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Old October 6th 05, 07:34 PM
mikeFNB
 
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Default Antenna Length Formula

if it's for RX the imp matters not

mike

wrote in message
ups.com...
2808 divided by the frequency in MHz will give
the length in inches for a 1/4 whip. Roughly
17.5 inches. Times 4 will give you a full wave.

Can't understand why you would want a full wave
whip. The impedence would be very high and
would not match a scanner or two way radio. 1/4,
5/8, or 3/4 in much easier to match.

Jim, K5DIE/9


Al wrote:
(Don Forsling) wrote in
:

Folks, I'm old, I'm tired, and I'm lazy. I'm also forgetful.

Would someone kindly provide the formula for deterring the length of a
full-wave antenna for a given frequency ( a full-wave whip comes to
mind)? Then, I can do the math. Better yet, I'll give you the frequency
and _you_ can do the math. It's 160.890 mHz.

I will never ask this question again. Sorry. Thanks, etc.

Best,


Once upon a time when I was taught physics, I was told that full wave
lenght should be
calculated by dividing the speed of a light (299820km/s) with the
frequency(in MHz)/1000,
so for full wave dipole it should be 299820*160.89/1000=1.864m, for
half-wave dipole
divide the result by two.

Albert




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Old October 7th 05, 08:33 AM
Al Klein
 
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Default Antenna Length Formula

On Thu, 06 Oct 2005 17:34:46 GMT, "mikeFNB"
said in rec.radio.scanner:

if it's for RX the imp matters not


That old nonsense again?

SWR isn't directional. Of course impendence matters, unless you don't
care how much signal you lose between the source and load.
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Old October 8th 05, 03:46 AM
Jerry
 
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Default Antenna Length Formula

On Fri, 07 Oct 2005 02:33:10 -0400, Al Klein
wrote:

On Thu, 06 Oct 2005 17:34:46 GMT, "mikeFNB"
said in rec.radio.scanner:

if it's for RX the imp matters not


That old nonsense again?

SWR isn't directional. Of course impendence matters, unless you don't
care how much signal you lose between the source and load.


Ah yes, that old nonsense again,

Yes, it is true that you will not damage a receiver with impedance
mismatch, but you will have less signal. Signal budget, system budget,
call it what you may.

And the beat goes on . . . . .

Jerry
ARINC LAXMM

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Old October 17th 05, 03:38 AM
Brian Aase
 
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Default Antenna Length Formula

Does this (or should it?) include any correction for propagation
factor?
---
On Sat, 15 Oct 2005 13:53:29 GMT, kla1899 wrote:

wrote in
oups.com:

2808 divided by the frequency in MHz will give
the length in inches for a 1/4 whip. Roughly
17.5 inches. Times 4 will give you a full wave.

cut

Due it's to simple, click the link:

http://mysite.verizon.net/moment_1/s...alculation.htm

put in your frequ hit Calculate "DUNE"



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Old October 17th 05, 03:51 AM
Al Klein
 
Posts: n/a
Default Antenna Length Formula

On 17 Oct 2005 01:38:34 GMT, Brian Aase said in
rec.radio.scanner:

Does this (or should it?) include any correction for propagation
factor?


For a whip? Not unless you're running a ground wire alongside it. Did
you mean correction for end effect? (The prop factor is affected
mainly by the capacitance between conductors along their length.)
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