Keep in mind that the ground for these resistors doesn't have to be
anywhere near as good as for a ground plane, for example. In that case a
few ohms of resistance reduces your efficiency .
In this case, any loss resistance is just part of the resistance, which
is only approximate anyway. The consequences of not having the
resistance exactly correct (which will never happen without a lot of
fuss anyway, and then probably only correct on one band), is just a less
than optimum F/B. The forward gain should be unchanged.
FWIW
73, Joel, W1ZR
Ken Brown wrote:
Omitting the resistors and substituting a quarter wave stub is not
the same
thing. In order for a Vee beam to be unidirectional, you have to
terminate
the ends in the characteristic impedance of the wire. For lengths
longer
than two wavelengths, the characteristic impedance is about 500
ohms. So
you put a 500 ohm resistor to ground. If you don't have a good
ground, you
can use a 500 ohm resistor to a quarter wavelength counterpoise.
And a quarter wave stub, or a quarter wavelength counter poise are
only a quarter wave on one band. Maybe it will also work on another
band where is is 3/4 or 5/4 wavelengths. Resistors to a good ground
will make the antenna unidirectional over several bands. Quarter wave
counterpoises may work for 40 and 15 with just one wire per counterpoise.
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|