DPRG
DPRG List  



DPRG: Ming Modules?!@$#@@!

Subject: DPRG: Ming Modules?!@$#@@!
From: Robert L. Jordan rljordan at airmail.net
Date: Mon Nov 8 18:12:44 CST 1999

Thanks Doug. I like Math when it is in English!-)
Robert Jordan

Douglas Kilgore wrote:

> The formula given in the ARRL Handbook for calculating antenna length:
>
> 1/4 wave:
> 234/Mhz = Length in Feet
>
> Therefore
> 234/310 = .755 ft  = 9.06 inches
> That length should be attached on one end only ie;  an end fed  antenna.
>
> Doug
>
> MIKE MCCARTY -- 93789 wrote:
>
> > )I am probably wrong here, but I thought that only worked
> > )in a vacuum and that for air, the number was significantly
> > )different.  (something like 10% different??????????)
> >
> > In normal air, the difference is completely negligible. Up in the
> > ionosphere, it is a different matter, which is what allows us to listen
> > to radio broadcasts from far away.
> >
> > The issue with propagation speed has to do with the speed of propagation
> > in the *conductor* which makes up the antenna, and may be as low as 75%
> > of c or so.
> >
> > )Using Ming's numbers: 9.08 * 4 = 36.24 inches = 0.9205 meters
> >
> > 1 yard = 0.9144 meters.
> >
> > )OOPS! I just noticed that's for 310 MHz (not 300).
> > )0.9205 * 310 / 300 = 0.9512 meters for 300Mhz
> >
> > 1 meter is not 36.24 inches. 1m = 39.37 inches (closely enough). That
> > gives
> >
> >         (310/300)*39.37 = 40.68 inches
> >
> > )Either way, if you believe Ming, it appears to me that
> > )the 3x10^8 m/s doesn't work for air.
> >
> > It's not the air that matters, really.
> >
> > But I haven't measured the speed of propagation in the telephone wire I
> > used for the antenna to within 10% anyway.
> >
> > Mike
> > ----
> > char *p="char *p=%c%s%c;main(){printf(p,34,p,34);}";main(){printf(p,34,p,34);}
> > I do not speak for Alcatel. <- They make me say that.
> > This message made from 100% recycled bits.

------------------------------

More information about the DPRG mailing list