miles
easily. Of course I know everyone on the basic stamps
yahoo group is very ethical and would only purchase
these modules to evaluate their performance through a
dummy load.
-=Randy Knutson
Does anyone know whether the fixed/duck bill style
antenna on
an rf module gives any kind of advantage over the
single wire
type?
thanks
James
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As far as anteannas go you will want to go with an
anteanna that approaches the *true* length of either
5/8 or 1/4 wavelength for the frequency you are
transmitting at for lowest losses. Generally speaking
a rubber duck anteanna will have a higher loss because
what they do with a rubber duck is wind a loading coil
at the base to simulate a longer anteanna length. This
longer anteanna length is what provides the 52 ohms
necessary for most impedance mathing situations. There
are some cases such as in the microwave region where a
rubber duck anteanna is actually the size of 1/4 or
5/8 the wavelength in which case the loss would be the
same. What really matters as far as anteannas are
concerned is how high up they are.
On another note lately i have been reading many
inquiries on how to improve the transmitting distance
of an rf module. The key to this would be to go to
www.rfparts.com or www.motorola.com and look up the
little rp power amplifier modules. Take for instance
the M57721M which can be found at www.rfparts.com.
This module provides a bandwidth of 400-450 mhz. For
10 mW input you can get 7 Watts output. It has class
AB bias point and costs $31.30. From my experience 7
watts of rf power can go somewhere around 5-10 miles
easily. Of course I know everyone on the basic stamps
yahoo group is very ethical and would only purchase
these modules to evaluate their performance through a
dummy load.
-=Randy Knutson
Does anyone know whether the fixed/duck bill style
antenna on
an rf module gives any kind of advantage over the
single wire
type?
thanks
James
__________________________________________________
Do You Yahoo!?
Yahoo! Health - Feel better, live better
http://health.yahoo.com